Influenza virus attaches itself to sialic acids on the surface of epithelial cells of the upper respiratory tract of the host using its own protein hemagglutinin. Species specificity of influenza virus is determined by the linkages of the sialic acids. Birds and humans have α2-3 and α2-6 linked sialic acids, respectively. Viral hemagglutinin is a homotrimeric receptor, and thus, tri- or oligovalent ligands should have a high binding affinity. We describe the in silico design, chemical synthesis and binding analysis of a trivalent glycopeptide mimetic. This compound binds to hemagglutinin H5 of avian influenza with a dissociation constant of K(D) = 446 nM and an inhibitory constant of K(I) = 15 μM. In silico modeling shows that the ligand should also bind to hemagglutinin H7 of the virus that causes the current influenza outbreak in China. The trivalent glycopeptide mimetic and analogues have the potential to block many different influenza viruses.
The comparison of the self-assembly
9,9′-bisheptahelicene
on the Au(111) surface, studied with scanning tunneling microscopy,
with the self-assembly of the same species obtained by on-surface
synthesis via Ullmann coupling from 9-bromoheptahelicene reveals a
diastereomeric excess for the (M,P)-meso-form of 50%. The stereoselectivity is explained
by a topochemical effect, in which the surface-alignment of the starting
material and the organometallic intermediate sterically favor the
(M,P)-transition state over the
homochiral transition states.
Stereochemical effects during two-dimensional crystallization of bisheptahelicene diastereomers on a Cu(111) surface have been studied with scanning tunnelling microscopy. The (M,M)- and (P,P)-enantiomers crystallize into a monolayer racemate lattice, whereas the (M,P)-diastereomers aggregate into their own monolayer phase.
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