Quantitative structure-activity relationship study on some dihydropteridine reductase inhibitors

The dihydropteridine reductase (DHPR) inhibitory potencies of some 4-phenyltetrahydropyridines, 4-phenylpiperidines, and 4-phenylpyridines, are analyzed in relation to their physico-chemical and molecular properties. They are found to have significant correlation with Hammett constant sigma and the van der Waals volume Vw. The correlation is linear with sigma and parabolic with Vw. Hence, it is argued that DHPR inhibition involves dispersion interaction and is enhanced by electron donation from the substituents but hindered by steric effects produced by large substituents. It is also found that these electronic and steric effects are significant only when they are produced by substituents being at specific position in the molecules.     

Molecular mapping and transfer of a novel brown planthopper resistance gene bph42 from Oryza rufipogon (Griff.) To cultivated rice (Oryza sativa L.)

Molecular Biology Reports - Brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests of rice accounting for 52% of annual yield loss. The breakdown of...     

Continuous production of pectic oligosaccharides from sugar beet pulp in a cross flow continuous enzyme membrane reactor

Bioprocess and Biosystems Engineering - Sugar beet pulp pectin is an attractive source for the production of pectic oligosaccharides, an emerging class of potential prebiotics. The main aim of the...     

Obligatory and period specific requirement of iron for microspore embryogenesis inDatura metel anther cultures

The experiments to assess the role of iron in morphogenesis of microspore-derived plantlets in anther cultures ofDatura metel revealed that even on iron-deficient medium androgenesis is initiated but the induced units fail to grow beyond multicellular stage, if anthers are not transferred to iron-incorporated medium. Another important conclusion drawn from an experiment involving weekly transfer of anthers from nutrient medium lacking both iron source (ferrous sulfate, FeSO₄·7H₂O, 10^?4 M) and chelate (disodium salt of ethylene diamine tetraacetic acid, C₁₀H₁₄N₂Na₂O₈·2H₂O, 10^?4 M) to that containing both of these or vice-versa, is that iron if present during the initial culture period, in fact affects the plantlet yield adversely. Thus, anthers cultured on iron-deficient medium, for initial one or two weeks and then transferred to iron-containing medium, yielded higher number of plantlets than those developed from anthers cultured continuously on complete basal medium having both iron and chelate.     

Fucose and sialic acid contents of intestinal microvillus membranes from different animal species

Fucose and sialic acid contents of intestinal microvillus membranes isolated from different animal species have been analysed. Expressed on protein basis, brush borders from fish contained considerably high amounts of sialic acid (298 +/- 16 nmole/mg protein), while rat, goat, sheep and guinea pig membranes showed 41-61 nmole/mg protein. Pig, frog, monkey rabbit and chicken membranes exhibited low levels of sialic acid (10-13 nmole/mg protein). Fucose content of the brush borders was quite high (203-212 nmole/mg protein) in frog and fish intestines. It was least in rabbit (54 +/- 3) and of intermediate levels (80-122 nmole/mg protein) in various other animal species analysed. Fucose to sialic acid molar ratio was less than 1 in fish microvillus membranes. In all other animal species, the ratio was however, greater than one and ranged between 1.65 and 15.20.     

pH-dependent glycine uptake in the presence and absence of sodium ions from rat small intestine

Intestinal uptake of glycine in rats was stimulated 15-20% in the presence of 120 mM Na at pH 6.0 and below but around neutral pH, the amino acid uptake was augmented to 60% compared to that in the Na-free medium. Glycine uptake was 30% more at pH 5.5 compared to that at pH 7.3 in the absence of Na. Kinetic analysis revealed a decrease in Kt for glycine uptake (9.62 mM) at pH 5.5 compared to that at pH 7.3 (Kt = 16.67 mM) with no change in maximal velocity (1.51 mumole/10 min/g tissue) in Na-free buffer. Addition of -SH group reacting reagents to the incubation medium produced 36-58% inhibition of glycine uptake in the presence of Na. However, in absence of Na, inhibition of the order of 21-35% and 8-23% was observed at pH 5.5 and 7.0, respectively. These findings suggest that glycine uptake in rat intestine is influenced by pH and -SH groups are implicated in the process(es).     

Milk-Clotting Enzymes From Microorganisms

A total of 230 cultures of fungi and 43 cultures of bacteria, isolated from such sources as soil, butter, and milk, were screened for their milk-clotting activity. The fungi were cultivated on semisolid media, and the bacteria were grown in milk media in shake culture. Phytic acid, added as calcium phytate, was found to stimulate production of the enzyme in most of the bacterial isolates. Proteolytic activity was invariably found to be associated with the milk-clotting enzyme in bacterial isolates. There was considerable variation in the ratio of the two enzymes from strain to strain.