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Biomedical subjects

A Rich

Publications and source records attributed to A Rich.

At least 415 records · Page 23Linked to original sources
PubMed1969

Crystalline transfer RNA: the three-dimensional Patterson function at 12-angstrom resolution.

An orthorhombic form of crystalline formylmethionine transter RNA has been obtained which contains one molecule as the asymmetric unit of the unit cell. Three-dimensional x-ray diffraction data have been collected up to a resolution of 12 angstroms, and from this a Patterson function has been calculated. The function contains an elongated ridge of interatomic vectors parallel to the c-axis of the crystal. Analysis of the function suggests that the molecules are elogated and dimerized in an overlapping antiparrael fashion along the c-axis. The dimer has a length near 109 angstroms and a width of 35 angstroms in one direction. The individual molecular length is approximately 80 angstroms with an irregular cross section measuring 25 by 35 angstrms.

Crystallization↗
PubMed1969

Spin-labeled transfer RNA.

The alpha-amino group of valyl-tRNA has been combined chemically with a nitroxide spin label through an amide linkage. This spin-labeled aminoacyl-tRNA has an electron paramagnetic resonance spectrum which reflects the mobility of the aminoacyl end of the tRNA molecule. The rate of tumbling of the spin label has been measured as a function of temperature and ionic strength. An abrupt transition in the nature of the motion occurs at a temperature which is sensitive to the ionic strength of the medium. This change in behavior of the aminoacylated spin label occurs at the same temperature as the midpoint of the optical density melting curves in dilute salt solutions. However, when denaturing agents such as dimethylsulfoxide or urea are added to the solution, the spin melting temperature is lower than the melting temperature as measured by the change in optical density. This suggests that under these conditions the local region of the aminoacyl end of the molecule denatures before the rest of the molecule is disrupted.

Carbon Isotopes↗
PubMed1969

Two rapidly labeled RNA species in the polysomes of antibody-producing lymphoid tissue.

Popliteal lymph nodes of rabbits stimulated to produce antibodies were pulse labeled in vivo by direct injection of (3)H-uridine. RNA was then extracted from isolated polysomes and single ribosomes. Fractionation of this RNA by polyacrylamide gel electrophoresis revealed the synthesis of two discrete peaks of labeled RNA migrating in the region between 18S ribosomal and 4S transfer RNA. These peaks were found in the RNA extracted from polysomes but were absent from single ribosomes. When the polysomes were disrupted by EDTA treatment the RNA species no longer appeared as rapidly sedimenting material. These two RNA's have molecular weights near 2.2 x 10(5) and 3.7 x 10(5) daltons. The chemical and biological properties of these species as well as the molecular weights are consistent with those expected for monocistronic messenger RNA coding for the antibody L and H chains, respectively.

Animals↗
PubMed1968

Single crystals of transfer RNA: an x-ray diffraction study.

Large single crystals of formylmethionyl transfer RNA have been prepared. An x-ray diffraction study shows that the material crystallizes in a hexagonal lattice with a equal to 170 angstroms, c equal to 234 angstroms. The diffraction pattern extends to spacings just under 20 angstroms at present. The crystals are heavily hydrated, containing 88 percent water.

Benzene↗