A theoretical study of the dielectric constant of protein

The dielectric properties of a protein molecule were investigated by calculating a 'local dielectric constant' with the aid of normal mode analysis. This local dielectric constant was calculated from the electronic polarization of atoms and the orientational polarization of local dipoles. The former was obtained from atomic polarizations of the whole atoms in a protein molecule. The latter was determined from the fluctuation-dissipation theorem. The degree of dipole fluctuation was calculated from the positional fluctuation of each atom obtained by the normal mode analysis. Assuming a minimum volume for a continuum model, the resulting local dielectric constants ranged from 1 to 20 inside the protein.     

Copper absorption in young men fed adequate and low zinc diets

Copper absorption was measured at two levels of dietary zinc in six healthy young men who were confined to a metabolic unit for a 75 d study of zinc utilization. A diet of conventional foods was fed, providing either 16.5 or 5.5 mg zinc and 1.3 mg copper daily. Copper absorption was determined by feeding⁶⁵Cu, a stable isotope of copper, once during the 16.5 mg Zn diet and near the beginning and end of the 5.5 mg Zn diet. Apparent copper absorption averaged 48.1% when the 16.5 mg Zn diet was fed. This was significantly higher than the averages of 37.2 and 38.5% when the 5.5 mg Zn diet was fed. Absorption also differed significantly among subjects. Fecal copper did not differ between diets or among subjects. All subjects were in positive copper balance at both levels of dietary zinc. These results suggest that a dietary zinc intake slightly above the Recommended Dietary Allowance of 15 mg/d does not increase fecal copper loss and does not interfere with copper absorption.     

The effects of guanine and cytosine variation on dinucleotide frequency and amino acid composition in the human genome

Summary One hundred twelve human DNA sequences were analyzed with respect to dinucleotide frequency and amino acid composition. The variation in guanine and cytosine (G+C) content revealed: (1) at 2–3 and 3-1 doublet positions CG discrimination is attenuated at high G+C, but TA disfavor is enhanced, and (2) several amino acids are subject to G+C change. These findings have been reported in part for collections of sequences from various species. The present study confirms that in a single organism-the human-the G+C effects do exist. Aspects of the argument that connects G+C with protein thermal stability are also discussed.     

Inhibition of bovine adrenocortical mitochondrial cytochrome P-450(11)beta-mediated reactions by imidazole derivatives and mineralocorticoid analogs

The effects of several imidazole antimycotic agents, an imidazole and several mineralocorticoid analogs on the cytochrome P-450(11)beta-catalyzed 11 beta-hydroxylation of 11-deoxycorticosterone and aldosterone synthesis were examined. Ketoconazole, clotrimazole, miconazole and etomidate were found to be potent inhibitors of the reactions, causing 50% inhibition of the 11 beta-hydroxylase activity at concentrations between 10(-8) and 10(-7) M. The potency of etomidate as to the inhibition of aldosterone- and 18-hydroxycorticosterone-production was found to be almost equal to that in the case of 11 beta-hydroxylation. Spironolactone and other newly synthesized mineralocorticoid analogs were also found to inhibit the cytochrome P-450(11)beta-mediated reactions. The ID50 values of these drugs for inhibition of the 11 beta-hydroxylase activity were almost equal to those in the case of the aldosterone- and 18-hydroxycorticosterone-biosynthetic activities. The results of kinetical studies indicated that one of the mineralocorticoid analogs, Compound 23-0586, acts as a competitive inhibitor for the cytochrome P-450(11)beta-mediated reactions.     

Analysis of human plasma as an exposure level monitor for carcinogenic tryptophan pyrolysis products

A high-performance liquid chromatography method for detecting 3-amino-1,4- dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in human plasma was developed. Plasma samples of 10 normal subjects were examined. Trp-P-1 and Trp-P-2, carcinogenic tryptophan pyrolysis products, were detected in all specimens, and the concentrations of Trp-P-1 and Trp-P-2 in plasma were 68.31 +/- 24.03 fmoles/ml (mean +/- S.D., n = 10) and 18.79 +/- 4.99 fmoles/ml, respectively. Our results suggest that plasma levels of carcinogenic tryptophan pyrolysis products may be useful indicators for estimating the exposure levels of the dietary carcinogens.     

