CCL: Planarity of an amide group

[Mariusz Radon <mariusz.radon _ gmail.com>]

 Sent to CCL by: Mariusz Radon [mariusz.radon###gmail.com]
 Dear Sanghwa:
 Just few suggestions/questions concerning your question about the non-planarity:
 - Do you expect the steric interactions between the aminoacids
 residues could be important for the adopted conformation? If your
 non-planarity were physical, there must be some reason for it...
 - Does the non-planarity remain at any correlated level, even simply
 DFT:B3LYP? Or, ideally, DFT+D (with dispersion correction)?
 Hope that it can be useful.
 Best regards and all the best in New Year 2010,
 Mariusz Radon
 On Thu, Dec 31, 2009 at 4:11 AM, Sanghwa Han hansh,kangwon.ac.kr
 <owner-chemistry..ccl.net> wrote:
 >
 > Sent to CCL by: "Sanghwa  Han" [hansh~~kangwon.ac.kr]
 > Dear colleagues,
 >
 > In Biochemistry textbooks, an amide bond (NH-CO) in a peptide is explained
 to be planar.
 > But when I optimize a capped amino acid (e.g. ACE-Amino Acid-NME) using
 HF/6-31G* for RESP charge derivation, the dihedral HN-CO often deviates from
 planarity by as much as 20 degrees.
 > Do I need to constrain the HN-CO to 0 degrees to obtain an optimized
 structure that is used in a RESP charge derivation?
 > Does anybody know if the amide group can be non-planar in experimentally
 determined structures?
 >
 > Thanks.
 >
 > Sanghwa Han
 >
 >
 >
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 --
 Mariusz Radon, PhD student
 Department of Theoretical Chemistry
 Jagiellonian University
 http://www.chemia.uj.edu.pl/~mradon
 mradon /at/ chemia.uj.edu.pl
 (PGP public key available on the website)