Characterization and partial purification of the human receptor for the heat-stable enterotoxin

The receptor for the Escherichia coli heat-stable enterotoxin has been characterized and partially purified from the T84 human colonic cell line. Using a novel mutant heat-stable enterotoxin peptide as a radioligand (the C-terminal tyrosine residue is replaced by phenylalanine in the mutant), a single class of high-affinity receptor sites was detected in T84 cells, with a K<SUB>d</SUB> of 0.1 nM, similar in affinity to the receptor described in human intestinal tissue. The receptor was solubilised from T84 cell membranes and affinity cross-linking of the solubilised preparation indicated that a single species of M<SUB>r</SUB> 160000 served as the receptor. Freshly solubilised preparations of the receptor retained heat-stable enterotoxin-activable guanylyl cyclase activity. Purification of the receptor was achieved through sequential affinity chromatography on GTP-epoxy-Sepharose and wheat-germ-agglutinin columns resulting in purification of the receptor by 3000 fold. The heat-stable enterotoxin-binding characteristics of the receptor were unchanged during the purification and silver staining of the purified receptor preparation indicated a band of M<SUB>r</SUB> 160000, which was specifically cross-linked to the <SUP>125</SUP>I-labeled mutant peptide. The purified receptor retained guanylyl cyclase activity, but the activity was not stimulated on addition of human heat-stable enterotoxin, suggesting that accessory structural factors may be involved in the activation of the guanylyl cyclase/receptor

Use of bacterial lipase for scouring of cotton fabrics

299-302Attempt has been made to analyse the efficiency of bacterial lipase as a scouring agent for raw cotton fabrics to remove the natural hydrophobic substances present in the fibre. Improvement in the drop absorbency is observed to significant extent in the lipase scoured fabric samples and the lowest absorbency time of the treated sample is observed at 2 s, though the extractable impurities are at higher levels (2.14%). FTIR results show reduction in the band intensities related to hydroxyl stretch, and symmetric and asymmetric stretching of alkyl groups attributable to the waxy substances present in the raw cotton fibres

Bleaching of cotton fabrics using hydrogen peroxide produced by glucose oxidase

281-283Bleaching effect of cotton fabrics using hydrogen peroxide produced by glucose oxidase enzyme from Aspergillus niger has been studied. It is observed that enzymes are highly active at acidic pH under room temperature in terms of peroxide release during the reaction. Incomplete conversion of glucose by the enzyme results in discolouration of the reaction bath and the fabrics under alkaline pH conditions. External supply of oxygen and mechanical agitation during initial stage of reaction influence the conversion of glucose into hydrogen peroxide and whiteness index of bleached samples

2-Amino-5-nitropyridinium trifluoroacetate

The title salt, C5H6N3O2+&#183;C2F3O2&#8722;, crystallizes with two cations and two anions in the asymmetric unit. In the crystal, the acetate and pyridine groups are linked by a pair of N&#8212;H...O hydrogen bonds, forming loops described by the graph-set motif R22(8). These loops are linked via N&#8212;H...O hydrogen bonds, forming chains along [001]. The chains are in turn linked by C&#8212;H...O and C&#8212;H...F hydrogen bonds, generating a three-dimensional supramolecular network. In both anions, the O and F atoms are disordered over two sites, with occupancy ratios of 0.852&#8197;(3):0.148&#8197;(3) and 0.851&#8197;(3):0.149&#8197;(3)

Simple and Rapid Method To Determine Antimycobacterial Potency of Compounds by Using Autoluminescent Mycobacterium tuberculosis

A major obstacle in the process of discovery of drugs against Mycobacterium tuberculosis is its extremely slow growth rate and long generation time (similar to 20 to 24 h). Consequently, determination of MICs and minimum bactericidal concentrations (MBCs) of potential drug candidates using current methods requires 7 days (resazurin-based MIC assay [REMA]) and 1 month (CFU enumeration), respectively. We employed a synthetic luciferase operon optimized for expression in high-GC-content bacteria and adapted it for use in mycobacteria. Using luminescence-based readouts, we were able to determine the MICs and bactericidal activities of approved tuberculosis (TB) drugs, which correlated well with currently used methods. Although luminescence-based readouts have been used previously to determine the MICs and bactericidal activities of approved TB drugs, in this study we adapted this assay to carry out a pilot screen using a library of 1,114 compounds belonging to diverse chemical scaffolds. We found that MICs derived from a 3-day luminescence assay matched well with REMA-based MIC values. To determine the bactericidal potencies of compounds, a 1:10 dilution of the cultures from the MIC plate was carried out on day 7, and the bactericidal concentrations determined based on time to positivity in 2 weeks were found to be comparable with MBC values determined by the conventional CFU approach. Thus, the luminescent mycobacterium-based approach not only is very simple and inexpensive but also allowed us to generate the information in half the time required by conventional methods

Biarylmethoxy Nicotinamides As Novel and Specific Inhibitors of <i>Mycobacterium tuberculosis</i>

A whole cell based screening effort on a focused library from corporate collection resulted in the identification of biarylmethoxy nicotinamides as novel inhibitors of <i>M. tuberculosis</i> (Mtu) H37Rv. The series exhibited tangible structure–activity relationships, and during hit to lead exploration, a cellular potency of 100 nM was achieved, which is an improvement of >200-fold from the starting point. The series is very specific to Mtu and noncytotoxic up to 250 μM as measured in the mammalian cell line THP-1 based cytotoxicity assay. This compound class retains its potency on several drug sensitive and single drug resistant clinical isolates, which indicate that the compounds could be acting through a novel mode of action