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71.
John M. Olson 《BBA》1981,637(1):185-188
Two reaction center complexes prepared from cytoplasmic membranes of Chlorobium limicola f. thiosulfato-philum were compared by absorption and CD spectrophotometry. Bacteriopheophytin c (670 nm), which is optically active in one complex but not in the other, may serve as a secondary electron acceptor in the reaction center. 相似文献
72.
Rhodospirillum rubrum strain F24.1 is a spontaneous revertant of nonphototrophic mutant F24 derived from wild-type strain S1. Strain F24 shows no detectable photochemical activity and contains, at most, traces of the photoreaction center polypeptides. Strain F24.1 has a phototrophic growth rate close to that of the wild-type strain (Picorel, R., del Valle-Tascón, S. and Ramírez, J.M. (1977) Arch. Biophys. Biochem. 181, 665–670) but shows little photochemical activity. Light-induced absorbance changes in the near-infrared, photoinduced EPR signals and ferricyanide-elicited absorbance changes indicate that strain F24.1 has a photoreaction center content of 7–8% as compared to strain S1. Polyacrylamide gel electrophoresis of isolated F24.1 chromatophores shows the photoreaction center polypeptides to be present in amounts compatible with this value. Photoreaction center was prepared from strain F24.1 and showed no detectable difference with that of strain S1. It is concluded that strain F24.1 photosynthesis is due entirely to its residual 7–8% of typical photoreaction center. 相似文献
73.
74.
Fifteen amines having a profound effect on carotenogenesis in Marsh seedless grapefruit are reported. The compounds fall into three series: Et2N(CH2)nMe (n = 4–8), Et2N(CH2)nPh (n = 1–5), and Et2NCH2CH2OC6H4R (R=H, p-Me, p-Et, p-iso-Pr, p-tert-Bu), There was up to an 11-fold increase in the total carotene content. Lycopene, not normally accumulated, became a major pigment. The inducing ability of the amines on carotenoid biosynthesis is correlated with the octanol-water partition coefficient. The mode of action appears to be similar to that of 2-(4-chlorophenylthio)triethylamine hydrochloride. 相似文献
75.
Developing desorption isotherms for inorganic phosphorus (P) is a time-consuming and non-standardized procedure. Anion exchange
membranes (AEMs) have been successfully used in studies of P desorption kinetics and total membrane-desorbable P, but rarely
have they been used for developing P desorption isotherms. Our study had two objectives: (1) to evaluate the suitability of
using multiple strips of AEMs (termed the Multiple AEM Method) to develop P desorption isotherms; and (2) to compare the Multiple
AEM Method with a sequential-extraction approach using AEMs (termed the Sequential AEM Method) to determine if the manner
in which AEMs were used would influence the slope of the desorption isotherm, i.e. the partition coefficient. Both methods
yielded well-defined, but numerically different desorption isotherms for all levels of sorbed P. However, estimated K
d
values among methods were equivalent in the low and medium levels of P sorbed. The Multiple AEM method was quicker than the
Sequential AEM method, but both gave similar K
d
values in an agriculturally significant range of soil solution concentrations. These methods should be tested on a range
of soil type to determine their suitability in developing P desorption isotherms and to move toward method standardization
for desorption isotherms. 相似文献
76.
Growing evidence demonstrates that fluctuating metal stressors can have profound impact on the ecophysiological responses in aquatic species. However, how environmental stochasticity affects the complex damage-recovery dynamics in organisms remains difficult to predict. The objective of this paper was to investigate the stochastic behavior in the damage-recovery dynamics in tilapia in response to pulse waterborne copper (Cu). We developed a mathematical framework that allows discrimination between damage and recovery processes in tilapia exposed to designed pulse Cu scenarios. We built deterministic nonlinear models for the damage-recovery dynamics that produce response surfaces describing killing/recovery rate–Cu-pulse interval interactions. Here we showed that the stochastic switching behavior arose from competition among killing, recovery rates, and Cu pulse frequency. This competition resulted in an ultrasensitivity appeared in whole body, gills, muscle, liver, and kidney with Hill coefficients of ≥7, 4, 7, 5, and 5, respectively, at Cu 3 mg L−1, dilution rate 0.05 h−1, and pulse interval 72 h, indicating that a stochastic switch-like response was generated. We argue that the role of gill-associated Hill coefficient as a direct signal of the stochastic switch-like response in the damage-recovery dynamics in response to pulse metal stressor can serve as a sensitive indicator for risk detection in fluctuating environments. Our approach constitutes a general method to identify the stochastic switch-like response for aquatic species exposed to fluctuating metal stressors, which may help to predict and, eventually, expand our understanding of the damage-recovery dynamics. Finally, we implicate that Hill coefficient-based switch-like signal and its damage with hazard response can be linked in an information theoretic framework to handle environmental stochasticity. 相似文献
77.
