RNA cleavage and inhibition of protein synthesis by bleomycin

Bleomycin is a clinically used antitumor antibiotic long thought to function therapeutically at the level of DNA cleavage. Recently, it has become clear that bleomycin can also cleave selected members of all major classes of RNA. Using the computer program COMPARE to search the database established by the Anticancer Drug Screening Program of the National Cancer Institute, a possible mechanism-based correlation was found between onconase, an antitumor ribonuclease currently being evaluated in phase III clinical trials, and the chemotherapeutic agent bleomycin. Following these observations, experimentation revealed that bleomycin caused tRNA cleavage and DNA-independent protein synthesis inhibition in rabbit reticulocyte lysate and when microinjected into Xenopus oocytes. The correlation of protein synthesis inhibition to the previously reported site-specific RNA cleavage caused by bleomycin supports the thesis that RNA cleavage may constitute an important element of the mechanism of action of bleomycin.     

Sound absorption in a colloidal solution of interacting particles

The absorption of sound in a colloidal solution is studied with allowance for interaction between microparticles or nanoparticles. It is shown that electrostatic repulsion, which is typical of charged colloids used in science and engineering, leads to an increase in absorption, all other factors being the same. This is related to the fact that the effective correlation length characterizing the motion of particles increases when the interparticle interaction becomes stronger.     

Electrical and magnetic properties of mercury selenide doped with nickel and chromium

The electrical properties of mercury selenide single-crystals doped with nickel and chromium are studied over the temperature range 80–400 K in magnetic fields of 0–8 kOe. It is established that in the mercury selenide lattice the impurity Ni is electrically and magnetically inactive. With growth in Cr concentration the paramagnetism of mercury selenide specimens increases. Results of a study of magnetic susceptibility are compared to theoretical calculations for a point model and a point model with consideration of covalence effects.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 44–47, November, 1990.     

On generation of sound by an internal bore

Internal bores are nonlinear internal waves that move toward the coast and have a characteristic steplike shape to their fronts. The bore is a frequent phenomenon for shelf zones of seas and oceans. The passage of the bore leads to a substantial change in the conditions of sound propagation in the sea medium and, generally, to the formation of a near-bottom sound channel. In this work, we theoretically consider another effect of the aforementioned phenomenon on underwater acoustics, namely, the generation of sound by the internal bore propagating over the bottom.     

Formation of silver nanoparticles at the air-water interface mediated by a monolayer of functionalized hyperbranched molecules

Nanofibrillar micellar structures formed by the amphiphilic hyperbranched molecules within a Langmuir monolayer were utilized as matter for silver nanoparticle formation from the ion-containing water subphase. We observed that silver nanoparticles were formed within the multifunctional amphiphilic hyperbranched molecules. The diameter of nanoparticles varied from 2-4 nm and was controlled by the core dimensions and the interfibrillar free surface area. Furthermore, upon addition of potassium nitrate to the subphase, the Langmuir monolayer templated the nanoparticles' formation along the nanofibrillar structures. The suggested mechanism of nanoparticle formation involves the oxidation of primary amino groups by silver catalysis facilitated by "caging" of silver ions within surface areas dominated by multibranched cores. This system provides an example of a one-step process in which hyperbranched molecules with outer alkyl tails and compressed amine-hydroxyl cores mediated the formation of stable nanoparticles placed along/among/beneath the nanofibrillar micelles.