Chloroplast proliferation based on their distribution and arrangement inAdiantum protonemata growing under red light

Chloroplast proliferation was investigated inAdiantum protonemata growing under continuous red light. Cell division is absent when cells are grown under red light. The chloroplast number increases as the cell length increases, therefore the chloroplasts divide in the absence of cell division. Chloroplasts in the basal part of the filamentous protonemal cell migrate gradually toward the cell apex, but there is no large net migration from the tip to the base or vice versa, indicating that chloroplast division takes place in the apical part of the protonemata. Chloroplast number in the apical 100 μm was maintained at about 200 during cell growth at least over eight days. The chloroplasts were either dumbbell- or ellipsoid-shaped. Dumbbell-shaped chloroplasts are abundant everywhere in a protonema, ranging from 30 to 50% of the total chloroplasts. The dumbbell-shaped chloroplasts attached to or very close to the plasma membrane seem to be the ones that are dividing but the dumbbell-shaped ones in the other regions do not divide. These data support the hypothesis that a signal from the plasma membrane induces the dumbbell-shaped chloroplasts to divide.     

The usefulness of CHAPS as a non-cytotoxic stabilizing agent in purification of growth factors

Among several detergents, a zwitterionic detergent, 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS), was found to be least cytotoxic for cultured mammalian cells. CHAPS improved the activity recovery and elution profile of crude and purified fibroblast growth factors (FGFs) during chromatographies. Diluted preparations of FGFs were stabilized by CHAPS against the loss during storage. Amino acid sequence analysis was not disturbed by CHAPS. CHAPS was removable by reversed-phase high-performance liquid chromatography. These results indicate that CHAPS is useful as a non-cytotoxic stabilizing agent in purification of various kinds of bioactive polypeptides.Abbreviations -MEM Alpha Modification of Eagle's Minimal essential medium - CHAPS 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate - CHAPSO 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propane sulfonate - CS Calf Serum - EGF Epidermal Growth Factor - FGF Fibroblast Growth Factor - HPLC High-Performance Liquid Chromatography - NGF Nerve Growth Factor - NOG 1-O-n-octyl--D-glucopyranoside - NP-40 Nonidet P-40 - PBS Phosphate-Buffered Saline - SB 12 3-(dodecylmethylammonio)-1-propane sulfonate - SDS Sodium Dodecyl Sulfate - TGF- and Transforming Growth Factor type and      

Expression of intermediate filaments and other special markers by testicular germ cell tumors. With reference to embryogenesis.

Distribution of intermediate filament proteins (IFs) and several special markers was studied in 39 testicular germ cell tumors and 8 embryos and foetuses. The similarity and difference between development of germ cell tumor and embryogenesis were immunohistochemically investigated. Seminoma and embryonal carcinoma, as tumoral counterparts of undifferentiated germ cells, were characterized by little IF expression. This study revealed that the maturing and differentiating process in germ cell tumor is different from normal embryonal development and the tumor cells showed leaping maturing steps in tumorigenesis. Immunostaining for IFs helped to discover the further differentiation occurring in embryonal carcinoma and to demonstrate heterogeneous elements in non-seminoma germ cell tumors, which sometimes might not be apparent by light microscopical observation of H&E staining section. According to the findings, two patterns in mixed germ cell tumors are suggested; i.e., combined and diffuse types. The mechanism of tumorigenesis of the two types is supposed to be different. Clinically, the prognosis of most patients with testicular germ cell tumor is fairly good because of the improved chemotherapies that are dependent on histological diagnosis.     

Structural characterization of lipid A component of Erwinia carotovora lipopolysaccharide

The chemical structure of the lipid A component of lipopolysaccharide excreted into the liquid medium by the plant pathogenic enterobacterium Erwinia carotovora FERM P-7576 was characterized. It consists of a -1, 6-linked glucosamine disaccharide which carries ester-and amide-bound fatty acids and phosphate similar to the lipid A from other gram-negative bacteria. The lipid A preparation was not uniform in the number and composition of the fatty acids linked to the disaccharide. Four prominent lipids A were involved, they were composed of five to seven residues of fatty acid. Among them the major component was hexa-acyl lipid A, in which the hydroxyl group at position 3 and the amino group of the non-reducing glucosamine unit carry 3-dodecanoyl-oxytetradecanoyl residues. Positions 2 and 3 of the reducing glucosamine unit were substituted by 3-hydroxytetradecanoic acid. In the hepta-acyl lipid A, an additional hexadecanoic acid was linked to the hydroxyl group of the 3-hydroxytetradecanoyl residue at position 2 of the hexa-acyl lipid A. Two penta-acyl lipids A were the homologs of the hexa-acyl lipid A with decreasing acylation. Dodecanoic acid was missing from one, and 3-hydroxytetradecanoic acid from another. 3-Dodecanoyloxytetradecanoyl residue at position 3 differentiates E. carotovora lipid A from that of other gram-negative bacteria.Abbreviations LPS lipopolysaccharide - GlcN glucosamine - KDO 3-deoxy-d-manno-octulosonic acid - FAB-MS fast atom bombardment mass spectrometry - u atomic mass unit