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G R Barker

Publications and source records attributed to G R Barker.

64 records · Page 4Linked to original sources
PubMed1967

The degradation of ribonucleic acid in the cotyledons of Pisum arvense.

1. A ribonuclease has been partially purified from the cotyledons of germinating seed of Pisum arvense. 2. The enzyme degrades ribopolynucleotides to adenosine 3'-phosphate, guanosine 3'-phosphate and the cyclic nucleotides cytidine 2',3'-phosphate and uridine 2',3'-phosphate; no resistant ;core' remains. 3. The activity of RNA-degrading enzymes in the cotyledons increases to a maximum during the first 5 days of germination, passes through a minimum around the eighth day, and thereafter increases again. 4. Ion-exchange chromatography of methanol-soluble extracts of cotyledons revealed the presence, amongst other components, of the 2'-, 3'- and 5'-phosphates of cytidine and uridine, the 3'- and 5'-phosphates of adenosine, and guanosine 5'-phosphate. 5. Seed soaked in a solution containing [(32)P]orthophosphate gave a methanol-soluble fraction containing labelled nucleoside 5'-phosphates, but nucleoside 2'- and 3'-phosphates were not labelled. 6. It is believed that the nucleoside 2'- and 3'-phosphates arise by the action of ribonuclease on cotyledon RNA.

Chromatography, Ion Exchange↗
PubMed1967

The development of polysomes in the seed of Pisum arvense.

1. Ribosomal preparations from dormant seed, cotyledon and growing tissue from Pisum arvense were examined. 2. Polysomes were obtained from growing tissues under all conditions used. 3. Such particles were obtained from seed immediately after imbibition only when 5mm-zinc sulphate was included in the medium used for extraction. 4. No polysomes were obtained from dry seed. 5. Extracts of dry seed showed limited incorporation of phenylalanine into protein. 6. Extracts of seed after imbibition showed enhanced activity in incorporation of phenylalanine amounting to 72% of the activity found in extracts of growing tissue. 7. A nuclear fraction from dry seed was able to incorporate ATP into acid-precipitable material. 8. It is concluded that the protein-synthesizing system of the dry seed is limited by the low concentration of functional polysomes.

Journal Article↗