Recently, Roht et al. [J. Contam. Hydrol., 2013, 145, 10-16] observed that the presence of suspended non-Brownian macroscopic particles decreased the dispersivity of a passive solute, for a pressure-driven flow in a narrow parallel-plate channel at low Reynolds numbers. This result contradicts the idea that the streamline distortion caused by the random diffusive motion of the particles increas...

A cyclic sulfur compound, identified as cysteine thiolactone by several chemical and enzymatic tests, is formed from cysteine during in vitro tRNA(Cys) aminoacylation catalyzed by Escherichia coli cysteinyl-tRNA synthetase. The mechanism of cysteine thiolactone formation involves enzymatic deacylation of Cys-tRNA(Cys) (k = 0.017 s-1) in which nucleophilic sulfur of the side chain of cysteine in...

Moderately elevated plasma homocysteine levels are an important independent risk factor for arterial and venous thrombosis and for atherosclerosis. Some investigators have proposed that homocysteine's effects result from oxidant injury to the vascular endothelium or from an alteration in endothelial function. However, homocysteine may have other cellular targets. We now report that homocysteine...

A cyclic sulfonium compound, S-methyl homocysteine thiolactone (SMHT), is formed from methionine during in vitro tRNA aminoacylation catalyzed by Escherichia coli methionyl-tRNA synthetase. The mechanism of SMHT formation involves enzymatic deacylation of Met-tRNA (k = 0.06 s-1) and, to a lesser extent, Met-AMP (k = 0.02 s-1). Cyclization of methionine, reminiscent of cyclization of homocystein...

Homocysteine (Hcy) is an accepted independent risk factor for several major pathologies including cardiovascular disease, birth defects, osteoporosis, Alzheimer's disease, and renal failure. Interestingly, many of the pathologies associated with homocysteine are also linked to oxidative stress. The enzyme paraoxonase (PON1) - so named because of its ability to hydrolyse the toxic metabolite of ...

shop. I am indebted for capable research assistance to Naomi Roht-Arriaza and Ellen Hertz. Ellen played a particularly vital role, providing conceptual enrichment, incisive intellect and warm nurturance throughout the finishing stages of this project. My special thanks go to James Tessier whose intellectual and personal contributions extend far beyond ordinary research assistance. Without Jim's...

Accumulating evidence suggests that homocysteine (Hcy) metabolite, the thioester Hcy-thiolactone, plays an important role in atherothrombosis. Hcy-thiolactone is a product of an error-editing reaction in protein biosynthesis which forms when Hcy is mistakenly selected by methionyl-tRNA synthetase. The thioester chemistry of Hcy-thiolactone underlies its ability to from isopeptide bonds with pro...