The dissociation constants of the following substituted phenols in 50 wt percent methanol have been measured at 25 °C: o-nitrophenol, p-nitrophenol, 4-methyl-2-nitrophenol, 2,6-di chlorophenol , pentachlorophenol. The respective values found, expressed as pK values, are 7.91" 7.692 , 8.28" 7.680 , and 5.27.. The dissociation cons tants of 4-methyl-2-nitrophenol and pentachlorophenol, again exp ...

A prominent enzyme in organellar RNA metabolism is the exoribonuclease polynucleotide phosphorylase (PNPase), whose reversible activity is governed by the nucleotide diphosphate-inorganic phosphate ratio. In Chlamydomonas reinhardtii, PNPase regulates chloroplast transcript accumulation in response to phosphorus (P) starvation, and PNPase expression is repressed by the response regulator PSR1 (...

Purine nucleoside phosphorylase (PNP; EC: 2.4.2.1) is a key enzyme involved in the purine salvage pathway. A recent bioinformatic study by Yadav, P. K. et al. (Bioinformation 2012, 8(14), 664-672) reports PNP as an essential enzyme and potential drug target in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). We conducted an analysis using the methodology outlined by the...

BACKGROUND We measured 34 metabolites of current-use pesticides and other precursor compounds in urine samples collected twice during pregnancy from 538 women living in the Salinas Valley of California, a highly agricultural area (1999-2001). Precursors of these metabolites included fungicides, carbamate, organochlorine, organophosphorus (OP), and pyrethroid insecticides, and triazine and chlor...

A mixed microbial culture was adapted to growth on parathion to determine the feasibility of using microorganisms to detoxify concentrated parathion in agricultural wastes. In a 600-ml chemostat, the culture was able to degrade 50 mg of parathion per liter per h. Para-nitrophenol, produced by enzymatic hydrolysis of parathion, caused delays in exponential growth which were directly proportional...

An environmental actinomycetes, capable of utilizing p-nitrophenol as its sole carbon and nitrogen source, was starved for an 8-week period and showed no reduction in its ability to biodegrade p-nitrophenol. Microscopic examination revealed that starvation of the bacterium resulted in the fragmentation of filaments into individual cells.

Housefly UDP-glucosyltransferase activity towards p-nitrophenol was demonstrated in a system in vitro. The activity is localized in the microsomal fraction, requires UDPglucose, is slightly stimulated by Mg2+ and is activated optimally over a wide range of detergent concentration. Phenobarbital increases the enzyme(s) activity about 3-fold, with p-nitrophenol as substrate, which differs from th...

1. Two enzymes (A and B) which catalyse the sulphation of p-nitrophenol and l-tyrosine methyl ester have been isolated from female rat livers. One of these enzymes (A) also catalyses the sulphation of dehydroepiandrosterone. 2. The K(m) values for the sulphation of p-nitrophenol and l-tyrosine methyl ester by enzyme B at pH7.5 are 1.5mum and 2.9mm respectively. 3. Enzyme B is oxidized on keepin...

Harmful effects of contaminants on the ecosystem and humans cannot be assessed by standard chemical analyses of environmental samples, therefore toxicity tests using live organisms or cells represent a vital part of environmental monitoring. Biological methods based on microorganisms as test-species, have already successfully been applied to environmental toxicity/genotoxicity assessment. The e...