[Energy of cooperative transitions in bacteriophage SD].

Heat denaturation of native phages SD suspensions, phage "shadows", and isolated phage DNA solutions were studied by scanning microcalorimetry and viscosimetry. Energetic parameters of cooperative transitions of protein fraction and DNA were measured. DNA melting was shown to be preceded by the destruction of capsid and protein denaturation.

[Restriction endonuclease Sau 6782].

Data are described on identification, isolation and purification of restricting endonuclease Sau 6782 as well as on estimation of the enzyme recognition site. Conditions were developed for growing of Staphylococcus aureus 6782 strain, which enabled to produce a maximal yield of the restricting activity containing minimal level of nucleases. The procedure for isolation and purification of restrictase Sau 6782 involved affinity chromatography on Blue Sepharose and cation exchange chromatography on phosphocellulose PII.

[DNA structure in the particles of 5 bacteriophages from the data of circular dichroism].

DNA optical activities in situ were studied in the particles of five medium sized bacteriophages (SB1, F15; IRA, SD and T7). Delta epsilon in the CD spectrum of intraphage DNA is not shown to correlate with the sizes of phage heads or with the light scattering characteristics of phage suspension. Bacteriophage SB1, studied for the first time, has the amplitude of CD spectrum in the 260-300 nm region higher, than the CD spectrum of its free phage DNA.

[Modification of the modification-restriction system in staphylococci].

A new system of host specificity of DNA, called Sau67 according to the available nomenclature, was identified in Staphylococcus aureus 6782 strain by means of cross titration with staphylophage 729 considering that the phage exhibited the highly effective absorption properties. A total preparation of Sau67 methylases was isolated using ammonium sulfate fractionation. The enzyme preparation contained methylases of cytosine and adenine, where the activity of adenine methylases constituted only for 5% of the total methylase activity.

[Two types of structural organization of double-stranded DNA in phage particles].

Structural arrangement of linear unmodified duplex DNA in phage particles FI5 and SB1 was studied by the techniques of absorption spectrum, CD, scanning microcalorimetry. Hyperchromism is not registered for SB1 DNA in situ at 260 nm, in contrast to FI5 and other phages, but is visible at 260-290 nm. Phage SB1 had an unusual CD spectrum: intensity of the positive band at 280 nm was, practically, identical to the free SB1 DNA intensity.

[New type of DNA structural organization in the composition of bacteriophage Sb-1 particles].

Spectrophotometric melting and chemical modification procedures were used for comparative study of parameters of DNA structure in particles of phages Sb-1 and FI-5 possessing spherical symmetry of the heads. Like in other phages of this morphological group, some part of DNA structure in FI-5 phage particles is disarrayed and has changed reactive capacity of basic aminogroups. Another type of DNA structural organization in situ was found with staphylococcal phage Sb-1.

[Characteristics of the primary and secondary DNA structure of staphylococcal phage SB-1].

Equilibrium centrifugation, spectral analysis of thermal denaturation and direct chemical determinations showed staphylococcal phage Sb-I DNA to be characterized by a standard set of nitric bases (28.5 mol.2.

[Morphologic and physico-chemical characteristics of staphylococcal bacteriophage SB-1 virions].

Virions of polyvalent staphylococcal bacteriophage SB-I have an octaedric head (800 X 700 A) and a long contractive process (1800 X 150 A). The phage particle with a molecular weight of 150 X 10(6) daltons contains 48% double-stranded RNA and 52% protein. The proteinic component of the phage consists of 18 heterogeneic polypeptide chains.

[Investigation of serological features and molecular heterogeneity of virion proteins of morphologically related phages].

Some interaction process peculiarites of morphologically related phate T4, DDVI and FI1 with the corresponding antiphageous sera in cross reactions of neutralisation have been investigated. Close serological relationship of phage T4 and DDVI was demonstrated. Inactivation of phage FI1 in these serological reactions showed anomalous nature and did not submit to the rules of the first step reaction.

[Macromolecular organization and biochemical characteristics of the genome of phage FI-1].

The molecular weight of phage FI-1 DNA is determined by the methods of sedimentation and kinetics of reassociation, as well as from buoyant density values of virion components and specific partial volume of DNA (85X10(6) daltons). The spectral analyses showed that the distribution of guanine-cytosine pairs along the whole length of the molecule is Gaussian. The DNA content in the particle of FI-1 makes up to 41%, which is 7% less as compared to the morphologically related phage T4.

[Peculiarities of primary and secondary structure of phage FI-1 DNA].

The composition of nitrous bases of phage FI-1 DNA was studied. As is evidenced from the values of buoyant density in CsCl (p=1,7093 g/cm(3)), melting temperature (T degrees m=86,05 degrees), spectral parameters and direct chromatographic determination, the DNA analysed contains 41,5 mole% pairs of guanine-cystosine. 5-hydroxymethylcytosine and other anomalous bases were not found.

[Physicochemical characteristics and macromolecular organization of bacteriophage FI-5 (author's transl)].

Physico-chemical parameters and features of macromolecular orgnization of FI-5 phage were studied. This virus was shown to contain a molecule of double-strander DNA with the standard set of nitrous bases (37.8 mol% GC).