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T Nagamura

Publications and source records attributed to T Nagamura.

11 recordsLinked to original sources
PubMed2001

Unusual electronic absorption changes in the 800-2200 nm region by intramolecular dimer radical cations from photoirradiated meso-2,4-bis[4-(4'-nitrostyryl)pyridinium]pentane ditetraphenylborates during storage in the dark.

Electronic absorption spectra were remarkably changed in the broad near-infrared region for photoirradiated meso-2,4-bis[4-(4'-nitrostyryl)pyridinium]pentane ditetraphenylborates during storage in the dark, which was attributed to conformational changes of the intramolecular dimer radical cations between sandwich and partially overlapped types.

Journal Article↗
PubMed1993

X-ray absorption spectroscopic studies of a transient intermediate in the reaction of cyanide metmyoglobin with dithionite by using rapid freezing.

The reaction of cyanide metmyoglobin (Mb+CN-) with dithionite produces a transient intermediate, supposed to be cyanide-ligated ferrous myoglobin. The Fe K-edge X-ray absorption spectrum of the intermediate has been measured by using rapid freezing and compared with those of Mb+CN- and deoxymyoglobin (deoxyMb). The shapes of the XANES (X-ray Absorption Near Edge Structure) spectra of Mb+CN- and the intermediate are very similar, including the intensity ratios of the peak C1 to D. This indicates that CN- remains bound with a linear Fe-C-N configuration in the intermediate. The absorption edge of the intermediate is shifted to 1.2 eV lower energy than that of Mb+CN-, reflecting a valence change in the heme iron. The EXAFS (Extended X-ray Absorption Fine Structure) spectrum of the intermediate closely resembles that of Mb+CN- but significantly differs from that of deoxyMb. Analysis shows that the average iron-nearest neighbor atom distance is 1.99 +/- 0.01 A for both Mb+CN- and the intermediate and 2.05 +/- 0.01 A for deoxyMb. These results imply that the local structure around the heme iron of Mb+CN- does not change upon reduction until the cyanide ligand is released.

Animals↗
PubMed1992

Study on the interaction between soybean beta-amylase and substrate by the stopped-flow method.

The hydrolysis of substrates (maltoheptaose, maltopentaose, and maltotetraose) catalyzed by soybean beta-amylase [EC 3.2.1.2] at pH 5.4 and 25 degrees C was followed by monitoring small changes in the quenching of fluorescence due to tryptophan residues by the stopped-flow method. By analysis of whole time course, the dissociation constants, KdS, of enzyme-substrate and enzyme-product complexes were reasonably evaluated; and the difference in fluorescence intensities per mol between the enzyme-complex (ES or EP) and the free enzyme, delta F, was determined. The molecular activity, k0, was also determined by a new method of half time analysis. The KdS and k0 values are in good agreement with our kinetic data reported previously. The delta Fs of substrates were of smaller magnitude than those of products (G2 and G3), which means that the higher the binding affinity of the ligand is, the smaller the delta F value is. This indicates that at least two tryptophan residues must be located in the active site if the enzyme is rigid, or that if there is only one, the active site must undergo a structural change caused by the binding of ligand.

Hydrolysis↗
PubMed1987

Rapid formation of secondary structure framework in protein folding studied by stopped-flow circular dichroism.

Kinetic refolding reactions of ferricytochrome c and beta-lactoglobulin have been studied by stopped-flow circular dichroism by monitoring rapid ellipticity changes of peptide backbone and side-chain chromophores. In both proteins, a transient intermediate accumulates within the dead time of stopped-flow mixing (18 ms), and the intermediate has an appreciable amount of secondary structure but possesses an unfolded tertiary structure. It is suggested that the rapid formation of a secondary structure framework in protein folding is a common property observed in a variety of globular proteins.

Circular Dichroism↗
PubMed1985

Stopped-flow X-ray scattering device with a slit-type mixer.

A slit-type mixer specially designed for stopped-flow X-ray scattering was constructed. It mixes two solutions at a time, allowing a large-sized window to be used immediately after mixing. Dead time of the mixer was 13 ms with 3.5 kg/cm2 of pressure at the piston head. It has been successfully used for studying the tetramer-dimer interconversion of phosphorylase a. The applicability of this mixer to other detection methods, far-UV circular dichroism, light scattering, EXAFS and fluorescence is also indicated.

2,6-Dichloroindophenol↗