Biophysicists apply tools and concepts from physics to the understanding of living systems at the molecular level. This field promises to yield answers to important questions about the structure, dynamics, function, and interactions of biological molecules such as proteins and nucleic acids. New instruments are allowing researchers to measure distances much shorter than the wavelength of light (nanometers) and forces as small as one trillionth of the force required to hold an apple against Earth's gravity (piconewtons). At JILA, researchers are currently studying protein motions, molecular motors & DNA-binding proteins, and the folding dynamics of RNA & DNA. They are looking for answers to the following questions:

• How do enzyme conformations change in response to light, chemical bonding, co-factor substitution, or voltage changes?
• How do enzyme inhibitors work?
• What happens to the shape of an enzyme when it binds to chemicals at sites different from its active site?
• What are the kinetics of binding and folding for single RNA molecules?
• What is the role of cations in RNA folding?
• What are the best materials to use in biological optical-trapping assays?
• What kinds of mechanical forces are generated by protein motors?

To answer these questions, JILA researchers use precision tools such as optical tweezers, lasers, laser microscopy, and high-resolution spectroscopy. Optical tweezers are a focused laser beam that can manipulate micron-sized beads in solution. Lasers emit bursts of photons in pulses ranging from femto- to nanoseconds (10^-15–10^-9 seconds), allowing scientists to take "photographs" of rapidly vibrating biomolecules under a variety of experimental conditions. This lets the scientists observe how proteins and nucleic acids move, twist, fold, and interact. Laser microscopes incorporating microfluidics technology for rapid mixing permit the study of protein motions on varying time scales in the same system. One type of high resolution spectroscopy, known as fluorescence resonance energy transfer (FRET) spectroscopy, employs laser-scanning microscopes to observe the motions and interactions of RNA pretreated to change color when it absorbs light.