Antibacterial effect of nisin in vitro

Results of experimental studies of antimicrobial action of gel compositions containing active substance nisin are presented in the article. It is shown that increasing concentration of nisin at constant concentrations of the other components in the mixture inhibits growth of Staphylococcus aureus and Pseudomonas aeruginosa. The optimal concentration of nisin at which the process of pathogens growth inhibition is the most effective was determined in the experiment

Investigation of physico-chemical characteristics of carboxymethylcellulose colloidal carriers for medical preparations

Introduction. Physico-chemical peculiarities of processes of preparation and aging of colloidal carriers (gels) based on carboxymethylcellulose (CMC) for medical preparations which are planned to be used as a treatment for burn wounds are considered in the article. Studies were conducted in the Central Scientific Research Laboratory of theKharkivNationalMedicalUniversity in 2019.The objectives of the study. The objective was to study the applicability of CMC solutions and their modified analogues for the gel-based pharmaceutical preparations.Material and methods. Experimental studies were carried out under laboratory conditions using equipment for viscosity and pH measuring.Results. The influence of concentration, temperature, and acidity on viscosity of gels was investigated. The gels were tested on aging during storage. The stability of these solutions and syneresis process were investigated. The influence of added modifiers – glycerol and ascorbic acid on the consistency, acidity, susceptibility to contamination and term of storage of the gels was determined.Conclusions. It is shown that unmodified solutions have the highest viscosity and the greatest stability. Increasing of temperature reduces duration of dissolution of CMC and viscosity of the gels. Modification by ascorbic acid significantly reduces viscosity and pH of gels, while addition of glycerol does not affect the stability but increases susceptibility of these solutions to contamination. Storage of obtained solutions for three months under normal conditions at room temperature leads to syneresis and total loss of initial consistency. The gels modified by ascorbic acid are shown to be the least stable. Graphic dependences of these processes are obtained and functions are calculated on the basis of experimental research with the use of mathematical modeling methods. The obtained models will allow to predict physical and chemical properties of gels in order to define the necessary parameters of preparation at the stage of development

Mie-resonances, infrared emission and band gap of InN

Mie resonances due to scattering/absorption of light in InN containing clusters of metallic In may have been erroneously interpreted as the infrared band gap absorption in tens of papers. Here we show by direct thermally detected optical absorption measurements that the true band gap of InN is markedly wider than currently accepted 0.7 eV. Micro-cathodoluminescence studies complemented by imaging of metallic In have shown that bright infrared emission at 0.7-0.8 eV arises from In aggregates, and is likely associated with surface states at the metal/InN interfaces.Comment: 4 pages, 5 figures, submitted to PR

Energy transfer from perovskite nanocrystals to dye molecules does not occur by FRET

Single formamidinium lead bromide (FAPbBr(3)) perovskite nanocubes, approximately 10 nm in size, have extinction cross sections orders of magnitude larger than single dye molecules and can therefore be used to photoexcite one single dye molecule within their immediate vicinity by means of excitation-energy transfer (EET). The rate of photon emission by the single dye molecule is increased by 2 orders of magnitude under excitation by EET compared to direct excitation at the same laser fluence. Because the dye cannot accommodate biexcitons, NC biexcitons are filtered out by EET, giving rise to up to an order-of-magnitude improvement in the fidelity of photon antibunching. We demonstrate here that, contrary to expectation, energy transfer from the nanocrystal to dye molecules does not depend on the spectral line widths of the donor and acceptor and is therefore not governed by Forster's theory of resonance energy transfer (FRET). Two different cyanine dye acceptors with substantially different spectral overlaps with the nanocrystal donor show a similar light-harvesting capability. Cooling the sample from room temperature to 5 K reduces the average transition line widths 25-fold but has no apparent effect on the number of molecules emitting, i.e., on the spatial density of single dye molecules being photoexcited by single nanocrystals. Narrow zero-phonon lines are identified for both donor and acceptor, with an energetic separation of over 40 times the line width, implying a complete absence of spectral overlap-even though EET is evident. Both donor and acceptor exhibit spectral fluctuations, but no correlation is apparent between the jitter, which controls spectral overlap, and the overall light harvesting. We conclude that the energy transfer process is fundamentally nonresonant, implying effective energy dissipation in the perovskite donor because of strong electron-phonon coupling of the carriers comprising the exciton. The work highlights the importance of performing cryogenic spectroscopy to reveal the underlying mechanisms of energy transfer in complex donor-acceptor systems

Detection of RNA Hydrolysis with Binase by Acridine Orange Fluorescence

© 2019, Pleiades Publishing, Inc. Abstract: Fluorescence spectroscopy was used to study the specific hydrolysis of ribosomal RNA by binase in aqueous buffer solutions. Acridine orange was used for RNA staining. When the dye was bound to RNA, its fluorescence intensity increased by two times due to the formation of a stable complex. During RNA hydrolysis by binase for 1–20 min, this complex was cleaved, which was accompanied by a nearly twofold decrease in fluorescence. The degree of polarization of the dye fluorescence during hydrolysis was reduced by a factor of 5.5. The hydrolysis reaction was slower at a pH of 5.0–6.0 than at a pH of 7.0–8.0, but it proceeded almost until the end. Hydrolysis was slowed with an increase in the ionic strength of the buffer and was suppressed by magnesium ions. The studied reaction can be further used as a convenient, selective, fluorometric method for the detection of single-stranded ribosomal RNA and the study of their properties

Detection of RNA Hydrolysis with Binase by Acridine Orange Fluorescence

© 2019, Pleiades Publishing, Inc. Abstract: Fluorescence spectroscopy was used to study the specific hydrolysis of ribosomal RNA by binase in aqueous buffer solutions. Acridine orange was used for RNA staining. When the dye was bound to RNA, its fluorescence intensity increased by two times due to the formation of a stable complex. During RNA hydrolysis by binase for 1–20 min, this complex was cleaved, which was accompanied by a nearly twofold decrease in fluorescence. The degree of polarization of the dye fluorescence during hydrolysis was reduced by a factor of 5.5. The hydrolysis reaction was slower at a pH of 5.0–6.0 than at a pH of 7.0–8.0, but it proceeded almost until the end. Hydrolysis was slowed with an increase in the ionic strength of the buffer and was suppressed by magnesium ions. The studied reaction can be further used as a convenient, selective, fluorometric method for the detection of single-stranded ribosomal RNA and the study of their properties