Effects of polyphenols on the gel and digestive properties of Penaeus vannamei myosin after freezing.

Polyphenols could inhibit the freezing-induced denaturation of myosin, and affect its nutritional and functional properties, which have rarely been studied to date. Therefore, the effects of interactions between polyphenols and myosin after freezing on myosin gel and digestive properties were investigated using low field NMR, a texture analyzer, a dynamic rheometer, ultraviolet-visible spectra, scanning electron microscopy, LC-MS/MS, an automatic amino acid analyzer, etc. Hesperetin (HE), dihydroquercetin (DI), salidroside (SA), and mangiferin (MA) increased the water-holding capacity, non-flowable water content, gel strength, texture, storage modulus, and fractal dimensions of the myosin gel, while modifying its leading force. The results of scanning electron microscopy revealed that the surfaces of polyphenol groups were relatively smoother than those of the control group. Meanwhile, the four types of polyphenols under study significantly improved the gastric and gastrointestinal digestibility of myosin. Furthermore, they significantly increased the contents of essential, flavor, and total free amino acids, as well as the unique peptide numbers in myosin digestion products. This work provides reliable guidance for polyphenols to improve protein function and nutritional properties.

Fluorescence spectra study the perturbations of CopC native fold by 2-p-toluidinynaphthalene-6-sulfonate.

2-p-Toluidinynaphthalene-6-sulfonate (TNS) was discovered to perturb native fold of CopC protein and to induce loss of biological activity to some extent which was dependent on TNS concentration. Hydrophobic and electrostatic interactions were revealed to account for the perturbation by comparison with some analogy. TNS, with far low concentration of 10(-5) to 10(-4)M, is presented as a denaturant. So TNS should be deliberated in detecting macromolecular conformation change as single evidence at higher concentration.