Inhibition of heat-induced protein aggregation by zirconium phthalocyanines.

Specific proteins found in food sources tend to aggregate into fibrils under heat treatment; studying these aggregation processes and developing tools to control protein heat-induced aggregation is an active area of research. Phthalocyanine complexes are known to exhibit antiprionic and anti-fibrillogenic activity. Thus, the anti-fibrillogenic effect of a series of Zr phthalocyanines with different out-of-plane coordinated ligands, namely positively charged (PcZrLys2 ), negatively charged (PcZrCitr2 ), and group able to form disulfide bridges (PcZrS2 ), on the heat-induced aggregation of such proteins as BLG, insulin, and lysozyme was studied. The inhibition of reaction activity up to about 90% was observed in the presence of these compounds for all proteins. The effective concentration of the inhibitor was calculated for the compound with the highest activity (PcZrS2 ) to be 10.6 ± 3.6 and 7.3 ± 1.2 µM/L, respectively. Fluorescence spectroscopy studies demonstrated similar binding constants of three phthalocyanines binding with BLG globule. This is consistent with the results of molecular dynamics simulation, which imply the interaction of the globule with the tetrapyrrole macrocycle of phthalocyanine, leading to the globule stabilization. At the same time, TEM shows that in the presence of phthalocyanine PcZrS2 , thinner and longer fibrils were formed compared to control in all three proteins (BLG, insulin, and lysozyme). Thus, we can conclude that phthalocyanine PcZrS2 affects the amyloid aggregation's general mechanism, which is typical for proteins of different structures. Therefore, the phthalocyanine PcZrS2 is proposed as an anti-amyloidogenic agent suppressing heat-induced aggregation of proteins of different structures, making it potentially suitable for application in the food industry.

Effect of Priestia endophytica on the metabolites accumulation in chicory and lettuce plants cultivated in vitro.

The influence of the culture medium without bacterial cells, obtained after the cultivation of endophytic bacteria Priestia endophytica UCM B-5715, on the growth and synthesis of some metabolites in lettuce and chicory seedlings under in vitro conditions was studied. Bacteria were cultivated in liquid LB medium at 37 ºC for 24 h with periodic stirring. The culture fluid was separated from the cell biomass. For preparing the test solution, the supernatant was sterilized by filtration through a filter with a pore diameter of 0.2 µm (Sartorius, Minisart) and diluted with sterile distilled water. The 20% culture fluid (30 µl/plant) was applied to 3-day-old seedlings. In 28 days root and shoot weights of treated chicory plants were 54.3 ± 6.9 and 260.0 ± 20.2 mg, respectively (8.0 ± 0.7 and 91.4 ± 7.0 mg for the control plants). Total flavonoid content and antioxidant activity increased only in chicory plants after the addition of the test solution. Significant changes in the metabolism of treated plants were detected. In the treated lettuce plants asparagine content increased compared to the control (90 vs 22 µg/g, p < 0.1). The median content of fructose was also higher in treated lettuce and chicory plants (1469 vs 73 µg/g and 2278 vs 1051 µg/g). Therefore, the use of culture fluid obtained after the cultivation of P. endophytica UСM B-5715 stimulated the growth of lettuce and chicory plants, affecting the synthesis of some compounds in single-treated plants. These results indicate the potential of compounds excreted during bacterial growth to create natural growth stimulators.