Association-dissociation processes and supermolecular organisation of the capsule antigen (protein F1) of Yersinia pestis.

The association-dissociation processes involving the capsule antigen of Yersinia pestis were investigated. In aqueous salt solutions the material of the capsule (protein F1) exists in the form of associated species containing identical monomeric protein subunits. Brief heating (100 degrees C, 3 min) of F1 dissolved in buffered salt solutions at pHs between 4.4 and 7.5 leads to dissociation of the antigen into oligomers which reassociate at room temperature into aggregates of high molecular mass. In the presence of 7 M urea and 0.1% SDS such reassociation is suppressed. It is shown that a few seconds after heat treatment the protein exists as the tetramer in phosphate buffer and as the dimer and the monomer in the presence of urea and SDS respectively. Interconversions of these three forms of the antigen were observed on replacement of one buffer by another. The effect of pH, ionic strength, F1 concentration, and temperature on the rate of association of F1 were also investigated. A decrease in pH, an increase in the ionic strength of the solution, and an increase in the concentration of the protein in aqueous buffered salt solutions all accelerate the F1 aggregation process. A model is proposed for the supermolecular structure of the F1 protein associated species in which the subunits are assembled into a single plane containing tens of dimers as a result of lateral interdimer hydrogen bonds. The dimer is stabilised by hydrophobic interactions of the nonpolar sections of the subunits, which in the associated protein form an internal hydrophobic surface analogous to that in lipid bilayer membranes.

[A rapid method of isolating phosphatidylcholine and phosphatidylethanolamine using high performance liquid chromatography]. / Uskorennyi metod vydeleniia fosfatidilkholina i fosfatidilétanolamina s ispol'zovaniem vysokoéffektivnoi zhidkostnoi khromatografii.

A modified procedure is described for isolation of lecithin and phosphatidyl ethanolamine by means of high pressure liquid chromatography, which enabled to decrease the purification period down to several hours and to use small volumes of eluents of simple composition. Extensive purification of the eluents was not required for separation of phospholipids on half-preparative scale.

[Synthesis and expression of the DNA fragment coding the antigenic determinant of the surface antigen protein of hepatitis B virus]. / Sintez i ékspressiia fragmenta DNK, kodiruiushchego antigennuiu determinantu belka poverkhnostnogo antigena virusa gepatita B.

With the use of chemical-enzymatic synthesis, a polynucleotide (I) has been obtained which codes the amino acid sequence 93-109 of the hepatitis B surface antigen (HBsAg). The plasmid pHS12, constructed by insertion of (I) into pBR325 between EcoRI and BamHI sites, transformed E. coli HB101 cells. The plasmid expression in cell-free system produced a chimeric protein, its molecular weight corresponding to that a polypeptide containing the heptadecapeptide from HBsAg. An approach is discussed for creating a new type of vaccines on the basis of chimeric proteins containing the antigenic determinants of virus proteins.

The distribution of guanine-cytosine pairs in adenovirus DNAs.

The distribution of guanine-cytosine (GC) pairs in the DNA of the highly oncogenic simian adenovirus type 7 (SA7) and the non-oncogenic human adenovirus type 6 (Ad6) has been studied by thermal denaturation and CsC1 density-gradient centrifugation. The differential of the DNA thermal denaturation curves shows the presence of pronounced peaks which indicates uneven distribution of GC pairs along the DNA chains and the presence of regions with GC content from 30 to 74% in SA7 DNA and from 40 to 68% in Ad6 DNA. The DNA restriction fragments obtained by treatment with EcoRI, BamHI, SalI, BglII and HindIII were subjected to CsC1 density-gradient centrifugation. GC content of the fragments ranged from 45 to 70% for SA7 DNA and from 43 to 61% for Ad6 DNA. The GC content of the extreme left-hand fragments, where the transforming gene(s) is located, was higher than the average for SA7 DNA and lower than the average for Ad6 DNA. The most GC-rich regions were localized in the centre of the genome. The GC content of the right-hand part of both viral genomes was lower than the average.

[Physical characteristics of simian adenovirus SA7]. / Fizicheskie kharakteristiki adenovirusa obez'ian SA7.

