Selwyn J. Rehfeld

The interaction of albumin and concanavalin a with normal and sickle human erythrocytes

Abstract The interaction of human albumin and concanavalin A with normal and sickle human red blood cells previously washed in phosphate buffer at pH = 7.4 was studied by titration calorimetry. The amount of albumin bound to normal cells was (6.8 ± 2.2) × 105 molecules/cell. An equilibrium constant of 5 × 1010 and an enthalpy change of −(280 ± 90) kcal/mol albumin was determined for albumin interaction with normal cells. The amount of albumin bound to sickle cells was (12.4 ± 1.0) × 105 molecules/cell and the enthalpy change for albumin interaction with sickle cells was −(390 ± 140) kcal/mol. Normal cells bound (5.7 ± 2.4) × 105 concanavalin A molecules/cell with an enthalpy change of −(840 ± 200) kcal/mol concanavalin. All experiments were conducted at 25°C.

Thallium in human erythrocyte membranes: An X-ray photoelectron spectroscopy study

Abstract X-ray photoelectron spectra were made of the surface of vacuum dried human red cells in an unetched state and after argon ion etching into the surface for various times. A thallium signal appeared after 30 minutes (at a depth of ∼100 A) and then disappeared with further etching. The region of the membrane containing thallium may be involved in ion transport, i.e., site of Na + K + ion activated adenosine triphosphate. A iron signal was observed after reaching a depth >500A.

Stability of hydrocarbon-in-water emulsions during centrifugation. Influence of dispersed phase composition

Abstract The coalescence of emulsions of pure hydrocarbons in water stabilized by sodium dodecyl sulfate was studied during centrifugation in order to investigate the influence of composition of the dispersed phase on emulsion stability. The hydrocarbons used as the dispersed phase included n C 6 to n C 17 alkanes, benzene, and various n -alkylbenzenes. Emulsions containing equal volumes of hydrocarbon and aqueous phase were prepared using an aqueous solution of 8.0 × 10 −3 moles/liter of sodium dodecyl sulfate (the critical micelle concentration). The initial particle size of these emulsions was determined by microscopic observation, by the sodium alignate creaming method or by the Coulter counter method. A large fraction of the continuous aqueous phase was separated from the emulsion and all the hydrocarbon droplets were deformed into polyhedra very early during centrifugation. The mechanical stability of these emulsions was found to be dependent upon buoyant pressure, dispersed phase composition and properties and interfacial tension. Plots of φ, the fraction of stable emulsion remaining uncoagulated versus centrifugation time ( t ) for n -C 17 to n C 8 -in-water emulsions are fitted for all values of φ by the empirical equation φ = φ o t − n , where n varies from 0.14 to 0.17. The aromatic hydrocarbon-in-water emulsions showed a different behavior during centrifugation. These emulsions coagulated slowly during the first 20 min or more after which a drastic increase in coagulation rate was observed. The possible causes for the differences between n -alkane and aromatic emulsions behavior during centrifugation are discussed. The emulsion stability is inversely correlated with spreading coefficient of the hydrocarbon on the aqueous surfactant solution. Hydrocarbons with the most negative spreading coefficients produce the most stable emulsions.

X-Ray Diffraction and Electron Paramagnetic Resonance Spectroscopy of Mammalian Stratum Corneum Lipid Domains

Publisher Summary This chapter discusses the application of X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy to elucidate the structure and organization of the lipid-enriched cellular peripheral domains of the stratum corneum. The two techniques provide confirmatory and complementary information about structure and physical properties on a molecular level. Traditionally, differential scanning calorimetry (DSC) is widely used to obtain information about the heat-induced phase changes in biological membranes, but it must be emphasized that calorimetry does not probe membrane structure. EPR has provided information about the stratum corneum that is both parallel and complementary to information provided by X-ray diffraction. Both techniques provide information on a molecular level about temperature-dependent phase behavior that correlates with DSC determinations. However, X-ray diffraction provides more direct information about structure, whereas EPR provides more direct information about the physical properties of membranes, including polarity, microviscosity, and phase transitions.

The binding of Ca2+ and Mg2+ to human serium albumin: A calorimetric study

Abstract The binding of calcium and magnesium to human serum albumin has been studied in the pH region 2.5–8.0 by a calorimetric procedure. Both metal ions bind to the carboxylate groups of albumin. 36 and 44 carboxylate groups appear to be involved in the binding of Ca 2+ and Mg 2+ , respectively. Based on previously reported results that twelve Ca 2+ ions are the maximum which can bind to albumin, the results given here support previous X-ray crystallographic evidence that three carboxylate groups can be involved in the binding of a Ca 2+ by a protein. The data also confirm that Ca 2+ and Mg 2+ binding is competitive. Binding of the cations to the carboxylate groups appears to involve the breaking of carboxylate-imidazole hydrogen bonds in the protein. Log K , Δ H and Δ S values obtained for the binding of metal ions to albumin in aqueous solution at 25°C are 2.72 ± 0.02, 0.0 ± 0.1 kcal/mole, and 12.4 ± 0.3 cal/mole K for Ca 2+ and 1.12 ± 0.05, −0.2 ± 0.1 kcal/mole, and 4.5 ± 0.3 cal/mole K for Mg 2+ , respectively.

Interaction of calcium ion with sodium triphosphate determined by potentiometric and calorimetric techniques

Abstract The stoichiometry of the interaction of Ca2+ with sodium triphosphate was determined using a Ca2+ sensitive electrode, divalent ion sensitive electrode, a glass electrode and by titration calorimetry, A 2:1 and 1:1 complex of Ca2+ and P3O5−10 is found when titrating calcium chloride with sodium triphosphate by the calcium ion sensitive electrode and tritation calorimetry. However, only by titration calorimetry is the 2:1 and 1:1 complex found when titrating sodium triphosphate with calcium chloride. Thermodynamic value (log K, ΔH and ΔS) are reported for the formation of CaP(in3)O−310 and Ca2P3O−10 in aqueous solution.