Torsional tension in metaphase chromosome DNA]

The torsional tension in DNA of isolated metaphase chromosomes from murine fibroblasts was measured by the microfluorescent method. The method is based on the ability of a fluorescent dye ethidium bromide to compensate for the negative torsional tension in topologically closed DNA by intercalation between DNA base pairs. The value of the relative twist difference delta Tw/Tw = -0.1 was found in a bulk (about 3/4) of unconstrained chromosomal DNA. In interphase nuclei, the torsionally stressed DNA comprises about 15%, with value of delta Tw/Tw = -0.075. We suppose that the tension in chromosomal DNA was created in the prophase stage of mitosis by condensines, the drivers of chromosomal condensation.     

Promoters of genes MTHFR from patients with hyperhomocysteinemia and PTEN from patients with malignant and benign endometrial and ovarian tumors

Mutational changes in the promoter regions of MTHFR genes from patients with hyperhomocysteinemia and PTEN genes from patients with endometrial and ovarian tumors were studied. An increased level of homocysteine was found in a part of the patients with a heterozygous C677T mutation in the MTHFR gene, although a moderate hyperhomocysteinemia is usually associated with homozygous mutation. We hypothesized that, in this case, the allele lacking the C677T mutation may be inactivated by the promoter mutation. The sequencing of both DNA strands of the minimal promoter region of the MTHFR gene in ten patients did not reveal any mutation, which implied another mechanism of the development of hyperhomocysteinemia in these patients. A PCR analysis of the minimal promoter region of the tumor suppressor PTEN in the presence of 2-pyrrolidone in 101 patients from Moscow clinics revealed changes in it in patients with endometrial (56%) or ovarian (29%) cancer, as well as in patients with endometrial hyperplasia and benign ovarian tumors (34 and 29%, respectively). It was presumed that the found modification of PTEN gene promoters may arise from epigenetic alterations (erroneous methylation) or may (more rarely) be induced by mutations. As a result of the studies, new molecular markers associated with endometrial and ovarian tumors were revealed and a simple and effective method of detection of these markers was developed.     

Inorganic models of photosystem II of plant photosynthesis. Catalytic and photocatalytic oxidation of water with participation of manganese compounds

Manganese dioxide is shown to be the catalyst of oxygen evolution at the oxidation of water by the one-electron oxidant Ru(bpy)₃³⁺ in neutral and slightly acidic media. Catalytic activity of MnO₂ depends on the method of preparation, the most active samples being those consisting of the smallest particles, i.e., having the largest surface-to-volume ratio. Ru(bpy)₃³⁺ was found to be formed at the irradiation of Ru(bpy)₃²⁺ solutions by visible light (λ = 436 nm) in the presence of such acceptors as Ce(IV), Hg(II), and Mn(IV) pyrophosphate. Continuous O₂ evolution from water is observed when the system Mn(IV) pyrophosphate plus Ru(bpy)₃²⁺ plus MnO₂ is irradiated by visible light. The system is discussed in connection with the active center of photosystem II of plant photosynthesis.     

Multielectron Oxidation of Water in a Chemical Model of the Active Center of Photosystem II of Natural Photosynthesis

Doklady Biochemistry and Biophysics -     

Comprehensive proteomic analysis of human cervical-vaginal fluid using colposcopy samples

Background  

Cervical-vaginal fluid (CVF) plays an important role in the prevention of gynecological infections, although little is known about the contribution of CVF proteins to the immunity of the lower female genital tract. In order to analyze the protein composition of human CVF, we used CVF samples that are routinely collected during colposcopy, but are usually discarded. Since these samples are available in large quantities we aimed to analyze their usefulness for proteomics experiments. The samples were analyzed using different prefractionation techniques (ultrafiltration and C₄(RP)-LC protein separation) followed by C₁₈(RP)-LC peptide separation and identification by MALDI-TOF-TOF mass spectrometry. To determine the reproducibility of this proteomics platform we analyzed three technical replicates. Using spectral counting, protein abundances were estimated in a semiquantitative way. We also compared the results obtained in this study with those from previous studies derived from patients with different physiological conditions in order to determine an overlapping protein set.     

Functional Interactions of the Influenza Virus Glycoproteins

Hemagglutinin (HA) and neuraminidase (NA) are functionally related envelope glycoproteins of the influenza virus (Flu). HA interacts with terminal sialyl residues of oligosaccharides and ensures the binding of the virus particle to the cell surface. NA is a receptor-destroying enzyme that removes sialyl residues from oligosaccharides contained in cell and virus components and thereby prevents aggregation of virus particles. Analysis of reassortants combining low-functional NA of human Flu with HA of avian Flu showed that sialyl residues are not completely removed in some cases. With high HA affinity for sialyl substrates, such virus particles aggregate, aggregates accumulate on the cell surface, and virus yield decreases. Serial passaging of low-yield aggregating reassortants may lead to selection of high-yield variants, which do not aggregate. The loss of aggregation is due to a decrease in HA affinity for high-molecular-weight sialyl substrates. On evidence of sequencing of the HA gene in original reassortants and their nonaggregating variants, for different HA antigenic subtypes (H2, H3, H4, and H13) the affinity is reduced and aggregation lost through a common mechanism: an increase in the negative charge as a result of an amino acid substitution in the vicinity of the receptor-binding pocket of HA. Taken together, these findings suggest a way of postreassortment adaptation, which improves the functional match of HA and NA. The experimental system employed provides a model of natural processes associated with emergence of Flu variants having a pandemic potential.