n-->pi* interactions in proteins.
Hydrogen bonds between backbone amides are common in folded proteins. Here, we show that an intimate interaction between backbone amides also arises from the delocalization of a lone pair of electrons (n) from an oxygen atom to the antibonding orbital (pi*) of the subsequent carbonyl group. Natural bond orbital analysis predicted significant n-->pi* interactions in certain regions of the Ramachandran plot. These predictions were validated by a statistical analysis of a large, non-redundant subset of protein structures determined to high resolution. The correlation between these two independent studies is striking. Moreover, the n-->pi* interactions are abundant and especially prevalent in common secondary structures such as alpha-, 3(10)- and polyproline II helices and twisted beta-sheets. In addition to their evident effects on protein structure and stability, n-->pi* interactions could have important roles in protein folding and function, and merit inclusion in computational force fields.
Bartlett
Gail J
GJ
School of Chemistry, University of Bristol, Bristol, United Kingdom.
Choudhary
Amit
A
Raines
Ronald T
RT
Woolfson
Derek N
DN
D019295:Computational Biology; D018360:Crystallography, X-Ray; D030561:Databases, Nucleic Acid; D004151:Dipeptides / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
D004151:Dipeptides; D011506:Proteins