Coherent anti-Stokes Raman scattering in silicon nanowire ensembles.

In this letter, we, for the first time, report on coherent anti-Stokes Raman scattering (CARS) spectroscopy of an ensemble of silicon nanowires (SiNWs) formed by wet chemical etching of crystalline silicon with a mask of silver nanoparticles. The fabricated SiNWs have diameter ranged from 30 to 200 nm and demonstrate both visible and infrared photolumine cence (PL) and spontaneous Raman signal, with their intensities depending on presence of silver nanoparticles in SiNWs. The efficiency of CARS in SiNW ensembles is found to be significantly higher than that in crystalline silicon. The results of CARS and PL measurements are explained in terms of resonant excitation of the electron states attributed to silicon nanoparticles.

Quantitative characterization of aqueous solutions probed by the third-harmonic generation microscopy.

Third-harmonic microscopy is one of the emerging techniques for noninvasive microscopic imaging of biological structures. We use a novel technique for nonlinear optical material characterization and study the effect of different environment and the structural sensitivity of the third harmonic. In particular, a transformation of collagen in solution is observed for the first time using third-harmonic generation. We also study the ultimate limits of the third harmonic to detect micro- and nanoscopic features inside living cells and find that structures as small as 50 nm can be detected using the current level of technology.

Nonlinear optical microscopy analysis of ultrafast phase transformation in vanadium dioxide.

The nonlinear optical properties of solid-solid phase transformation in vanadium dioxide are studied. It is found that the efficiency of the third-harmonic optical signal generated from the surface of the material increases by 1.5 orders of magnitude as a function of this phase transformation. Microscopy studies show the hysteresis of the phase transformation on a micrometer-size scale.

Polarization rotation induced by cascaded third-order processes.

Intensity-dependent polarization rotation that results from the simultaneous action of two third-order processes, self-phase modulation and four-wave mixing, is observed. The effect is recorded along the fourfold axis of a YVO(4) crystal. The angle of rotation is proportional to the square of the input intensity-crystal length product. This is to the authors' knowledge the first experimental evidence showing that intensity-dependent polarization rotation can be related to the real part of cubic susceptibility.

Cross-polarized wave generation by effective cubic nonlinear optical interaction.

A new cubic nonlinear optical effect in which a linearly polarized wave propagating in a single quadratic medium is converted into a wave that is cross polarized to the input wave is observed in BBO crystal. The effect is explained by cascading of two different second-order processes: second-harmonic generation and difference frequency mixing.

[Comparative study of lipoteichoic acid from Streptococcus pyogenes type 29 isolated by different methods]. / Sravnitel'noe izuchenie lipoteikhoevoi kisloty Streptococcus pyogenes tip 29, vydelennoi razlichnymi sposobami.

A comparative study of lipoteichoic acid preparations extracted from Streptococcus pyogenes with cold and hot phenol and trichloracetic acid was made. The most delicate way for isolation of lipoteichoic acid from the given microorganisms is cold phenol extraction.

[Quantitative determination of the protein and carbohydrate polymers in the cell wall of Streptococcus group A]. / Kolichetsvennoe opredelenie belkovykh i uglevodnykh polimerov kletochnoi stenki Streptococcus gruppy A.

The content of protein and carbohydrate polymers was estimated in the cell wall of Streptococcus, group A, type 29. A method was developed for analysing peptidoglycane in a polysaccharide-peptidoglycane complex after the prior oxidation by sodium periodate. It was found that the cell wall peptidoglycane bears two carbohydrate and three amino acid residues, i. e. N-acetylglucosamin, muramic acid, glutamic acid, alanine and lysine, in the ratio 1:1:1:4:1, respectively. The data on the cell wall composition prior to and after its oxidation with sodium periodate are given, and the ratio between the main structural components is determined: proteins (60% mol), polysaccharide (23% mol), peptidoglycane (17% mol).

[Determination of cell wall amino sugars in Streptococcus on a carbohydrate analyzer]. / Opredelenie aminosakharov kletochnoi stenki streptokokka na uglevodnom analizatore.

A method of determining aminosaccharides (muramic acid, glucosamine and galactosamine) by means of a carbohydrate analyzer "Biotronic" using the cation-exchange resin DC-6 A ("Durrum") was developed. Chromatographic conditions correspond to the conditions of neutral sugar analysis on a column with DCh-4 resin, that enables after a slight modification of the analyzer to pass from the determining of aminosaccharides to the determining of neutral sugars. The method was used for determining the carbohydrate composition of streptococcus cell walls. The results obtained allow to conclude that using this method one can get more information on the hydrocarbon composition of various biological objects than using the method of aminosaccharide determining by means of aminoacid anylyzer, which is widely in practice nowadays.

[Isolation and study of the properties of Streptococcus pyogenes ribosomes]. / Vydelenie i izuchenie svoistv ribosom Streptococcus pyogenes.

Ribosomes from Streptococcus pyogenes, group A, strain 29 were studied. A comparison of different methods of ribosomal isolations has shown that the homogenous ribosomal samples can be obtained by the method of differential ultracentrifugation using tris-HCl buffer. The ribosomes of S. pyogenes had the sedimentation coefficient of 70S and consisted of 65% of protein and 35% of nucleic acids; the ribosomes dissociated into subparticles with the sedimentation coefficients of 50S and 30S under a low magnesium concentration. Thus the S. pyogenes ribosomes do not differ from the ribosomes of procaryotes. It was shown that the ratios of 70S, 50S and 30S ribosomal subparticles in the cells depend on the growth phase of S. pyogenes. The cells of the middle and the late logarithmic phase contained 50S and 30S particles in a stoichiometric ratio. In the cells of the late stationary growth phase there was a deficiency of 30S ribosomal subparticles which does not result from a loss during the isolation procedure, as it was already observed in the initial 30S fraction.

[Isolation and evaluation of properties of muramidase causing the lysis of group A streptococci]. / Poluchenie i izuchenie muramidazy, liziruiushchei streptokokk gruppy A.

Muramidase which actively lyses the cell walls of group A hemolytic streptococci has been isolated from the culture fluid of Actinomyces levoris by precipitation on ammonium sulfate, gel filtration on Sephadex G-25, ion exchange chromatography on DEAE cellulose and double electrofocusing. The enzyme thus obtained has shown its maximum activity at 40-50 degrees C. At 60 degrees C muramidase was completely inactivated. The enzyme has a wide range of optimum pH values: 5.0-9.5. The highest percentage of lysis of streptococcal cell walls has been observed in plycine-NaOH and potassium phosphate buffers at pH 8.0. Muramidase completely lysed Streptococcus pyogenes cells of different serological groups except enterococci (group D) and staphylococci. This sign allows to differentiate group D streptococcus from streptococci of other groups.

[Endo-N-acetylglucosaminidase formed by Streptomyces levoris]. / Endo-N-atsetilgliukozaminidaza, obrazuemaia Streptomyces levoris.

Endo-N-acetylglucoseaminidase (EC 3.2.1.30) was prepared from the cultural broth of Streptomyces levoris 96 using precipitation with ammonium sulfate, gel filtration on Sephadex G-25 and ion exchange chromatography on DEAE-cellulose. The isoelectric point of the enzyme is 4.2 Str. levoris produces various quantities of the enzyme depending on the composition of the growth medium. A medium in which the enzyme is produced in maximal amounts has been selected. The effect of peptidoglycan, cell walls and chitin added to the medium on the enzyme biosynthesis was studied. Chitin induced biosynthesis of the enzyme by 35--45%.

[Isolation and characterization of endo-N-acetylmuramidase produced by Actinomyces levoris]. / Vydelenie i kharakteristika endo-n-atsetil-muramidazy, podutsiruemoi Actinomyces Levoris.

