Balance of macroergic compounds during the growth of Thiobacillus ferrooxidans

The balance of energy-rich compounds (ERC) was drawn up for the growth of Thiobacillus ferrooxidans in a medium with ferrous ions as an energy source. The balance items and the phosphorylating efficiency of oxidation (P/2e-) were calculated basing on the experimental yield values using the ERC balance equation. At a specific growth rate of 0.1 h-1, 55% of ferrous ions are used for the synthesis of cell biomass, 7.5% for maintainance, 4% of the ions are oxidized to reduce NAD+, and 34% are used to produce ERC necessary for the reduction. Here, 24% of ERC are used for the synthesis of monomers from CO2, 42% for the production of NADH, 24% for the biomass synthesis from monomers, and 10% for maintaining cell activity. The P/2e- for the oxidation of ferrous ions is 0.19 mole of ERC per 2e-. This is possible only when the [Fe3+]/[Fe2+] ratio in the cell periplasm is 1 X 10(3)-1 X 10(4).     

Preferential Photosynthetic Uptake of Exogenous HCO(3) in the Marine Macroalga Chondrus crispus

The rate of HCO₃⁻ uptake by the red macroalga Chondrus crispus has been investigated. Unbalanced concentrations of free CO₂ and HCO₃⁻, generated by the photosynthetic activity, were detected in steady state conditions by using an exchange column apparatus linked to an assimilation chamber. Observing the variations of this gradient as influenced by the time of seawater transit from the assimilation chamber towards the column allowed an experimental determination of: (a) the actual gradient created by the photosynthetic activity, (b) the rate constant of the chemical conversion of free CO₂ to HCO₃⁻. With a value of 0.115 per second at pH 8.92, this rate constant was in good agreement with a previous estimation. By using a simple model, we show that the photosynthetic rate of HCO₃⁻ consumption can be estimated by the product of the actual gradient and the rate constant. In the conditions of the experiments reported here, this rate represented more than 90% of the whole photosynthetic flux.     

Evaluation of quantitative parameters of the interaction of antibody-bearing liposomes with target antigens

The model system for the analysis of targeted liposomes is proposed--the layer of protein antigen adsorbed on polystyrene wells. Antibodies were treated with palmitoyl chloride and liposomes were produced by the cholate dialysis method in the presence of the modified protein (7 X 10(-4) mol protein/mol lipid). Affinity of antibody-bearing liposomes to the antigen on the surface of Multiwell plates was studied, and apparent dissociation constant value was estimated: KD was in the range 1.5 to 5 X 10(-9) M liposomes. Sequential transfers of liposomes in antigen-coated plates revealed that the high-affinity fraction of liposomes is adsorbed first. The bound fraction has 1.7-times-higher protein content. For effective in vivo targeting it would be necessary to have high-affinity liposomes and a high concentration of the target antigen.     

Transport of hydrophobic ions in erythrocyte membrane: I. Zero membrane potential properties

Summary The permeability and partition coefficients of tetraphenylarsonium (TPA) and several other organic cations were studied in the human erythrocyte using an ion-selective electrode. The permeability constant for the different cations could be explained quite well by differences in oil/water partition coefficients. No evidence for facilitated transport could be found. Binding of the organic ions occurred to both the cell membrane and to intracellular contents. Partitioning to the membrane remained relatively constant despite variation from ion intracellular binding with blood samples from different donors. TPA flux is stimulated by substoichiometric amounts of tetraphenylboron and other organic anions, suggesting an ion-pairing mechanism.     

