Examination of molecular mechanism for the enhanced thermal stability of anthocyanins by metal cations and polysaccharides.

Anthocyanins exhibit colour variation over wide pH range but the colour stability is relatively low at the physiological pH. To improve the stability of anthocyanins in neutral to weakly acidic pH region, effects of metal cations and polysaccharides on the colour stability of cyanidin-3-glucoside (C3G) were examined by ultraviolet-visible and resonance Raman spectroscopies. C3G was thermally stabilized by the addition of Fe(3+) but formed aggregation. However, further addition of anionic polysaccharides enhanced the thermal stability of C3G without aggregation. Similar stabilisation was confirmed for delphinidin-3-glucoside (D3G) but not for pelargonidin-3-glucoside. The stability of anthocyanins considerably varied depending on pHs and kinds of metal cations, polysaccharides and buffer molecules. The characteristic resonance Raman bands of C3G-Fe(3+) and D3G-Fe(3+) complexes were significantly affected by the addition of alginate, (18)O/(16)O-isotope substitution, and Fe(2+)/Fe(3+)-replacement. These results suggest that alginate associates with C3G through Fe(3+) to form a stable complex, which enhances the thermal stability of C3G.

Generation and evaluation of an anti-REV1 monoclonal antibody.

Continuous exposure of cells to exogenous and endogenous agents produces many types of DNA damage during normal cell cycles. Post-replication repair, consisting of error-free and error-prone sub-pathways, is required for tolerance of such DNA damage. REV1 plays a crucial role in regulation of the error-prone pathway. To facilitate analysis of its cellular functions, we here generated a mouse Rev1 monoclonal antibody, called D6, which also recognizes human REV1. The epitope for the antibody could be mapped between 860-877 amino acid residues of human REV1, which was located outside of the conserved catalytic domain. Although the antibody unfortunately could not specifically detect endogenous mouse and human REV1 by western blotting and immunohistochemistry, we established a method to identify endogenous human REV1 by immunoprecipitation-western blotting analysis combining D6 and separately generated polyclonal antibodies.