Search PubMed⌕ Search

Biomedical subjects

K Nitta

Publications and source records attributed to K Nitta.

At least 361 records · Page 20Linked to original sources
PubMed1976

Equilbrium and kinetics of the unfolding of alpha-lactalbumin by guanidine hydrochloride (II).

The reversible unfolding of alpha-lactalbumin by guanidine hydrochloride, was studied at 25.0 degrees C in a relatively low concentration range of the denaturant (0.80-2.00 mol/l) by means of difference spectra and pH-jump measurements. The unfolding was shown to occur between two states, N and D, because apparent rate-constants of the unfolding and the refolding reactions depended only on pH. All curves plotted as the logarithmical equilibrium constant log KD against pH could fall on the same base curve by shifting each curve along the log KD axis. From the dependence of the logarithmic rate constant on pH, master curves could also be made for the forward and the backward reactions. The dependence of these master curves on pH indicates that the groups affecting the pH dependence of the unfolding are three residues with pKN = 3.3 and pKA = pKD = 4.4, one residue with pKN = pKA = 3.8 and pKD = 4.4, and one residue with pKN = 5.8 and pKA = pKD = 6.3, where A indicates the activated state. On the other hand, from the denaturant activity dependence of the shift factors required for making the master curves, the value of the intrinsic binding constant of the denaturant to the protein was found to be similar to that obtained from previous measurements at pH 5.5. Differences between the numbers of the binding sites of the denaturant on the denaturated and the native proteins, and between those on the activated and the native proteins were shown to be 5.3 and 2.1, respectively. The free energy of stabilization in the native-like environment also shows that the protein in the native state is more unstable than lysozyme.

Animals↗
PubMed1975

Polymer concentration dependence of the helix to random coil transition of a charged polypeptide in aqueous salt solution.

The helix to coil transition of poly(L-glutamic acid) was investigated in 0.05 and 0.005 M aqueous potassium chloride solutions by use of potentiometric titration and circular dichroism measurement. Polymer concentration dependence of the transition was observed in the range from 0.006 to 0.04 monomol/e in 0.005 M KG1 solution. The polymer concentration dependence can be interpreted by current theories of the transition of charged polypeptides and of titration curves of linear weak polyelectrolytes taking the effect of polymer concentration into consideration.

Glutamates↗
PubMed1975

Revistin found by screening for inhibitors of reverse transcriptase of an oncogenic virus.

Revistin, a substance that strongly inhibits the reverse transcriptase activity of murine leukemia virus in our screening system, was obtained from a cultured broth of a soil streptomyces which was closely related to Streptomyces filipinensis. The assay method for the activity was based on the inhibition by a test material of the incorporation of 3H-dTMP into DNA synthesized by the reverse transcriptase of an oncogenic RNA virus. Crude revistin was isolated by serial procedures of salting out with ammonium sulfate and precipitation with cetylpyridinium chloride. The crude material showed neither antibacterial nor antifungal activity. It exhibited against splenomegaly in mice caused by Rauscher leukemia virus infection.

Animals↗
PubMed1975

New adrenal-scanning agent.

A new adrenal-specific compound, 6beta-iodomethyl-19-norcholest-5(10)-en-3beta-ol(NCL-3-I), which is derived from 19-iodocholesterol (CL-19-I), has been found. Tissue distribution studies have revealed that the rat adrenal gland accumulates ten times more NCL-6-131-I than CL-19-131-I. The advantage of NCL-6-131-I as a possible adrenal-scanning agent is discussed.

Adrenal Gland Diseases↗
PubMed1975

A kinetic aspect of the antibody production against Ehrlich tumor cells in mice bearing Ehrlich solid tumor.

The number of cells producing the anti-Ehrlich tumor antibody (antibody against Ehrlich tumor cells) in the spleen of mice bearing Ehrlich solid tumor was counted by the modified Cunningham method, in which the sheep red blood cells were conjugated with extracted specific Ehrlich tumor antigen and used. The antibody-producing cells appeared 6 days after the subcutaneous transplantation of Ehrlich tumor cells and increased in number with a peak around the 15th day. Humoral anti-Ehrlich tumor antibody estimated by immune adherence gradually increased in the tumor-bearing mice, reached the maximum 15 days after the transplantation or later, and maintained the high level for a long period. The subcutaneous solid tumor grew and reached the maximum in weight around the 15th day and regressed thereafter.

Animals↗
PubMed1975

Action of bacterial neutral protease on the dispersion of mammalian cells in tissue culture.

The effect of a bacterial neutral protease on cultured cells was examined with special reference to its activity on the detachment of cells from glass surface, dissociation into single cells and to the inhibitory effect on cell proliferation. Fibroblasts of strains L-929 and CHO-K1, and epithelial cells of strains HeLa-S3, JTC-16 and RLC-10(2) were employed. Fibroblasts were detached and dissociated when this protease was added to MEM supplemented with fetal bovine serum. The epithelial cells were detached but were scarcely dissociated. Kinetic data were obtained concerning the dispersing characteristics of this bacterial neutral protease together with a few aspects on the difference between epithelial cells and fibroblasts in the nature of cell to cell, and cell to substrate interactions.

Bacillus↗
PubMed1975

Electrophoretic investigations of the acid conformational change of alpha-lactalbumin.

In order to clarify how the electrophoretic behavior reflects the conformational transition of globular proteins, moving boundary electrophoresis was applied to analysis of the acid conformational change of alpha-lactalbumin. The appearance of only a single electrophoretic boundary in the transition region of the protein suggests a very rapid transition with a half-time estimated to be smaller than 7 min on the basis of the theory of isomerizing systems in electrophoresis. The transition is clearly reflected in the dependence of the mobility on the protein net charge, which shows a sigmoidal curve closely similar to that obtained by a Linderstrøm-Lang pH-tritration plot for the carboxyl groups of alpha-lactalbumin. It was also concluded from the transition curves that the acidfication does not result in complete unfolding, but that a compact structure is maintained in the acidic region with an apparently expanded form as compared to the native state of the protein. All results obtained by electrophoresis were also supported by the results of pH-jump studies, analytical gel chromatography, and CD measurements.

Circular Dichroism↗
PubMed1975

Tissue dispersion, cell harvest and fluid suspension culture by the use of bacterial neutral protease.

Bacterial neutral protease of Bacillus polymyxa was found to disperse mammalian tissues and cells. Primary cell cultures were obtained from several tissues after treatments with 200 to 2,000 Kunitz unit per ml of this protease in either a phosphate buffer solution, a balanced salt solution or a tissue culture medium supplemented with serum. Monolayer cultures wither in their early passage levels or of established strains were harvested by a treatment with this protease, and proliferated again in monolayer after its removal. A growing culture of strain L-929 was kept in monodisperse suspension in the presence of this protease. In contrast to trypsin, this protease was found active in the presence of serum, stable during incubation and scarcely injured cells.

Animals↗