Biochimica et Biophysica Acta
About: Biochimica et Biophysica Acta is an academic journal. The journal publishes majorly in the area(s): Membrane & Amino acid. It has an ISSN identifier of 0006-3002. Over the lifetime, 112333 publication(s) have been published receiving 4422307 citation(s). The journal is also known as: BBA & Biochim. Biophys. Acta.
Papers published on a yearly basis
Abstract: Measurements of the quantum yields of chlorophyll fluorescence and CO2 assimilation for a number of plant species exposed to changing light intensity and atmospheric CO2 concentrations and during induction of photosynthesis are used to examine the relationship between fluorescence quenching parameters and the quantum yield of non-cyclic electron transport. Over a wide range of physiological conditions the quantum yield of non-cyclic electron transport was found to be directly proportional to the product of the photochemical fluorescence quenching (qQ) and the efficiency of excitation capture by open Photosystem II (PS II) reaction centres (Fv/Fm). A simple fluorescence parameter, ΔφF/φFm, which is defined by the difference in fluorescence yield at maximal φFm, and steady-state φFs, divided by φFm, can be used routinely to estimate changes in the quantum yield of non-cyclic electron transport. It is demonstrated that both the concentration of open PS II reaction centres and the efficiency of excitation capture by these centres will determine the quantum yield of non-cyclic electron transport in vivo and that deactivation of excitation within PS II complexes by non-photochemical processes must influence the quantum yield of non-cyclic electron transport.
Abstract: Electron-transfer reactions between ions and molecules in solution have been the subject of considerable experimental study during the past three decades. Experimental results have also been obtained on related phenomena, such as reactions between ions or molecules and electrodes, charge-transfer spectra, photoelectric emission spectra of ionic solutions, chemiluminescent electron transfers, electron transfer through frozen media, and electron transfer through thin hydrocarbon-like films on electrodes.
Abstract: The extinction coefficients for chlorophylls a and b in diethylether (Smith, J.H.C. and Benitez, A. (1955) in Modern Methods of Plant Analysis (Paech, K. and Tracey, M.V., eds.), Vol. 4, pp. 143–196, Springer-Verlag, Berlin), used in this paper as primary standards, were verified, to within an error of less than 1%, by magnesium determination using atomic absorbance spectrophotometry. We also report the determination of accurate extinction coefficients for chlorophylls a and b in N,N ′-dimethylformamide, methanol or buffered 80% aqueous acetone. Highly purified chlorophylls were used and methods were employed which not only minimize errors due to evaporation of the volatile solvents employed in their estimation but also eliminate variable micro-contamination by chlorophyll degradation products, a potential source of inconsistency between the extinction coefficients obtained in each of these three solvents. Using these new coefficients, expressed as both millimolar and specific coefficients, we have derived new simultaneous equations to obtain chlorophyll concentrations as nmol/ml and μg/ml, respectively. These equations were applied to data obtained with leaf discs from spinach and Flindersia brayleyana extracted with the three specified solvents and to a concentrated solution (in N,N′ -dimethylformamide) of a chlorophyll a + b mixture added to the threesolvent systems. The validity of these equations is proven by the consistency of the chlorophyll determinations and of the chlorophyll a/b ratios. New simultaneous equations, compatible with the equations derived for the threesolvents, are presented for the assay of chlorophylls a and b converted to their cyclic hydroxylactone derivatives by extraction with alkaline pyridine reagent (2.1 M pyridine in 0.35 M NaOH). Most chlorophyll analyses in higher plants, including the chlorophyll content and chlorophyll a/b ratios of plant thylakoids and chlorophyll-protein complexes, have been obtained in 80% aqueous acetone with the much used simultaneous equations of Arnon (Arnon, D.I. (1949) Plant Physiol. 24, 1–15). For this reason we include conversion factors whichcorrect these earlier data and make it compatible with data calculated with the simultaneous equations presented in this paper. The importance of these corrections to the formulation of meaningful models of the photosynthetic apparatus is demonstrated. Our results also indicate that grinding leaf discs with N,N ′-dimethylformamide is a more reliable method for extracting all chlorophylls than shaking with this solvent for 24 h.
TL;DR: Although empirical predictions based on larger numbers of known protein structure tend to be more accurate than those based on a limited sample, the improvement in accuracy is not dramatic, suggesting that the accuracy of current empirical predictive methods will not be substantially increased simply by the inclusion of more data from additional protein structure determinations.
Abstract: Predictions of the secondary structure of T4 phage lysozyme, made by a number of investigators on the basis of the amino acid sequence, are compared with the structure of the protein determined experimentally by X-ray crystallography. Within the amino terminal half of the molecule the locations of helices predicted by a number of methods agree moderately well with the observed structure, however within the carboxyl half of the molecule the overall agreement is poor. For eleven different helix predictions, the coefficients giving the correlation between prediction and observation range from 0.14 to 0.42. The accuracy of the predictions for both beta-sheet regions and for turns are generally lower than for the helices, and in a number of instances the agreement between prediction and observation is no better than would be expected for a random selection of residues. The structural predictions for T4 phage lysozyme are much less successful than was the case for adenylate kinase (Schulz et al. (1974) Nature 250, 140-142). No one method of prediction is clearly superior to all others, and although empirical predictions based on larger numbers of known protein structure tend to be more accurate than those based on a limited sample, the improvement in accuracy is not dramatic, suggesting that the accuracy of current empirical predictive methods will not be substantially increased simply by the inclusion of more data from additional protein structure determinations.
TL;DR: The activities of some glutathione-metabolizing enzymes were observed to be 5-to 60-fold lower in lung tissue than in the liver, and that phenobarbital nor methylcholanthrene had a significant effect on the levels of reduced glutATHione in lung and liver.
Abstract: Levels of glutathione, glutathione reductase and glutathione S-transferase activities in rat lung and liver have been investigated. After perfusing the lung to remove contaminating blood, this organ was found to have an apparent concentration of glutathione (2 mM) which is approx. 20% of that found in the liver. Both organs contain very low levels of glutathione disulfide. Neither phenobarbital nor methylcholanthrene had a significant effect on the levels of reduced glutathione in the lung and liver. In addition, the activities of some glutathine-metabolizing enzymes — glutathione reductase and glutathione S-transferase activity assayed with four different substances — were observed to be 5- to 60-fold lower in lung tissue than in the liver.
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