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T Yamane

Publications and source records attributed to T Yamane.

At least 613 records · Page 34Linked to original sources
PubMed1970

Luminescence and binding studies on tRNA-Phe.

The phenylalanine transfer RNA of baker's yeast (tRNA(Phe)) contains a base Y of unknown molecular structure next to the anticodon triplet. Since the base Y fluoresces at room temperature (lambda(max) = 431 nm), its emission properties offer a unique tool for studying conformational and binding properties of tRNA(Phe). The results obtained by these experiments include the following: (1) The quantum yield of fluorescence of Y in tRNA(Phe) (phiF) is 0.07 +/- 0.01 at high Mg(2+) concentrations (>10(-2)M) and about half that at 10(-3)M or less, indicating a [Mg(2+)]-dependent conformational change of the anticodon loop. (2) The fluorescence of Y isolated from tRNAPhe (Y(+)) is red-shifted by 15 nm compared to Y in tRNA(Phe) which suggests a stacked (more hydrophobic) environment for Y in the intact anticodon loop. phiF of Y(+) is 0.035. (3) The solvent isotope effect phiF(D(2)O)/phiF(H(2)O) is 1.5 for tRNA(Phe) and 1.9 for Y(+) i.e., Y in tRNA is still hydrated. (4) The temperature dependence of phiF in a polar glass shows that quenching occurs only at temperatures at which the glass has sufficiently low viscosity to permit solvent shell relaxation in the excited state. The low-temperature (80 degrees K) fluorescence is blue shifted (lambda(max) = 409 nm) and the phosphorescence has a decay time of 1.5 seconds, a threshold at 392 nm and a spectral shape like that of guanine. (5) In the presence of 10(-2)M Mg(2+) penta-uridylate, which contains the codon triplet, a small blue shift and a decrease in phiF are observed. This shift can be used to establish the formation of a binary complex between the codon and the anticodon with an association constant of 4 x 10(2)M(-1), approximately. A similar complex is formed with poly-uridylate but not with poly-cytidylate. In the absence of Mg(2+) the binary complex is not formed.

Binding Sites↗
PubMed1970

Proton nuclear magnetic resonance studies of myoglobin in H2O.

Exchangeable hydrogens in proteins can be identified by comparison of nuclear magnetic resonance spectra obtained in H(2)O and in D(2)O. In oxymyoglobin and myoglobin we have been able to observe resonances of the NH protons of the two tryptophans, as well as one resonance from arginine and one from histidine in the range -10 to -15 ppm downfield from 3-(trimethylsilyl)propanesulfonic acid (sodium salt). These resonances have been identified by chemical modifications coupled with considerations of crystallographic structure and the dependence of the resonances on the species (sperm whale, porpoise, horse) from which the myglobin was obtained and on spin, pH, and temperature.

Animals↗
PubMed1969

Nuclear magnetic resonances of reconstituted myoglobins.

In proton nuclear magnetic resonance spectra of paramagnetic heme proteins, the resonances of the heme groups are shifted away from those of the many hundred protons of the polypeptide chains by interactions with the unpaired electrons and are therefore well resolved at 220 Mc. This paper describes experiments from which these resolved resonances are assigned to specific protons of the heme group in cyanoferrimyoglobin.From a comparison with the proton nuclear magnetic resonance spectra of reconstituted cyanoferrimyoglobins and the corresponding cyanoporphyrin iron (III) complexes, the following groups of heme-protons have been assigned to specific resonances in the NMR spectrum of native cyanoferrimyoglobin: the four ring methyls, the four meso protons, the two -CH groups of the vinyls, and the four methylenes of the propionate side chains. Two resonances of intensity one proton have been assigned to the proximal histidyl residue. The only heme protons whose resonances were not observed are the [unk]CH(2) groups of the vinyl groups which are probably buried in the bulk spectrum of the polypeptide chain. The present data indicate that the protein environment is more important in determining the distribution of unpaired electron density in the heme group than are the heme substituents.

Animals↗
PubMed1968

Proton magnetic resonance of transfer RNA.

The temperature dependence of the areas under the proton magnetic resonance spectra of unfractionated yeast transfer RNA in 1.0 molar NaCl is a consequence of salt-induced aggregation and does not constitute a monitor of the melting of secondary molecular structure. Such melting can be observed by following the widths of the resonances in the various regions of the spectra. Peaks attributable to dihydrouracil and the methyl groups of the methylated bases are detected in the spectra of unfractionated transfer RNA and alanine transfer RNA.

Chemical Phenomena↗