Phenylglyoxal modification of the Photosystem II reaction center

Time-resolved spectroscopic techniques, including optical flash photolysis and electron spin resonance (ESR), have been used in conjunction with fluorescence-induction and dye-reduction assays to monitor electron transport in Photosystem II (PS II) subchloroplast particles incubated with the covalent modifier, phenylglyoxal. Phenylglyoxal-modified digitonin (D-10) particles from spinach are characterized by a high initial fluorescence yield (Fi) and an abolition of the variable component of fluorescence (Fv); an inhibition of PS-II-mediated reduction of dichlorophenol indophenol (DPIP) by sym-diphenylcarbazide; an abolition of flash-induced absorption transients (t1/2 greater than 2 microseconds) at 820 nm attributed to the primary electron donor, P-680+; the inhibition of photoreduction of the acceptor Qa; and the elimination of the ESR Signal 2s and Signal 2f. These observations suggest the critical participation of specific arginine residues on both the oxidizing and reducing sides of Photosystem II and also implicate phenylglyoxal as a quinone-binding site inhibitor (Golbeck, J.H. and Warden, J.T. (1984) Biochim. Biophys. Acta 767, 263-271).     

Gibberellic acid by solid state fermentation: Consistent and improved yields

Five strains each of Gibberella fujikuroi and Fusarium monoliforme were screened to select G. fujikuroi P-3, a strain capable of giving consistent production of gibberellic acid (GA(3)) by solid state fermentation (SSF). The comparative production of GA(3) by SSF and submerged fermentation (SmF) indicated better productivity with the former technique. The accumulation of GA(3) was 1.626 times higher in the case of SSF. On the basis of available carbohydrates in the media, the percent conversions were 0.096 and 0.156 in SmF and SSF, respectively. The use of coarse wheat bran of the particle size of 0.3-0.4 cm resulted in an increase of 2.5 times in the yield of GA(3). The enrichment of commercial wheat bran with soluble starch gave enhanced accumulation to an extent of 3.5 times. The relation between GA(3) production and cell growth in SSF was similar to that encountered in SmF. The consistent and improved yields to a tune of 1.22 g GA(3) per kilogram dry moldy bran (DMB) establish the potential and feasibility of SSF for the production of GA(3) by G. fujikuroi P-3. On preliminary cost analysis, a net savings of about 60% and 50% on fermentation medium cost and the expenditure on down-stream processing, respectively, as compared to the presently employed SmF technique was evident.     

Influence of Co2+, Ni2+ and Fe2+ on the production of tetrapyrroles by Methanosarcina barkeri

Summary The selective formation of three tetrapyrroles, Co-containing corrinoids, Ni-containing factor F₄₃₀ and Fe-containing cytochromes (haems) by Methanosarcina barkeri Fusaro (DSM 804) was achieved as a function of the concentrations of Co²⁺, Ni²⁺ and Fe²⁺ in a methanol minimmum medium. It was found that about 70% of the total tetrapyrroles synthesized was excreted into the culture supernatant. Hence, the continuous production of tetrapyrroles in a fixed-bed reactor (supporter: porous diatomaceous clay) was carried out at a dilution rate of 10 day^-1 (850 ml medium/85 ml column/day). The effluent discharged from the reactor contained the excreted tetrapyrroles, the concentrations of which were dependent upon the Co²⁺, Ni²⁺ and Fe²⁺ concentrations in the feed medium. The maximum productivities from the reactor (1 l basis) were 52 M corrinoids/day, 24 M F₄₃₀/day and 8 M haems/day, respectively.     

Ultrasound induced damages and time bound recovery in mouse liver

Therapeutic ultrasound at 875 kHz at 10 and 15 W/cm2 intensity induced extensive damages in the liver of mouse. Total exposure of 5 min was spread over 5 days. Aqueous medium was avoided by coupling the transducer directly to the skin surface. Mild to extensive damages were noted. Complete distortion of hepatocellular architecture was noted in 15 W irradiated mice. However, there was almost complete recovery by 10th day following the last exposure.     

Distribution of charged residues stabilizes individual helices in myoglobins

The effect of the distribution of charged residues on stability of alpha helices in isolated peptides and in globular proteins exemplified by myoglobins from 62 different species is discussed. A highly simplified set of rules is used to account for the interaction of charged groups with the dipole of an alpha helix. Only the position and sign of a charge with respect to the center of the helix and its ability to participate in intrahelical salt bridges determine its effect. These rules lead to a linear correlation between the helicity in variant C-peptide helices from RNAse and the extent to which the charge distribution opposes the helix dipole. Of the sample of 496 helices in the myoglobins studied, 456 exhibit arrangements of charges which oppose the effective dipole moment of the helix according to this calculation. A number of variants occur which leave the backbone moment of helices A-D unchanged, or even add to it. However no such variants exist in the sequences of helices E-H. We suggest that the E, F, G and H helices in myoglobins which show the strongest reversal of the helix dipole participate in the structures of early intermediates in folding of the chain. Stable helix structures should be more likely to occur in these isolated sequences also, and introduction of charge alterations in helices E to H should affect the initial refolding rate of mutant myoglobins.     

