Single Molecule Biophysics

Enzymes are typically studied in ensembles. Enzyme mechanism has traditionally been elucidated from biochemical and structural experiments that involve thousands or millions of molecules. Enzymes, however, are complex molecular machines that, when subjected to individual scrutiny, reveal features that cannot be ascertained from ensemble approaches. Single-molecule visualization and manipulation techniques are at the technological forefront of biological inquiry; these techniques can probe distances on the sub-nanometer (10-9 M) scale and forces on the piconewton (10-12 N) scale with millisecond temporal resolution. Dr. Neuman employs these single-molecule techniques—including optical and magnetic tweezers and fluorescence imaging, in combination with molecular biology, biochemical, and molecular dynamics approaches—to answer fundamental questions concerning enzyme function and regulation. His research program is underpinned by single-molecule instrumentation that his laboratory designs and builds to elucidate enzyme mechanisms at the molecular level.

Approximately two meters of DNA is compacted into the nucleus of a human cell, which leads to topological complications during replication, transcription, and segregation of chromosomes. Topoisomerases are essential enzymes that regulate DNA topology and are important chemotherapeutic and antibiotic drug targets; Dr. Neuman focuses on elucidating the molecular mechanisms of topoisomerase activity and inhibition by chemotherapeutic agents.

Topoisomerases interact with many other enzymes that regulate DNA. Dr. Neuman is extending the use of single-molecule techniques to dissect multi-enzyme complex formation and activity. For this work, he focuses on the combination of RecQ helicase and topoisomerase III, which is a conserved interaction in organisms ranging from E. coli through humans that plays important roles in homologous recombination, genome stability, chromosome segregation.

The organization of the genome has emerged as an important regulator of physiological processes at multiple scales. An important aspect of this organization stems from the topology of the DNA; how it is over or underwound, knotted, or linked. Dr. Neuman employs single-molecule manipulation approaches to understand the mechanics and dynamics of DNA under topological constraints. Of particular interest recently is understanding how DNA mismatches or damaged bases impact the topology of DNA and how this may facilitate DNA repair in vivo.

Videos

Single Molecule Biophysics - Keir Neuman, NIH Scientist

Keir Neuman, Ph.D., applies physics to transform the field of biology at the National Institutes of Health (NIH) Intramural Research Program (IRP). Dr. Neuman is a Principal Investigator in the Laboratory of Single Molecule Biophysics at the National Heart Lung and Blood Institute (NHLBI).