Up next in our series on women who reshaped science is Marie Maynard Daly—the first Black woman in America to earn a PhD in Chemistry. At a time when scientists were only just discovering the function of DNA as hereditary material, Daly made many foundational discoveries about the chemical structure of nucleic acids and histones—the proteins that DNA wraps around. Perhaps even more influential though are Daly’s studies investigating the health impacts of cholesterol and sugar. Daly was one of the first scientists to discover the link between cholesterol and hypertension, which can lead to heart attacks. Her work as an investigator for the American Heart Association helped to uncover many of the causes of hypertension and led to better prevention strategies—likely saving countless lives.
Marie Maynard Daly was born in 1921, in Queens, New York. Her father immigrated to New York from the West Indies to study chemistry at Cornell University, but he was forced to leave his education due to lack of funds. Determined to help his children succeed, Daly’s father encouraged her and her siblings to read as much as possible. In high school, Daly demonstrated a particular talent for chemistry, and her teachers began giving her college-level chemistry material to learn. She went on to study chemistry at Queens College, which was free for New York residents, and graduated magna cum laude in 1942.
After graduating, Daly received a fellowship to continue working as a laboratory assistant at the college while she completed a master’s degree. She completed the master’s program in a year and was able to obtain a fellowship to pursue a doctoral degree at Columbia University. She worked under Mary Caldwell—who was herself the first woman at Columbia to be promoted to a senior faculty position—on a project investigating the properties of the digestive enzyme amylase. Amylase is actually a group of enzymes responsible for breaking down starches—complex carbohydrates like those found in potatoes or corn. Amylase is an important component of saliva where it begins breaking down stubborn starches as soon the food enters the mouth. This amylase continues to work until it is inactivated by acidic stomach secretions. But pancreatic amylase encounters the remaining starch in the small intestine. Starch is broken down into the simpler sugar maltose that is then broken down into singular unit glucose, and glucose is absorbed into the blood and moved to cells for conversion into energy.
After three years working on amylase, Daly published her dissertation “A Study of the Products Formed by the Action of Pancreatic Amylase on Corn Starch” and graduated with her PhD in chemistry. In 1947, she was the first Black woman in America to earn a doctorate in chemistry. After finishing her doctorate, Daly went on to teach chemistry for two years at Howard University in DC. In 1948, she received a grant from the American Cancer Society for a seven-year postdoctoral fellowship at the Rockefeller Institute of Medicine.
During her postdoc, Daly worked with microbiologist Alfred Mirsky to study the contents of the cell nucleus—where DNA is stored. This was before the structure of DNA was elucidated by Rosalind Franklin, Watson, and Crick. It was also before anyone had pinned down the function of DNA as hereditary material. Daly’s research provided an initial characterization of purines and pyrimidines—the two categories of nucleotides that fit together to create DNA—which was fundamental to those subsequent discoveries (Watson and Crick even acknowledged her contribution during their Nobel prize acceptance). She was also responsible for determining much of the structure and composition of histones—the protein spools that DNA wraps around to pack inside the nucleus. At the time, little was known about the role of histones, but now we know that they profoundly impact the way DNA is expressed. Modification of the histones determines how closely wrapped the DNA is around them, which in turn influences how accessible certain genes are to being transcribed and translated.
In 1955, Daly returned to Columbia University to work with Dr. Quentin B. Deming studying the causes of heart attacks. In 1958, they moved the study to the Albert Einstein College of Medicine where they made several impactful discoveries on the role of hypertension in the development of atherosclerosis—the build-up of fat on artery walls that is a leading cause of heart attacks and strokes. Daly and Deming were the first to discover a link between high levels of cholesterol in the blood and the development of hypertension and atherosclerosis. Cholesterol is a fat-like substance found in meat and animal products that your body normally uses to make hormones and vitamin D. But too much cholesterol can clump together into plaques that gum up the walls of the major arteries, leading to a higher risk of heart attack. As an investigator for the American Heart Association, Daly also studied how smoking and sugar consumption could worsen hypertension.
Daly retired from research in 1986. And in 1989, she established a scholarship fund, in honor of her father, for Black students studying science at Queens College. She died in 2003.
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