Properties and Activity of Peptide Derivatives of ACE2 Cellular Receptor and Their Interaction with SARS-CoV-2 S Protein Receptor-Binding Domain.

The aim of this work was to design and characterize peptides based on the α-helices h1 and h2 of the ACE2 receptor, forming the interaction interface between the receptor-binding domain (RBD) of the SARS-CoV-2 S protein and the cellular ACE2 receptor. Monomeric and heterodimeric peptides connected by disulfide bonds at different positions were synthesized. Solubility, RBD-binding affinity, and peptide helicity were experimentally measured, and molecular dynamics simulation was performed in various solvents. It was established that the preservation of the helical conformation is a necessary condition for the binding of peptides to RBD. The peptides have a low degree of helicity and low affinity for RBD in water. Dimeric peptides have a higher degree of helicity than monomeric ones, probably due to the mutual influence of helices. The degree of helicity of the peptides in trifluoroethanol is the highest; however, for in vitro studies, the most suitable solvent is a water-ethanol mixture.

Procoagulant Platelets: Mechanisms of Generation and Action.

During the past decades, it has been increasingly recognized that the major function of accelerating membrane-dependent reactions of blood coagulation is predominantly implemented by a subset of activated platelets. These procoagulant platelets (also called collagen- and thrombin-activated or COAT, coated, necrotic, although there could be subtle differences between these definitions) are uniquely characterized by both procoagulant activity and, at the same time, inactivated integrins and profibrinolytic properties. The mechanisms of their generation both in vitro and in situ have been increasingly becoming clear, suggesting unique and multidirectional roles in hemostasis and thrombosis. In this mini-review, we shall highlight the existing concepts and challenges in this field.

Programmed Cell Death and Functional Activity of Platelets in Case of Oncohematologic Diseases.

Programmed cell death of non-nucleated blood cells - platelets - could be associated with pathophysiology of oncologic and oncohematologic diseases. It contributes to both bleedings (caused by the thrombocytopenia, which is induced by elimination of the platelets) and thrombosis (caused by the processes of blood coagulation on the surface of phosphatidylserine exposing platelets). Here we characterized functional responses of platelets from the patients with various oncological disorders undergoing chemotherapy and compared them to the platelets from the healthy donors and platelets pre-incubated with apoptosis inducer ABT-737. Some patients exhibited diminished capability of platelets to aggregate. Immunophenotyping of these platelets revealed their pre-activation in comparison to the platelets from the healthy donors. Calcium signaling analysis revealed that in the patient-derived platelets, as well as in the apoptotic platelets, intracellular calcium levels were increased in resting cells. However, moderate level of this increase together with weak expression of phosphatidylserine allows us to assume that apoptotic processes in the circulating platelets from the patients are limited.

New insights into ligand binding by plant lipid transfer proteins: A case study of the lentil Lc-LTP2.

Lipid transfer proteins (LTPs) are an important class of plant proteins containing an internal cavity and binding hydrophobic ligands. Although LTP structures and functions are well studied, mechanisms of ligand binding remain unclear. Earlier, we discovered the lentil lipid transfer protein Lc-LTP2 capable of binding and transfer various ligands. We have shown that the "bottom" entrance of the Lc-LTP2 cavity takes part in attachment to the micelle surface and in lipids uptake. Here, we studied the role of Arg45 and Tyr80, located at the "bottom" entrance, in Lc-LTP2 ligand binding. We obtained recombinant mutant analogs of Lc-LTP2 (R45A, Y80A, R45A/Y80A), investigated their ability to bind fatty acids and lysolipids, as well as performed molecular modeling of the protein-ligand complexes. We showed that replacement of one or both residues led to a change of the internal hydrophobic cavity dimensions. As a result, lipids may change their orientation into the protein cavity, and thereby binding ability of mutant analogs may be affected as well. In the present work, we revealed an important role of Arg45 and Tyr80 in stabilization of the Lc-LTP2 complexes with both fatty acids and lysolipids with different ligand orientation.

Functional characteristics and clinical effectiveness of platelet concentrates treated with riboflavin and ultraviolet light in plasma and in platelet additive solution.

BACKGROUND AND OBJECTIVES: Pathogen reduction technologies may affect platelet quality during storage. We studied functional characteristics and clinical effectiveness of platelet concentrates (PCs) treated with Mirasol in plasma and in platelet-additive solution SSP+. MATERIALS AND METHODS: Mirasol-treated, gamma-irradiated and untreated apheresis PCs were examined on days 0, 1, 3 and 5 of storage. Phosphatidylserine, P-selectin and active glycoprotein IIb/IIIa were analysed using flow cytometry before and after platelet stimulation. Platelet count increments, the numbers of inefficient transfusions and post-transfusion reactions were analysed to estimate clinical effectiveness. RESULTS: A significant increase in all platelet activation markers occurred during storage in all PC groups. Activation markers in Mirasol-treated samples were already significantly higher compared with the control ones on the day of harvesting, and continued to grow during the storage. Mirasol treatment increased the number of platelets with a mitochondrial membrane potential loss. On the 3rd day of storage, 50% of Mirasol-treated platelets did not respond to activation; on the 5th day, none did. This agreed well with a decrease (approximately twofold) in the effectiveness of Mirasol-treated PC transfusions. Transfusions of PCs stored in SSP+ were accompanied by fewer inefficient transfusions and post-transfusion reactions than of PCs stored in plasma. CONCLUSION: Treatment with Mirasol decreased platelet function, particularly profoundly on the 5th day of storage, and led to a decrease in the effectiveness of transfusions. SSP+ did not affect laboratory parameters significantly compared with plasma, but decreased the percentage of transfusion complications.

[Interaction of the photosensitizer 13,15-N-(3'-hydroxypropyl)cycloimide of chlorin p(6) with normal and cancerous blood cells].

The interaction of 13,15-N-(3'-hydroxypropyl)cycloimide of chlorin p(6) (CIC) with normal blood cells and human K562 and HL60 myeloid leukemia cells was studied. CIC was found to be bound by the erythrocyte membrane but did not penetrate into the cytoplasm. It is characterized by a diffuse distribution in the cytoplasm of normal leukocytes, whereas its diffuse distribution in K562 and HL60 cells is accompanied by perinuclear accumulation and binding to the plasma membrane. The average cytoplasmic concentration corresponding to the CIC accumulation in leukemic cells at saturation is 2.2 to 2.6 times higher than that in normal leukocytes. CIC is more intensely accumulated in granulocytes than in lymphocytes. The kinetics of the cellular uptake and efflux was characterized. The normal leukocytes and erythrocytes were found to be 1.5 times and 3 to 4 times less sensitive, respectively, to the photodynamic action of CIC than the K562 and HL60 cells.

[Effect of catabolic plasmids on physiological parameters and efficiency of oil destruction by bacteria of the genus Pseudomonas].

The ability of microbial degraders of polycyclic aromatic hydrocarbons to grow at 24 degrees C in liquid mineral medium supplemented with oil as the sole source of carbon and energy was studied. Growth characteristics (CFU) and the level of oil destruction by plasmid-bearing and plasmid-free strains were determined after seven days of cultivation. The presence of catabolic plasmids in the degrader strains, including rhizosphere pseudomonads, was shown to increase cell growth and enhance the level of oil degradation. Strain Pseudomonas chlororaphis BS 1391 bearing plasmid pBS216 was found to be the most effective oil degrader.