Solution effects on the self-association of a water-soluble peptoid

A desire to replicate the structural and functional complexity of proteins with structured, sequence-specific oligomers motivates study of the structural features of water-soluble peptoids (N-substituted glycine oligomers). Understanding the molecular-level details of peptoid self-assembly in water is essential to advance peptoids' application as novel materials. Peptoid 1 , an amphiphilic, putatively helical peptoid previously studied in our laboratory, shows evidence of self-association in aqueous solution. In this work, we evaluate how changes to aqueous solution conditions influence the self-association of 1 . We report that changes to pH influence the fluorescence and CD spectroscopic features as well as the peptoid's interaction with a solvatochromic fluorophore and its apparent size as estimated by size exclusion chromatography. Addition of guanidine hydrochloride and ammonium sulfate also modulate spectroscopic features of the peptoid, its interaction with a solvatochromic fluorophore, and its elution in size exclusion chromatography. These data suggest that the ordering of the self-assembly changes in response to pH and with solvent additives and is more ordered at higher pH and in the presence of guanidine hydrochloride. The deeper understanding of the self-association of 1 afforded by these studies informs the design of new stimuli-responsive peptoids with stable tertiary or quaternary structures.     

Transmission Distortion Affecting Human Noncrossover but Not Crossover Recombination: A Hidden Source of Meiotic Drive

Meiotic recombination ensures the correct segregation of homologous chromosomes during gamete formation and contributes to DNA diversity through both large-scale reciprocal crossovers and very localised gene conversion events, also known as noncrossovers. Considerable progress has been made in understanding factors such as PRDM9 and SNP variants that influence the initiation of recombination at human hotspots but very little is known about factors acting downstream. To address this, we simultaneously analysed both types of recombinant molecule in sperm DNA at six highly active hotspots, and looked for disparity in the transmission of allelic variants indicative of any cis-acting influences. At two of the hotspots we identified a novel form of biased transmission that was exclusive to the noncrossover class of recombinant, and which presumably arises through differences between crossovers and noncrossovers in heteroduplex formation and biased mismatch repair. This form of biased gene conversion is not predicted to influence hotspot activity as previously noted for SNPs that affect recombination initiation, but does constitute a powerful and previously undetected source of recombination-driven meiotic drive that by extrapolation may affect thousands of recombination hotspots throughout the human genome. Intriguingly, at both of the hotspots described here, this drive favours strong (G/C) over weak (A/T) base pairs as might be predicted from the well-established correlations between high GC content and recombination activity in mammalian genomes.     

Applications in Biocatalysis of Glycosyl Hydrolases from the Hyperthermophilic Archaeon Sulfolobus solfataricus

Abstract

Carbohydrates serve as structural components and energy sources of cells. More interestingly, however, these biomolecules are involved in a variety of molecular recognition processes in intercellular communication and signal transduction such as cell adhesion, differentiation, development and regulation. For these reasons, great interest has arisen in carbohydrate-based pharmaceuticals and on the development of techniques for the analysis and synthesis of oligosaccharides. In this respect, enzymes involved in carbohydrates hydrolysis and modification are increasingly being utilised for the bioconversion of sugars, for the synthesis of oligosaccharides with potential application, and for the characterisation of carbohydrate compounds of unknown structure.

In this review, the enzymology and the applications of three glycosyl hydrolases from the archaeon Sulfolobus solfataricus are described. In particular, we focus on the enzymological properties of β-glycosidase, an α-xylosidase, and an α-fucosidase; their exploitation in oligosaccharides synthesis will also be discussed.     

Studies on the cardiovascular response to hypoxia

Fifty-eight adults, nearly all male, aged between 35 and 50, with slight bronchiopneumopathy in a state of functional compensation, were subjected to hypoxia by rerespiration. Heart rate and oxyhaemoglobin saturation were observed. In nearly all cases, hypoxia caused an increase in heart rate that varied considerably from subject to subject, but seemed more marked between the 1st and 2nd minute after start of the trial. Normalization of heart rate, similarly very variable, reflected the increase phase and was complete in periode varying between 30 and 210 seconds. It may be supposed that as regards heart rate the wide variety of responses to the same stimulus is due to individual states of equilibrium of a predominantly vegetative nature. There was no relation between duration of the hypoxia trial, extent of desaturation and time of resaturation in air because the rate of haemoglobin desaturation and resaturation varied from case to case.     

The wine yeasts of the Cape

Summary Ascospore formation has been observed in three species of the genusBrettanomyces, viz. Brett. bruxellensis. Brett, intermedius andBrett. schanderlii. On media of adequate vitamin content these species form 1–4 hat-shaped ascospores. The spores are liberated rather soon after maturation. Heat treatment of ascogenous cultures indicated that these species are homothallic. In view of the fact that ascospore formation has been observed in the type species,Brett. bruxellensis, the transfer of the genus to theEndomycetaceae should be considered. Part I, II and III: Antonie van Leeuwenhoek 24, 239, 1958;25, 145, 1959;25, 449, 1959.