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Biomedical subjects

Y Kyogoku

Publications and source records attributed to Y Kyogoku.

At least 163 records · Page 9Linked to original sources
PubMed1983

Behavior of the imino protons of the lambda OR3 17mer studied by high resolution NMR.

Imino proton resonances of lambda OR3 17mer were observed with time-shared Redfield pulse method by using a JEOL 500 MHz NMR instrument. They show gradual broadening and disappearance with the elevation of temperature indicating the stepwise melting of the duplex. By the selective irradiation at each peak position nuclear Overhauser effects were observed between the imino and adenine C2H protons and between imino protons themselves. Combining these data, fifteen imino proton resonances could be assigned to each base pair except two terminal AT base pairs. Based on the assignment it can be said that AT rich regions near the terminal melt first, followed by the melting of the inside GC rich core. The two AT base pairs in the middle of the GC core are resistant to heat. Spin lattice relaxation times were also observed and the results are consistent with the melting profile.

Bacteriophage lambda↗
PubMed1983

H NMR detection of the specific change to the uncoupled state of the mitochondrial membrane.

The spin-lattice relaxation times T1 of H2O in mitochondrial suspensions at various energy states were measured at 28 degrees C. It was found that de-energization on the addition of an uncoupler of oxidative phosphorylation affects T1: after the addition of the uncoupler, T1 first decreases and then increases to a value greater than those at other different energy states. The T1 values of the unfrozen water in mitochondrial suspensions were measured at -15 degrees C after the energy state of the mitochondria was freeze-trapped. It was found that they increase only in the presence of an uncoupler. These changes in T1 are discussed in relation to the specific change of the mitochondrial membrane in the uncoupled state.

Animals↗
PubMed1982

Detection of separated amino proton resonance signals of adenine derivatives of low temperature and its application to estimation of population of the adenine-uracil dimers in solution.

Splitting of the amino proton signals of 9-ethyladenine derivatives was found in proton nuclear magnetic resonance spectra at low temperature (ca. -30 degrees C). One of the separated signals corresponds to the syn amino proton relative to the N(1) nitrogen in the adenine ring and the other to the anti one. The phenomenon is ascribable to slowing down of the hindered rotation around the N(6)-C(6) bond, which has partial double bond character. On the addition of 1-cyclohexyluracil derivatives, one of the separated signals shifts downfield. From the analysis of the concentration dependence of the signals we could estimate the population of two kinds of adenine-uracil (AU) dimers that employ the syn and anti protons, respectively. i.e. the Watson-Crick-type and the Hoogsteen-type dimers. Independent of the substitution on the uracil ring, the Hoogsteen type is predominant at 70% and the Watson-Crick type at 30% (at -56 degrees C). On the other hand, with mixtures of general kinds of 9-ethyladenine derivatives with 1-cyclohexyluracil. the substituents on the adenine ring cause the population to deviate to extreme values; i.e., either the Watson-Crick-type or the Hoogsteen-type dimer predominates. 2-Chloro-9-ethyladenine and N2-(dimethylamino)-9-ethyladenine take almost completely the Hoogsteen-type dimers, while 8-bromo-9-ethyladenine, N2-(methylamino)-9-ethyladenine, and 2-amino-9-ethylpurine predominant in the Watson-Crick-type dimers.

Adenine↗
PubMed1982

A 15N-NMR study on ribonuclease T1-guanylic acid complex.

Ribonuclease T1 is highly specific for the guanylic acid residue in polyribonucleotides. To clarify the origin of the substrate specificity, the interaction sites of guanylic acid with ribonuclease T1 were investigated by the use of 15N-NMR. 95% 15N-enriched guanosine-3'-phosphate was prepared and mixed with purified ribonuclease T1. 15N-NMR spectra of the mixtures at different concentrations were obtained and compared with that of the 15N-enriched substrate alone. Upon complex formation, a 15N signal assigned to the amino group nitrogen at position 2 of guanine shifted and was significantly broadened, suggesting a strong interaction with the enzyme through the amino group. This observation is consistent with the results of studies on the substrate specificity of chemical modification. Nuclear Overhauser effects of signals assigned to N-7 and N-3 were also changed, but not shift was observed. The observations do not support the occurrence of protonation at N-7 upon complex formation, which was previously proposed.

Guanine Nucleotides↗
PubMed1982

Structure of the lambda tof repressor protein in solution. Heat stability and its relation to binding ability to DNA.

