Plasma glutathione peroxidase activity and selenium levels of newborns with jaundice

The plasma glutathione peroxidase (GSH-Px) and selenium (Se) levels were determined in 31 newborns affected by jaundice (NWJ). The GSH-Px levels of both full-term and premature newborns exhibiting jaundice and having a birthweight lower than 2000 g were significantly low (p<0.05) when compared to controls. No significant differences were found in the corresponding Se levels, which were similar in all groups and independent of the pregnancy period and birthweight.     

Endosomal vacuoles of the prepupal salivary glands of Drosophila play an essential role in the metabolic reallocation of iron

In the recent past, we demonstrated that a great deal is going on in the salivary glands of Drosophila in the interval after they release their glycoprotein‐rich secretory glue during pupariation. The early‐to‐mid prepupal salivary glands undergo extensive endocytosis with widespread vacuolation of the cytoplasm followed by massive apocrine secretion. Here, we describe additional novel properties of these endosomes. The use of vital pH‐sensitive probes provided confirmatory evidence that these endosomes have acidic contents and that there are two types of endocytosis seen in the prepupal glands. The salivary glands simultaneously generate mildly acidic, small, basally‐derived endosomes and strongly acidic, large and apical endosomes. Staining of the large vacuoles with vital acidic probes is possible only after there is ambipolar fusion of both basal and apical endosomes, since only basally‐derived endosomes can bring fluorescent probes into the vesicular system. We obtained multiple lines of evidence that the small basally‐derived endosomes are chiefly involved in the uptake of dietary Fe³⁺ iron. The fusion of basal endosomes with the larger and strongly acidic apical endosomes appears to facilitate optimal conditions for ferrireductase activity inside the vacuoles to release metabolic Fe²⁺ iron. While iron was not detectable directly due to limited staining sensitivity, we found increasing fluorescence of the glutathione‐sensitive probe CellTracker Blue CMAC in large vacuoles, which appeared to depend on the amount of iron released by ferrireductase. Moreover, heterologous fluorescently‐labeled mammalian iron‐bound transferrin is actively taken up, providing direct evidence for active iron uptake by basal endocytosis. In addition, we serendipitously found that small (basal) endosomes were uniquely recognized by PNA lectin, whereas large (apical) vacuoles bound DBA lectin.     

Luminescence of aqueous solutions of glycine and its N-methyl derivatives

A nonmonotonous dependence of luminescence intensity of aqueous solutions of 0.1 M glycine and its N-methyl derivatives on the number of methyl groups in the solute molecule was found. A correlation between luminescence intensities and optical density at the excitation wavelength of 300 nm was revealed. Possible causes of the phenomenon observed were analyzed. Among these are: luminescence of admixtures, intrinsic luminescence of dissolved molecules, and luminescence related to the formation of nanoscale complexes in solution. On the basis of the data, it is impossible to make a final choice between the three above-mentioned mechanisms of luminescence of aqueous solutions of glycine and its N-methyl derivatives.     

A molecular dynamics simulation study of human alpha-fetoprotein-derived peptide and its analogues. Influence of dielectric constant

A comparative study of the conformation dynamics of a series of heptapeptides: the human alpha-fetoprotein fragment LDSYQCT and its seven analogues has been conducted. The effect of the dielectric constant of medium on the dynamics of heptapeptide conformation is considered. It is shown that electrostatic interactions have a marked effect on several accessible conformations and the dynamics of the behavior of amino acid residues.     

Optical properties of mixtures of beta-carotene and chlorophyll a adsorbed on bovine serum albumin

The fluorescence of the natural photosynthetic pigments beta-carotene (beta-K) and chlorophyll a (Chl) and their mixtures with bovine serum albumin (BSA) in different molar ratios has been studied. An increase in the fluorescence intensity in a pigment mixture-BSA complex was found. The highest possible (four- to sixfold) increase in the fluorescence intensity compared with fluorescence intensity of one-pigment BSA complexes BSA (beta-K) and BSA (Chl) was achieved at the ratio 11-27% beta-K/89-73% Chl in the BSA complex. A considerable overlap of fluorescence spectra of BSA (Chl) complex (lambda(max) at 690 nm) and BSA (beta-K) complex (lambda(max) at 684 nm) was observed.     

Analysis of the distribution of the nucleotide sequence and electrostatic potential of the Escherichia coli genome

The oligonucleotide composition of the E. coli genome and its sigma70-specific promoters has been analyzed. The promoter DNA was shown to contain mainly AT-rich hexanucleotides having functionally important physical properties such as the ability to form easily melting sites and induce the bending of the double helix. A comparative analysis of the electrostatic characteristics of hexanucleotides within the whole sequence of the E. coli genome and its promoter regions was made. Hexanucleotides possessing a more electronegative surrounding were found to predominate in the nucleotide sequence of the promoter DNA.     

Molecular dynamics simulations of migration of ions and molecules through the acetylcholine receptor channel

A dynamic model of the channel of an acetylcholine receptor in a closed state has been proposed. The channel is formed by five a-helices of subunit M2 and stabilized by the cyclic hydrocarbon (CH2)105. The migration of charged and unchanged van der Waals particles with a diameter of 7.72 A equivalent to the diameter of a hydrated sodium ion has been studied. The migration occurred by the action of external force applied to the complex along the channel axis. In the closed state, the inhibition of ions is due to two components: electrostatic interaction and steric constraints. The van der Waals channel gate is formed by residues 13'-A-Val255, B-Val261, C-Val269, D-Val255, and E-Ile264, and the negatively changed residues occurring in the upper part of the channel have a great effect on ion selectivity.