Precise measurement of the half-life of 6¹Cu.

The decay characteristics of (61)Cu allow for a precise determination of its half-life. In order to search for a possible influence of the chemical environment on the decay rate, the half-life of (61)Cu in nickel and nickel-oxide was measured with high precision. The results show a small difference in the half-life that can be explained by the differences in electron density at the site of the nucleus. A discussion about the validity of the adopted value of the total angular momentum of the 656 keV state in (61)Ni is presented.

Complexes of green tea polyphenol, epigalocatechin-3-gallate, and 2S albumins of peanut.

2S albumins of peanuts are seed storage proteins, highly homologous in structure and described as major elicitors of anaphylactic reactions to peanut (allergens Ara h 2 and Ara h 6). Epigallocatechin-3-gallate (EGCG) is the most biologically potent polyphenol of green tea. Non-covalent interactions of EGCG with proteins contribute to its diverse biological activities. Here we used the methods of circular dichroism, fluorescence quenching titration, isothermal titration calorimetry and computational chemistry to elucidate interactions of EGCG and 2S albumins. Similarity in structure and overall fold of 2S albumins yielded similar putative binding sites and similar binding modes with EGCG. Binding affinity determined for Ara h 2 was in the range described for complexes of EGCG and other dietary proteins. Binding of EGCG to 2S albumins affects protein conformation, by causing an α-helix to ß-structures transition in both proteins. 2S albumins of peanuts may be good carriers of physiologically active green tea catechin.

Interactions of epigallo-catechin 3-gallate and ovalbumin, the major allergen of egg white.

Polyphenols, the potent plant secondary metabolites, have beneficial effects on human health, but the mechanism(s) by which these effects are exerted is not well understood. Here, we present the detailed analysis of the interactions between the major green tea catechin, epigallo-catechin 3-gallate (EGCG), and the major dietary protein and allergen, ovalbumin (OVA). We show that EGCG binds to the pocket that partly overlaps with the previously identified IgE-binding region in OVA, and that this interaction induces structural changes in the allergen. Moreover, our ex vivo studies reveal that OVA binds IgE and stimulates degranulation of basophils, and that its uptake by monocytes proceeds at a slower rate in the presence of EGCG. This study provides further evidence in support of the proposed mechanism by which EGCG interactions with the food allergens contribute to its diverse biological activities and may impair antigen uptake by antigen-presenting cells.

Binding affinity between dietary polyphenols and ß-lactoglobulin negatively correlates with the protein susceptibility to digestion and total antioxidant activity of complexes formed.

Non-covalent interactions between ß-lactoglobulin (BLG) and polyphenol extracts of teas, coffee and cocoa were studied by fluorescence and CD spectroscopy at pH values of the gastrointestinal tract (GIT). The biological implications of non-covalent binding of polyphenols to BLG were investigated by in vitro pepsin and pancreatin digestibility assay and ABTS radical scavenging activity of complexes formed. The polyphenol-BLG systems were stable at pH values of the GIT. The most profound effect of pH on binding affinity was observed for polyphenol extracts rich in phenolic acids. Stronger non-covalent interactions delayed pepsin and pancreatin digestion of BLG and induced ß-sheet to α-helix transition at neutral pH. All polyphenols tested protected protein secondary structure at an extremely acidic pH of 1.2. A positive correlation was found between the strength of protein-polyphenol interactions and (a) half time of protein decay in gastric conditions (R(2)=0.85), (b) masking of total antioxidant capacity of protein-polyphenol complexes (R(2)=0.95).