Going green: What we can learn from a little alga

By Yasemin Saplakoglu

Discovery magazine cover

Researchers led by Martin Jonikas, an assistant professor of molecular biology, are studying a component of algae called the pyrenoid (pictured) that concentrates carbon dioxide for photosynthesis. The blue ball-like structures are enzymes that help convert carbon into sugars for plant growth. The yellow tubules inside the green tubes are thought to bring carbon and other materials into the pyrenoid. COVER IMAGE COURTESY OF BENJAMIN ENGEL, MAX PLANCK INSTITUTE OF BIOCHEMISTRY

WE ARE CONCERNED, rightly so, about the amount of carbon dioxide accumulating in the Earth’s atmosphere. But to most plants, which use carbon for photosynthesis, the amount we have is not enough.

Far back in Earth’s history, the atmosphere is thought to have contained a thousand times as much carbon dioxide as it does today. Over the years, photosynthetic bacteria, and later, algae and plants, gradually consumed the carbon dioxide to a point where it now makes up just a tiny fraction of air. In today’s atmosphere, many plants, including most crops, are literally starving for carbon dioxide.

Download this article as a PDF

But some of these enterprising organisms have come up with ingenious ways to overcome this limitation by siphoning carbon dioxide from the air and concentrating it for use in photo-synthesis. These carbon-concentrating mechanisms make algae and a handful of land plants able to grow faster than they otherwise would.

Could scientists learn the secrets of carbon- concentrating mechanisms so that they can engineer crops to grow more quickly?

One scientist who thinks this may eventually be possible is Martin Jonikas, an assistant professor of molecular biology at Princeton. He and his team are trying to reverse engineer the carbon-concentrating machinery in algae to find out how it works, with the idea that researchers could apply some of these tricks to crops.

Jonikas’ companion in this quest is a single-celled, freshwater alga named Chlamydomonas reinhardtii, which grows naturally in ponds and lakes throughout eastern North America and is known to the plant biology community by the nickname “Chlamy.” In Jonikas’ lab, Chlamy is the main character. Deep green soups of Chlamy fill the flasks that sit in the laboratory incubator. Plastic plates dotted with Chlamy colonies are stacked on the laboratory benches. This unassuming alga plays the starring role in the researchers’ mission to understand the molecular machinery that enables carbon concentration.

“Chlamy is evolutionarily related to higher plants, so most of what we learn from it still applies to them,” Jonikas said. “But because Chlamy is a single-celled organism, we can work with it much more easily and much more rapidly than we can with other organisms.”

From the sky to the lakes

That Jonikas studies molecular machines for a living is no surprise. Since childhood he has been fascinated with machines, especially those that fly. As a child, he would build remote-controlled airplanes and spend his afternoons chasing after them. He followed this fascination by studying aerospace engineering at the Massachusetts Institute of Technology.

His career took an unexpected turn late during his undergraduate years. “An inspiring biology professor opened my eyes to the concept that living organisms are actually complex machines that can be engineered,” he said. He soon transitioned from aerospace engineering to pursuing a Ph.D. in bio-chemistry and molecular biology at the University of California-San Francisco. One day, a colleague gave a talk on biofuels — fuels produced from plants. “It got me interested in biofuels, but more generally it opened my eyes to the importance of photosynthetic organisms to life on Earth,” Jonikas said.

By 2010, Jonikas had earned his Ph.D. and had started his own laboratory at the Carnegie Institution for Science’s Department of Plant Biology, located on the campus of Stanford University. He began studying the molecular machinery that makes photosynthesis possible using Chlamy as a model, and moved his laboratory to Princeton in the fall of 2016. Soon after his arrival, Jonikas was named a Howard Hughes Medical Institute-Simons Foundation Faculty Scholar.

Martin Jonikas

Martin Jonikas, assistant professor of molecular biology, studies how algae are able to grow so quickly, with the goal of eventually engineering faster growth of crops such as wheat and rice.

Alga as muse
In his office at Princeton, Jonikas picks up an oval stuffed animal from the windowsill. It’s a green, plush version of Chlamy. It has a red dot representing the part that the alga uses like an eye, two antenna-like protrusions that the alga uses for movement, and a silver spot on its abdomen where carbon is concentrated. Jonikas’ lab members had the toy made by a craftsperson they found online.

Pointing to the circle of silver cloth sewn on its front, Jonikas says it represents a structure inside the cell called the pyrenoid.

He explains that all photosynthetic plants, including algae, use an enzyme called Rubisco to “fix” carbon dioxide as the first step in converting carbon into sugars that the plant can use for growth. But in most plants, Rubisco does not work at maximum capacity because there isn’t enough carbon dioxide to keep it running at full steam. “Humans have been working for decades to make Rubisco run faster, and nature has been working on it for much longer than we have, but so far, neither has been successful,” Jonikas said.

Many plants — including rice and potatoes — have tried to deal with this problem by making huge amounts of the enzyme. As a result, Rubisco makes up nearly half of all the protein in the leaves of many plants, making it the most abundant protein on Earth. But this strategy only goes so far, because making Rubisco uses up resources that plants could other-wise use for growth.

Algae and some other fast-growing plants like corn have found other solutions. They use carbon- concentrating mechanisms to suck carbon dioxide from the environment and force-feed it to Rubisco. This solution allows Rubisco to run at maximum speed, leading to faster growth.

Diagram of an alga cell

Researchers are exploring how single-celled algae like the one pictured are able to grow so quickly. The secret of this growth stems from a structure called the pyrenoid, which concentrates carbon dioxide from the air to make photosynthesis run faster. By learning the secrets of algae’s success, the researchers hope eventually to engineer the faster growth of crops such as wheat and rice. ILLUSTRATION BY YASEMIN SAPLAKOGLU

Chamy’s solution is to crowd its Rubisco into the pyrenoid, ensuring that high amounts of carbon dioxide come in contact with Rubisco enzymes. The pyrenoid remains something of a black box, which is what makes it so interesting to study, Jonikas said. “Researchers have been very limited by the few tools that are available for studying algae, so we know almost nothing about the protein composition of the pyrenoid, or even how it functions,” he said. “Even the simplest of experiments reveals a lot of interesting new biology.”

