Proton transport by bacteriorhodopsin through an interface film

Summary Interface films of purple membrane and lipid containing spectroscopically intact and oriented bacteriorhodopsin have been used as a model system to study the function of this protein. Small positive charges in surface potential (<1 mV) are detected upon illumination of these films at the air-water interface. These photopotentials, are not affected by overlaying the interface film with a thin layer (0.3 mm) of decane. However, they are dramatically increased when lipid soluble proton carriers FCCP or DNP are added to the decane. The polarity of the photopotential indicates that, in the light, positive charges are transported through the interface from the aqueous to the organic phase. The action spectrum of the photopotential is identical to the absorption spectrum of bacteriorhodopsin. Since bacteriorhodopsin molecules are oriented with their intracellular surface towards the aqueous subphase, the characteristics of the photopotential indicate that in the light bacteriorhodopsin translocates protons from its intracellular to its extracellular surface. The kinetics of the photopotential reveal that the rate and extent of proton transport are proportional both to the fraction of bacteriorhodopsin molecules excited and to the concentration of proton acceptor. The photopotentials result from changes in the ionic distribution across the decane-water interface and can be cancelled by lipid soluble anions.     

Concept of energy in biological systems and the effects of irradiations of low energies on enzyme-substrate systems

The recent mathematical formalization of the concepts of matter and extrinsical energy, which are used for the relational representation of biological systems, is employed in the analysis of the important experimental discoveries of Comorosanet al. related to low energy electromagnetic irradiations on enzyme substrates. By means of the present analysis one of the properties inherent to the experimental phenomena is more precisely exposed, and theoretical developments corresponding to “energetical evolutions” in a biological system (Leguizamón, 1976) may now have an experimental basis. Important limitations are introduced for the validity of the commutativity and associativity of cartesian product of sets, when they represent matter and its linked extrinsical energy. In connection with this last aspect, new important knowledge is obtained for the relational mathematical representation of biological systems.     

The B-chromosome system of the grasshopper Eyprepocnemis plorans subsp. plorans (Charpentier)

Supernumerary chromosomes of two types have been observed in the grasshopper Eyprepocnemis plorans subsp. plorans. One of these (the B-type) is similar in size to an S autosome; the other is smaller (B-type). Both are telocentric and mitotically stable. The frequencies of individuals with the B-type supernumeraries in five natural populations were 56, 56, 70, 71 and 30 per cent respectively. The equivalent levels of the B-type supernumerary were 0, 0, 13, 3 and 0 per cent respectively. Because of the relative infrequency of the B-type only the B-type has been studied in detail. In males with 1B, anaphase I segregation of X and B was random in four populations but non-random in that from Otivar. Here the B was distinctive in having a secondary constriction near the centromere. A study of chiasma frequency among A-chromosomes revealed that the B-type supernumerary increases significantly both the mean chiasma frequency and the between-cell variance. A comparison of body morphometrics failed to reveal any effect of these B-chromosomes on the exophenotype.     

Theory of lipid bilayer phase transitions as detected by fluorescent probes

Summary We present a quantitative theory that relates the fluorescence intensityvs. temperature (I vs. T) profile of a fluorescent-labeled two-component lipid bilayer to the phase diagram of the bilayer and the partition coefficientK of the fluorophore between fluid and solid phases of the bilayer. We show how the theory can be used to evaluateK from experimentalI vs. T profiles and the appropriate phase diagrams as well as to understand the different shapes ofI vs. T profiles obtained with particular fluorophores and phase diagrams. Using calculatedI vs. T graphs, we discuss the meaning of parameters, such as midpoint of the phase transition and onset and termination of a transition, which are often used to characterize phase transitions on the basis of fluorescence intensityvs. temperature profiles.     

Karyology and evolution inSesamoides (Resedaceae)

The meiotic behaviour abnormalities, fertility and size of pollen of 6 taxa ofSesamoides have been analysed. Besides diploids (2x), polyploids (4x, 6x, 8x) have been found. The chromosome base number is x = 10, but an origin from x = 5 is suggested.     

