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Biomedical subjects

B Lindman

Publications and source records attributed to B Lindman.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effect of NaCl on kinetics of D-glucosamine uptake in yeasts differing in halotolerance.

The initial rate of D-glucosamine uptake by the non-halotolerant yeast Saccharomyces cerevisiae was approximately halved as the apparent half saturation constant (Km) and the apparent maximum velocity (Vmax) changed from 6.6 mM to 16.4 mM and from 22 mumol.g-1.min-1 to 16 mumol.g-1.min-1, respectively, when the salinity in the medium was increased from zero M to 0.68 M NaCl. Corresponding changes in a high affinity transport system in the halotolerant yeast Debaryomyces hansenii were from 1.1 mM to 4.6 mM and from 3.1 mumol.g-1.min-1 to 4.5 mumol.g-1.min-1, implying a practically unchanged transport capacity. In 2.7 M NaCl, Km and Vmax in this system were 24.5 mM and 1.1 mumol.g-1.min-1, respectively, representing a marked decrease in transport capability. Nevertheless, the degree of affinity in this extreme salinity must still be regarded as noteworthy. In addition to the high affinity transport system in D. hansenii, a low affinity system, presumably without relevance in D-glucosamine transport, was observed.

Ascomycota↗
PubMed1981

Magnesium and membrane function in vascular smooth muscle.

Since a tight electromechanical coupling exists in vascular smooth muscle, even small shifts of the membrane potential are sufficient to change the vascular lumen. The extracellular H+ and K+ concentrations are important effectors for the adjustment of the membrane potential. The ion concentrations in the immediate neighbourhood of the cell membrane can be influenced by the microdynamic binding properties of the basement membrane and the other vascular connective tissue. These structures are polyanionic macromolecules to which mono- and divalent cations are extensively bound, and which are separated from the vascular smooth muscle cell membranes by tiny cleft spaces. The ion binding properties of vascular connective tissue were therefore studied in dependence on proton and cation concentration. The pH-dependent binding of monovalent cations to vascular connective tissue is dependent on the concentration and affinity constant of the ion species in question. The mode of interaction is competition. For instance, the actual K binding characteristic means that an increase of [K+]o close to the cell membrane cold ensue from a diminished K+ binding ability under alkalosis. Depolarization and contraction of vascular smooth muscle cells result. Divalent cation binding to vascular connective tissue it additionally dependent on conformational changes. Already physiological concentrations of Mg++ ions can induce a specific change in configuration, which enables K+ ions to bind cooperatively. This means that with extracellular Mg++ deficiency not only less Mg++ ions are bound to vascular connective tissue but also less K+ ions. [K+]o would increase near the cell membrane, depolarization and vasoconstriction would occur.

Animals↗
PubMed1978

Chloride ion binding to human plasma albumin from chlorine-35 quadrupole relaxation.

The 35Cl nuclear magnetic quadrupole relaxation enhancement on binding of chloride ions to human plasma albumin (HPA) has been studied under conditions of variable temperature, pH, ionic strength, protein, and sodium dodecyl sulfate concentration. A small number (less than 10) of chloride ions, most of which are bound to the primary detergent binding sites, contribute a major portion of the relaxation enhancement (greater than 80% at neutral pH). A comparison of the pH dependence of the relaxation rate with the hydrogen ion titration curve, which was determined and analyzed, identified ten lysyl and arginyl residues as being involved in the chloride ion binding. These data, in conjuction with NaDodSO4 titrations at different pH values and the amino acid sequence of HPA, suggests that the high-affinity chloride-binding sites are doubly cationic at neutral pH. An irreversible dimerization at acidic pH and 5 x 10(-5) m HPA was detected. The data also indicate the presence of internal modes of motion in the expanded forms of the HPA molecule, probably an independent reorientation of domains. The rate of exchange of chloride ions was shown to be much higher than the corresponding intrinsic relaxation rate in the temperature range 2--26 degrees C and pH values ranging from 4.0 to 10.5. No indications of protein-protein interaction could be found up to the physiological concentration of ca. 6 x 10(-4)m HPA at either neutral or alkaline pH. The mechanistic basis for HPA's exceptional capacity for binding of inorganic anions was discussed.

Chlorides↗