Learning how nature builds a pyrenoid, so we can too
One of the key questions has to do with understanding the structure of the pyrenoid. Without a basic understanding of these organelles, building one from scratch in a higher plant seems like an unachievable dream.

Years ago, scientists who took some of the first electron microscopy images of the pyrenoid concluded that the structure was a crystalline solid. But some-thing wasn’t adding up for Jonikas and his colleagues. They observed that when algae reproduce — which they do by dividing in half — the pyrenoids also usually divide, with a portion going to each daughter cell. But how could they do this if the structure is so rigid?

To explore this question, Elizabeth Freeman Rosenzweig, then a graduate student, and Luke Mackinder, then a postdoctoral researcher in the lab, attached a fluorescent protein called Venus to Rubisco enzymes in some Chlamy cells. In each cell, this fluorescently labeled Rubisco made the pyrenoid light up. The researchers used a high-powered laser to turn off the fluorescence in one half of the pyrenoid and observed what happened to the fluorescent Rubisco remaining in the other half. Within minutes, some of the fluorescent Rubisco had moved to the dark side, indicating that the contents of the pyrenoid were mixing like a liquid.

Cryo-EM of the pyrenoid

A cryo-electron micrograph of the pyrenoid, which concentrates carbon dioxide from the air to make photosynthesis run faster. IMAGE COURTESY OF URSULA GOODENOUGH, UNIVERSITY OF WASHINGTON IN ST. LOUIS

The finding that the inside of the pyrenoid is liquid-like, published in a September 2017 issue of the journal Cell, is a step in the direction of transferring the carbon-concentrating mechanism to higher plants, said Freeman Rosenzweig, who recently earned her Ph.D. in Jonikas’ lab. “If we can figure out how nature does it, maybe we can engineer it.”

In another set of experiments, Mackinder and colleagues identified a protein that they think serves as a molecular glue that holds Rubiscos in the pyrenoid. This protein, which they named Essential Pyrenoid Component, or EPYC-1, appears to be necessary for packaging Rubisco into the pyrenoid. Another study, published in the same issue of Cell, revealed 89 new pyrenoid proteins and gave the most detailed look yet at how the pyrenoid is structured.

To learn more about what is going on in the pyrenoid, Jonikas and his team are looking at the genes involved, starting with those involved in concentrating carbon. To do that, the researchers created thousands of Chlamy strains, identical except for the fact that each one has a different single gene disrupted in its genetic code. Each one of these cells is a mutant.

“To study the function of a gene, you can make its mutant — a strain that lacks that gene — so that you can watch how the mutant performs differently than the original organism,” said Xiaobo Li, an associate research scholar in Jonikas’ lab. “But in algae, for many years, we only had a few mutants so we had no idea what most genes were doing.”

Xiaobo Li

Xiaobo Li, an associate research scholar, extracts frozen trays of algae from a storage vessel filled with liquid nitrogen. The trays contain individual strains of algae that have been mutated so that each strain lacks a single gene, allowing researchers to study how the loss of that gene affects growth and other functions.

Li led the development of a “mutant library” that helped the team study the pyrenoid, revealing dozens of candidate pyrenoid proteins. The library is also helping researchers around the world, who frequently request mutants that they can use to do their own research. “This is the first genome-wide collection of mutants in any single-celled photosynthetic organism,” Jonikas said. In the past year, through a collaboration with the Chlamydomonas Resource Center at the University of Minnesota and funding from the National Science Foundation, Jonikas and his team have made available over 2,300 mutants to nearly 200 labs around the world.

When Jonikas first moved his lab to Princeton, he sat down with Ned Wingreen, the Howard A. Prior Professor in the Life Sciences and professor of molecular biology and the Lewis-Sigler Institute for Integrative Genomics. Wingreen, whose team uses computational models to study biological systems, remembered that within 10 minutes both professors had an “aha!” moment.

Wingreen was working on how different polymers could undergo phase separations, such as when steam condenses into water droplets. He became interested in pyrenoids after speaking with Jonikas. His team created a simulation of Rubisco and the linker protein that glues Rubiscos together. The researchers found that the number of binding sites on both the Rubiscos and the linker proteins precisely dictated whether they were condensed into a liquid-like structure, like the pyrenoid, or dissolved into the surrounding chloroplast, as happens during cell division. The work provided a possible explanation for how the pyrenoid can rapidly switch between the two forms.

“Martin has been a tremendous force in the field by taking the modern tools of genomics and adapting them to this understudied organism,” Wingreen said. “He has this wonderfully powerful and motivating vision that what we learn from Chlamy may eventually be immensely beneficial for society.”

The dream

Flasks of algae

Researchers grow algae for experiments aimed at discovering how the single-celled aquatic plants are able to concentrate carbon dioxide and thus grow more quickly than most land plants.

Jonikas and his team have a vision of meeting the world’s rising food demand by engineering pyrenoids into crops such as rice and wheat, so the crops can feed on carbon as efficiently as Chlamy does.

In parallel to studying the genes of the pyrenoid to explore how it photosynthesizes so efficiently, the team has already begun early efforts to inject Rubisco and other algal proteins into higher plants. In collaboration with Alistair McCormick, a molecular plant scientist, and his team at the University of Edinburgh, the researchers found that most of the carbon-concentrating proteins taken from Chlamy traveled to the correct location in tobacco when injected into the plant, as published in the journal Plant Biotechnology in 2015.

“These two organisms are a billion years evolutionarily diverged and yet the little ZIP codes on the algal proteins that point them to their destinations still work in higher plants,” Jonikas said. “They know where to go in a new land.”

Jonikas and his team hope in the coming years to successfully identify and transfer enough components of Chlamy’s carbon-concentrating machinery to produce a functional pyrenoid in higher plants and increase crop yields.

