TWO-LAYER PHASE COMPENSATING INTERFERENCE SYSTEMS

The paper deals with creation of optical interferential coatings, giving the possibility to form the wave front without the change of energy characteristics of the incident and reflected radiation. Correction is achieved due to the layer, which thickness is a function of coordinate of an optical element surface. Selection technique is suggested for refractive index materials, forming two-layer interference coating that creates a coating with a constant coefficient of reflection on the surface of the optical element. By this procedure the change of coefficient of reflection for the optical element surface, arising because of the variable thickness is eliminated. Magnesium oxide and zirconium dioxide were used as the film-forming materials. The paper presents experimentally obtained thickness distribution of the layer, which is a part of the phase compensating coating. A new class of optical coatings proposed in the paper can find its application for correcting the form of a wave front

О протеолитической активности субклеточных фракций клеток Chlorella vulgaris штамма С 111 IBCE C-19

Subcellular particles of Chlorella vulgaris C 111 IBCE C-19 were isolated by differential centrifugation in sucrose density gradient. It was stated for the first time, that these particles can cleave casein, gelatin, fibrinogen and hemoglobin at pH 7.4 and 9.0. Using group-specific proteinase inhibitors, a set of serine-, cysteine- and metalloproteinases was identified in this material. However, the detection of this set of proteolytic enzymes is only possible when several different proteins are used as substrates. In some cases, virtually all of the used arsenal of group-specific proteinase inhibitors proved to be little effective. This suggests that these are proteinases of a different nature than those listed above, which requires further perspective research.Установлено, что выделенные методом дифференциального центрифугирования и в градиенте плотности сахарозы субклеточные частицы клетки Chlorella vulgaris штамма С 111 IBCE C-19 способны расщеплять казеин, желатин, фибриноген и гемоглобин при рН 7,4 и 9,0. С использованием группоспецифических ингибиторов протеиназ выявлено присутствие в клетках хлореллы сериновых, цистеиновых и металлопротеиназ. Однако выявление этого набора протеолитических энзимов возможно лишь при использовании в качестве субстратов нескольких разных белков. В отдельных случаях практически весь использованный арсенал группоспецифических ингибиторов протеиназ оказался малоэффективен. Это дает основания полагать, что существуют протеиназы иного плана, чем перечисленные выше, что требует дальнейших исследований в перспективе

TiO2 nanoparticles suppress Escherichia coli cell division in the absence of UV irradiation in acidic conditions

TiO2 nanoparticles (NPs) activated by UV irradiation are known to have a bactericidal effect. In this study we report the details of TiO2 NPs influence on the colony-forming capacity of E. coli in the dark at pH 4.0-4.5. At this pH the bacterial cells are negatively charged and TiO2 NPs present a positive charge. A 60 min contact between E. coli with TiO2 at concentrations of 0.02-0.2 mg/mL led to a reduction of E. coli cell number from 10(8) to 10(4) CFU/mL. After the reduction the system remains unchanged during the subsequent incubation. The observed reduction was a function on the initial E. coli concentration. In the presence of 0.04 mg/mL TiO2 the colony-forming units (CFU) reduction after 60 min was of four-five orders of magnitude when the initial concentration was 10(8) cells/mL. But when starting with an E. coli concentration of 10(7) cells/mL the cell number reduction was less than one order of magnitude. Less than one order of magnitude cell number reduction was also observed for suspensions of E. coil 10(8) cells/mL and 0.002 mg/mL of TiO2. The bacteria number reduction was always accompanied by the formation of cell aggregates. During cell incubation with TiO2, the pH of the suspension increased, but did not reach the TiO2 isoelectric point (IEP). E. coil cells stained with the fluorescent dye acridine orange (AO) showed that the fluorescence of single cells remained unchanged after incubation in the presence of TiO2. The color change of fluorescence was revealed only in aggregated cells. This suggests changes in the physiologic state of E. coli incorporated into the aggregates. Aggregates of E. coil occur due to the electrostatic interaction between TiO2 NPs and the bacterial cell surface. A hypothesis is suggested in this study to explain the CFU reduction and the retention of a certain irreducible number of cells capable of further division in the suspension in the presence of TiO2 in the dark. (c) 2012 Elsevier B.V. All rights reserved