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.     

Longitudinal age changes in a fishermen population of West Bengal

The longitudinal anthropological age changes in a sample of coastal fishermen in West Bengal are discussed. The results show that some traits follow the trends observed in ageing of Western populations, for instance nasal length and breadth continue to increase throughout life in both sexes. Stature follows also the trend generally observed: a decrease occurs indeed from 35 years of age in both sexes, the decline is becoming higher with increasing age. The typical ecological conditions of our population influence the rate of change in other traits, such as weight and biacromial diameter. Weight is known to be influenced by the nutritional status and the way of life. It explains that in our study of males an early increase of weight and biacromial diameter is observed first and a decrease afterwards. In females, however, a decrease is observed already from 35 years of age. This kind of analysis was only possible with the help of longitudinal data and in a well defined population: only longitudinal data is free from the effect of secular changes and of selective death.     

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.     

Abnormalities of the erythrocyte membrane in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a hematologic malignancy characterized by excessive growth of myeloid cells and their progenitors. The proportion of spectrin dimers compared to tetramers extracted from membranes at 4 degrees C, under low ionic strength conditions, increased in CML erythrocytes. These also displayed abnormal thermal sensitivity (between 45 and 46 instead of 49 degrees C). Crosslinking with the bifunctional reagent, dimethyl adipimidate (8.6 A) showed significant organizational modification of not only spectrin, but other cytoskeletal components such as ankyrin, bands 4.2 and 5. Enhanced concanavalin A (Con-A) agglutinability of CML erythrocytes also suggests altered topographic distribution of a functionally important membrane protein, band 3. The anion transport activities of erythrocytes from patients with CML and normal donors were comparable. In CML erythrocytes, significant reduction in the number of ankyrin-binding sites, present in the cytoplasmic domain of band 3, may lead to partial loss of cytoskeletal anchorage to the bilayer and account for their increased Con-A agglutinability and heat sensitivity and may lead to their premature removal from the circulation.     

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.