On Jonikas’ windowsill, propped up next to the Chlamy, are other plush toys in the shape of crops — a pea pod, a cabbage, a carrot and stalk of wheat. These characters starred in a video that Jonikas’ team created and posted online to explain their re-search to a broader audience. In the video, the other plants make fun of Chlamy for being different, but when they realize that Chlamy is so good at photosynthesis, they come to respect the lime-colored alga. From Chlamy, they learn the secrets of carbon concentration and become fast-growing crops. Perhaps, someday, this story will come true.


Coming home to document a rapidly changing China

By Catherine Zandonella

SOCIOLOGIST Yu Xie is the director of Princeton’s Paul and Marcia Wythes Center on Contemporary China, which aims to conduct research on Chinese society through an interdisciplinary approach. 

ON A VISIT TO CHINA in 2003, sociologist Yu Xie realized he had something to offer that no one else did.

He’d been living and working in the United States for 21 years and was a highly regarded social scientist with a reputation for applying numbers-driven analysis to study the breadth of human experience. “My whole career has been devoted to the systematic and empirical understanding of the social world around us,” said Xie, the Bert G. Kerstetter ’66 University Professor of Sociology and the Princeton Institute for International and Regional Studies.

Download this article as a PDF

Xie had come to the U.S. in 1983 as part of an academic program that sent a select few Chinese students abroad for graduate study. At the University of Wisconsin-Madison, he studied the history of science and then earned a Ph.D. in sociology. He became a professor at the University of Michigan and went on to publish on provocative subjects like why women haven’t reached the same levels as men in science, and why there is a growing achievement gap between Asian American students and white classmates.

Yu Xie

After spending decades studying the U.S., sociologist Yu Xie has turned his efforts toward capturing the cultural shifts in his native China.

Settling in Ann Arbor, Xie focused primarily on U.S. issues during his early career. Xie’s wife, who had earned her Ph.D. in materials science, climbed the career ladder in industry. They raised children. Xie wrote papers and books, mentored students, and became one of the University of Michigan’s most respected faculty members in the study of structural shifts in populations.

By 2003, it was clear to Xie that a significant structural shift was occurring in one of the largest populations on the planet. China was changing rapidly in every area — income, education, urban migration — and the cultural changes alone dwarfed anything going on in the U.S. “It was like witnessing the Renaissance, or the French Revolution,” Xie said. “In the past, researchers didn’t have the tools to analyze societal change as it was happening. Now, we do.”

Only, in 2003, China didn’t. Chinese social scientists were not trained in the empirical methods that Xie and others had pioneered while at the University of Michigan’s Institute for Social Research’s Survey Research Center. These methods can separate opinion from fact and reveal trends across large swaths of populations.

Also missing were data. The government collected limited information — mainly population statistics — and released even less. Without quality metrics on the everyday experience of Chinese people across various backgrounds and geographical locations, Xie knew it would be impossible to make solid conclusions about how people’s lives were changing.

It was here that Xie saw that he could make a difference. He dreamed of conducting a large-scale study to gather data on typical Chinese households. He knew it wouldn’t be easy. Xie had already tried collecting data in the 1990s. He and his graduate students made trips from Michigan to China to interview families, but the researchers faced obstacles in gaining the consent of local officials.

Xie needed a trusted Chinese entity to support the study and, ideally, to help fund it. He eventually found both at Peking University, one of the top universities in China.

After some negotiations, the university’s Institute of Social Science Survey agreed to organize a comprehensive study that would follow Chinese families over several years to obtain information about family size and composition, marital status, education level, health and many other aspects of daily life.

Called the China Family Panel Studies (CFPS) — a panel study is one that tracks the same research subjects at different time points — the project would survey 15,000 randomly selected families, covering a total of more than 40,000 people in 25 provinces across the country and representing 95 percent of the Chinese population.

The effort kicked off in 2008 with a pilot study. Xie led the study design, traveling frequently from Michigan to Peking University, where Xie holds a visiting professorship, to train the staff and put in place procedures for storing and processing the data.

Yan Sun, an assistant research scientist at Peking University, remembers those early days. She joined the project in 2009 and today is the manager of survey operations for the CFPS. She oversees the recruitment and training of interviewers, mostly students at colleges and universities in each study region, who go house to house. Conducting the interviews wasn’t always easy, especially at the outset of the initiative. “You would have people calling the police to ask, ‘Why is this person in my neighborhood walking around with a lap-top?’” Sun recalled.

Researcher conducting interview

A researcher (right) conducts an interview as part of the China Family Panel Studies, a comprehensive effort to capture China’s fast-changing culture through interviews with over 40,000 individuals in 25 provinces across the country.

The interviewers enter the respondents’ answers into a computer-assisted interview system, and Sun tracks the responses, using them to improve the questions. Sun can find out how long the interviewer took between questions and whether the interviewer went back to a previous question. “We use these data to analyze the interviewer performance and whether the questions were clearly understood by the respondents,” she said.

One of the CFPS’s findings is that inequality in China is steadily climbing. In an article published in 2014 in the journal Proceedings of the National Academy of Sciences, Xie and then-graduate student Xiang Zhou, now an assistant professor at Harvard University, reported that China’s income inequality was among the highest in the world. The extra data were essential for this finding, Xie said, because the government’s official estimate of income inequality was much lower. He and Zhou attributed the in- equality to regional economic differences and the urban-rural divide.

An issue that the CFPS has revealed more recently is the rise in cohabitation in place of marriage among young Chinese. Xie and Jia Yu, now an assistant professor at Peking University, looked at data from the CFPS in 2010 and 2012, which, before the CFPS, had never been collected in a systematic way.

They found that cohabitation is becoming more common among young, educated, primarily urban Chinese professionals, a finding they reported in the journal Population and Development Review in 2015. This contrasts with the pattern in the U.S., where living together is more common among people of lower socioeconomic status.

‘Do not play poker with him’
Robert Hauser, a professor of sociology emeritus at the University of Wisconsin-Madison and one of Xie’s advisers when Xie was earning his Ph.D., serves on the advisory board for the CFPS. “There are three aspects of this survey in China that are really import-ant: First, it is comparative — the whole scheme is designed to be comparable with surveys in the U.S.; second, it is state-of-the-art in field methods used; and third, the data are all public,” he said.

