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G Atfield

Publications and source records attributed to G Atfield.

6 recordsLinked to original sources
PubMed1976

Application of a spectrophotometric method to the determination of the composition of oligonucleotides obtained from cysteine transfer ribonucleic acid.

1. The applications of methods for determining the composition of oligonucleotides from u.v.-absorption spectra is described. 2. In the first method absorbances at selected wave-lengths were read from the spectra of oligonucleotides in solution in 7 M-urea which had been recorded at acid and alkaline pH values. 3. In the second method absorbances were sampled automatically at regular time-intervals during scans at acid and alkaline pH of each spectrum, converted into digital signals and recorded on paper take for computer processing. The holmium spectrum in the region of the holmium peak at 333.7 nm was superimposed on each nucleotide spectrum. The position of this peak maximum was used as a standard reference point in the computer-based analysis. 4. By using either method the composition was calculated by a least-squares procedure by using a library of values for five standard nucelotides obtained in a similar manner. 5. The methods gave satisfactory compositions for mixtures of mononucleotides as well as for five dinucleoside monophosphates. 6. Methods of minimizing the effects on the nucleotide composition of spectural changes due to base stacking are discussed. 7. The compositions of some oligonucleotides obtained during an investigation of the nucleotide sequence of tRNA (Cys) were determined and agreed with the sequences found by other methods.

Base Sequence↗
PubMed1976

The extraction and purification of a cysteine transfer ribonucleic acid from baker's yeast.

1. A modification of the RPC 1 system of A.D. Kelmers, G.D. Novelli & M.P. Stulberg (1965) (J. Biol. Chem. 240, 3979-3983) is described in which the support medium is a Celite of narrow range particle size treated with dichlorodimethylsilane. 2. By using this system an apparently pure preparation of tRNA Cys was isolated from baker's yeast tRNA. 3. This preparation accepted at least 60% of the theoretical quantity of [3-14C]cysteine in a conventional assay and failed to accept isoleucine, phenylalanine, proline, serine or tyrosine. 4. A theoretical countercurrent-distribution curve calculated by assuming a distribution coefficient K of 2.03 was in excellent agreement with the profiles of E260 and cysteine-acceptor ability after 537 transfers in the 1.85 M-phosphate/formamide/propan-2-ol system of C.M. Connelly & B.P. Doctor (1965) (J. Biol. Chem. 241, 715-719). 5. Chromatography of tRNA Cys on Bio-Gel P100 polyacrylamide beads afforded two components one of which was far less efficient than the other in accepting cysteine. The base compositions of the two were similar.

Amino Acids↗
PubMed1976

The nucleotide sequence of cysteine transfer ribonucleic acid from baker's yeast. Products of complete digestion with pancreatic ribonuclease and ribonuclease T1.

1. The nucleotide chain of tRNA Cys from baker's yeast was readily split at the anticolon into two large fragments by brief treatment with ribonuclease T1.2. The whole molecule and the two derived large fragments were completely digested with (a) pancreatic ribonuclease and (b) ribonuclease T1. The fragments present in each of the digests were separated and sequenced by conventional methods. 3. The groups of fragments derived from the two methods of digestion were entirely compatible with each other. 4. The molecule is 75 nucleotides long, but, as isolated, lacks the terminal adenosine and the neighboring cytidylic acid residue. The minor nucleotides 1-methyladenylic acid, 7-methylguanylic acid, 5-methylcytidylic acid and N6 (gamma gamma-dimethylallyl)adenylic acid (isopentenyladenylic acid) were identified.

Base Sequence↗
PubMed1976

The nucleotide sequence of cysteine transfer ribonucleic acid from baker's yeast. Identification of the products from partial degradation of the molecule and derivation of the complete sequence.

1. A series of large oligonucleotide fragments derived from tRNA Cys, were separated chromatographically and the sequence of each was deduced by examination of the products of digestion with pancreatic and T1 ribonucleases. 2. The location of the specific cleavage points in the nucleotide chain was similar to that produced by brief treatment with pancreatic ribonuclease. 3. The fragments could be arranged into two alternative sequences. The correct sequence was deduced by the sequential removal and identification of the first nine nucleotides from the 3'-end of the terminal half of the molecules.

Base Sequence↗