Recombinant Protein L 1

Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), a leaf protein, has an interesting amino acid profile and promising functional properties. Incorporated in wheat-based products, it would increase their protein content and improve their essential amino acid profile, particularly lysine. The impact of rubisco enrichment on wheat dough mechanical properties and protein-protein interactions was investigated using Dynamic Mechanical Thermal Analysis and Size-Exclusion chromatography, respectively. Experiments were also performed on gluten and pea protein enriched doughs as a comparison. Wheat doughs with increasing concentrations of rubisco, gluten or pea proteins (from 0 to 33% of total proteins) were prepared using a 2 g-mixograph at constant hydration. In contrast to pea proteins and gluten, rubisco does not reduce dough stiffening during heating, probably due to its own reactivity to temperature and to low competition with starch for water. Detailed analysis of protein interactions showed that rubisco is part of the gluten network formed during dough mixing through the establishment of weak and disulphide bonds. In addition, rubisco subunits form new covalent bonds during the heat treatment thereby increasing the concentration of SDS insoluble high molecular weight aggregates. These results suggest that rubisco actively participates in the formation of the dough protein network. The colocation of gluten and rubisco proteins on micrographs supports the hypothesis that they form a co-protein network.

The interaction of L-cysteine with bismuth compounds bismuth(III) salicylate, bismuth(III) citrate, and bismuth(III) nitrate, was studied at pH 1.0 (0.100 M HNO(3)and 0.100 M HCl) and pH 7.4 MOPS buffer by cyclic voltammetry at glassy carbon and boron-doped diamond electrodes. pH 1.0, at which bismuth (III) exists as the simple Bi(3+)ion, was chosen to approximate the acid strength of stomach contents. pH 7.4, at which bismuth(III) exists as BiO, was used for its similarity to general physiological conditions. The amino acid L-cysteine was chosen because its sulfhydryl group undergoes intense interaction with many metal cations, serving as a model for cysteine-containing proteins in the digestive system. It was determined that Bi(III) and L-cysteine (Cys) form soluble complexes at both pH 1.0 and pH 7.4. UV-vis spectroscopic investigations support interaction of Bi(III) and L-cysteine to form a 1:2 Bi(III): Cys complex in pH 7.4 MOPS buffer. L-cysteine addition to solutions of the pharmaceutical bismuth(III) salicylate was found to alter the voltammetric behavior of the salicylate complex. These results, especially at pH 1.0, are relevant to understanding the interaction of various cysteine-containing proteins in the human digestive system with bismuth pharmaceuticals and may help guide future explorations of bismuth formulations.