Influence of chitin nanofibrils ultrasonic treatment on structure and properties of chitosan-based composite materials.

The influence of ultrasonic treatment parameters of chitin nanofibrils aqueous suspension on structure, strength and deformation properties of chitosan-based composite films and fibers was investigated. Model calculations of ultrasound-induced cavitation parameters in the aqueous suspension of the chitin nanofibrils showed that an increase in the field power up to 630 W led to destruction of the cavity, to an increase in the temperature in the vicinity of cavitation area (up to 507 °C) and, as a consequence, to destruction of chitin glycoside ring (which is confirmed by the IR data). The results of light scattering, IR spectroscopy, and electron microscopy investigations indicated that the optimal duration of ultrasonic treatment of the chitin nanofibrils aqueous solution was 4-10 min (depending on oriented state of the scaffold). Tensile strength of the composites was 130 ± 11 MPa (films), 226 ± 4.8 MPa (fibers); deformation at break was 43 ± 7.5% (films), 10 ± 0.6% (fibers).

[Effect of synthetic cationic peptides on activation of the adenylyl cyclase signaling system by biogenic amines in muscle tissue of molluscs and rats]. / Vliianie sinteticheskikh kationnykh peptidov na aktivatsiiu adenilattsiklaznoi signal'noi sistemy biogennymi aminami v myshechnykh tkaniakh molliuskov i krys.

The hormone-sensitive adenylyl cyclase signaling system (ACS), made of serpentine receptor, heterotrimeric G-protein and enzyme adenylyl cyclase (AC), regulates a wide spectrum of growth and metabolic processes in the cell. Molecular mechanisms of functional coupling of ACS components still remain obscure. We examined the influence of synthetic cationic peptides Ac-Ala-His(Ala)2-His-Ala-NH2 (I), Ac-Ala-His-(Ala)3-His-(Ala)2-His-Ala-NH2 (II), and Ac-(Pro)2-His-(Ala)2-His-(Ala)3-His-(Ala)2-His-Ala-NH2 (III) on the basal AC activity and that stimulated by nonhormonal (NaF) and hormonal reagents (serotonin--molluscs, beta-isoproterenol--rats) in smooth muscles of the freshwater bivalve molluscs Anodonta cygnea and in skeletal muscles of rats. Peptides II and III (the latter more effective) were shown to decrease hormone-stimulated AC activity in both tissues, in a dose-dependent manner. Peptide III strongly reduced NaF stimulating effect to AC, which suggests the involvement of this peptide in the functional coupling of both receptors with G-proteins, and of G-proteins with AC. A correlation was found between the efficacy of peptide action on the functional activity of ACS components and peptide length. As shown by IR-spectroscopy, in water all peptides can form helical structures. However, alpha-helicity of peptides I and II was higher than that of peptide III, which does not conform to a power series in efficacy of these peptides. Thus, it is the length of cationic peptides that plays a key role in hormonal regulation of the functional activity of ACS, especially on the step of receptor-G-protein coupling.