Dataset Information

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

ABSTRACT: 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.

SUBMITTER: Tomsett M

PROVIDER: S-EPMC5380885 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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

Tomsett Michael M Maffucci Irene I Le Bailly Bryden A F BAF Byrne Liam L Bijvoets Stefan M SM Lizio M Giovanna MG Raftery James J Butts Craig P CP Webb Simon J SJ Contini Alessandro A Clayden Jonathan J

Chemical science 20170125 4

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 sc ...[more]

PMID: 28451368

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Project description:ObjectiveCephalomedullary nails (CMN) are implants with a high success rate in the surgical treatment of trochanteric fractures. The aim of this study is to compare the radiological outcomes and mechanical complications of femoral trochanteric fractures treated with three different CMNs.MethodsIntertrochanteric fractures in patients aged 50 years and older treated with CMN between January 2016 and December 2021 were reviewed retrospectively. A total of 158 cases meeting the criteria were included to final analysis. Cases were divided into three groups based on the type of nail used (helical blade: group 1, n = 54; screw: group 2, n = 53; winged screw: group 3, n = 51). Demographic characteristics, mechanical complications, reduction quality, tip-apex distances (TAD) and Cleveland zones were compared between the groups. Femoral neck shortening, varus collapse, lag sliding, changes in abductor length were compared between study groups. Factors affecting mechanical complications were also analyzed.ResultsStudy groups were homogenic in terms of demographic characteristics, fracture type and reduction quality. Regarding mechanical complications, no statistically significant difference was found between groups. All three implants had similar outcomes on femoral neck shortening, varus collapse and lag sliding. Pooled analysis of 158 cases showed that mechanical complications increase as the quality of reduction decreases (p = 0.000) same applies when TAD alters from the desired range (p = 0.025) and with non-optimally implanted blade according to Cleveland zones (p = 0, 000).ConclusionThe radiological outcomes and mechanical complications of helical blade, screw type blade and winged screw type blade proximal femoral nails are similar in selected group. Regardless of the device type, it is necessary to obtain high reduction quality, obtain TAD within described range and optimally place the blade according to Cleveland Zones to reduce the failure rate and avoid complications.

Dataset Information

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

Publications

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

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