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P KAESBERG

Publications and source records attributed to P KAESBERG.

At least 19 recordsLinked to original sources
PubMed1964

A PH-INDUCED STRUCTURAL CHANGE IN BROMEGRASS MOSAIC VIRUS.

Bromegrass mosaic virus undergoes a reversible decrease in its sedimentation coefficient when the pH is raised above pH 6.7. At pH 6 the sedimentation coefficient is 87 S, at pH 7 it is 79 S. Intrinsic viscosities determined at pH 6 and 7 are 3.64 and 5.5 x 10(-2) dl/gm. Diffusion coefficients are 1.56 x 10(-7) cm(2)/sec. and 1.44 x 10(-7) cm(2)/sec., respectively. Radii of gyration, measured by x-ray scattering, are 106 and 128 A. However, appropriate combination of sedimentation, diffusion, and viscosity coefficients at pH 6 and 7 yield the same molecular weight. Also, the zero-angle value of x-ray-scattered intensity, which is a function of molecular weight, is the same at the two pH's. These results suggest that bromegrass mosaic virus particles undergo a pH-induced change in structure. This change causes, among other things, an increase in the susceptibility of the particles to degradation by pancreatic ribonuclease. The shape of the titration curve between pH 6.3 and 6.9 is anomalous.

Biochemical Phenomena↗
PubMed1963

An x-ray scattering study of bromegrass mosaic virus.

X-ray scattering data and electron microscope observations are presented for bromegrass mosaic virus. Its radial density distribution is obtained from the Fourier transform of the amplitudes of the scattered x-rays. The results indicate that the virus is 260 A in diameter, it has an almost empty central cavity which is about 80 A in diameter, and the regions occupied by RNA and protein are approximately equal in average density. Electron micrographs of negatively stained preparations also give an outside diameter of 260 A and indicate that there is a central region about 90 A in diameter into which uranyl acetate can penetrate. Positively stained preparations indicate that the nucleic acid is concentrated in a shell-shaped region which is in turn surrounded by a shell of protein. In order for the RNA and protein regions to have the same average electron density the RNA must have a hydration of 1.29 gm of water per gm of RNA and the protein must have a hydration of 0.24 gm of water per gm of protein.

Bromovirus↗
PubMed1962

The adsorption of bacteriophage phi-X174 to its host.

The adsorption of purified varphiX174 to E. coli C and to E. coli C cell walls was investigated. Adsorption was measured by assaying for unadsorbed plaque formers. The amount of irreversible and reversible adsorption depends upon pH and divalent ion concentration. Maximum irreversible adsorption occurs in 0.1 M CaCl(2) at 36 degrees C. There is no detectable reversible adsorption at conditions of pH and CaCl(2) concentration optimum for irreversible adsorption. Under these optimum conditions, diffusion is not the rate-limiting factor, and the encounter efficiency appears to be low. The rate constant is 1.0 x 10(-10) ml/sec. Phages adsorbed irreversibly to live cells cause infection and to the isolated cell walls apparently cause release of DNA. There is a specific varphiX174 receptor site on the mucocomplex portion of the cell wall.

Adsorption↗
PubMed1961

An x-ray scattering investigation of wild cucumber mosaic virus and a related protein.

X-ray scattering data are presented on solutions of wild cucumber mosaic virus and the associated "top component" particles which have little or no RNA. The radii of gyration are 112 A and 135 A for bottom and top component, respectively. The radial density distribution within each particle is calculated by Fourier inversion of the scattered amplitudes. The virus particle or bottom component has approximately uniform density with an outer radius of about 140 A. The transform of the top component shows an almost hollow center extending out to 105 A with a surrounding shell of high density about 35 A thick. Thus the RNA would appear to occupy the region inside 105 A and does not overlap appreciably the region occupied by protein. The virus has associated with it approximately 0.38 gm of water per gm of virus, resulting in an average electron density of 1.25 times that of water.

Cucumovirus↗