Phospholipid-induced structural changes to an erythroid beta spectrin ankyrin-dependent lipid-binding site

The region of beta-spectrin that is responsible for interactions with ankyrin was shown to comprise an ankyrin-sensitive lipid-binding site. Structural studies indicate that it exhibits a mixed 3(10)/alpha helical conformation and is highly amphipathic. These features together with the distinctively conserved sequence of the lipid-binding site motivated us to explore the mechanism of its interactions with biological membranes. A series of singly and doubly spin-labeled erythroid beta-spectrin-derived peptides was constructed, and the spin-label mobility and spin-spin distances were analyzed via electron paramagnetic resonance spectroscopy and two different calculation methods. The results indicate that in beta-spectrin, the lipid-binding domain, which is part of the 14(th) segment, has the topology of typical triple-helical spectrin repeat. However, it undergoes significant changes when interacting with phospholipids or detergents. A mechanism for these interactions is proposed in this paper.     

Heightened aberrant deposition of hard-wearing elastin in conduit arteries of prehypertensive SHR is associated with increased stiffness and inward remodeling

Elastin is a major component of conduit arteries and a key determinant of vascular viscoelastic properties. Aberrant organization of elastic lamellae has been reported in resistance vessels from spontaneously hypertensive rats (SHR) before the development of hypertension. Hence, we have characterized the content and organization of elastic lamellae in conduit vessels of neonatal SHR in detail, comparing the carotid arteries from 1-wk-old SHR with those from Wistar-Kyoto (WKY) and Sprague Dawley (SD) rats. The general structure and mechanics were studied by pressure myography, and the internal elastic lamina organization was determined by confocal microscopy. Cyanide bromide-insoluble elastin scaffolds were also prepared from 1-mo-old SHR and WKY aortas to assess their weight, amino acid composition, three-dimensional lamellar organization, and mechanical characteristics. Carotid arteries from 1-wk-old SHR exhibited narrower lumen and greater intrinsic stiffness than those from their WKY and SD counterparts. These aberrations were associated with heightened elastin content and with a striking reduction in the size of the fenestrae present in the elastic lamellae. The elastin scaffolds isolated from SHR aortas also exhibited increased relative weight and stiffness, as well as the presence of peculiar trabeculae inside the fenestra that reduced their size. We suggest that the excessive and aberrant elastin deposited in SHR vessels during perinatal development alters their mechanical properties. Such abnormalities are likely to compromise vessel expansion during a critical period of growth and, at later stages, they could compromise hemodynamic function and participate in the development of systemic hypertension.     

Structure and dynamics of a DNA duplex containing single alpha-anomeric deoxyadenosine residue.

Structure and dynamics of an undecamer DNA duplex containing a single alpha-anomeric deoxyadenosine residue placed in opposition to a thymidine unit have been studied using simulation of molecular dynamics in aqueous solution. Despite several noticeable deviations from the B-DNA duplex structure caused by the anomerisation, such as: West type puckering of the alpha-anomeric sugar, disrupted base stacking pattern and unstable duplex bending, the formation of a non-classical alpha-dA-T pair was observed. A novel way of visual presentation of trajectory data allowing high throughput screening of the conformational parameters is presented.     

Collagenous constituents of amniotic fluid.

The amniotic fluid (AF) was fractionated by dialysis, gel filtration and SDS/PAGE, and submitted to the assay of collagenous constituents. The collagenous character of peptides and proteins of amniotic fluid was confirmed by hydroxyproline (Hyp) assay and treatment with bacterial collagenase followed by electrophoresis and gel filtration of the digestion products. It was found that AF contains collagen degradation products but the classical method of Hyp determination described by Woessner (Arch. Biochem. Biophys., 1961, 93, 440-447) gives overestimated values due to the interference with other AF components. Fractionation of AF on Sephadex G-100 column allowed to remove the interfering material and to estimate the actual Hyp content which equals to approx. 6.2 microg/ml. About 70% of Hyp was found in low molecular dialyzable products and the rest (about 30%) appears to be a constituent of nondialyzable collagenous polypeptides of the molecular mass of about 7.9-26.3 kDa. It is suggested that such collagenous polypeptides may be the products of proteolytic conversion of collagen precursor (procollagen) into the monomeric form of this protein. No high molecular forms of collagen, corresponding to alpha-subunits, were found.     

Fluorescent α-Anomeric 1,N(6)Etheno- Deoxyadenosine in DNA Duplexes. the α-εdA / dG Pair

Abstract

Structural properties of the fluorescent α-anomeric 1,N(6)ethenodeoxyadenosine residue placed in opposition to all four canonical deoxynucleotide units within 11-mer DNA duplexes have been studied. The duplex with α-εedA / dG pairing is most thermodynamically stable while the α-edA / dC one is the least stable. Fluorescence measurements confirm the thermodynamic data and indicate base-pair dependent stacking properties of α-edA within duplex structures. Results of molecular dynamics (MD) simulations in aqueous solution for the most stable duplex point to the presence of different conformational states of the α-1,N(6)etheno-deoxyadenosine residue, including formation of a hydrogen bonded pair with the dG and possible occurrence of severe kinking in the duplex.     

Selection of the conodont Idiognathodus simulator (Ellison) as the event marker for the base of the global Gzhelian Stage (Upper Pennsylvanian, Carboniferous)

Studies carried out for more than 10 years by the Task Group to establish GSSPs at the base of the Moscovian–Kasimovian and Kasimovian–Gzhelian boundaries have resulted in the proposal that the level at which the conodont species Idiognathodus simulator (Ellison, 1941) first appears be selected to mark the base of the Gzhelian Stage. This expands this eastern European chronostratigraphic unit to a global scale.I. simulator (sensu Barrick et al., 2008) has been identified so far in Midcontinent and eastern North America, the Moscow and Donets basins and southern Urals of eastern Europe, and in south-central China. Correlation of this level based on this species and other conodont species can be reinforced in some areas by ammonoid and fusulinid data.     

Locus-aware decomposition of gene trees with respect to polytomous species trees

Background

Horizontal gene transfer (HGT), a process of acquisition and fixation of foreign genetic material, is an important biological phenomenon. Several approaches to HGT inference have been proposed. However, most of them either rely on approximate, non-phylogenetic methods or on the tree reconciliation, which is computationally intensive and sensitive to parameter values.

Results

We investigate the locus tree inference problem as a possible alternative that combines the advantages of both approaches. We present several algorithms to solve the problem in the parsimony framework. We introduce a novel tree mapping, which allows us to obtain a heuristic solution to the problems of locus tree inference and duplication classification.

Conclusions

Our approach allows for faster comparisons of gene and species trees and improves known algorithms for duplication inference in the presence of polytomies in the species trees. We have implemented our algorithms in a software tool available at https://github.com/mciach/LocusTreeInference.

     

Male reproductive health statement (XIIIth international symposium on Spermatology,may 9th–12th 2018, Stockholm,Sweden

On the occasion of the XIIIth International Symposium on Spermatology held from 9 to 13 May 2018 in Stockholm (Sweden), participants (guest speakers and audience) collectively felt the need to make a public statement on the general issue of male reproductive health. Our intention is to raise awareness of what we believe is a neglected area of research despite alarming situations around the world. The disclosure strategy desired by the co-authors is to bring it to the attention of the greatest number partly by considering co-publication in the various periodicals dealing with Reproductive Biology and Andrology. BaCA’s editorial office accepted this mission and found it natural that our periodical, the official journal of the French Andrology Society (SALF), should carry this message.