N-Terminal segment of potato virus X coat protein subunits is glycosylated and mediates formation of a bound water shell on the virion surface.

The primary structures of N-terminal 19-mer peptides, released by limited trypsin treatment of coat protein (CP) subunits in intact virions of three potato virus X (PVX) isolates, were analyzed. Two wild-type PVX strains, Russian (Ru) and British (UK3), were used and also the ST mutant of UK3 in which all 12 serine and threonine residues in the CP N-terminal segment were replaced by glycine or alanine. With the help of direct carbohydrate analysis and MS, it was found that the acetylated N-terminal peptides of both wild-type strains are glycosylated by a single monosaccharide residue (galactose or fucose) at NAcSer in the first position of the CP sequence, whereas the acetylated N-terminal segment of the ST mutant CP is unglycosylated. Fourier transform infrared spectra in the 1000-4000 cm(-1) region were measured for films of the intact and in situ trypsin-degraded PVX preparations at low and high humidity. These spectra revealed the presence of a broad-band in the region of valent vibrations of OH bonds (3100-3700 cm(-1)), which can be represented by superposition of three bands corresponding to tightly bound, weakly bound, and free OH groups. On calculating difference ('wet' minus 'dry') spectra, it was found that the intact wild-type PVX virions are characterized by high water-absorbing capacity and the ability to order a large number of water molecules on the virus particle. This effect was much weaker for the ST mutant and completely absent in the trypsin-treated PVX. It is proposed that the surface-located and glycosylated N-terminal CP segments of intact PVX virions induce the formation of a columnar-type shell from bound water molecules around the virions, which probably play a major role in maintaining the virion surface structure.     

Effect of Low-Intensity Pulsed Electric Fields on the Respiratory Activity and Electrosurface Properties of Bacteria

A change in the respiratory activity (RA) of the resistant to cyanide bacteria Pseudomonas fluorescens under the pulsed electric field treatment has been found experimentally. The bacteria reaction to the field treatment (rectangular impulses with the duration of 1 ms, voltage of 20 V, and frequency of 100 Hz) varied from the RA suppression of active culture to restoration and even stimulation of RA in cells with the decreased respiratory function, caused by the cyanide introduction. The interconnection of energetic membrane processes with the electrosurface properties of biocolloids has been demonstrated: The electrokinetic potential had been varied simultaneously with the respiratory activity change. Theoretical analysis of the experimental data indicates the change of quantity of active respiratory centers in cells under the influence of the pulsed electric field. These changes have reversible character. Depending on the state of bacteria, the processes of inhibition or restoration of the respiratory centers by the pulsed electric field can be observed.     

Anti-inflammatory properties of intestinal Bifidobacterium strains isolated from healthy infants

Certain Bifidobacterium strains have been shown to inhibit inflammatory responses in intestinal epithelial cells. However, the precise mechanisms of these effects, including the chemical nature of the active compounds, remain to be elucidated. Here partial characterization of the anti-inflammatory properties of Bifidobacterium strains isolated from feces of healthy infants is reported. It was found that conditioned media (CM) of all strains studied are capable of attenuating tumor necrosis factor-α (TNF-α) and lipopolysaccharide- (LPS) induced inflammatory responses in the HT-29 cell line. In contrast, neither killed bifidobacterial cells, nor cell-free extracts showed such activities. Further investigations resulted in attribution of this activity to heat-stable, non-lipophilic compound(s) resistant to protease and nuclease treatments and of molecular weight less than 3 kDa. The anti-inflammatory effects were dose- and time-dependent and associated with inhibition of IκB phosphorylation and nuclear factor-κ light chain enhancer of activated B cells (NF-κB)-dependent promoter activation. The combined treatments of cells with CMs and either LPS or TNF-α, but not with CMs alone, resulted in upregulation of transforming growth factor-β1, IκBζ, and p21(CIP) mRNAs. Our data suggest certain species-specificities of the anti-inflammatory properties of bifidobacteria. This observation should prompt additional validation studies using larger set of strains and employing the tools of comparative genomics.     

