Hi Frank, such interactions are certainly possible, in particular if additional H-bonding side chains are available to stabilize the arrangement. I'm not aware of any examples involving main chain carbonyls, but for a discussion of carbonyl-carbonyl side chain interactions see the following paper:
Flocco, M.M. and Mowbray, S.L. (1995) Strange Bedfellows: Interactions between Acidic Side-Chains in Proteins, J. Mol. Biol. 254 96-105 Best wishes, Sebastiaan Werten. ----- Original Message ----- From: Frank Lee To: CCP4BB@JISCMAIL.AC.UK Sent: Saturday, April 25, 2009 7:47 AM Subject: [ccp4bb] hydrogen bond between aspartate side chain and main chain carbonyl group? Hi, In a new structure we observed a hydrogen bond between an aspartate side chain and a main chain carbonyl group. Because both of them are electronegative, I am puzzled. My questions are: does this hydrogen bond make sense at all? any precedent for such a hydrogen bond? I would appreciate your help very much! Frank
