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Biomedical subjects

I Tinoco

Publications and source records attributed to I Tinoco.

At least 145 records · Page 8Linked to original sources
PubMed1976

Circular dichroism calculations for polyinosinic acid in proposed multi-stranded geometries.

Circular dichroism spectra have been calculated for multi-stranded polyinosinic acid using three different right-handed structures proposed from X-ray diffraction studies. Agreement between calculated spectra and spectra measured at high salt concentration is best for a four strand structure in which the bases are tilted with respect to the helix axis, as proposed by Arnott et al. (1974). For structures in which the bases are perpendicular to the helix axis, the characteristic negative circular dichoroism of polyinosinic acid at long wavelength no longer appears in the calculated spectra. It is clear that a negative circular dichroism at long wavelength does not indicate a left-handed polynucleotide helix.

Circular Dichroism↗
PubMed1976

The kinetics of binding of U-U-C-A to a dodecanucleotide anticodon fragment from yeast tRNA-Phe.

The kinetics of U-U-C-A binding to the dodecanucleotide (A-Cm-U-Gm-A-A-Y-A-psi-m5C-U-Gp) isolated from the anticodon region of yeast tRNA-Phe are similar to the kinetics of binding of U-U-C-A to intact tRNA-Phe. A large enhancement in binding constant over that predicted for U-U-C-A-U-G-A-A is observed for both the complexes of dodecanucleotide and tRNA-Phe with U-U-C-A. This strongly suggests that both the anticodon loop in tRNA-Phe and the dodecanucleotide can form four base pairs with U-U-C-A. Furthermore, the enhanced stability cannot be attributed to a special conformation of the anticodon loop, but instead the anticodon loop is probably flexible. A likely explanation for the increased binding is the effect of non-base-paired ends. This increased thermodynamic stability comes from a larger entropy gain rather than a larger enthalpy decrease.

Adenine Nucleotides↗
PubMed1975

Fluorescence detected circular dichroism study of the anticodon loop of yeast tRNAPhe.

Fluorescence detected circular dichroism (FDCD) measurements have been used to study the conformations of the anticodon loop of yeast phenylalanine tRNA. To our knowledge this is the first application of fluorescence detected circular dichroism. Much smaller amounts of tRNA are needed for the measurement of FDCD than for the conventionally measured circular dichroism. Furthermore, FDCD is specific for conformational changes near the anticodon loop. The FDCD measurements suggest a transition in the anticodon loop near 20 degrees in 0.01 M MgCl2-0.1 M NaCl (pH 7). This is followed by a broad transition from 30 to 60 degrees and finally a sharp melting at 75 degrees consistent with the absorbance detected melting of the entire tRNA. Removal of Mg2+ from the tRNA at 1 degrees causes nearly a factor of two decrease in the FDCD near 230 nm. This indicates a decrease in conformational rigidity in the anticodon loop on removal of Mg2+.

Anticodon↗
PubMed1975

The binding of complementary oligoribonucleotides to yeast initiator Transfer RNA.

Oligoribonucleotide binding to baker's yeast initiator tRNA was measured by equilibrium dialysis in order to determine which regions of the tRNA were free to bind complementary oligomers and which were involved in secondary and tertiary structure. Association constants of trinucleoside diphosphates and tetranucleoside triphophates complementary to the single-stranded regions of the cloverleaf structure of yeast tRNAfMet were measured at o degrees in 1.0 M NaCl, and 0.01 M MgCl2. The only regions of the tRNA whose complementary oligomers bound to the tRNA were the amino acid acceptor end and the five nucleotides at the 5' end of the anticodon loop. These results differ from those for the other tRNAs studied by this technique; usually oligomers complementary to the dihydrouracil loop bind to the tRNA. The sequence of yeast tRNAfMet and other eucaryotic initiators is unusual. The "TpsiC loop" contains the sequence A-U-C instead of T-psi-C, yet the binding pattern to the THE TpsiC LOOP IS LIKE THAT FOR OTHER TRNAs; no oligomers bind.

Binding Sites↗