A Comparison of Brain Gene Expression Levels in Domesticated and Wild Animals

Domestication has led to similar changes in morphology and behavior in several animal species, raising the question whether similarities between different domestication events also exist at the molecular level. We used mRNA sequencing to analyze genome-wide gene expression patterns in brain frontal cortex in three pairs of domesticated and wild species (dogs and wolves, pigs and wild boars, and domesticated and wild rabbits). We compared the expression differences with those between domesticated guinea pigs and a distant wild relative (Cavia aperea) as well as between two lines of rats selected for tameness or aggression towards humans. There were few gene expression differences between domesticated and wild dogs, pigs, and rabbits (30–75 genes (less than 1%) of expressed genes were differentially expressed), while guinea pigs and C. aperea differed more strongly. Almost no overlap was found between the genes with differential expression in the different domestication events. In addition, joint analyses of all domesticated and wild samples provided only suggestive evidence for the existence of a small group of genes that changed their expression in a similar fashion in different domesticated species. The most extreme of these shared expression changes include up-regulation in domesticates of SOX6 and PROM1, two modulators of brain development. There was almost no overlap between gene expression in domesticated animals and the tame and aggressive rats. However, two of the genes with the strongest expression differences between the rats (DLL3 and DHDH) were located in a genomic region associated with tameness and aggression, suggesting a role in influencing tameness. In summary, the majority of brain gene expression changes in domesticated animals are specific to the given domestication event, suggesting that the causative variants of behavioral domestication traits may likewise be different.     

Co-expression of the Thermotoga neapolitana aglB gene with an upstream 3'-coding fragment of the malG gene improves enzymatic characteristics of recombinant AglB cyclomaltodextrinase

A cluster of Thermotoga neapolitana genes participating in starch degradation includes the malG gene of sugar transport protein and the aglB gene of cyclomaltodextrinase. The start and stop codons of these genes share a common overlapping sequence, aTGAtg. Here, we compared properties of expression products of three different constructs with aglB from T. neapolitana. The first expression vector contained the aglB gene linked to an upstream 90-bp 3'-terminal region of the malG gene with the stop codon overlapping with the start codon of aglB. The second construct included the isolated coding sequence of aglB with two tandem potential start codons. The expression product of this construct in Escherichia coli had two tandem Met residues at its N terminus and was characterized by low thermostability and high tendency to aggregate. In contrast, co-expression of aglB and the 3'-terminal region of malG (the first construct) resulted in AglB with only one N-terminal Met residue and a much higher specific activity of cyclomaltodextrinase. Moreover, the enzyme expressed by such a construct was more thermostable and less prone to aggregation. The third construct was the same as the second one except that it contained only one ATG start codon. The product of its expression had kinetic and other properties similar to those of the enzyme with only one N-terminal Met residue.     

Analysis of the role of the coat protein N-terminal segment in Potato virus X virion stability and functional activity

Previously, we have reported that intact Potato virus X (PVX) virions cannot be translated in cell-free systems, but acquire this capacity by the binding of PVX-specific triple gene block protein 1 (TGBp1) or after phosphorylation of the exposed N-terminal segment of intravirus coat protein (CP) by protein kinases. With the help of in vitro mutagenesis, a nonphosphorylatable PVX mutant (denoted ST PVX) was prepared in which all 12 S and T residues in the 20-residue-long N-terminal CP segment were substituted by A or G. Contrary to expectations, ST PVX was infectious, produced normal progeny and was translated in vitro in the absence of any additional factors. We suggest that the N-terminal PVX CP segment somehow participates in virion assembly in vivo and that CP subunits in ST virions may differ in structure from those in the wild-type (UK3 strain). In the present work, to test this suggestion, we performed a comparative tritium planigraphy study of CP structure in UK3 and ST virions. It was found that the profile of tritium incorporation into ST mutant virions in some CP segments differed from that of normal UK3 virions and from UK3 complexed with the PVX movement protein TGBp1. It is proposed that amino acid substitutions in ST CP and the TGBp1-driven remodelling of UK3 virions induce structural alterations in intravirus CPs. These alterations affect the predicted RNA recognition motif of PVX CP, but in different ways: for ST PVX, labelling is increased in α-helices 6 and 7, whereas, in remodelled UK3, labelling is increased in the β-sheet strands β3, β4 and β5.     