Physical characteristics of simian adenovirus SA7 virion were studied. The buoyant density of SA7 virions was found to be 1.356 g/cm3. The percentage of DNA calculated from the buoyant density value and determined with phosphorus directly was 11.6% and 11.8%, respectively. The S020,w and D020,w were 740 S and 3.34 x 10(-8)/cm2, respectively. From the hydrodynamic parameters of the virion and its volume and specific partial volume as well as percentage of DNA and DNA molecular weight, the molecular weight of SA7 virion was calculated and found to be 185.5 Mdaltons.

[GC-pair distribution in the DNA of simian SA7 and human type 6 adenoviruses]. / Raspredelenie GTs-par v DNK adenovirusov obez'ian SA7 i cheloveka tipa 6.

The buoyant density values in cesium chloride of DNA fragments of simian adenovirus SA7 obtained with restricting endonucleases of R. EcoRI, R. BamHI, R. SalI and human adenovirus type 6 DNA fragments obtained with restricting endonucleases of R. EcoRI and R. BamHI were determined. On the basis of the buoyant density values for these fragments the content of GC pairs in them was calculated. Using the known position of the fragments in the physical map of these DNAs, the distribution of GC pairs along the examined DNA molecules was constructed.

[Physicochemical properties of the DNA of simian adenovirus type 38]. / Fiziko-khimicheskie svoistva DNK adenovirusa tipa 38 obez'ian.

The sedimentation constant, specific viscosity, and the length of DNA molecule of simian adenovirus type 38 were measured and the molecular weight was estimated. The melting temperature and buoyant densities of this virus DNA in cesium chloride and cesium sulphate density gradients were determined, and the content of GC-pairs was calculated.

Biophysical properties of virions of human adenovirus of the type 6 and its DNA.

A study has been made of human adenovirus type 6 (Ad 6) which belongs to the C subgroup of the nononcogenic adenoviruses. The buoyant density of the Ad 6 virions in CsCl gradient was 1.3545 +/- 0.0010 g/cm3. The DNA content determined from the buoyant density values and direct phosphorus analysis was 11.2 +/- 0.5 and 11.5 +/- 0.5 per cent, respectively. The S20,w0 and D20,w0 values for the Ad 6 virions were 795 +/- 18S and (3.255 +/- 0.035) X 10-8 cm2/s. The hydrodynamic parameters of the viral particle and its volume as well as the specific partial volume, the content and the molecular weight of the DNA have yielded a molecular weight of the virions of (203.6 +/- 10.0) X 10(6). The sedimentation constant and the intrinsic viscosity of the DNA have been found to be 32.7 +/- 0.7S and 93.5 +/- 5.0 dl/g, respectively. The molecular weight of the DNA found from these results is (23.4 +/- 0.8) X 10(6). The buoyant density of the Ad 6 DNA measured in CsCl and Cs2SO4 density gradients was 1.7128 +/- 0.0010 and 1.427 +/- 0.001 g/cm3, respectively. The GC content found from the buoyant density and the melting temperature (90.5 +/- 0.1 degrees C in 1 SSC and 75.0 +/- 0.1 degrees C in 0.1 SSC) was 52.6 +/- 1.0 per cent, that is, it is considerably lower than the GC content of 56-60 per cent which, according to the "Green's rule", should be typical of the DNAs of all the human adenoviruses of the subgroup C (30).

[Physical characteristics of human adenovirus type 6]. / Fizicheskie kharakteristiki adenovirusa cheloveka tipa 6.

The size, chemical composition and the buoyant density of the virion, sedimentation and diffusion constants of human adenovirus type 6 were determined. The molecular mass of the virion was calculated on the basis of the values of sedimentation and diffusion constants and electron microscopy data.

[Physico-chemical properties of DNA of human adenovirus type 6]. / Fiziko-khimicheskie svoistva DNK adenovirusa cheloveka tipa 6.

Physico-chemical characteristics of human adenovirus type 6 DNA were studied. The sedimentation constant of adenovirus type 6 DNA was shown to be 32.7S. The intrinsic viscosity of DNA was on the average 93.8 dl/g. The average size of the molecular mass determined by the results of sedimentation and viscosimetry was 23.5 X 10(6) daltons which agreed favourably with the value calculated from the data of electron microscopic determination of the length of DNA molecule. The buoyant density of DNA in cesium chloride density gradient was 1.7126 g/cm3. The melting temperatures were 90.5 and 75 degrees C for 1 X SSC and 0.1 X SSC, respectively. Adenovirus type 6 DNA contained 52.6% GC pairs on the average.