Dynamic properties of bacteriorhodopsin exposed to ultrashort light pulses.

Bacteriorhodopsin (BR) in its metastable form was used for pulsed holographic recording at lambda~400nm . It is shown that the properties of BR are insensitive to changes in the writing light's pulse width. When holograms are recorded in the BR stable form (lambda~600 nm) , the sensitivity of the medium and the diffraction efficiency of those holograms are reduced proportionally to the decrease in the light's pulse width.

[A model of positive rRNA gene expression regulation based on complementary interaction of transcripts of the prealbumin gene introns with its promotors].

The present paper is concerned with computation of the homology between the promoter and spacer sequences of the rRNA gene and the prealbumin introns. Both the sense and antisense strands of the promoters were compared with the introns. The rRNA promoters were found to contain a considerable number of prealbumin-homologous intron sites on the coding strand only, whereas the spacer sequence had the intron-homologous sites on both strands.

[Radiosensitivity of coding and noncoding DNA sequences of various organisms].

Relationship between pyrimidine distribution patterns and radiosensitivity (Z) of DNA molecules of different species was derived by computer analysis of recurrence frequency of pyrimidine clusters. Blocking factors (beta) and Z for coding and non-coding DNA sequences of species from different taxonomic classes have been calculated within a new model. The radiosensitivity of coding DNA sequences practically does not vary whereas Z values were increased during evolution from simplest to higher organisms.

[Structural characteristics of DNA from the rat liver during inhibition of protein synthesis with cycloheximide].

At cot around 20, the rat liver DNA reassociation curves were obtained 12-48 hours after injection of the animals with sublethal doses of cycloheximide. In total preparations of DNA-24 and DNA-36 at cot 0.02-0.

[Structural changes in chromatin during activation of transcription coupled with translation inhibition by cycloheximide].

A chromatin preparation isolated one hour after cycloheximide injection possesses a higher RNA-synthesizing activity and is split by DNAase I to a greater extent as compared to chromatin of control hepatocytes. Thermal denaturation of this preparation causes a considerable increase (about 2-fold) in the content of the thermolabile fraction melting in the free DNA denaturation zone. The relative content of fast repetitions in the thermolabile fraction (1 hour after the beginning of experiment) is lower than that in control.

[Peculiarities of the reassociation kinetics of fast repeating sequences of thermolabile fractions of hepatoma Zaidel DNA].

The six fractions of rat liver DNA (DNAL) and hepatoma Zaidel DNA (DNAHZ) were obtained by thermal fractionation of these DNAs on a HAP column at equivalent temperature intervals. The percent of two thermolabile fractions obtained at 62--78 degrees is approximately 10% higher for DNAHZ than for DNAL. The reassociation kinetics were carried out till Cot = 5.

[Use of angular rotors for analysis and fractionization of calf thymus DNA].

Behaviour of calf thymus heterogenous DNA was studied in the angular rotor Ti50 of the preparation ultracentrifuge. A drop in DNA polymericity from 8-10(6) to 4-10(5) daltons and decrease in the amount of the applied material result in detecting the known satellite component with delta1 = 1.714 g/cm3, the value of the floating density of the main peak takes on the "true" value delta = 1.

[Preparative isolation and study of the reassociation kinetics of a T2 phage DNA fraction containing readily melting regions].

A DNA fraction comprising 6% of total DNA and containing readily-melting regions is isolated from phage T2 DNA using preparative chromatography on MAK columns at T congruent to T m--3 degrees C. Two denaturation regions, differing in the stability for 7 degrees, were observed on this DNA melting curve. A sharp increase of the reassociation rate at initial moments under reassociation temperatures T r approximately less than m --25 degrees C was observed.

[Application of DNA sonication in the study of reassociation kinetics].

Single-stranded breaks arising is DNA under sonication divide the molecule in short double-stranded regions of lengths depending on sonication conditions. The reassociation rate of DNA with single-stranded breaks is considerably lowered as compared with intact DNA of the same length. For sonicated DNA the slowing of reassociation and the deflection to higher orders of C(o)t of the reaction is observed at the late stages.