Search PubMed⌕ Search

Biomedical subjects

A Klug

Publications and source records attributed to A Klug.

At least 109 records · Page 6Linked to original sources
PubMed1977

Structure of nucleosome core particles of chromatin.

Cystals have been obtained on nucleosome cores and analysed by X-ray diffraction and electron microscopy. The core is a flat particle of dimensions about 110 X 110 X 57 A, somewhat wedge shaped, and strongly divided into two 'layers', consistent with the DNA being wound into about 1 3/4 turns of a flat superhelix of a pitch about 28 A. The organisation of the DNA can be correlated with the results to enzyme digestion studies. A change in the screw of the DNA double helix on nucleosome formation can be deduced.

Animals↗
PubMed1976

A speculation on the origin of protein synthesis.

It is suggested that protein sythesis may have begun without even a primitive ribosome if the primitive tRNA could take up two configuration and could bind to the messenger RNA with five base-pairs instead of the present three. This idea would impose base sequence restriction on the early messages and on the early genetic code such that the first four amino acids coded were glycine, serine, aspartic acid and aspargine. A possible mechanism is suggested for the polymerization of the early message.

Anticodon↗
PubMed1976

Correlation between structural transformation and cleavage of the major head protein of T4 bacteriophage.

We have studied the maturation of T4 polyheads, the aberrant tubular structures related to the capsid of T4 bacteriophage. Conditions have been found under which more than 95% of the major head protein (P23) undergoes the same cleavage that occurs during development of the normal capsid. The concomitant structural changes in the polyheads have been followed using electron microscope image filtering techniques. As a result of the cleavage, a radical transformation of the hexagonal lattice occurs, involving a 10-15% expansion in the lattice dimensions. However, a metastable intermediate state similar to the uncleaved structure has been observed immediately after cleavage of the protein subunits. Some kind of additional physical stimulus seems to be required to trigger the major structural change, which appears to be highly cooperative.

Capsid↗
PubMed1976

Solenoidal model for superstructure in chromatin.

Chromatin prepared by brief digestion of nuclei with micrococcal nuclease, and extracted in 0.2 mM EDTA, appears in the electron microscope as filaments of about 100 A diameter which coil loosely. In 0.2 mM Mg++ these "nucleofilaments" condense into a supercoil or solenoidal structure of pitch about 110 A corresponding to the diameter of a nucleofilament. It is proposed that the x-ray reflections at orders of 110 A observed in chromatin originate in the spacing between turns of the solenoid rather than that between nucleosomes along the nucleofilament. The solenoidal structure appears to need histone H1 for its stabilization. Under certain conditions, isolated nucleosomes can also aggregate into a similar structure. The solenoidal structure can be correlated with the "thread" of diameter about 300 A observed by other workers in nuclei.

Animals↗
PubMed1975

Kinky helix.

Explore the source record for details and available documents.

Base Sequence↗
PubMed1975

Structure of yeast phenylalanine transfer RNA at 2.5 A resolution.

The x-ray analysis of the monoclinic form of yeast tRNAPhe has been taken to a resolution of 2.5 A by the method of isomorphous replacement. The model proposed at 3 A has been confirmed and extended to reveal additional features of the tertiary structure and of the stereochemistry. An extensive hydrogen bonding network is described involving specific interactions between bases and the ribose-phosphate backbone. The structure of a G-U base pair has been solved.

Base Sequence↗