Scientific work (1923–1928) Yen was hired by the China Medical Board of the
Rockefeller Foundation as an assistant professor in biochemistry at
Peking Union Medical College and contracted for a year from September 1923. The biochemistry department had just been founded and Yen was its second employee. She lectured and worked as an assistant to
Hsien Wu, whose research initially focused on blood chemistry. She assisted in his research on
protein denaturation and published several papers with him:
关于稀酸、稀碱对蛋白质作用的一些新观察 (Some New Observations on the Effects of Dilute Acids and Bases on Proteins, 1924),
蛋白质变性的研究，I．稀酸和稀碱对蛋白质的影响 (Research on Protein Denaturation, I: The Effect of Dilute Acid and Alkali on Protein, 1924),
蛋白质的热变性 (Thermal Denaturation of Protein, 1925), and
乳胶体对有色溶液的作用 (The Effect of Latex on Colored Solution, 1926). These studies would later become the basis for Hsien Wu's theory on protein denaturation first presented in 1931. Despite her contract being renewed for another year, when Yen and Wu decided to marry, she knew her position would be terminated, as there was a policy that spouses could not work together. The couple married on 20 December 1924 in Shanghai and Yen Wu resigned. They honeymooned in the United States and Yen Wu made plans to resume her studies and complete her doctoral work under Sherman at Columbia. She accompanied Hsien Wu to Europe and discovered she was pregnant, which put an end to her pursuit for further education, and she returned to China. Working as unpaid staff in Hsien Wu's lab, she continued to assist in research, but papers published rarely listed her name as the primary researcher. She also temporarily taught organic chemistry for students at the Xiehe Nursing School. Yen Wu conducted her own research on nutrition for the biochemistry department, believed to be the first such studies carried out by a woman in China. She analyzed the chemical composition of many types of Chinese foods. Vitamin research was still in its infancy, but she determined the amount of carbohydrates, fat, fiber, protein, and water in various foods. Together with Hsien Wu, she began researching
vegetarianism, the predominant Chinese diet at the time, using white mice as subjects, a technique Yen had learned from Sherman. By feeding one set of mice a typical diet based on grains such as corn, rice, sorghum, and wheat combined with peas, soybeans, and other vegetables; and another mouse group a diet of grain and meat, they discovered significant growth differentials and problems with
rickets in the vegetarian group. Altering the vegetarian diet by adding
bell peppers,
cabbage,
mustard greens, or
rapeseed they found that growth rates were similar to the meat-eating mice and the animals had no signs of vitamin deficiencies. Her next joint project with Hsien Wu was to conduct research on the diet of people in Beijing. The Department of Public Health and Sanitation collected materials from various groups throughout the country, including businesses, factories, farms, households, restaurants, and schools and presented their survey results to Yen and Hsien. They analyzed the survey, determining daily consumption rates of carbohydrates, fats, and proteins finding that the diet of people in Beijing was fairly representative of a typical diet throughout the country. They noted that compared to a Western diet, there were deficiencies in high-quality protein, calcium, phosphorus, and vitamins A and D. Their conclusions were that
malnutrition was the cause of the high rates of disease and mortality, as well as
intellectual disabilities and short stature, prevalent among Chinese children at the time. Their collaboration produced
营养概论 (Introduction to Nutrition, 1929) the first textbook on nutrition in China. Hsien Wu also published
中国食物之营养价值 (The Nutritional Value of Chinese Food, 1928) incorporating Yen's research.
Family and philanthropy (1929–1949) In 1928, after the birth of her third child, Yen Wu withdrew from active work in the laboratory and focused on raising her children while compiling the research notes of her husband and assisting him in the development of his career. Within seven years of marrying, she had given birth to five children and was concerned about the level of educational opportunities available for them. She founded the Mingming School () in 1934 with the aim of providing a modern comprehensive education and hired Wang Suyi, an alumnus of Columbia, as principal and a full-time teacher. The private school was operated by a board of her friends upon which she served as treasurer. Yen Wu was a member of various civic improvement clubs and worked with her sisters to raise funds in 1936 to build a school hospital for their alma mater, the Jinling Women's College. She returned to school, studying French at the and graduating in 1944. In 1947, Hsien Wu went to the United States to work as a visiting professor at Columbia University, but was unable to return because of the
Chinese Communist Revolution. When the communists took over their home in Beijing in 1949, Yen Wu decided to join him abroad.
Life abroad (1949–1992) Yen Wu brought the children to
Birmingham, Alabama, where Hsien Wu had become chair of the biochemistry department at the University of Alabama. In 1950, she was hired to work as a biochemical researcher for the
Medical College of Alabama. As before, she conducted research jointly with her husband, until he suffered a heart attack in 1953 and retired. They moved to
Boston, where Yen Wu cared for Hsien Wu and compiled their research. Between 1949 and 1959, they published four papers and wrote three abstracts for presentation at academic conferences, mostly about amino acid metabolism. After Hsien Wu died on 8 August 1959, Yen Wu published her husband's biography and in 1960, moved to New York City, to be near her children. In the spring of 1960, Yen Wu was hired as a researcher by the Food Conservation Division of the
United Nations Children's Fund. She was tasked with testing various foods and making recommendations to improve nutritional standards for children. In 1961, she established the Yen Tse-King Memorial Scholarship, in honor of her father, and the Wu Hsien Memorial Scholarship, in honor of her husband, at the
Tunghai University in
Taichung, Taiwan. The scholarships were intended to be awarded annually to assist women students in become physicians or any student of biological chemistry in completing their education. In August 1964, Yen Wu went to work at the Institute of Human Nutrition at
Columbia University College of Physicians and Surgeons, where she built a reference library and organized
finding aids for the materials for the staff and students of the college. In 1971, she retired but began working three days a week as a consultant in nutrition and metabolism for
St. Luke's Hospital Center. Her work there was to establish the library for the New York Obesity Research Center. She also lectured on public health and nutrition at Columbia University. In addition to her employment, Yen Wu began editing and updating the publication
营养概论 (Introduction to Nutrition). She wrote eight supplemental chapters and a new edition of the book was published in Taiwan in 1974, and remained in print until the 1990s. After a thaw in the
Cold War relations between China and the US leading to
normalization in the 1970s, Yen Wu returned to China. She visited relatives in 1980 and 1984. In 1983, she attended the celebration for the 70th anniversary of the founding of Jinling Women's University with family and former classmates. That year, she established a scholarship fund named after her husband to be awarded by the
Chinese Academy of Medical Sciences to fund the research of professors who have contributed to the development of Chinese biochemistry and molecular biology. She retired in 1987 and lived alone until 1992, when she moved to the home of her eldest son in
Ithaca, New York. In 1993, to honor her husband's 100th birthday, she donated funds to the Chinese Academy of Medical Sciences to establish a biochemical library and purchase books, and created a scholarship at
Harvard Medical School, both bearing his name. ==Death and legacy==