The influence of sunlight on the localized corrosion of UNS S31600 in natural seawater

Tests were conducted on the performance of UNS S31600 stainless steel (SS) in a natural day/night cycle vs full darkness under conditions of natural marine biofilm accumulation. In quiescent flowing seawater tests in the laboratory as well as under natural immersion in the sea, diffuse sunlight (～10% of natural) counteracted the influence of marine biofilms and produced substantial inhibition of the corrosion of SS. Thus, the probabilities (percentage attack) and propagation rates (depths of attack) in multiple crevice tests were substantially lower in the day/night cycle than in the dark. A benefit was also observed for welded SS in terms of the time to corrosion initiation and the mass loss. SS in the passive state showed broader passive regions, well-defined breakdown potentials and markedly smaller anodic and cathodic current densities under the diurnal cycle. The overall reduction in corrosion is attributed to a combination of electrochemical photoinhibition and simultaneous photoinactivation of microbially mediated metal redox reactions linked to cathodic kinetics. These data offer fresh insights into the behaviour of SS under practical seawater situations and the proposed potential use of illumination in the mitigation of biologically influenced consequences.     

Epidemiology of typhoid carriers among blood donors and patients with biliary, gastrointestinal and other related diseases

Enteric fever due to Salmonella Typhi is a major public health problem. Typhoid carriers have high titres of Vi agglutinins in their sera. We worked out the baseline data for Vi agglutinins from 705 healthy blood donors (controls) by ELISA and compared it with 446 patients with biliary, gastrointestinal and other related diseases (cases). The samples were divided into five groups based on the disease condition of the patients from whom they were collected. Group A (n=196) consisted of patients with stones in the gall bladder/common bile duct and Group B (n=27) with gall bladder carcinoma. Group C (n=33) comprised patients with carcinoma of the pancreas/ampulla, obstructive jaundice and/or cholangiocarcinoma. Group D (n=112) had patients with acute/chronic pancreatitis, abdominal pain, intestinal obstruction, peritonitis, carcinoma oesophagus, chronic diarrhoea, gastrointestinal bleeding and dyspepsia. Group E (n=78) included patients with miscellaneous diseases. The mean absorbance value obtained for healthy subjects +3 standard deviations was taken as the cut-off value for a positive typhoid carrier. In Group A, 10.2% samples were positive; in Group B, 7.4%; in Group C, 12.0%; in Group D, 9.8% and in Group E, 9.0%. There was a highly significant (P <0.001) increase in the presence of Vi agglutinins in the cases compared to the controls. High prevalence of typhoid carriers occurs in patients with biliary, gastrointestinal and other related diseases. Vi serology employing highly purified Vi antigen offers a practical and cost-effective way of screening for S. Typhi carriers.     

Thermo-optically Induced Reorganizations in the Main Light Harvesting Antenna of Plants. I. Non-Arrhenius Type of Temperature Dependence and Linear Light-intensity Dependencies

Thermo-optically induced structural reorganizations have earlier been identified in isolated LHCII, the main chlorophyll a/b light harvesting complexes of Photosystem II, and in granal thylakoid membranes [Cseh et al. (2000) Biochemistry 39: 15250–15257; Garab et al. (2002) Biochemistry 41: 15121–15129]. According to the thermo-optic mechanism, structural changes can be induced by fast, local thermal transients due to the dissipation of excess excitation energy. In this paper, we analyze the temperature and light-intensity dependencies of thermo-optically induced reversible and irreversible reorganizations in the chiral macrodomains of lamellar aggregates of isolated LHCII and of granal thylakoid membranes. We show that these structural changes exhibit non-Arrhenius type of temperature dependencies, which originate from the ‘combination’ of the ambient temperature and the local thermal transient. The experimental data can satisfactorily be simulated with the aid of a simple mathematical model based on the thermo-optic effect. The model also predicts, in good accordance with experimental data published earlier and presented in this paper, that the reorganizations depend linearly on the intensity of the excess light, a unique property that is probably important in light adaptation and photoprotection of plants.     

Features of ribosome-peptidyl-tRNA interactions essential for tryptophan induction of tna operon expression

Certain nascent peptide sequences, when within the ribosomal exit tunnel, can inhibit translation termination and/or peptide elongation. The 24 residue leader peptidyl-tRNA of the tna operon of E. coli, TnaC-tRNA(Pro), in the presence of excess tryptophan, resists cleavage at the tnaC stop codon. TnaC residue Trp12 is crucial for this inhibition. The approximate location of Trp12 in the exit tunnel was determined by crosslinking Lys11 of TnaC-tRNA(Pro) to nucleotide A750 of 23S rRNA. Methylation of nucleotide A788 of 23S rRNA was reduced by the presence of Trp12 in TnaC-tRNA(Pro), implying A788 displacement. Inserting an adenylate at position 751, or introducing the change U2609C in 23S rRNA or the change K90H or K90W in ribosomal protein L22, virtually eliminated tryptophan induction. These modified and mutated regions are mostly located near the putative site occupied by Trp12 of TnaC-tRNA(Pro). These findings identify features of the ribosomal exit tunnel essential for tna operon induction.     