The lambda tof repressor protein was purified from E. coli cells retaining lambda dv plasmids by applying DNA-cellulose chromatography. 3H-labeled lambda dv and lambda imm21dv DNA, carrying and lacking lambda operators, respectively, were prepared and the binding activity of the lambda tof protein to the DNA was examined. Non-specific binding to lambda imm21dv DNA is completely lost at 30 degrees C, whereas specific binding to the DNA carrying the operators is retained even above 40 degrees C. The conformation of the lambda tof protein was analysed by means of circular dichroism and 1H-NMR spectra. The change in the molar ellipticity at 222 nm vs. temperature in CD spectra indicated a transition between two states with Tm at 42 degrees C. The 360 MHz 1H-NMR spectra revealed the presence at 20 degrees C of another change in local conformation of interaction which was not detected by the CD spectra. 1H-NMR also indicated the coexistence of thermal transitions with exchange rates faster and slower than the NMR time scale at about 50 degrees C, which is explained by the presence of domain structures. The NMR titration curve of the His residue gave a normal pK value showing its location on the surface of the protein. These conformational behaviors are well correlated to the specific and non-specific DNA binding activity of the lambda tof protein. The assignments of 1H resonance signals to some specific residues, including His 35 and Tyr 26, were established. It will be useful to determine the tof-DNA interaction.

Bacterial Proteins↗
PubMed1982

N-Trimethylalanine, a novel blocked N-terminal residue of Tetrahymena histone H2B.

Our previous study showed that the amino acid sequence of Tetrahymena histone H2B has a blocked N-terminal residue followed by 119 amino acid residues, X-Pro-Lys.... [J. Biochem. (1982) 91, 897-904]. Now, X has been found to be N-trimethylalanine by 1H nuclear magnetic resonance spectroscopy of the isolated X-Pro-Lys and X. This identification was supported by mass spectrometry of X-Pro-Lys and by column and paper chromatography of X. This is the first time that N-terminal blocking by methylation has ever been found in histones.

Alanine↗
PubMed1982

The effect of protamine on proteinuria and glomerular sclerosis in aminonucleoside nephropathy.

An administration of protamine sulfate combined with aminonucleoside of puromycin (AN) could produce in rats severe nephrotic syndrome and histological changes similar to focal glomerular sclerosis more distinctly than AN alone. This may be attributed to the action of protamine which seemed to enhance the effect of AN, causing polyanion loss at the glomerular basement membrane.

Animals↗
PubMed1982

Deoxyoligonucleotide chain cleavage reactions by phenanthroline and bleomycin.

To elucidate the mechanisms of double-stranded DNA chain cleavage by 1,10-phenanthroline-Cu(I) and bleomycin-Fe(II) complexes in oxygen-dependent reactions, self-complementary deoxyoligonucleotides were treated with the complexes and the degradation products were characterized. The degradation products of d(C-G) by the phenanthroline complex were fully identified by UV, proton and carbon-13 NMR and paper electrophoresis. It is assumed that the DNA chain cleavage and concomitant base release are caused by oxidation of Cl' of the deoxyribose moiety. A duplex of d(ATACGCGTAT) was cleaved by both complexes. Bleomycin shows some sequence specificity but phenanthroline does not.

Base Sequence↗
PubMed1982

NMR studies of base-pairing in 15N-labeled ribotetranucleotide GGCUp.

95% N-15 enriched ribotetranucleotide GGCUp was prepared. Its aqueous solution gives three imino-proton resonances at 10.6, 12.0 and 13.6 ppm. The peak at 10.6 ppm split by N-15 into a doublet with coupling constant 90 Hz. On the preirradiation at this peak, the intensity of the 12.0 ppm peak decreased and the peak at 13.6 ppm remained unchanged. Therefore the 10.6 ppm peak was unambiguously assigned to the G imino proton and the 12.0 ppm peak to the U imino proton in the G:U base pair. By raising temperature the former two peaks coalesced at around 25 degrees C, while the signal of the G imino proton in the G:C pair was observed up to 35 degrees C. The G:U base pair seems to be disrupted first, then the break of the G:C pair is followed. Temperature dependences of the CH proton, N-15 and P-31 nuclei resonances were also measured.

Kinetics↗
PubMed1981

Detection of proton-acceptor sites of hydrogen bonding in adenine X uracil base pairs by the use of 15N magnetic resonance.

