Tannin-albumin particles as stable carriers of medicines.

Background: The effectiveness of a drug is dependent on its accumulation at the site of therapeutic action, as well as its time in circulation. The aim of the research was the creation of stable albumin/tannin (punicalagin, punicalin) particles, which might serve for the delivery of medicines. Methods: Numerous chromatographic and analytical methods, docking analyses and in vivo testing were applied and used. Results: Stable tannin-albumin/medicine particles with a diameter of ∼100 nm were obtained. The results of in vivo experiments proved that tannin-albumin particles are more stable than albumin particles. Conclusion: Based on the experiments and docking analyses, these stable particles can carry an extended number of medicines, with diverse chemical structures.

Experimental Clarification of PRPS-1 Structural Essentials.

Phosphoribosyl pyrophosphate synthetase-1 (PRPS-1; EC 2.7.6.1.) catalyzes the binding of phosphate-group to ribose 5-phosphate, forming the 5-phosphoribosyl-1-pyrophosphate, which is necessary for the salvage pathways of purine and pyrimidine, pyridine nucleotide cofactors - NAD and NADP, the amino acids histidine and tryptophan biosynthesis. We aimed to investigate the impact of the different effectors on the activity of PRPS-1, to check the activity of the enzyme in vitro in a wide range of pHs and investigate some structural essentials of the enzyme, isolated from brain and liver. Molecular docking analyses were used to delineate the essentials of PRPS-1 structure, to find out the existence of enzyme effectors. Previously created by us kit was used for determination of the activity of PRPS-1 based on the formation of the inorganic phosphates (λ = 700 nm, Cary 60, Agilent, USA). Effectors impact on the activity of PRPS-1 was evaluated. In silico results of the effectors were later proven by in vitro experiments. For the first time biochemical essentials, including the existence of the multiple pockets, involvement of the amino acids into the processes of interactions with the effectors, evolutional of the sequence conservation, tissue depended Vmax differences were identified.

Molecular Simulations and Markov State Modeling Reveal Inactive Form of Quorum Sensing Regulator SdiA of Escherichia Coli.

Enteropathogenic Escherichia coli remains one of the most important pathogens infecting children and it is one of the main causes of persistent diarrhea worldwide. Enteropathogenic Escherichia coli is capable of forming biofilms. Several E. coli mechanisms are regulated by quorum sensing, including virulence factors and biofilm formation. Quorum sensing is the communication system of bacteria with the ability to respond to chemical molecules known as autoinducers. Suppressor of division inhibitor (SdiA) is a quorum sensing receptor present in enteropathogenic E. coli in humans that detect acyl-homoserine lactone type autoinducers. SdiA receptor can also respond to autoinducers produced by other bacterial species that control cell division and virulence. SdiA is regulated by 1-octanoyl-rac-glycerol, which serves as an energy source, signaling molecule, and substrate for membrane biogenesis. SdiA is a potential target, which can be used as an anti-infectious technique. Current crystallographic structures for virtual screening may not be sufficient for molecular docking. So they are not very predictive, because the structures are in the active form. It has been shown that SdiA protein is not activated without a ligand. Generally, ligands bind to the ligand binding domain of SdiA. We employ Markov modeling and molecular dynamics simulations to understand the behaviour of SdiA protein and find the possible inactive form. We find an unknown conformation after 24 molecular dynamics simulation runs with random initial velocities and Markov state modeling. In summary, using molecular simulations and Markov state modeling, we have obtained an unknown conformation, which is not available in the crystallographic structures of SdiA. This unknown conformation could be the structure of the inactive form without a ligand. The obtained ensemble structures could be used for virtual screening.

Biphasic dose-response of antioxidants in hypericin-induced photohemolysis.

In the present paper the photodynamic effect of hypericin on superoxide dismutase activity and the possibility of reduction of hypericin phototoxicity by antioxidants were studied. It was shown an almost twice decrease in superoxide dismutase activity of red blood cells under the photosensitization by hypericin. The influence of antioxidants (ascorbic acid and quercetin) on hypericin photodynamic action has revealed that these antioxidants suppress or stimulate photohemolysis caused by hypericin. The photosensitization reaction realized by hypericin could be shifted from type II to type I or vice versa by manipulating the antioxidant concentration. Strengthening of photohemolysis by antioxidants in some concentrations indicates the switching of alternative mechanisms of hypericin photodynamic action and its complicated manner. Thus the selection of antioxidant concentrations is of extreme importance for changing the efficacy of photodynamic therapy with hypericin.