Distribution of intermediate filaments in amphibian oxyntic cells

Summary Intermediate filaments of toad oxyntic cells were isolated and analysed by SDS-PAGE. The major proteins of the residue were identified as actin and a 51,000 dalton polypeptide. Immunological crossreactivity between toad oxyntic cell intermediate filament components and anti-prekeratin, was shown by double immunodiffusion tests and indirect immunofluorescence. The immunofluorescent decoration of oxyntic cells and the electron microscope images are coincident in locating the intermediate filaments mainly at the cortical and perinuclear basal zones. Furthermore, the cortical zone appears especially rich in prekeratin-like material at its adluminal third. This results in a cup-like structure that encloses the cell portion occupied by the tubulovesicular system, which does not contain intermediate filaments. The translocation of membranes occurring during the secretory cycle of the oxyntic cell, has been attributed to a system of contractile proteins. The disposition of the prekeratin-like material suggests a role for intermediate filaments in the generation of movement, produced by actin and myosin interaction, by providing a fixed plane for the anchoring of actin microfilaments.     

A thermodynamic analysis of the interaction between the mitochondrial coupling adenosine triphosphatase and its naturally occurring inhibitor protein

1. The naturally occurring ATPase (adenosine triphosphatase)-inhibitor protein, from bovine heart mitochondria, was obtained as a single pure protein. It was not identical with any of the five subunits (alpha-epsilon) of the isolated ATPase, and appeared to be a single polypeptide chain. 2. The inhibitor combined with the ATPase in a 1:1 molar ratio, producing a completely inhibited ATPase molecule. The affinity of the ATPase for its inhibitor is high; the K(d) is of the order of 10(-8)m. 3. The enthalpy of the ATPase-inhibitor complex-formation is positive, the value of K(d) decreasing as the temperature is raised. This suggests that the forces involved are largely hydrophobic in nature. 4. Hydrolysis of a nucleoside triphosphate promoted formation of the ATPase-inhibitor complex, although the equilibrium position was almost unaffected by the rate of hydrolysis. At low salt concentration, less than 200 turnovers of the ATPase suffice for the ATPase to combine with the inhibitor protein. At higher salt concentrations, a larger number of turnovers is required. It is suggested that the inhibitor binds to a form of the ATPase that is produced transiently during hydrolysis. 5. In the presence of 75mm-K(2)SO(4), the rates of association and dissociation are slow enough to allow their kinetics to be studied. Association is first-order in inhibitor concentration, but fractional order in ATPase concentration. Dissociation is first-order in ATPase-inhibitor complex concentration. The temperature coefficients of the ;on' and ;off' processes were also measured. 6. A simple kinetic model for the ATPase-inhibitor interaction is proposed that can be extended to take into account release of inhibitor protein under energized conditions on the membrane. 7. The isolated ATPase is inhibited by preincubation with Mg(2+), reversible by subsequent addition of EDTA, and by ADP, reversible by subsequent addition of ATP. These effects are not found on the membrane-bound ATPase. The mechanism of these effects is discussed.     

Evolution of the nucleotide sequence of influenza virus RNA segment 7 during drift of the H3N2 subtype

The complete genetic information contained in the influenza virus RNA segment 7 of the A/Bangkok/ $\text{1}\text{79}$ (H3N2) strain has been cloned by in vitro synthesis of the complementary dsDNA and its insertion into plasmid pBR322. The nucleotide sequence of the viral RNA segment has been determined from the cDNA insert. It is 1027 nucleotides long, and contains two open reading frames, as shown for other influenza virus strains. When compared with the previously published sequence for the A/Udorn/72 (H3N2) strain, 15 nucleotide exchanges are observed, most of them silent mutations, and only two causing amino acid changes in each of the M1 and M2 protein sequences.     

Risk sensitivity in starlings: variability in food amount and food delay

Starlings' preferences for constant versus variable food sourceswere studied in the laboratory. The constant alternative gavea fixed amount of food after a fixed delay. The variable alternativeoffered either a varying amount of food after a fixed delay(treatment A) or a fixed amount of food after a variable delay(treatment B). In both treatments the ratio of amount of foodover trial length (the sum of intertrial interval plus delayand handling times) of the constant alternative equaled theaverage of the two ratios of the variable alternative. The variableratios were 30% higher and 30% smaller than the fixed ratio.In free-choice trials (both options available in each trial),the subjects were risk-averse or indifferent in treatment Aand indifferent or riskprone in treatment B. In no-choice trials(only one source available per trial), the latency to respondwas longer in the variable than in the constant source in treatmentA and the opposite in treatment B. The greater preference forvariability in time than for variability in reward amount isnot consistent with either maximizing the ratio of expectedenergy over expected time or the expected ratio of energy overtime for individual trials. There was a negative correlationbetween individual intake rate and degree of risk pronenessfor both kinds of variability. We present a model of choicebased on an information-processing theory for temporal memorythat accounts for the different effects of variability in delayand in amount but cannot explain the effects of intake rate.[Behav Ecol 1991;2:301–308]