From chemistry-request@ccl.net Mon Jul 1 16:04:39 1991 Date: Mon, 1 Jul 1991 14:22 CDT From: Andy Holder Subject: Tin disulfide stuff. To: CHEMISTRY@ccl.net Status: R We have recently published a pretty good set of AM1 parameters for tin that you can perhaps use to get a start on your problem on the tin disulfide stuff: Dewar, M. J. S.; Healy, E. F.; Kuhn, D. R.; Holder, A. J. Organomet. (1991) Vol. 10, 431. Andy Holder =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= DR. ANDREW HOLDER Department of Chemistry || BITNET Addr: AHOLDER@UMKCVAX1 University of Missouri - Kansas City || Internet Addr: aholder@vax1.umkc.edu Kansas City, Missouri 64110 || Phone Number: (816) 235-2293 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= From chemistry-request@ccl.net Mon Jul 1 16:27:25 1991 Date: Mon, 1 Jul 1991 16:18 EDT From: "DOUGLAS A. SMITH" Subject: H-bonding To: chemistry@ccl.net Status: R OK, what do you do when the molecular mechanics results disagree with experiment, and (of course) experiment is "right." First, you check to make sure you haven't goofed, then you look for alternate explanations. Then you try to find out if the experimentalists goofed, then you say "we're right and they are wrong." BUT... Does anybody have any references which show and/or explain that molecular mechanics does a poor job on hydrogen bonding in peptide or polyamide systems, particularly that it overestimates the attraction, leading to small ring h-bonding interactions? In particular, gamma turns in proteins (7-membered ring interactions) are predicted by molecular mechanics to be favored, but are very rare in proteins. I would like data on MM2, MM3, AMBER and OPLS (although any information would be welcome). I would also like to hear about the ability of discrete solvation versus contimuum methods to handle this question of h-bonding. I will summarize for the net. Doug Smith Assistant Professor of Chemistry The University of Toledo Toledo, OH 43606-3390 voice 419-537-2116 fax 419-537-4033 email fax0236@uoft02.utoledo.edu