Study of DNA films by the CD, X-ray and polarization microscopy techniques.

DNA films with psi +/- CD spectra have been investigated. X-ray analysis has shown the sign of the psi spectra to be independent of the secondary structure of DNA. The appearance of the psi spectra is attended by the formation of a characteristic polygonal texture of the cholesteric type in the DNA film.     

Substrate specificity of Escherichia coli thymidine phosphorylase

Substrate specificity of Escherichia coli thymidine phosphorylase to thymidine derivatives modified at 5' -, 3' -, and 2' ,3' - positions of the sugar moiety was studied. Equilibrium and kinetic constants (K(m), K(I), k(cat)) of the phosphorolysis reaction have been determined for 20 thymidine analogs. The results are compared with X-ray and molecular dynamics data. The most important hydrogen bonds in the enzyme-substrate complex are revealed.     

Proteome analysis of chloroplasts from the moss Physcomitrella patens (Hedw.) B.S.G.

Intact chloroplasts were prepared from protoplasts of the moss Physcomitrella patens according to an especially developed method. They were additionally separated into stroma and thylakoid fractions. The proteomes of intact plastids, stroma, and thylakoids were analyzed by 1D-electrophoresis under denaturing conditions followed by protein digestion and nano-LC-ESI-MS/MS of tryptic peptides from gel bands. A total of 624 unique proteins were identified, 434 of which were annotated as chloroplast resident proteins. The majority of proteins belonged to a photosynthetic group (21.3%) and to the group of proteins implicated in protein degradation, posttranslational modification, folding, and import (20.6%). Among proteins assigned to chloroplasts, the following groups are prominent combining proteins implicated in metabolism of: amino acids (6.9%), nucleotides (2.5%), lipids (2.2%), carbohydrates (2.4%), hormones (1.5%), isoprenoids (1.25%), vitamins and cofactors (1%), sulfur (1.25%), and nitrogen (1%); as well as proteins involved in the pentose-phosphate cycle (1.75%), tetrapyrrole synthesis (3.7%), and redox processes (3.6%). The data can be used in physiological and photobiological studies as well as in further studies of P. patens chloroplast proteome including structural and functional specifics of plant protein localization in organelles.     

见血封喉乳汁脂溶性成分及其抗氧化活性研究

首次采用气相色谱.质谱联用技术(GC-MS)对见血封喉(Antiaris toxicaria(Pers.)Lesch.)乳汁的脂溶性成分进行了分析,共鉴定了27个化学成分,占其总量的91.7%.用清除DPPH自由基能力的方法测定了见血封喉乳汁脂溶性部位的抗氧化活性,结果显示出一定的抗氧化活性,SC50值为500μg ml-1.     

Patterson methods in fibre diffraction analysis.

The potential of the Patterson methods for X-ray diffraction studies of textures is examined in DNA fibres. Patterson analysis, which is rarely used in these situations, is shown to yield important information on the preliminary interpretation of diffraction patterns and to increase the reliability of the three-dimensional structural pattern obtained for polymeric molecules. We also show how the screw symmetry of helical molecules can be used to calculate their electron density by means of the three-dimensional Patterson function.     

Synthesis of Fluorine-Containing Analogues of Purine Deoxynucleosides: Optimization of Enzymatic Transglycosylation Conditions

Doklady Biochemistry and Biophysics - In this work, a comparative analysis of the conditions of transglycosylation reactions catalyzed by E. coli nucleoside phosphorylases was carried out, and the...     

Molecular Hazard Identification of Non-O157 Shiga Toxin-Producing Escherichia coli (STEC)

The complexity regarding Shiga toxin-producing Escherichia coli (STEC) in food safety enforcement as well as clinical care primarily relates to the current inability of an accurate risk assessment of individual strains due to the large variety in serotype and genetic content associated with (severe) disease. In order to classify the clinical and/or epidemic potential of a STEC isolate at an early stage it is crucial to identify virulence characteristics of putative pathogens from genomic information, which is referred to as ‘predictive hazard identification’. This study aimed at identifying associations between virulence factors, phylogenetic groups, isolation sources and seropathotypes. Most non-O157 STEC in the Netherlands belong to phylogroup B1 and are characterized by the presence of ehxA, iha and stx ₂, but absence of eae. The large variability in the number of virulence factors present among serogroups and seropathotypes demonstrated that this was merely indicative for the virulence potential. While all the virulence gene associations have been worked out, it appeared that there is no specific pattern that would unambiguously enable hazard identification for an STEC strain. However, the strong correlations between virulence factors indicate that these arrays are not a random collection but are rather specific sets. Especially the presence of eae was strongly correlated to the presence of many of the other virulence genes, including all non-LEE encoded effectors. Different stx-subtypes were associated with different virulence profiles. The factors ehxA and ureC were significantly associated with HUS-associated strains (HAS) and not correlated to the presence of eae. This indicates their candidacy as important pathogenicity markers next to eae and stx _2a.     

The structure of poly(dA).poly(dT) as revealed by an X-ray fibre diffraction

X-ray diffraction in fibres revealed that the calcium salt of poly(dA).poly(dT) is a 10-fold double helix with a pitch of 3.23 nm. The opposite sugar-phosphate chains in the refined model are characterized by a complete conformational equivalence and contain sugars in a conformation close to C2'-endo. As a result a new model of the sodium salt of poly(dA).poly(dT) has been constructed, which is different from the Heteronomous DNA proposed earlier (S. Arnott et al., Nucl. Acids Res. 11, 4141 (1983)). The new model of Na-poly(dA).poly(dT) has conformationally similar opposite chains; it is a structure of the B-type, rather like that of Ca-poly(dA).poly(dT).