Shape Persistence of Polyproline II Helical Oligoprolines. Issue 30 (18th June 2015)

• Record Type: Journal Article
• Authors: Garbuio, Luca; Lewandowski, Bartosz; Wilhelm, Patrick; Ziegler, Ludmila; Yulikov, Maxim; Wennemers, Helma; Jeschke, Gunnar
• Is Part Of: Chemistry. Volume 21:Issue 30(2015)
• Page Start: 10747
• Page End: 10753
• Publication Date: 2015-06-18
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201501190
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Oligoprolines are commonly used as molecular scaffolds. Past studies on the persistence length of their secondary structure, the polyproline II (PPII) helix, and on the fraction of backbone <italic>cis</italic> amide bonds have provided conflicting results. We resolved this debate by studying a series of spin‐labeled proline octadecamers with EPR spectroscopy. Distance distributions between an N‐terminal Gd^III‐DOTA (DOTA=1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetraacetic acid) label and a nitroxide label at one of five evenly spaced backbone sites allowed us to discriminate between the flexibility of the PPII helix and the <italic>cis</italic> amide contributions. An upper limit of 2 % <italic>cis</italic> amide bonds per residue was found in a 7:3 (v/v) water/glycerol mixture, whereas <italic>cis</italic> amides were not observed in trifluoroethanol. Extrapolation of Monte Carlo models from the glass transition to ambient temperature predicts a persistence length of ≈3–3.5 nm in both solvents. The method is generally applicable to any type of oligomer for which the persistence length is of interest.</p> </abstract>