Effect of methionine-sulfoximine on nitrate uptake and photosynthesis in the cyanobacteriumAnabaena doliolum Bharadwaja

l-Methionine-dl-sulfoximine (MSX) stimulated nitrate uptake but inhibited¹⁴CO₂ fixation and O₂ evolution inAnabaena doliolum. Nitrate uptake was inhibited by ammonium (NH ₄ ⁺ ) in the absence of MSX, but not in the presence of MSX. Glutamine or a derivative of it appears to be the actual negative effector of nitrate utilization. In presence of nitrate, MSX-treated cells ofA. doliolum evolve more O₂ than do untreated cells. Our results suggest a close relation between photoassimilation of carbon and utilization of nitrogen.     

The dynamics of quadrupedal locomotion

This paper presents a dynamical analysis of quadrupedal locomotion, with specific reference to an adult Nubian goat. Measurements of ground reaction forces and limb motion are used to assess variations in intersegmental forces, joint moments, and instantaneous power for three discernible gaits: walking, running, and jumping. In each case, inertial effects of the torso are shown to dominate to the extent that lower-extremity contributions may be considered negligible. Footforces generated by the forelimbs exceed those exerted by the hindlimbs; and, in general, ground reactions increase with speed. The shoulder and hip dominate mechanical energy production during walking, while the knee plays a more significant role in running. In both cases, however, the elbow absorbs energy, and by so doing functions primarily as a damping (control) element. As opposed to either walking or running, jumping requires total horizontal retardation of the body's center of mass. In this instance, generating the necessary vertical thrust amounts to energy absorption at all joints of the lower extremities.     

Effect of Maternal Alcohol Consumption on the Lipid Composition of CNS in the Offspring

Maternal alcohol consumption at a level that does not affect calorie intake increases cholesterol concentration and content as well as incorporation of labeled glucose into cholesterol in the brain and spinal cord of newborn rat pups. Continued consumption of alcohol during lactation also affects the galactolipid concentration in the brain and spinal cord of pups at 21 days of age, and this increase seems mainly to be due to an increase in content of myelin lipids. Analysis of myelin shows that the concentration of phospholipids also increases in this fraction. The increase in incorporation of labeled glucose into these membrane lipids suggests an increase in the synthesis of these lipids, which prevents fluidization of the membrane by alcohol. That in the brainstem the increase in levels of cholesterol and galactolipids is higher than in other regions and that there is also an increase in content of sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine suggest that the brainstem needs better protection against fluidization.     

Mediated uptake of folate by a high-affinity binding protein in sublines of L1210 cells adapted to nanomolar concentrations of folate

An L1210 cell line (JT-1), which can grow in medium supplemented with 1 nM folate, has been isolated. These cells exhibit a slower growth rate than folate-replete parental cells and have a lower ability to transport folate or methotrexate via the reduced folate transport system. Measurements at nanomolar concentrations of folate revealed that the adapted cells have acquired a high-affinity folate-binding protein. Binding to this component at 37 degrees C was rapid and reached a maximum value after 30 min which corresponded in amount to 0.23 +/- 0.3 pmol/mg protein, and excess unlabeled folate added 30 min subsequent to the [3H]folate led to a rapid release of the bound substrate. Radioactivity bound to or released from the cells after 30 min at 37 degrees C remained as unmetabolized folic acid. Binding was also rapid at 0 degrees C but uptake at the plateau was only one-half the value obtained at 37 degrees C. Half-maximal saturation of the binding component (KD) occurred at a folate concentration of 0.065 nM at pH 7.4, while the affinity for folate decreased 30-fold when the pH was reduced to 6.2 (KD = 2.0 nM). 5-Methyltetrahydrofolate was also bound by this component (Ki = 13 nM at pH 7.4) but with a much lower affinity than for folate, while progressively weaker interactions were observed with 5-formyltetrahydrofolate (Ki = 45 nM) and methotrexate (Ki = 325 nM). When the same adaptation procedure was performed with limiting amounts of 5-formyltetrahydrofolate, two additional cell lines, JT-2 and JT-3, were isolated which expressed elevated levels of the folate-binding protein. The binding activity of the latter cells was 0.46 and 1.4 pmol/mg protein, respectively. When the level of binding protein was compared in cells grown at different concentrations of folate, an increase in medium folate from 1 to 500 nM caused a sevenfold reduction in binding activity in the JT-3 cell line, while these same growth conditions had no effect on binding by the other cells. These results indicate that L1210 cells adapted to low concentrations of folate or 5-formyltetrahydrofolate contain elevated levels of a high-affinity binding protein and that this protein is able to mediate the intracellular accumulation of folate compounds. L1210 cells thus appear to have two potential uptake routes for folate compounds, the previously characterized anion-exchange system and a second route mediated by a high-affinity binding protein.(ABSTRACT TRUNCATED AT 400 WORDS)