Hauser has known Xie since shortly after Xie arrived in the U.S. and remembers him as one of the most energetic, assertively intellectual and driven students of the time. “He is utterly brilliant and good at everything,” Hauser said. “Do not play poker with him.”

Another long-time friend and mentor of Xie agrees. “He seeks advice, he is thoughtful, and then he makes up his own mind,” said Donald Treiman, a professor emeritus of sociology at the University of California-Los Angeles. “He is a strong mentor and he goes out of his way to make sure that his students are prepared for future careers in academia. That is an important part of his persona.”

In addition to holding a visiting professorship at Peking University, Xie is an adjunct professor at the Chinese University of Hong Kong and three other Chinese universities (Shanghai University, Renmin University and the Hong Kong University of Science and Technology). These appointments allow him to mentor and serve as a graduate adviser to a large number of Chinese sociology students.

Chunni Zhang is one of Xie’s former students from the Chinese University of Hong Kong. Now an assistant professor of sociology at Peking University, Zhang said Xie has been instrumental not only in introducing sociological study methods in China, but also in shifting the conversation about what should be studied.

“In the past, most scholars focused their research interests on ‘major’ social issues such as economic reform,” Zhang said. “Xie and his students, however, conducted studies on ‘smaller’ issues in China, family topics in particular, which broadened people’s vision and attracted more interest in studying these issues. Today, family-related issues are very hot topics in China.”

Xie’s studies serve as examples of how China’s issues could be framed into the research questions that have also been asked and answered in the West, Zhang said. “Instead of copying the Western studies, however, he maintained that Chinese studies should highlight the uniqueness or variation of the social context and tell different stories,” she said.

‘I want to find the truth’
In addition to his interest in Chinese society, Xie studies matters relating to Asian Americans, including why Asian Americans have higher grades and standardized test scores, and are more likely to attend college, than whites in the U.S. With Amy Hsin of the City University of New York, Xie reported in a study published in the Proceedings of the National Academy of Sciences in 2014 that academic effort, and not advantages in tested cognitive abilities or sociodemographics, was the greatest factor in Asian American successes.

A subsequent study, however, did uncover some relevant socioeconomic factors, especially among non-Asians. With Airan Liu of the University of Michigan, Xie found differences between Asian American parents and non-Asian parents with regard to educational aspiration for their children. Asian parents, regardless of socioeconomic status, wanted the best possible education for their children. Among non-Asian U.S. parents, however, parents from low socioeconomic backgrounds tended not to have high expectations for their children, while more affluent and educated non-Asian parents did hold high expectations. The study was published in 2016 in the journal Social Science Research.

These studies on the Asian American achievement gap got a lot of attention, and references to Xie’s publications appear frequently in articles in the mainstream media. Xie resists getting pulled into discussions about the policy implications of his work. “I want to find the truth,” he said.

Two years ago, Xie moved to Princeton to head up its new Paul and Marcia Wythes Center on Contemporary China, part of the Princeton Institute for International and Regional Studies (PIIRS). The center focuses on studying the sociology of China through an interdisciplinary approach. “Princeton was one of the few places that could tempt me to leave Ann Arbor,” he said.

The center aims to study the social changes in China from an interdisciplinary perspective that combines faculty expertise in economics, East Asian studies, anthropology, politics, religion and Princeton’s Woodrow Wilson School of Public and International Affairs. The center also hosts visiting scholars and holds lecture series and graduate-level workshops.

Each summer, Xie leads groups of Princeton under-graduates to study in China through the PIIRS Global Seminars program. “There is no better way to educate future scholars about China than by having them visit the country and teaching them firsthand,” Xie said.

“Some students arrive at Princeton having studied Mandarin in high school. Even those who have never studied Chinese are ready for new challenges.”

These summer trips, combined with regular visits to monitor the progress of the CFPS and advise graduate students at the five universities where he serves as an adjunct or visiting professor, mean that Xie spends about a quarter of each year in China. But that is as it should be, he said.

“You need to visit often or you might miss something.”

Princeton project explores past ties to slavery

By Catherine Zandonella

“TO BE SOLD AT PUBLIC VENUE on the 19th of August next all the personal effects of Revd. Dr. Samuel Finley, consisting of two Negro women, a Negro man, and three Negro children, household furniture, horses … some hay and grain, together with a variety of farming utensils.”

Download this article as a PDF

The “personal effects” belonged to the estate of the Reverend Dr. Finley, the fifth president of the College of New Jersey, now known as Princeton University. The sale, advertised in the Pennsylvania Journal and Weekly Advertiser, took place in 1766 in front of the President’s House near two newly planted sycamore trees. The house and the trees still stand today near the north border of campus.

That a slave sale took place on campus and that the first nine Princeton presidents were slaveholders at some point in their lives are two of the major findings from a sweeping new endeavor by Princeton scholars and students to explore the ties of early University trustees, presidents, faculty and students to the institution of slavery.

The Princeton and Slavery Project has released the findings on a public website. The online materials include over 80 articles, video documentaries, interactive maps and several hundred primary source documents.

Leading the project is Professor of History Martha Sandweiss, who was surprised when she joined the faculty in 2009 to find that Princeton had never conducted a comprehensive study of its ties to slavery, as many other universities had done. Those studies revealed that slavery was an integral part of the history of American higher education, in both the North and the South.

The Princeton project did not find evidence that the University as an institution owned slaves, nor that students brought slaves to campus, but the scholars and student researchers involved in the project did establish that the man who deeded the University’s original 4.5 acres, Nathaniel FitzRandolph, was a slave owner. Funds from donors with ties to slavery funded the construction of several prominent campus buildings, and all seven of Princeton’s founding trustees were slave owners.

