Format

Send to

Choose Destination
Science. 1996 Apr 5;272(5258):97-101.

The energetics of hydrogen bonds in model systems: implications for enzymatic catalysis.

Author information

1
Department of Biochemistry, Stanford University, CA 94305-5307,USA.

Abstract

Low-barrier or short, strong hydrogen bonds have been proposed to contribute 10 to 20 kilocalories per mole to transition-state stabilization in enzymatic catalysis. The proposal invokes a large increase in hydrogen bond energy when the pKa values of the donor and acceptor (where Ka is the acid constant) become matched in the transition state (delta pKa=0). This hypothesis was tested by investigating the energetics of hydrogen bonds as a function of delta pKa for homologous series of compounds under nonaqueous conditions that are conducive to the formation of low-barrier hydrogen bonds. In all cases, there was a linear correlation between the increase in hydrogen-bond energy and the decrease in delta pKa, as expected from simple electrostatic effects. However, no additional energetic contribution to the hydrogen bond was observed at delta pKa=0. These results and those of other model studies suggest alternative mechanisms by which hydrogen bonds can contribute to enzymatic catalysis, in accord with conventional electrostatic considerations.

PMID:
8600542
DOI:
10.1126/science.272.5258.97
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center