Continuous Measurements of the Free Dissolved CO(2) Concentration during Photosynthesis of Marine Plants: Evidence for HCO(3) Use in Chondrus crispus

An experimental system consisting of a gas exchange column linked to an assimilation chamber has been developed to record continuously the free dissolved CO₂ concentration in seawater containing marine plants. From experiments performed on the red macroalga Chondrus crispus (Rhodophyta, Gigartinales), this measurement is in agreement with the free CO₂ concentration calculated from the resistance to CO₂ exchanges in a biphasic system (gas and liquid) as earlier reported. The response time of this apparatus is short enough to detect, in conditions of constant pH, a photosynthesis-caused gradient between free CO₂ and HCO₃⁻ pools which half-equilibrates in 25 seconds. Abolished by carbonic anhydrase, the magnitude of this gradient increases with decreasing time of seawater transit from the chamber to the column apparatus. But its maximum magnitude (0.35 micromolar CO₂) is negligible compared to the difference between air and free CO₂ (11.4 micromolar CO₂). This illustrates the extent of the physical limiting-step occurring at the air-water interface when inorganic carbon consumption in seawater is balanced by dissolving gaseous CO₂. The direction of this small free CO₂/HCO₃⁻ gradient indicates that HCO₃⁻ is consumed during photosynthesis.     

Stoichiometry of proton uptake in isolated pea chloroplasts under different light intensities

The number of protons released inside the chloroplast thylakoids per electron which is transferred through the electron transport chain (H⁺/e^– ratio) was measured in isolated pea chloroplasts at pH 6.0 under continuous illumination and with methyl viologen as an electron acceptor. At saturating light intensity (200 W · m^–2) (strong light) the H⁺/e^– ratio was 3. At low intensity (0.9 W · m^–2) (weak light) the H⁺/e^– ratio was 2 with dark-adapted chloroplasts, but it was close to 3 with chloroplasts that were preilluminated with strong light. It is shown that the presence of azide in the reaction mixture leads to errors in the determination of the H⁺/e^– ratio due to underestimation of the initial rate of H⁺ efflux on switching off the light. To explain the above data, we assume that transformation of the electron transport chain occurs during illumination with strong light, namely, the Q cycle becomes operative.     

Binding of antibodies in liposomes to extracellular matrix antigens

We have incorporated antibodies against fibronectin or laminin into liposomes and studied their interaction with insoluble forms of these antigens. The antibodies, after modification by palmitoylchloride, were incorporated into the lipid bilayer by the cholate dialysis method. The antibodies in the liposomes recognized their specific antigen with little reaction to the alternative attachment protein or to albumin (less than 2%). The binding of antibody-containing liposomes to insoluble antigen was inhibited by soluble antibodies to the respective antigens but not by antibodies to other antigens. The affinity constant of the liposome-antibody complex with the antigen was estimated at 1-10 X 10(-9) M liposomes. Thus, antibodies in liposomes retain their reactivity and specificity, and the reaction constant is comparable to that observed for immune complexes.     

The absence of non-local conformational changes in OR3 operator DNA on complexing with the cro repressor

The Interaction of the cro protein of lambda phage with a synthetic OR3 operator having 17 base pairs in length and with its 9 bp fragment has been studied using the circular dichroism (CD) method. In both cases, a considerable change in the CD of the samples was found in the region 260-300 nm upon the addition of the cro protein. The stoichiometry obtained by the CD titration was identical for OR3 and its 9 bp fragment: one duplex per dimeric cro. NaCl addition makes the complexes dissociate so that the 9 bp fragment becomes free at [NaCl] greater than 0.2 M while the whole OR3 becomes free at [NaCl] greater than 0.5 M. The CD spectra of both the free duplexes show a typical B-form conservative pattern with a positive CD band (270 nm) and a negative one (250 nm). The specific complexing of both the duplexes results in a substantial CD depression in the positive band. The most pronounced effect occurs at 280 nm. This spectral change is quite distinct from those in the B to A transition and in the non-cooperative winding of the DNA within the B-family of forms. The interaction of the cro protein with the non-operator DNAs, calf thymus DNA and a synthetic 10 bp duplex, reveals no visible CD changes at all. An inference is drawn that the CD change in the specific complexes is mainly due to the induced CD in tyr-26 upon its interaction with a specific base pair in the operator or its fragment, the operator DNA conformation being conserved in a B-like form as a whole.(ABSTRACT TRUNCATED AT 250 WORDS)