Martha Sandweiss

Professor of History Martha Sandweiss, second from right, leads a research project to explore the role slavery played in the early days of Princeton University. PHOTO BY DENISE APPLEWHITE

Much of the research was conducted by undergraduates in Sandweiss’ upper-level history seminars, which she organized starting in 2013 with the dual goals of investigating slavery and exposing students to methods of archival research. The project received support from the University’s Humanities Council, as well as the Princeton Histories Fund, which provides funding to explore “aspects of Princeton’s history that have been forgotten, overlooked, subordinated or suppressed.” Many other departments contributed to the project.

“Professor Sandweiss and her colleagues and students have brought creativity, diverse perspectives and rigorous academic standards to bear on research that sheds new light on previously unexamined aspects of this University’s past. Although the project began before we established the Histories Fund, it exemplifies the innovative work that we hope the fund will support,” said Princeton President Christopher L. Eisgruber. “The symposium that the project has organized brought a remarkable group of scholars and artists to our campus to reflect on its findings; I expect that the symposium and the project will stimulate ongoing discussion, additional research, and a more comprehensive and nuanced understanding of our history.”


A 1764 copper engraving by artist Henry Dawkins of the earliest campus buildings, Nassau Hall (left) and the President’s House (now Maclean House), which still stand today.

For help finding original materials, she approached University Archivist Daniel Linke. Linke taught students to navigate the nearly 400 collections in the University archives, which include alumni records, student letters, Commencement speeches, sermons, treasurers’ reports, and trustee and faculty meeting minutes. Students also used digital resources purchased by the Princeton University Library such as newspaper collections and business and court records. “When students would make a discovery, I would help them find additional documents to identify the context of the information and corroborate their findings,” Linke said.

The nation’s fourth-oldest college
Chartered in 1746 as British North America’s fourth college, the institution then known as the College of New Jersey was located first in nearby Elizabeth and then Newark before moving in 1756 to its current location in “Prince-Town.” The University took its present name in 1896.

The young college, founded by Presbyterian ministers who embraced the Enlightenment, nurtured several American independence leaders, including John Witherspoon, Princeton’s sixth president and a signer of the Declaration of Independence, and James Madison, the nation’s fourth president. Both were slave owners.

To fund the college’s growth, Witherspoon actively cultivated students from well-off Southern and Caribbean families. Before his tenure as college president began in 1768, about 20 percent of students came from the South, but by 1790 the percentage was 67 percent.

As cotton plantations spread into states such as Mississippi and Louisiana, and slavery spread westward, so too did the states of origin of the student body. Between 1746 and 1865, Southern-born students made up about 40 percent of the class on average. “You can see the westward spread of slavery as you track our student body,” Sandweiss said.

Slavery Ad

This page from the July 31, 1766, Pennsylvania Journal and Weekly Advertiser lists six people among the items for sale from the estate of the fifth president of the College of New Jersey, now known as Princeton University.

The finding helps explain why the anti-slavery movement at Princeton was relatively weak compared to peers like Harvard and Yale universities. Princeton was the founding location of the American Colonization Society, which was a movement to send free blacks back to Africa. “Princeton was a place where people with vastly different viewpoints came together, and the emphasis was on ‘keeping the peace,’” Sandweiss said.

Southern wealth was not the only money that came tainted by human bondage, however. One of the most prominent donors in Princeton’s history is Moses Taylor Pyne, a Northerner whose name adorns several campus buildings and a prestigious undergraduate prize.

In the records of the New York Historical Society, Maeve Glass, who earned her Ph.D. in history at Prince-ton in 2016 and is now an academic fellow at Columbia University, discovered that Pyne’s fortune — which he inherited from his grandfather — stemmed from a shipping business that transported sugar grown by slaves on Cuban plantations. Glass and other students traced the sources of funding for many of Princeton’s buildings to slavery.

Gown and town
Despite its location in the North, New Jersey was one of the last Northern states to ban slavery, and its “gradual emancipation” law, enacted in 1804, kept some individuals in bondage right up until the end of the Civil War. But the town of Princeton was home to a vibrant free black community — in 1862, one-sixth of Princeton’s 3,700 residents were of African descent — a fact that did not sit well with some of the Southern- born students.

In 1846, when a black man accused two students of harassing a black woman on a town street, violence broke out. A mob of 14 students, angered by the black man’s “insolence,” went to the farm where the man worked. Despite resistance from a “dozen brawny Irish laborers” who tried to protect the man, the mob forcibly took him into town, threatening to lynch him. A professor, John Maclean Jr. — a future president of the college — tried to stop the mob but failed, and the students whipped the man to “within an inch of his life,” according to a classmate’s account.

Isabela Morales, a graduate student in history, described how she felt when she read about this event. “I was sitting in Firestone Library, reading the diary of a long-ago student, John Robert Buhler,” she said, “and I gasped at what I found. In some ways this incident was a preview of the kinds of divisions that would happen among the students at the start of the Civil War. Some would go home to fight for the Confederacy and others would fight for the Union.”

Another spate of violence broke out in 1843 over the plight of a fugitive slave named James (Jimmy) Collins Johnson. He’d escaped from a Maryland plantation and was working as a janitor at the college when a student from a nearby plantation recognized him. Although the law required Johnson to be returned to his master, many townspeople came out in his support, and the case was settled only when a local citizen paid $500 for his free-dom. Johnson was allowed to stay, and over his lifetime he worked off his debt, including by selling sundries to students outside Nassau Hall.

A long reach into people’s lives
To make these and other findings available to the public, Sandweiss and her team created a public website hosted by the University library. Joseph Yannielli, a post-doctoral research associate with the Humanities Council and the Center for Digital Humanities, is the website’s project manager and lead developer.

“The sheer size of the project is staggering,” Yannielli said. “It is, by far, one of the largest studies of a university’s relationship to slavery yet attempted. We have over 6,000 files in our archive, covering thousands of students and dozens of faculty members across three centuries of history. Grappling with all of that data is an ongoing challenge.”

To ensure that the local community learns of the findings, Sandweiss collaborated with the Princeton-area public schools to create lesson plans for high school students. “Most students are surprised to find that there was slavery in the town of Princeton,” Sandweiss said. “I hope that high school teachers not just in Princeton but around the country will be able to use the lessons we’ve developed.”

