Boris Rotman  Marcos Boris Rotman (born 1924) is an American immunologist–molecular biologist and professor emeritus of Medical Science at Alpert Medical School of Brown University. He is widely recognized for performing the first single molecule experiments in biology. Rotman attended elementary and high school at the Instituto Nacional of Chile. In 1942, he won a scholarship to attend the Universidad Técnica Federico Santa Maria, from where he graduated with a chemical engineering degree in 1948. In 1950, he entered the University of Illinois and in 1952 earned a PhD in biochemistry/microbiology. His mentors at University of Illinois were Salvador E. Luria (Nobel laureate 1969) and Sol Spiegelman (Albert Lasker Award for Basic Medical Research, 1974). After graduation, Rotman was a postdoctoral researcher in the group of Joshua Lederberg (Nobel laureate 1958) at University of Wisconsin-Madison, and later, in the laboratory of Bernard D. Davis at Harvard Medical School. In 1961, Rotman developed a system capable of measuring the enzymatic activity of individual molecules of beta-galactosidase and used it to conduct the first single-molecule experiment in biology. These early experiments remained obscure for more than 30 years, but they are now recognized as pioneering and highly influential. A review states, "Indeed, this paper is the origin not only of the field of single-molecule enzymology, but also of much subsequent single-molecule research." The significance of single-molecule experiments derives from their capacity to provide fundamental insights that are not attainable by conventional experimentation. For example (a) Enzyme turnover can be measured directly from the number of fluorescent molecules of product produced by an individual enzyme molecule. (b) Studying heat inactivation of an enzyme at the single molecule level uncovered unprecedented mechanisms. Namely, heating causes an all-or-none distribution of enzymatic activity, i. e., the molecular population consists of either fully active or completely inactive enzyme molecules. This experiment rules out an alternative plausible mechanism postulating that partial heat inactivation produces enzyme molecules with partial activity; (c) In contrast, partial inactivation of beta-galactosidase resulting from storing crystalline enzyme under ammonium sulfate at low temperature (3-6 °C) for several years, causes a uniform distribution of partially inactivated enzyme molecules, (d) A point mutation in the lacZ gene alters beta-galactosidase activity producing a uniform populations of beta-galactosidase molecules with individual partial activity.