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Microsomal nucleoprotein particles from pea seedlings

Ts'o, Paul O. P. and Bonner, James and Vinograd, Jerome (1956) Microsomal nucleoprotein particles from pea seedlings. Journal of Biophysical and Biochemical Cytology, 2 (4). pp. 451-467. ISSN 0095-9901.

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Ultracentrifugal analysis of an extract of pea epicotyls, previously freed of debris and larger particles by centrifugation at 40,000 g for 10 minutes, has revealed the presence of a major component which possesses a sedimentation coefficient of 74 S. This component constitutes about 25 per cent of the TCA-precipitable material in the clarified epicotyl extract and is estimated to make up 1 to 2 per cent of the dry weight of the original tissue. In size, chemical composition, and morphology, the 74 S component resembles the nucleoproteins of the microsomes from animal tissues. The 74 S component of pea epicotyl extracts has been purified by repeated cycles of differential centrifugation to yield a preparation which is 80 per cent homogeneous in the analytical ultracentrifuge. It has been found to contain 30 to 37 per cent RNA as judged by a variety of analytical techniques. Approximately 55 per cent of the weight of the material is protein and a further 4.5 per cent phospholipide. Electron micrographs of air-dried specimens of the purified preparation show the 74 S constituent to be flattened spheres with an average height of 180 A and an average diameter of approximately 280 A. The molecular weight of the 74 S particles is computed from sedimentation, viscosity, and partial specific volume data to be 4.5 million ± 10 per cent in agreement with the value estimated from electron micrographs. The 74 S or microsomal component of pea epicotyls is rapidly aggregated in the presence of low concentrations of Mg ions or by somewhat higher concentrations of Ca or K salts. ATP on the contrary causes resolution of electrolyte-induced microsomal aggregates with simultaneous degradation of the particles to an ultracentrifugally inhomogeneous mixture of lower molecular weight materials.

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Additional Information:Copyright © 1956 by Rockefeller University Press (Received for publication, April 25, 1956) Report of work supported in part by a grant No. H-1645 from the National Institutes of Health, United States Public Health Service. Contribution No. 2092 from the Gates and Crellin Laboratories of Chemistry, California Institute of Technology, Pasadena.
Issue or Number:4
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4933
Deposited By: Archive Administrator
Deposited On:13 Sep 2006
Last Modified:02 Oct 2019 23:17

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