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Hi Bernhard, the interaction you are referring to is usually referred to as CH-pi interaction and not 'stacking', and that notation implies, as was pointed out, that the hydrophobic face of pyranose rings (most often GAL) is positioned such that the CH bond vectors interact with the aromatic orbitals. This interaction is a signature of lectin-glycan complexes - aromatic residues, especially tryptophan residues, are massively enriched in lectin binding sites. Despite the name the major energy gain of the apparant 'stacking' is, however, due to vdw interactions, with only about 0.5 kcal/mole contribution form the CH-pi interaction. Regards from the ACS meeting Carb session :) Bärbel Zitat von Bernhard Rupp <[log in to unmask]>: > Thanks to all the respondents. Very useful links on a generally interesting > topic. I was pretty sure > > that this is another case of imprecise notation/definition because even with > my limited QM I cannot see a > > true pi-stacking in the sense of the narrow definition. > > > > But, it seems to be frequently used in the context with sugarCH-aromatic > interaction, which is not good. > > > > Much obliged, BR > > _____ > > From: CCP4 bulletin board [[log in to unmask]] on behalf of Bernhard Rupp > [[log in to unmask]] > Sent: Wednesday, August 23, 2017 8:18 PM > To: [log in to unmask] <mailto:[log in to unmask]> > Subject: [ccp4bb] Sugar-Pi-stacking > > Hi Fellows, > > > > there are some smart chemists amongst you, so I wonder - what precisely am I > to understand is > > the nature of pi-stacking between an aromatic residue or (whatever > pi-orbital moiety) and a sugar moiety, disaccharide etc.? > > > > Thanks for your help, > > > > BR > > > > ------------------------------------------------------ > > Bernhard Rupp > > http://www.hofkristallamt.org/ > > [log in to unmask] <mailto:[log in to unmask]> > > +1 925 209 7429 > > +43 767 571 0536 > > ------------------------------------------------------ > > All models are wrong > > but some are useful. > > ------------------------------------------------------ -- Bärbel Blaum, Ph.D. Interfakultäres Institut für Biochemie (IFIB) Hoppe-Seyler-Strasse 4 D-72076 Tübingen Germany +49 70 71 29 75 359