Sandweiss also reached out to the University’s arts community to suggest creating public works of art and theater. “I believe in sharing history with the broadest possible audience,” Sandweiss said, “so I wanted to collaborate with artists who, while honoring the facts of the past, can elaborate and speculate in ways that historians — always bound by footnotes — cannot.”

Sandweiss said she is touched by how the findings about the University’s past resonate with today’s students and alumni. In a freshman seminar, Sandweiss asked students to create videos from interviews with their peers, alumni and others with Princeton connections who are descended from slaveholders, slaves or both. For example, in one video, a student of African American descent learns that she is descended from a family of mixed-race slaveholders in New Orleans.

“This isn’t a story that ended in 1865,” Sandweiss said. “This is a story that has a long reach into people’s lives.”

Impact on students
The project has been a rare opportunity for students to conduct original archival research that will reach a wide audience. Many of the historical articles on the website were written by Princeton undergraduates under the guidance of Sandweiss and graduate students. “Each time the class was taught, the students had greater success, because we became better at framing questions for them to research,” Sandweiss said. “But it is impossible to overstate how open-ended this was at the beginning.”

Craig Hollander recalls the excitement of those early days of discovery. He was then a postdoctoral researcher at Princeton and is now an assistant professor of history at today’s The College of New Jersey, located about

10 miles from Princeton. Hollander spent hours hunched over boxes of documents, photographing them as fast as possible, and then bringing them back to the computer to blow up the images so he could examine them.

“We would marvel over the discoveries we were making every day,” Hollander said. “You had to read these documents with a fine-tooth comb, because you didn’t know if a sentence or phrase was the smoking gun that provided evidence for a larger finding. Some-times I would come away from a day’s work with a single document and say to myself, ‘This is why I got up in the morning.’”

One undergraduate who contributed to the project is Sven (Trip) Henningson. Although he graduated with a bachelor’s degree in history in 2016 and now works in Washington, D.C., Henningson still spends some of his free time on the research.

Henningson remembers going to the Library of Congress one Saturday morning and finding an original 1864 memorandum from a former Princeton student demanding that his escaped slaves hiding behind Northern lines be returned to him. “Holding that document in your hand is just something that gets you fired up and ready to go for another round in the archives,” he said.

An American story
This fall, a new group of students enrolled in Sandweiss’ research seminar and began to delve into Princeton’s history, this time in the post-Civil War era. “We’ve been examining issues of how people were talking about race in the aftermath of the Civil War,” Sandweiss said, “and how people wrote the history about what the war meant.”

The natural question to ask is what do these findings mean for Princeton? But the broader question, Sandweiss said, is how does what we are learning change our feelings about America’s history?

In many ways, the story of Princeton is the story of America writ small — how its leaders ignored the economy’s ties to slavery so that it could continue to thrive on the fruits of human bondage. The young nation espoused liberty while rationalizing its deeply troubling footings.

“To acknowledge that history, to be upfront about it, that is what universities do best,” Sandweiss said.

“Educational institutions should sponsor this kind of inquiry no matter where it goes, and Princeton has done that. What we’ve uncovered does not set us apart in any way, nor should it embarrass us. Our institutional history embeds us in the paradox of liberty and bondage that underlies the development of our nation.

“We are not special, we are simply American.”

The more than 600 pages of documents, maps, videos and essays are available at slavery.princeton.edu.


Let it flow: The ideas, the creativity, the findings, the impacts, the benefits to society

By Yasemin Saplakoglu

THE RESEARCHERS in Princeton’s Complex Fluids laboratory are sometimes inspired by a cup of coffee or a permanent marker.

Such everyday items may seem like odd subjects of inquiry in a lab known for its cutting- edge research, but in fact the coffee — a latte actually — acts as a model system to study pattern formation in liquids, which could lead to applications in food science, and the permanent markers may suggest ways to transfer patterns of micro-fabricated electronics from one surface to another.

Download this article as a PDF

These seemingly unconnected experiments are tied together by the study of fluids and how they move and change in space and over time.

At the head of the lab is Howard Stone, a professor in the School of Engineering and Applied Science, whose mentorship of graduate students and postdoctoral researchers has led to a multitude of papers on topics that have the potential to address societal problems, from coping with climate change to purifying water using the technology that adds fizz to soda.

“I encourage the members of my lab to do things that excite them, things they’re very curious about,” said Stone, Princeton’s Donald R. Dixon ’69 and Elizabeth W. Dixon Professor and chair of the Department of Mechanical and Aerospace Engineering. “It is a little different than how other groups sometimes run, and in part that’s because I’m not focused on trying to solve only one problem. Instead I am serious about seeking new understanding as well as potential applications.”

Stone’s lab attracts students and postdoctoral researchers from around the world, with backgrounds ranging from chemistry and math to physics and engineering. These scholars combine their talents with a lot of energy, laboratory camaraderie and a spirit of exploration, turning creativity into results that have the potential to make a difference in areas such as health and the environment.

Using gelatin to study fracking
Ching-Yao Lai recalls the first time she heard the term “fracking” as a newly arrived graduate student from Taiwan five years ago. “I had absolutely no idea what that was,” she said. She soon became immersed in studying hydraulic fracturing, which involves injecting high-pressure liquids into underground rock to generate fractures that allow oil and gas to come to the surface. But the liquid can also bring contaminants — such as brine, naturally occurring radioactive material and metals — into contact with underground drinking water sources.

“It’s very important to know how fast a fracture grows and how far it can go,” Lai said. To study this, she uses a substance that bears little overt resemblance to rock: a block of gelatin.

Gelatin mimics the brittle and elastic properties of rocks, and it is convenient in other ways. It is trans- parent, so Lai and her co-investigators can see what happens to the liquid and where it goes.

Ching-Yao Lai

A block of gelatin mimics the brittle and elastic properties of rocks, making it a convenient model for graduate student Ching-Yao Lai to use when studying how fluids spread underground during hydraulic fracturing for the extraction of gas and oil.

