Life is impossible without enzymes, and science is still working towards achieving the goal of understanding their remarkable catalytic efficiency at the atomic level. The knowledge gained to date has already had profound effects on biotechnological processes and drug design. However,
many questions about the mechanisms of enzymatic reactions and drug binding remain unanswered. Enzymes rely on moving hydrogen (H) atoms and water molecules and on utilizing molecular motionson various time scales for their function.X-ray crystallography is typically incapable of locating Heven at ultra-high resolutionsdue to the weak sensitivity of X-rays to H atoms, while most spectroscopic techniques cannot probe protein dynamics in the sub-THz regime (<50 cm-1).With one electron, H is hard to observe in X-ray structures.Thus, protonation states of amino-acid residues and ligandsremain unknown.Moreover, incorrect inference of H
positions in protein structures often leads to significant gaps in our knowledge of how they function and can lead to wrong computational models.Neutron crystallography provides a direct means for accurate determination of the locations of H even at medium resolutions of 2.0-2.5 Å,
because neutrons are scattered strongly by H and its isotope D.With neutron vibrational spectra collected by measuring inelastic neutron scattering, low-amplitude protein dynamics can be probed on the picosecond time scale (5-50 cm-1) where collective vibrations of the secondary structure elements occur. Our research focuses on usingneutron diffraction and scattering techniques in combination with computational biochemistry to better understand enzymes and aid structure-based drug design.Recent results from the studies of HIV-1 protease (PR), aspartate aminotransferase (AAT) and human acetylcholinesterase (hAChE)will be discussed.
Dr. Christian Franz