In the course of the reaction catalyzed by rhodanese, the enzyme cycles between two catalytic intermediates, the sulfur-free and the sulfur-substituted (persulfide-containing) forms. The crystal structure of sulfur-free rhodanese, which was prepared in solution and then crystallized, is highly similar to that of sulfur-substituted enzyme. The inactivation of sulfur-free rhodanese with a small molar excess of hydrogen peroxide relies essentially on a modification limited to the active site, consisting of the oxidation of the essential sulfhydryl to sulfenyl group (-S-OH). Upon reaction of the sulfur-free enzyme with monoiodoacetate in the crystal, the Cys-247 side chain with the bound carboxymethyl group is forced into a conformation that allows favorable interactions of the carboxylate with the four peptide NH groups that participate in hydrogen bonding interactions with the transferable sulfur atom of the persulfide group in the sulfur-substituted rhodanese. It is concluded that active site-specific chemical modifications of sulfur-free rhodanese do not lead to significant changes of the protein structure, consistent with a high degree of similarity of the structures of the sulfur-free and sulfur-substituted forms of the enzyme both in solution and in the crystal.

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Background: The relationship between suicide and alcohol consumption is well established at the individuallevel. In this article we examine this relationship at a national level across 98 different countries.Methods: The suicide and alcohol consumption rates considered were those calculated by the WHO (2008and 2004 database respectively). A simple correlation analysis was conducted and cross-national variationswere shown in cartograms with the values of the standard deviation as class breaks.Results: A significant positive association (r = 0.42 in the case of men, r = 0.34 in the case of women) emergedbetween per capita alcohol consumption and gender-specific suicide rates when we considered all the 98countries around the world for which data were available. When considering the group of ex-communistcountries alone, the correlation coefficient between alcohol consumption and suicide rates was higher andstatistically significant for both men (0.51) and women (0.47).Conclusions: Bivariate analysis at the country level delineates a worldwide association between suicide ratesand alcohol consumption. There were no countries where a high or moderate-high alcohol consumption ratecoincided with a low or medium-low suicide rate. Where alcohol consumption is high, there is an impacton suicide rates. Where it is low, this seems to have a protective effect, unless other suicide determinantsacquire a major role.Suicide is multi-factorial and the determinants may be different in any given country, multivariate analysisand local studies are therefore required.

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