To model fracking in the cube of gelatin, the researchers poke cracks in the springy solid to represent the fissures and faults in the Earth. Then they push mineral oil through the cracks and, while shining a green light on the block to illuminate the spread of the oil, take photos for later measurements of the size and extent of the cracks.

With this experimental system, Lai and colleagues are exploring what happens to liquid injected into the gelatin. Some of the questions are why not all of the injected liquid comes back to the surface, and how much fluid gets trapped in various types of fractures.

One of their next areas of study involves an entirely different type of liquid — foam. Lai is exploring whether foam could be use in place of today’s high-pressure liquids. Foam uses 90 percent less water and may be less likely to travel to groundwater sources.

Tangled fibers for wound healing
At the next lab bench over, Janine Nunes holds a vial of tiny polymer fibers that could someday become wound-healing bandages or provide scaffolding for repairing damaged tissues in the body. Nunes is developing liquids that solidify into small fibers. These fibers could be injected into a damaged part of the body where they then tangle to provide a scaffold on which cells can regrow.

Janine Nunes

Janine Nunes, an associate research scholar, develops liquids that solidify into fibers for applications in wound healing. Such a liquid could be injected into the body, where it could solidify into a scaffold on which cells can regrow.

Nunes, an associate research scholar, makes the slender fibers using a device that works sort of like a pasta maker and that fits in the palm of her hand. She injects a polymer liquid into a slender pipe. Then, by sending pulses of ultraviolet light into the device, she converts the light-sensitive liquid into a hair-thin, solid fiber.

By changing the duration of light pulses, Nunes can control the shapes of the fibers. She and Antonio Perazzo, a postdoctoral research associate, found that longer fibers are more likely to entangle, creating a semisolid gel, while the shorter fibers stay suspended in the liquid.

The microfluidic device produces one fiber at a time, but the team plans to improve the process to churn out many fibers at once. She is also exploring what would happen if she mixes in ingredients that make the gel degradable, to make tissue scaffolding or internal bandages that can biodegrade when they are no longer needed.

Arctic ice bridges
Outside the glass doors of the lab, postdoctoral research associate Bhargav Rallabandi sits across from a white-board filled with geometrical figures and equations, the evidence of a day in the life of a theorist. Rallabandi’s latest project is a theoretical model of the formation of Arctic ice bridges.

Ice bridges form when chunks of ice, flowing through a narrow strait between two bodies of land, form a clog. The bridges can prevent ice from flowing south and melting due to warmer temperatures, and may also enable polar bears to reach their hunting grounds.

Using pen and paper, and later, computer simulations, Rallabandi calculated the critical thickness, wind speed and ice compactness necessary for ice bridges to form. The team found that the formation of ice bridges can be understood as a balance between wind stresses that drive motion and frictional stresses in the ice that resist motion. These frictional stresses arise from the motion of ice floes relative to each other and to the land boundaries of the strait. The results were published earlier this year in the journal Physical Review Letters.

“This gives you a way to think about what factors we need to measure in the Arctic to predict ice bridge formation,” Rallabandi said. Now that he figured out how ice bridges form, he plans to tackle the other side of the question: How do they break up?

Barista science

Nan Xue

Graduate student Nan Xue studies how two fluids — in this case, coffee and milk — settle into layers. The results could have applications for food science or improving personal care products.

When Nan Xue joined the lab as a new graduate student last year, the first thing he did was buy a coffee machine, and it wasn’t to stay awake. He needed to brew a lot of the stuff for his studies on how two liquids — in this case, coffee and milk — can settle into layers. What he finds could have applications for food science or improving personal care products.

The idea for the study originated with the observation that pouring hot coffee into warm milk leads to the formation of layers that are progressively darker from the top of the cup to the bottom. “In the beginning, we thought maybe this was something related to the oil particles in the milk or the foam,” said Xue. “That was totally wrong.”

Coffee is less dense than milk, so, in the absence of stirring, it normally floats atop the milk. Making a latte, however, involves pouring hot coffee into a cup of warm milk, forcing coffee to the bottom where it slowly separates into regions of different coffee-to-milk ratios. The liquid at the exterior of the cup is slightly cooler than the liquid in the interior, and cooler liquids are denser, so this liquid sinks until it is stopped by a section of denser coffee-milk. Over several minutes, these processes lead to the formation of layers.

Xue found that a large factor dictating the layering was speed. When he poured the coffee quickly into the milk, the layers formed, but when he poured slowly, no layering occurred. Xue and his colleagues developed a model system to show how the layers form, and they are now exploring the effects of volume, speed and density differences on the pattern formations. The team has also created a material that gels to form a solid containing these layers.

Writing on water
The layered lattes are not the only example of an every-day observation that became a research question. Sepideh Khodaparast, a postdoctoral research associate, was working with bacteria when she noticed something curious.

Khodaparast was studying the slimy bacterial films that adhere to surfaces and can contaminate medical tubing, stents and implants. In her primary research, she investigates how the interfaces between air and water, such as those that occur in bubbles, can be harnessed to remove pathogenic bacterial cells from different surfaces. She has found that bubbles are highly effective at preventing the formation of more mature layers of bacteria.

One day she was trying to remove bacteria from a glass surface, which was labeled with permanent marker ink, when she observed that, under the right conditions, dipping the slides in water caused the ink to slip off the slides and onto the surface of the water with the words intact.

Writing on slides dipped in water

Under the right conditions, dipping slides in water caused permanent ink to slip off the slides and into the water.

With further investigation, Khodaparast and François Boulogne, a former postdoctoral researcher who is now at Paris Saclay University in France, found that when they quickly dipped the glass into a tub of water, the words did not peel off. But if they did it slowly, the words slid off and floated on the water. “This mechanism could be useful for removing water-resistant stains and transferring thin elastic films, patterned with micro-fabricated electronics, from one surface to another,” Khodaparast said.


In the laboratory led by Howard Stone, a professor in the School of Engineering and Applied Science, the flow of creativity among the postdoctoral researchers, graduate students and undergraduates leads to findings with the potential to benefit society.

