Configuration of the acetal carbon atom of pyruvic acid acetals in some bacterial polysaccharides

The configuration at the acetal carbon atom of pyruvic acid acetals present in some extracellular bacterial polysaccharides has been investigated. Assignment of the absolute configuration was made by comparing signals in the ¹³C- and ¹H-n.m.r. spectra of the polysaccharides with those of model substances. The S-configuration was demonstrated in eight polysaccharides in which pyruvic acid is linked to O-4 and O-6 of D-glucopyranosyl or D-mannopyranosyl residues. The R-configuration was demonstrated in four polysaccharides in which pyruvic acid is linked to O-4 and O-6 of D-galactopyranosyl residues. Consequently, in each of these acetals, which form 1,3-dioxane rings, the methyl group is equatorial and the carboxyl group axial. The S-form was further demonstrated in four polysaccharides in which the pyruvic acid is linked to O-3 and O-4 of D-galactopyranosyl groups.     

Structural studies of the O-specific side-chain of the lipopolysaccharide from Escherichia coli O 55

The structure of the O-specific side-chains of the lipopolysaccharide from Escherichia coli O 55 has been investigated, methylation analysis, specific degradations, and n.m.r. spectroscopy being the principal methods used. It is concluded that the O-specific side-chains are composed of pentasaccharide repeating-units having the following structure [where Col stands for colitose (3,6-dideoxy-l-xylo-hexose)].

     

Using lognormal distributions and lognormal probability plots in probabilistic risk assessments

Lognormal distributions play a central role in human and ecological risk assessment, so every risk assessor needs to understand and exploit their basic properties. Similarly, Lognormal probability plots are invaluable because they provide a powerful way to visualize measured data or simulated results.     

Structural studies of the capsular polysaccharide of Klebsiella type 33.

The structure of the capsular polysaccharide from Klebsiella type 33 has been investigated. Methylation analysis, various specific degradations, graded hydrolysis with acid, and n.m.r. spectroscopy were the principal methods used. It is concluded that the polysaccharide is composed of pentasaccharide repeating-units having the following structure. (formula, see manual). The D-galactopyranosyl group, with pyruvic acid linked as a ketal to O-3 AND O-4, was degraded on treatment of the fully methylated polysaccharide with strong base. It is proposed that methyl pyruvate is eliminated, in an E2 type of reaction.     

Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: an in situ ellipsometry and atomic force microscopy study

This paper describes a combined investigation of the salivary and MUC5B films structure and topography in conditions similar to those found in the oral cavity in terms of ionic strength, pH, and protein concentration. AFM and ellipsometry were successfully used to give a detailed picture of the film structure and topography both on hydrophilic and on hydrophobic substrata. Regardless of the substrata, the salivary film can be described as having a two sublayer structure in which an inner dense layer is decorated by large aggregates. However, the shape and height of these larger aggregates largely depend on the type of substrata used. Additionally, we show that the adsorption of MUC5B is controlled by the type of substrata and the MUC5B film topography is similar to that of the larger aggregates present in the salivary films, especially on hydrophobic substrates. Therefore, we conclude that MUC5B is a major component in the salivary film when formed on hydrophobic substrates. Furthermore, we studied how resistant the salivary and MUC5B films are against elutability by buffer rinsing and addition of SDS solution. We conclude that the adsorbed proteins contain fractions with varying binding strengths to the two types of surfaces. Specifically, we have shown that the large MUC5B biomacromolecules on the hydrophobic substrates are especially resistant to both elution with buffer solution and SDS. Therefore, these large mucins can be responsible for the increased resistance of HWS films on hydrophobic substrates and can protect the intraoral surfaces against surface-active components present in oral health care products.     

DDB2 promotes chromatin decondensation at UV-induced DNA damage

Nucleotide excision repair (NER) is the principal pathway that removes helix-distorting deoxyribonucleic acid (DNA) damage from the mammalian genome. Recognition of DNA lesions by xeroderma pigmentosum group C (XPC) protein in chromatin is stimulated by the damaged DNA-binding protein 2 (DDB2), which is part of a CUL4A-RING ubiquitin ligase (CRL4) complex. In this paper, we report a new function of DDB2 in modulating chromatin structure at DNA lesions. We show that DDB2 elicits unfolding of large-scale chromatin structure independently of the CRL4 ubiquitin ligase complex. Our data reveal a marked adenosine triphosphate (ATP)-dependent reduction in the density of core histones in chromatin containing UV-induced DNA lesions, which strictly required functional DDB2 and involved the activity of poly(adenosine diphosphate [ADP]-ribose) polymerase 1. Finally, we show that lesion recognition by XPC, but not DDB2, was strongly reduced in ATP-depleted cells and was regulated by the steady-state levels of poly(ADP-ribose) chains.     

Adventitious shoot regeneration of pear (<Emphasis Type="Italic">Pyrus</Emphasis> spp.) genotypes

Adventitious shoot regeneration of twenty-four pear genotypes was compared in a common in vitro shoot induction and development protocol. This study also compared cultures newly established from scionwood with cultures that been in long-term cold storage. In vitro cultures of 13 Pyrus genotypes and budwood from 23 Pyrus genotypes were obtained from the National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon. With the exception of one genotype of P. elaeagrifolia Pall., and ‘Ya Li’ (P. pyrifolia var. sinensis Teng & Tanabe), all were P. communis L. cultivars. The basal shoot induction media consisted of Chevreau and Leblay (CL) basal nutrients, vitamins, and organics (Chevreau and Leblay in Acta Hortic 336: 263–268, 1993). The analysis of variance indicated that differences among genotypes were highly significant and the main effect of culture origin was non-significant. However, there was a significant interaction between genotype and culture origin, with percentage regeneration of ‘Abate Fetel’ from new budwood significantly greater than that from long-term in vitro cultures, while ‘Jesinji Vodenac’ cultures derived from the old NCGR cultures regenerated significantly more adventitious shoots. The ranges of mean regeneration frequency were similar for both in vitro (0–87.7%) and scionwood-derived cultures (0–70.7%). Maximum regeneration was observed for ‘Conference’, followed by ‘Magness’, ‘Dr. Jules Guyot’, and Packham’s Triumph’. The range of number of adventitious shoots was relatively narrow, with the minimum of 1.0 for seven genotypes to 2.2 for ‘Conference’.     

Midgut bacterial dynamics in Aedes aegypti

In vector mosquitoes, the presence of midgut bacteria may affect the ability to transmit pathogens. We have used a laboratory colony of Aedes aegypti as a model for bacterial interspecies competition and show that after a blood meal, the number of species (culturable on Luria-Bertani agar) that coexist in the midgut is low and that about 40% of the females do not harbor any cultivable bacteria. We isolated species belonging to the genera Bacillus, Elizabethkingia, Enterococcus, Klebsiella, Pantoea, Serratia, and Sphingomonas, and we also determined their growth rates, antibiotic resistance, and ex vivo inhibition of each other. To investigate the possible existence of coadaptation between midgut bacteria and their host, we fed Ae.?aegypti cohorts with gut bacteria from human, a frog, and two mosquito species and followed the bacterial population growth over time. The dynamics of the different species suggests coadaptation between host and bacteria, and interestingly, we found that Pantoea stewartii isolated from Ae.?aegypti survive better in Ae.?aegypti as compared to P.?stewartii isolated from the malaria mosquito Anopheles gambiae.