2',3',5'-Tri-O-acetyl[1,3,7,9,amino-15N]adenosine(ac3Ado) and its 8-2H and 8-bromo derivatives (ac3[8-2H]Ado and ac3br8Ado) were synthesized from 95% 15N-enriched adenosine which was obtained by microbial fermentation. The chemical shifts and nuclear Overhauser effects of 15N NMR of the adenosine derivatives were measured by changing the concentration of the mixed 1-cyclohexyluracil (cHxUra) in chloroform. The limiting shift of each 15N resonance was calculated by using the association constants obtained from proton magnetic resonances of the ac3Ado/cHxUra and ac3br8Ado/cHxUra systems. From the quantitative analysis of the 15N chemical shifts of the N-1 and N-7 atoms it could be concluded that ac3Ado X cHxUra dimers prefer the Hoogsteen-type pair while the Watson-Crick-type pairs are predominant in the ac3br8Ado X cHxUra dimers. The N-3 atom, which does not locate at the interaction site, showed a fairly large induced shift. Thus the induced shift of 15N resonance by association does not always mean the involvement of the corresponding nucleus to the interaction site. The effect of intermolecular hydrogen bonding on the nuclear Overhauser enhancement of the 15N-7 resonance was observed in the ac3[8-2H]Ado/cHxUra mixture. The presence of the Hoogsteen-type hydrogen bonding was proposed by the use of 15N NMR spectra. The present information will be useful for the elucidation of non-Watson-Crick-type base-pair interaction in transfer TNA and oligonucleotides.

Adenine↗
PubMed1980

Evidence for phase separation in the membrane of an osmotically stabilized fatty acid auxotroph of E. coli and its biological significance.

1. An unsaturated fatty acid auxotroph of Escherichia coli accumulated a high content of saturated fatty acids in its membrane when it was cultured under osmotically stabilized conditions. The physicochemical properties of the phospholipid extracts and of the membrane fraction from the cells were investigated by means of proton magnetic resonance, infrared spectroscopy and differential scanning calorimetry. 2. Physicochemical studies indicate that the phospholipid bilayers in the membranes exhibit at least two phase transitions, a minor one at approx. 19 degrees C and a major one at approx. 43 degrees C. Between the two temperatures, gel and liquid crystalline domains co-exist. Moreover, even in the gel state, phospholipids seem to segregated into domains containing different proportions of unsaturated fatty acids. 3. The Arrhenius plot of beta-galactoside transport rates is biphasic. The inflection point is at 22 degrees C. This means that the appearance of the fluid region in the bilayer at approx. 19 degrees C is important in the activation of membrane transport.

Biological Transport↗
PubMed1980

Morphological changes in an early phase of norepinephrine-induced acute renal failure in unilaterally nephrectomized dogs.

The morphological factors contributing to the reduction GFR in an early phase of NE-induced ARF (0.75 microgram/kg/min) were evaluated by comparing renal morphology at the end of NE infusion with that 2 hr later in unilaterally nephrectomized dogs. GFR 2 hr after NE infusion was reduced to 50% of the preinfusion level in a 30 min infusion group (N = 6), to 13% in a 60 min infusion group (N = 7), and to 2% in a 120 min infusin group (N = 5). On the other hand, simultaneous RBF was not significantly reduced in any group. Dilated PT lumina filled with eosinophilic granular materials in paraffin sections fixed in Zenker-Formol or with impacted swollen blebs in Epon sections fixed in diluted Karnovsky's solution and osmium were found diffusely immediately following 60 and 120 min NE infusion, but patchily after 30 min infusion. Similar changes were found 2 hr after the infusion, except that some PTs came to have dilated but transparent lumina in the 60 and 120 min NE infusion groups. Electron microscopic studies revealed that a part of the membrane-bounded cytoplasm of PT cells extruded into the tubular lumen and became impacted swollen blebs during NE-induced ischemia. There was no prominent foot process fusion in any group. It is concluded that the tubular obstruction by impacted swollen blebs generated in PT during ischemia is a major factor responsible for the reduction in GFR in the early phase of NE-induced ARF.

Acute Kidney Injury↗
PubMed1979

Conformational studies of oxytocin analogues with different ring sizes. I. Circular dichroism.

Circular dichroic spectra were measured for three analogues of deamino-oxytocin of different ring sizes where the disulfide group of oxytocin is replaced by the (CH2)n group. Their backbone rings are composed of different numbers of atoms, i.e., they are nineteen, twenty and twenty-one for [1,6-aminopimelic acid]oxytocin (n = 1), [1,6-aminosuberic acid]oxytocin (n = 2) and [1,6-aminoazelaic acid]oxytocin (n = 3), respectively. The pH dependence of the circular dichroism spectra indicates that the conformation of [1,6-aminoazelaic acid]oxytocin is different from those of others and the temperature dependency reveals that the conformation of [1,6-aminopimelic acid]oxytocin is most rigid. [1,6-Aminosuberic acid]oxytocin is biologically most active among three derivatives and their biological activities are related to the conformation and internal motions of the peptide hormone analogues.

Circular Dichroism↗