Ab Initio Calculations of Deuterium Isotope Effects on Chemical Shifts of Salt-Bridged Lysines

作者：Ullah Saif^*; Ishimoto Takayoshi; Williamson Mike P; Hansen Poul Erik

来源：Journal of Physical Chemistry B, 2011, 115(12): 3208-3215.

DOI：10.1021/jp1111789

Deuterium isotope effects measure the change in chemical shift on substitution of a proton by deuterium. They have been calculated by direct treatment of the H/D nuclear quantum effect using a multicomponent ab initio molecular orbital method based on a non-Born-Oppenheimer approximation. This method enables the determination of both the electronic and the protonic (deuteronic) wave functions simultaneously and can directly calculate the geometrical difference induced by HID isotope effects. The calculations show that the one-bond deuterium isotope effects on (15)N nuclear shielding, (1)Delta(15)N(D), in ammonium and amines decrease as a counterion or water molecule moves closer to the nitrogen. (1)Delta(15)N(D) and (2)Delta(1)H(D) of the NH(3)(+) groups of lysine residues in the B1 domain of protein G have been calculated using truncated side chains and also determined experimentally by NMR. Comparisons show that the structures in solution are different from those in the crystal and that solvation plays an important role in weakening the hydrogen bonds.

• 出版日期2011-3-31