Makoto Tomimoto 《仿生工程学报(英文版)》2014,11(1):98-108
To achieve favorable Frictional Tactile Sensation (FTS) for robot and humanoid fingers, this report investigated the effects of human finger sweat on Friction Coefficient (FC) and verified the effectiveness of artificial sweat on FTS tbr a humanoid finger. The results show that the model sweat (salt and urea water faked real sweat) increases the FC of the real finger sliding on the high hygroscopic and rough surface (paper), whereas on the low hygroscopic and smooth surface (PMMA), the sweat forms a fluid film and decreases FC, restricting severe finger adhesion. Further, the film formation and capillary adhesion force of sweat were discussed. The experimental results with the artificial sweats (ethanol and water) and humanoid finger (silicone rubber skin with tactile sensors) verifies the effectiveness. The artificial sweat restricts severe adhesion (stick-slip vibration), and enhances cognitive capability of FTS. 相似文献
78.
Hanna Grajek Regina Drabent Grażyna Żurkowska Czesław Bojarski 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(3):456-460
The electronic absorption spectra of the flavomononucleotide (FMN) in aqueous solution and in glycerine-water solution with change of the dye concentration have been measured. The FMN dimer absorption spectrum, monomer absorption spectrum, dimerization constant K and molar fraction of the monomer were calculated. It was found that FMN dimerization constants in aqueous solution were Ka = 118.0 l/mol and in glycerine Kg = 20.5 l/mol. In the region of the monomer absorption band two dimer absorption bands appear, in accordance with the Kasha molecular exciton theory. 相似文献
79.
George K. Wolfer Jr. Jay L. Neil Jr. W. Barton Rippon 《Journal of Protein Chemistry》1987,6(5):441-454
A general monomer-dimer equilibrium system involving ligand interactions ispresented. Cooperativity features of specific limited
models are analyzed by selecting the appropriate family of equilibrium constants from this general scheme. Each system is
then characterized in terms of Hill coefficient dependency on alterations in values of equilibrium constants and total acceptor
concentration. This method permits comparison of predicted cooperativity trends between systems. Contrasting reports concerning
cooperativity dependencies for certain defined equilibrium systems are compared and the discrepancies resolved. Characteristics
of cooperativity binding patterns are shown to include symmetry about dimerization association constant values, both positive
and negative cooperativity for a single set of parameters, and significant changes in cooperativity features with relatively
small changes in equilibrium parameters. 相似文献
80.
Piyush Parkhey Aadil Keshaw Ram Batul Diwan J. Satya Eswari 《Preparative biochemistry & biotechnology》2020,50(8):768-780
AbstractThe present study demonstrates a comparative analysis between the artificial neural network (ANN) and response surface methodology (RSM) as optimization tools for pretreatment and enzymatic hydrolysis of lignocellulosic rice straw. The efficacy for both the processes, that is, pretreatment and enzymatic hydrolysis was evaluated using correlation coefficient (R2) & mean squared error (MSE). The values of R2 obtained by ANN after training, validation, and testing were 1, 0.9005, and 0.997 for pretreatment and 0.962, 0.923, and 0.9941 for enzymatic saccharification, respectively. On the other hand, the R2 values obtained with RSM were 0.9965 for cellulose recovery and 0.9994 for saccharification efficiency. Thus, ANN and RSM together successfully identify the substantial process conditions for rice straw pretreatment and enzymatic saccharification. The percentage of error for ANN and RSM were 0.009 and 0.01 for cellulose recovery and for 0.004 and 0.005 for saccharification efficiency, respectively, which showed the authority of ANN in exemplifying the non-linear behavior of the system. 相似文献