A tendril perversion in a helical oligomer: trapping and characterizing a mobile screw-sense reversal.

Autor:	Tomsett M; School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , UK . Email: j.clayden@bristol.ac.uk., Maffucci I; Dipartimento di Scienze Farmaceutiche - Sezione di Chimica Generale e Organica 'Alessandro Marchesini' , Università degli Studi di Milano , Via Venezian , 21 20133 Milano , Italy., Le Bailly BAF; School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , UK . Email: j.clayden@bristol.ac.uk., Byrne L; School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK., Bijvoets SM; School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK., Lizio MG; School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK.; Manchester Institute of Biotechnology , University of Manchester , 131 Princess St , Manchester M1 7DN , UK., Raftery J; School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK., Butts CP; School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , UK . Email: j.clayden@bristol.ac.uk., Webb SJ; School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK.; Manchester Institute of Biotechnology , University of Manchester , 131 Princess St , Manchester M1 7DN , UK., Contini A; Dipartimento di Scienze Farmaceutiche - Sezione di Chimica Generale e Organica 'Alessandro Marchesini' , Università degli Studi di Milano , Via Venezian , 21 20133 Milano , Italy., Clayden J; School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , UK . Email: j.clayden@bristol.ac.uk.
Jazyk:	angličtina
Zdroj:	Chemical science [Chem Sci] 2017 Apr 01; Vol. 8 (4), pp. 3007-3018. Date of Electronic Publication: 2017 Jan 25.
DOI:	10.1039/c6sc05474a
Abstrakt:	Helical oligomers of achiral monomers adopt domains of uniform screw sense, which are occasionally interrupted by screw-sense reversals. These rare, elusive, and fast-moving features have eluded detailed characterization. We now describe the structure and habits of a screw-sense reversal trapped within a fragment of a helical oligoamide foldamer of the achiral quaternary amino acid 2-aminoisobutyric acid (Aib). The reversal was enforced by compelling the amide oligomer to adopt a right-handed screw sense at one end and a left-handed screw sense at the other. The trapped reversal was characterized by X-ray crystallography, and its dynamic properties were monitored by NMR and circular dichroism, and modelled computationally. Raman spectroscopy indicated that a predominantly helical architecture was maintained despite the reversal. NMR and computational results indicated a stepwise shift from one screw sense to another on moving along the helical chain, indicating that in solution the reversal is not localised at a specific location, but is free to migrate across a number of residues. Analogous unconstrained screw-sense reversals that are free to move within a helical structure are likely to provide the mechanism by which comparable helical polymers and foldamers undergo screw-sense inversion.
Databáze:	MEDLINE
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