A survey of toxicity of cyanobacterial blooms in Lake Ladoga and adjacent water bodies

Twentyfive cyanobacterial blooms in Lake Ladoga and adjacent water bodies were studied in the summer of 1990–1992. Toxicity of the water bloom material for mice was detected in 9 cases. The maximal tolerable doses (MTD) of the material extracted from biomass varied within 3–30 mg kg^–1 mouse body weight; 50% lethal doses (LD₅₀) were within 45–125 mg kg^–1. Toxic water blooms were registered in Karelian lakes and in the Neva Bay, Gulf of Finland. Cyanobacterial samples collected on the eastern coast of Lake Ladoga proved to be non-toxic. The species identified in toxic bloom material included Anabaena circinalis, A. flos-aquae, A. lemmermannii, Anabaena sp., Aphanizomenonflos-aquae, Gloeotrichia echinulata, G. pisum, Microcystis aeruginosa and Oscillatoria sp. These data suggest that toxic forms of cyanobacteria are widespread in Karelian lakes belonging to the drainage basin of Lake Ladoga.     

An Air‐Stable and Dendrite‐Free Li Anode for Highly Stable All‐Solid‐State Sulfide‐Based Li Batteries

Li metal is a promising anode material for all‐solid‐state batteries, owing to its high specific capacity and low electrochemical potential. However, direct contact of Li metal with most solid‐state electrolytes induces severe side reactions that can lead to dendrite formation and short circuits. Moreover, Li metal is unstable when exposed to air, leading to stringent processing requirements. Herein, it is reported that the Li₃PS₄/Li interface in all‐solid‐state batteries can be stabilized by an air‐stable Li_xSiS_y protection layer that is formed in situ on the surface of Li metal through a solution‐based method. Highly stable Li cycling for over 2000 h in symmetrical cells and a lifetime of over 100 cycles can be achieved for an all‐solid‐state LiCoO₂/Li₃PS₄/Li cell. Synchrotron‐based high energy X‐ray photoelectron spectroscopy in‐depth analysis demonstrates the distribution of different components within the protection layer. The in situ formation of an electronically insulating Li_xSiS_y protection layer with highly ionic conductivity provides an effective way to prevent Li dendrite formation in high‐energy all‐solid‐state Li metal batteries.     

Characterization and potential antitumor effect of a heteropolysaccharide produced by the red alga Porphyridium sordidum

Taking into account the rising trend of the incidence of cancers of various organs, effective therapies are urgently needed to control human malignancies. However, almost all chemotherapy drugs currently on the market cause serious side effects. Fortunately, several studies have shown that some non‐toxic biological macromolecules, including algal polysaccharides, possess anti‐cancer activities or can increase the efficacy of conventional chemotherapy drugs. Polysaccharides are characteristic secondary metabolites of many algae. The efficacy of polysaccharides on the normal and cancer cells is not well investigated, but our investigations proved a cell specific effect of a newly isolated extracellular polysaccharide from the red microalga Porphyridium sordidum. The investigated substance was composed of xylose:glucose and galactose:manose:rhamnose in a molar ratio of 1:0.52:0.44:0.31. Reversible electroporation has been exploited to increase the transport through the plasma membrane into the tested breast cancer tumor cells MCF‐7 and MDA‐MB231. Application of 75 µg/mL polysaccharide in combination with 200 V/cm electroporation induced 40% decrease in viability of MDA‐MB231 cells and changes in cell morphology while control cells (MCF10A) remained with normal morphology and kept vitality.