muramidase and 2-5-dihydroxybenzoic-acid

Both microbiological and chemical food spoilages remain to be the major challenges in the food industry's efforts to combat food waste and loss because of the lack of high efficacy food preservatives. In this study, dual-functional conjugates that simultaneously suppress both lipid oxidation and microorganism growth are fabricated by covalently conjugating natural antioxidant gentisic acid (GA) on native antibacterial lysozyme (Lys). The mixing ratio of Lys and GA determines the particle size, morphology, antioxidant activity, and antimicrobial performance of the ensuing conjugates. With more of GA being grafted, a drastic decrease in the net surface charge with the concomitant occurrence of aggregations are observed in the conjugates. The maximum antioxidant activity and antibacterial performance of the conjugates is achieved when Lys:GA molar ratio is 1:112. The findings could guide the rational design of future functional food ingredients that combine multiple natural bioactive compounds to effectively intervene food waste and loss.

Topics: Anti-Bacterial Agents; Anti-Infective Agents; Antioxidants; Food; Gentisates; Muramidase; Refuse Disposal

Ions in Matrix-Assisted Laser Desorption/Ionization (MALDI) are predominantly singly charged for small analyte molecules. With the estimated high number density and low temperature of electrons, the three-body recombination mechanism is attractive and should be considered as an important cause for the charge reduction in the plume. Theoretical calculations indicate that the rate coefficient of the three-body recombination is about 50 times higher than that of the two-body recombination if the analyte molecule has insufficient degrees of freedom. Experimental results show that, for small analyte molecules, the ratio of AH2(2+)/AH(+) is close to the theoretical 5% value from the three-body recombination modeling and this ratio declines with the increasing electron and matrix molecule number density caused by greater laser irradiance. The ratio of [A + 2](+)/[A + 1](+) is higher than the theoretical isotopic value, and the excess [A + 2](+) could exclusively result from the three-body recombination collisions. Further evidence demonstrates that [A + 2](+)/[A + 1](+) increases with electron number density, which is in correspondence with the model. All of these theoretical and experimental results indicate that three-body recombination is an essential charge reduction mechanism for small molecules in the MALDI plume.

Topics: Bacitracin; Coumaric Acids; Gentisates; Lasers; Muramidase; Oncogene Protein pp60(v-src); Oxidation-Reduction; Peptide Fragments; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization