[An analysis of a process for culturing Lactobacillus acidophilus using a method of spectroturbidimetry]. / Analiz protsessa kul'tivirovaniia Lactobacillus acidophilus metodom spektroturbidimetrii.

Changes in the spectrum of the opacity of biodispersions containing L. acidophilus at the stage of growth have been studied. The pronounced positive correlation between the opacity of dispersion and the titer of cells, determined by the method of ultimate dilutions, have been shown.

[Refractive index and thickness of the outer layer of particles of dispersed perfluorochemical-based blood substitutes]. / Opredelenie pokazatelia prelomleniia i tolshchiny obolochki chastits dispersnogo krovezamenitelia na osnove perftorsoedinenii.

A calculation of the refractive index of particles of a disperse perfluorochemical-based (PFC-based) blood substitute has been made taking into account particular features of the structure of PFC emulsion particles and the equations earlier obtained by one of the authors in the studies on light interaction with optically inhomogeneous 2- and 3-layer spheres. The possibility of averaging by volume the refractive index of 2-layer emulsion particles has been shown. The refractive index of PFC particles has been experimentally determined using independent optical methods, and the thickness of the particle shell formed by a surfactant has been evaluated.

[Characteristics of erythrocyte diagnostic agents studied using optical methods]. / Kharakteristika éritrotsitarnykh diagnostikumov opticheskimi metodami.

The quantitative characterization of erythrocyte diagnosticums (ED) has been made by optical methods (light microscopy with the use of an image analyzer, model Magiscan 2, and the opacity spectrum technique). The following parameters of ED have been determined: the average of the major axis (5.25 +/- 0.57 micron for ED from Shigella sonnei and 5.53 +/- 0.50 micron for ED from Shigella flexneri), the ratio of semiaxes (p approximately equal to 3), the major axis length distribution, the refractive index (1.076 +/- 0.002). For controlling the concentration of ED the use of the opacity spectrum technique is recommended.

[Information value of light scattering parameters in cell study (a review of the literature)]. / Informativnost' parametrov svetorasseianiia pri issledovanii kletok (obzor literatury).

Different methods of light scattering measurements for cell suspension and cells in flow are reviewed. The intensity of light scattered at different angles suggests information about the cell size, the nucleus to cell diameter ratio, the thickness of surface membrane, the changes in the internal cell structure state, and about the heterogeneity of cell population. The efficiency of information obtained from the turbidity measurements depends on the geometry of the spectrophotometer. Measurements made with diaphragms allow us to get information about the mean size of biological particles, their form, refractive index, concentration etc. The main advantages of light scattering methods are their high sensitivity, a possibility to use the same species before and after the experiment, and a compatibility with other methods.

Gamma-irradiated chymotrypsin-like proteins. II. Connection between inactivation and structural changes.

The radiation yeilds of unfolding (Gconf) determined by the method of tryptophan fluorescence coincide with the radiation yields of proteolytic inactivation (Gin) for chymotrypsin-like (CT-like) enzymes on irradiation in air, both in solution and in the dry state with futher dissolution at pH7. It can be supposed that the unfolding is the main process determining the proteolytic gamma-inactivation of CT-like enzymes. It was also shown that the transition of chymotrypsin and trypsin gamma-irradiated at acid pH to neutral pH is an additional action, leading to unfolding of part of the molecules.

Gamma-irradiated chymotrypsin-like proteins. I. Structural changes.

The chymotrypsin-like proteins (chymotrypsin-CT,chymotrypsinogen-CTG, trypsin-T and modified chymotrypsins-at Met 192-MCT and at Tyr 146, 171-TCT), gamma-irradiated in the presence of air, were investigated. Irradiation leads to the unfolding of the native structure of CT-like proteins both in solution and in the dry state, which was shown by the tryptophan fluorescence, viscosimetry and microcalorimetry. The radiation yield of unfolded molecules Gconf was estimated and compared with (1) the rate constants for the reactions of OH-radicals with the proteins as determined by the p-nitrosodimethylaniline, (2) general stability of protein globule using the difference of the energies of the unfolded and globular conformations and (3) the radiation yield of tryptophan destruction in proteins-G-trp. There was a correlation between the values of Gconf and G-trp. The ratio G-trp/Gconf, which defines the number of destroyed tryptophan residues for one unfolded protein molecule, was constant within the limits of error. For CT, MCT, TCT and CTG, this ratio was on the average 3-2, and for T it was 2-2 residues. These facts point to the role of tryptophan destruction in the unfolding of the native structure of CT-like proteins on irradiation.

[pH-dependence of fluorescence parameters of chymotrypsin, chymotrypsinogen, trypsin and lysozyme]. / Zavisimost' Parametorov fluorestsentsii khimotripsina, khimotripsinogena, tripsina i lizotsima ot velichiny pH.

The alterations of tryptophan fluorescence parametres with pH may be due to: 1) conformational changes; 2) changes in the ionic state of groups capable of quenching the tryptophan fluorescence. The applications of the model of discrete forms of tryptophan allow one to separate these mechanisms and estimate the middle points of conformational changes and pK's of quenching groups. For chymotrypsin (CT) and chymotrypsinogen (CTG) conformational changes were registrated with middle points: CT pH 4.1 and 8.8; CTG -- pH 3.2 and 9.8, and pK's of histidines: CT -- 5.4 and 6.6; CTG -- 5.6 and 7.0. For trypsin conformational changes were shown with middle points: pH 3.2; 5.8; 8.5 and for lysozyme -- pH 5.9.