Biophysical approaches for studying the integrity and function of tight junctions

Cell-cell adhesion is an extremely important phenomenon as it influences several biologically important processes such as inflammation, cell migration, proliferation, differentiation and even cancer metastasis. Furthermore, proteins involved in cell-cell adhesion are also important from the perspective of facilitating better drug delivery across epithelia. The adhesion forces imparted by proteins involved in cell-cell adhesion have been the focus of research for sometime. However, with the advent of nanotechnological techniques such as the atomic force microscopy (AFM), we can now quantitatively probe these adhesion forces not only at the cellular but also molecular level. Here, we review the structure and function of tight junction proteins, highlighting some mechanistic studies performed to quantify the adhesion occurring between these proteins and where possible their association with human diseases. In particular, we will highlight two important experimental techniques, namely the micropipette step pressure technique and the AFM that allow us to quantify these adhesion forces at both the cellular and molecular levels, respectively.     

Protective effect of active oxygen scavengers on protein degradation and photochemical function in photosystem I submembrane fractions during light stress

The protective role of reactive oxygen scavengers against photodamage was studied in isolated photosystem (PS) I submembrane fractions illuminated (2000 microE x m(-2) x s(-1)) for various periods at 4 degrees C. The photochemical activity of the submembrane fractions measured as P700 photooxidation was significantly protected in the presence of histidine or n-propyl gallate. Chlorophyll photobleaching resulting in a decrease of absorbance and fluorescence, and a blue-shift of both absorbance and fluorescence maximum in the red region, was also greatly delayed in the presence of these scavengers. Western blot analysis revealed the light harvesting antenna complexes of PSI, Lhca2 and Lhca1, were more susceptible to strong light when compared to Lhca3 and Lhca4. The reaction-center proteins PsaB, PsaC, and PsaE were most sensitive to strong illumination while other polypeptides were less affected. Addition of histidine or n-propyl gallate lead to significant protection of reaction-center proteins as well as Lhca against strong illumination. Circular dichroism (CD) spectra revealed that the alpha-helix content decreased with increasing period of light exposure, whereas beta-strands, turns, and unordered structure increased. This unfolding was prevented with the addition of histidine or n-propyl gallate even after 10 h of strong illumination. Catalase or superoxide dismutase could not minimize the alteration of PSI photochemical activity and structure due to photodamage. The specific action of histidine and n-propyl gallate indicates that 1O2 was the main form of reactive oxygen species responsible for strong light-induced damage in PSI submembrane fractions.     

Molecular docking of potential inhibitors with the mTOR protein

The mTOR (mammalian or mechanistic Target of Rapamycin) is linked with oral cancer. Therefore, it is of interest to study the molecular docking-based binding of paclitaxel (a FDA approved drug for oral cancer) and its analogues with mTOR. Hence, we report the binding features of 10-Deacetyltaxol, 7-Epi-10-deacetyltaxol, 7-Epi-Taxol and 6alpha-Hydroxypaclitaxel with mTOR for further consideration.     

Assessment of dominance hierarchy through urine scent marking and its chemical constituents in male blackbuck Antelope cervicapra, a critically endangered species

In ungulates the process of chemical communication by urinary scent marking has been directly related to reproductive dominance, territorial defense and proximity to resources. The differences in the frequency of urine marking and chemical composition of urine of males Antelope cervicapra before, during and after the dominance hierarchy period were assessed. The variations in the urine marking and its chemical profiles of dominant males (n = 9), bachelors (n = 5) and sub-adult males (n = 5) were compared to find out how the dominance hierarchy influences the confined blackbuck herd under semi-natural captive conditions. The frequency of urine marking is significantly higher (p < 0.001) in dominant males. Twenty-eight major constituents were identified in the urine of dominant males (before, during and after the dominance hierarchy period), bachelor and sub-adult males. Among these, three specific compounds namely, 3-hexanone (I), 6-methyl-5-hepten-2-one (II) and 4-methyl-3-heptanone (III) were seen only in dominant males urine during the dominance hierarchy period. Based on the behavioural observation and the unique chemical constituents in the urine, it is concluded that the dominant male scent odor suppresses aggression, scent marking, scent production and territorial patrolling activities of subordinate males, through which the dominant male establish their hierarchy and attains success in reproduction.