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Biomedical subjects

M Cannon

Publications and source records attributed to M Cannon.

126 records · Page 7Linked to original sources
PubMed1973

Association of nascent polypeptide with 30S ribosomal subunits.

1. Crude extracts of Escherichia coli were used to synthesize nascent peptides under the direction of endogenous mRNA and in the presence of radioactive amino acids. Analysis of such extracts by sucrose-gradient centrifugation in low Mg(2+) concentration has shown that after 2min of incubation approximately 14% of the total labelled protein recovered on the gradient, in association with whole ribosomes, sediments with 30S ribosomal subunits; this value rises to approximately 24% after 30min of incubation. The labelled protein associated with 30S ribosomal subunits is insoluble in hot trichloroacetic acid. 2. Similar results were also obtained in extracts that synthesized polypeptides under the direction of either of the synthetic polyribonucleotides poly(A) or poly(A,G,C,U). In contrast, however, analysis of crude extracts programmed in protein synthesis by poly(U) has indicated that under these conditions 30S ribosomal subunits have no associated polyphenylalanine; similarly there is little associated peptide after programming of extracts by poly(U,C).

Amino Acids↗
PubMed1973

Association of nascent polypeptide and transfer ribonucleic acid with 30S ribosomal subunits.

1. Crude extracts of Escherichia coli programmed in protein synthesis by endogenous mRNA have incorporated amino acids into protein. Analysis of such extracts by sucrose-gradient centrifugation in low Mg(2+) concentration has revealed that 30S ribosomal subunits carry associated radioactive material of which a considerable proportion can be removed from ribosomes by treatment of pre-labelled extracts with puromycin. 2. Gradient analyses of incorporations carried out in the additional presence of added (32)P-labelled tRNA have indicated that tRNA sediments in the regions of the newly synthesized nascent protein and that both labels are associated with all ribosomal components detected on the gradients under the experimental conditions employed. 3. 30S ribosomal subunits carrying both (32)P and (14)C labels have been isolated, disrupted with sodium dodecyl sulphate, and analysed by chromatography on Sephadex G-200 columns. Both labels elute closely together and well away from a tRNA marker analysed under identical conditions. 4. It is proposed that 30S ribosomal subunits, isolated from extracts which have synthesized nascent peptides under the direction of endogenous mRNA, carry associated peptidyl-tRNA.

Amino Acids↗
PubMed1967

The ribosomal binding site for peptidyl-transfer-ribonucleic acid.

The properties of a site, on Escherichia coli ribosomes, which binds peptidyl-s-RNA (where s-RNA refers to ;soluble' or transfer RNA) have been investigated. The binding is stable both in low Mg(2+) concentration (0.1mm), and in high Mg(2+) concentration (10mm) in the absence or presence of potassium chloride (86mm). Puromycin has been used to break the bond between the s-RNA and the polypeptide, and in the absence of further protein synthesis this technique exposes free s-RNA molecules on the ribosomes. The s-RNA exposed remains bound in high Mg(2+) concentration, but the binding is unstable in high Mg(2+) concentration with potassium chloride and the s-RNA can be freed completely from the ribosomes by lowering the Mg(2+) concentration. It can also be displaced by s-RNA in the medium. It is suggested that this ribosomal binding site for peptidyl-s-RNA is the site for peptide bond formation. Further, it is proposed that it is the same site that can be demonstrated on ribosomes not engaged in protein synthesis and that, in high Mg(2+) concentration, will bind s-RNA molecules charged or uncharged with amino acids.

Binding Sites↗
PubMedDate not supplied

Rapid determination of low pg/mg amounts of N-nitrosodimethylamine in rodent body fluid and tissue samples by low resolution mass spectrometry.

A rapid, sensitive, specific, and cost-effective method for the determination of N-nitrosodimethylamine (NDMA) in rodent tissue and body fluid samples is reported. The method involves isolation of the NDMA from the samples with subsequent detection and quantitation of observed NDMA against a mass labeled N-[15N]nitrosodimethyl-[15N]amine ([15N]NDMA) internal standard by capillary gas chromatography/mass spectrometry with selected ion monitoring. Validation of the method includes linearity studies of NDMA response, calculation of the relative response factor (RRF) for NDMA vs. [15N]NDMA, and absolute recovery studies. Estimates of precision, detection limit, and minimum quantifiable limit are also reported.

Animals↗