Precipitation by ammonium sulfate and a subsequent purification of the culture fluid of Actinomyces levoris by gel-filtration through Sephadex G-25, ion-exchange chromatography on DEAE-cellulose and CM-cellulose resulted in an enzyme which activley lyzes the cell walls of a hemolytic streptococcus of group A. The molecular weight (12,500), isoelectric point (pI 10,6) and amino acid composition of the enzyme were determined. The enzyme specificity was assayed using peptidoglycane isolated rom the cell walls of streptococcus of group A used as a substrate. An analysis of the hydrolysis products of peptidoglycane showed that the enzyme under study is an endo-beta-N-acetylmuramidase (EC 3.2.1.17).

[Autolysis of hemolytic streptococcus group A]. / Avtoliz gemoliticheskogo streptokokka gruppy A.

As revealed, autolytic enzymatic system of hemolytic streptococcus, group A, expressed the maximal activity at the end of the exponential growth phase. Autolysis was accompanied by the release of N-acetylaminosugars and of free amino group. Optimal conditions for the lytic system function were chosen (composition, ionic strength, and buffer pH). The activating action of trypsin and chemotrypsin was demonstrated.

[Lysis of the cellular walls of Streptococcus group A by enzymes produced by actinomycetes]. / Izuchenie lizisa kletochnykh stenok sterptokokka gruppy A fermentami, produtsiruemymi aktinomitsetami.

More than 80 cultures of actinomycetes belonging to different taxanomic groups were studied with a purpose of screening actinomycetes actively producing enzymes lyzing the cell walls of group A streptococci. 31 strains of the actinomycetes producing enzymes which lyzed the cell walls by 20-50 and 60-80 per cent within 1 and 4 hours respectively were selected. The proteolytic activity of the enzymes produced by these strains was also studied. It was shown that 4 cultures, i.e. Actinomyces albus, strains 6 and 9, Actinomyces levoris, strain 29 and Actinomyces gibsonii, strain 42 were of interest as organisms producing enzymes which lyzed the streptococcal cell wall without impairing its antigenic components.

[Lytic enzymes produced by Actinomyces levoris]. / Liticheskie fermenty, produtsiruemye Actinomyces levoris.

The composition of the enzyme complex produced by Actinomyces levoris which exhibits lytic action on the cell walls of Streptococcus lactis was studied by gel filtration on Sephadex G-25, ion exchange chromatography and isoelectric focusing. The complex was found to contain at least seven enzymes having different isoelectric points and substrate specificity. The enzymes were divided into three groups. (1) The enzyme with pI 10.2 seems to be a specific glucosidase; it possesses a high activity of the cell wall lysis and lacks a proteolytic activity. (2) The enzymes with pI 9.2 and 9.0 are, apparently, specific lytic proteases; they display both lytic and proteolytic activities. (3) The enzymes with pI 10.0, 9.5, 5.7 and 4.2 are, presumably, non-specific lytic proteases; they have a low lytic activity and a high proteolytic activity.

[Lysis of the cell walls of streptococcus group A by Streptomyces griseus pronase]. / Lizis kletochnykh stenok streptokokka gruppy A pronazoi Streptomyces griseus.

The effect of Streptomyces griseus pronase on Streptococcus group A cell walls was studied. Cell walls were shown to be lysed by pronase, the lysis level being dependent on the molarity of the potassium-phosphate buffer used. With an increase in the buffer molarity from 0.005 M to 0.05 M lysis of cell walls decreased from 70-80% to 30%. By DEAE-cellulose chromatography lysates were separated into two fractions the first of which contained a group specific polysaccharide. A preparative method of obtaining a group specific polysaccharide of Streptococcus group A using Streptomyces griseus pronase under mild conditions is described.

[Preparation of cell walls of group A Streptococcus. Methods of disintegration, isolation and control]. / Poluchenie kletochnykh stenok streptokokka gruppy A. Metody dezintegratsii, vydeleniia i kontrolia

A method for disintegration of cells of group A streptococcus on the Edebeau extrusion press was developed. The level of disintegration was controlled by cell count in stained preparations, Coultier electronic counter and electron microscope. The streptococcus cell disintegration in the Edebeau extrusion press at a temperature of --40 degrees, a pressure of 3200 kg/cm2 and two cycles of the process was completed by 96-98%.