The broad range of inquiry in the lab has produced numerous technologies with the potential to benefit society. Early this year, the group published a study showing that carbon dioxide gas — the substance that gives soda its fizz — can remove contaminating particles from water, suggesting a low-cost, low-energy water treatment system.

“You could potentially use this to clean water from a pond or river that has bacteria and dirt particles,” said Sangwoo Shin, who performed the research as a postdoctoral researcher in the laboratory and is now an assistant professor of mechanical engineering at the University of Hawaii at Manoa. The study was published earlier this year in Nature Communications.

By bringing together talent from around the globe in the form of postdoctoral fellows, graduate students and undergraduates, and letting the ideas flow, Stone and the Complex Fluids Group are making new discoveries while also probing deeply to understand fundamentals. As mentor to this diverse team of early-career scientists and engineers, Stone is modest when it comes to taking credit for their accomplishments. Instead, he said, “I am incredibly lucky to work with such smart, talented, hard-working and kind people.”


Bound in wedlock: Professor of history explores slavery’s shackles on black families

For her new book, Bound in Wedlock: Slave and Free Black Marriage in the Nineteenth Century (Harvard University Press, 2017), Tera Hunter, a professor of history and African American studies, meticulously researched court records, legal documents and personal diaries to illustrate the constraints that slavery placed on intimate relationships. In this article she talks about the very personal side of her research and the importance of this chapter of history in understanding American society today.

By Tera Hunter, professor of history and African American studies

I HAVE A COPY OF THE MARRIAGE CERTIFICATE of my great-great-grandparents, Ellen and Moses Hunter, from 1873. They were both enslaved, freed and then married during Reconstruction. I posted the document on my bulletin board, which served as a source of inspiration as I researched slave and free black marriage in the years before and after the Civil War. Their marriage was the first among my direct paternal ancestors, and they were the first non-interracial couple in my paternal lineage after arriving in the New World. It became increasingly clear how much my own family history was evocative of the larger history that I was researching.

Download this article as a PDF

Marriage certificate

Marriage certificate of the great-great-grandparents of Tera Hunter, professor of history and African American studies.

I was especially drawn to documents that I found from the period of Reconstruction, which demonstrated the depth of feelings and the challenges that former slaves faced in reconstituting their family ties after slavery ended. These records are tremendously rich, and they raised a lot of interesting questions that could not be easily answered by focusing on the period following emancipation alone. To fully under-stand post-slavery marriage and family, I needed to trace these relations over the entire 19th century.

One of the topics I explored was how marriage was not an inviolable union between two people but an institution defined and controlled by the superior relationship of master to slave. Women have literally borne many of slavery’s burdens not just as laborers but also as the literal reproducers of capital that enriched slave owners, making them among the wealthiest people on the planet. Exploiting women’s sexuality and denying legal rights to marriage, maternity and paternity were inextricably linked to preserving slavery as a profitable, permanent, inheritable system of labor.

Christianity was closely tied to supporting and rationalizing this system of labor, with little dissent from mainstream clergy or laypersons. Despite the fact that marriage was held as one of the most important sacraments of Christianity, in the United States the Church supported the property rights of masters above all else. Readers are often shocked to learn such facts about the complicity of their own faith traditions.

My research on free blacks produced some surprises. I do not think historians have fully captured the extremity of the constraints faced by African Americans who were either born free or born into slavery and later freed. We certainly have not paid adequate attention to the repercussions that they faced in building and sustaining their marriages and families. Slaves could not marry legally in the South, but neither was legal marriage guaranteed to free blacks. Their relationships were even more compromised when they were married to slaves because they were reduced to their enslaved spouse’s lack of standing in society and the law. In some cases, they even voluntarily submitted to (re)enslavement just to keep their families together, as laws were passed to evict newly manumitted free people in the South.

Free black couples faced constraints above the Mason-Dixon Line as well, which is probably more surprising to people who are less familiar with slavery in the North. For example, New York state passed a law that supported slave marriage. But slaves were required to get the consent of owners first, and, in practice, the law did not guarantee that their relationships were respected as legally inviolable.

My research on marriage allowed me to examine the internal lives of African Americans. The existing scholarship on black families was preoccupied with whether or not they conformed to the nuclear structure and gender norms of male-headed house-holds. This led to a very limited view of both the internal values and meaning of marriage to African Americans and also the external constraints that they faced in creating and sustaining these relationships.

Slave family

Marriage between slaves was discouraged or illegal; individuals could be sold away from their spouses at any time. This photo, taken in 1862, is of an extended family of slaves on a plantation in Beaufort, South Carolina.

Debates about the status of black families in the 21st century have often invoked the legacy of slavery. In the epilogue to the book, I scrutinize and challenge the misinformed assumptions articulated by both liberal and conservative scholars, commentators and political pundits regarding the impact of slavery on marriage and family today. Despite centuries of degradation, adult African Americans were nearly universally married by the turn of the 20th century, only decades after legalization. That pattern would begin to change post-World War II, and marriage rates began a downward slope to the point now that most African Americans are not married. There are many factors that explain this, but slavery is not one of them. We need to look to factors in the 20th and 21st centuries.

I hope that my work contributes to deepening the knowledge of the history of slavery and its consequences for American society and for African American lives. We cannot fully appreciate how the nation has come to be what it is without the knowledge of how slavery and freedom were intertwined. We cannot fully understand the harms done to African Americans without accounting for how they impacted marriages and family.

African Americans have always been creative, resourceful and practical in building meaningful relationships. There is “a great black river” along an enduring freedom struggle, as historian Vincent Harding wrote. We keep going back to the future.

And yet, despite the distinct disabilities that black families suffered under, there is a long legacy of stigmatizing the bonds they created, of using the failure to meet dominant societal norms as a barometer to judge black fitness for civilization and citizenship negatively. No matter what period of history, black families are always judged to be deficient as compared to whites, with little regard for the systems that structure those inequities.

We need to understand those patterns and the legacies that are continually replicated with each iteration of the seemingly forward movement toward greater freedom and justice.