Bond dissociation energies of small biomolecules from quantum mechanical and Monte Carlo calculations.

摘要

Two studies are made into the bond dissociation energies (BDEs) of C-H bonds of small, biologically relevant molecules. The first determined that proline has a higher BDE on its alpha-carbon than all other amino acids, approximately 370 kJ mol-1in a protein environment. A peptide model was developed to mimic a beta-turn environment, where proline is often found in nature. The constraints of beta-turn secondary structure may serve to protect the proline alphaC-H bond from attack by weak oxidizing species, such as glutathione radical. The second study attempted to determine the effect of solvent (water) on the BDEs of several model systems. A hybrid Monte Carlo/Quantum Mechanics approach was developed. The results were impressive for a series of simple alcohols, matching experiment within 2 kJ mol-1, but less so for a similar set of simple amines and glycine. The lack of polarizability is the primary weakness in the method.