Thermal techniques in biomembrane and lipoprotein research

Calorimetric investigation of the phase partitioning of the fluorescent carbocyanine probes in phosphatidylcholine bilayers

“…DSC measurements were made with a Du Pont 1090 thermal analyzer. The general methodology is similar to that described previously (Melchior et al, 1977). Peak areas, onset temperatures, and completion temperatures were calculated by using Du Font's Advanced DSC VI.O and General Utility Programs.…”

Effect of thermal lag and measurement precision in differential scanning calorimetry: theoretical guidelines for enzyme-substrate reactions by the method of orthogonal collocation

“…Very few studies after the initial work of Borchardt and Daniels have been concerned with solution phase measurements of kinetic parameters. However, during the past few years DSC has been applied to helix-coil transitions in DNA (3) and poly (A) (4), conversion of ovalbumin to S-ovalbumin (5), shrinkage of collagen fibers (6), thermal stability toward denaturation of soluble and immobilized nicotinamide adenine dinucleotide dependent dehydrogenases (7), complex transitions in whole blood and serum involving different molecular forms of hemoglobin (8), and investigations of phase transitions and stability of lipids, lipoproteins, and biomembranes (9,10). In spite of this great interest in biological applications, the study of enzyme catalyzed reactions by DSC has not been pursued in depth (17).…”

Biomembrane phase transitions

“…In addition to permeability, another dynamical property of lipid bilayers that (r 2 ) = W L t (1) Some of the first quantitative measurements of DL were made by McConnell and his co-workers at Stanford by analyzing the time dependence of the esr spectra that result when multibilayers are prepared with a high concentration of spin label in a localized region. 4 They find D[, * 2 X lO" 8 cm 2 /sec.…”

“…When these cells are grown at different growth temperatures, the calorimetric anomaly follows the change in Tg. 1 (For a review, see reference 2.) This suggests that the phase transition is not just some physical phenomenon that happens to occur, but that it has real biological relevance.…”

“…Experiments have conclusively demonstrated that the phase transition in Acholeplasma laidlawii is due exclusively to the lipid component of the membrane. 1 2 Therefore physical techniques that elucidate structure, and theory that deals with extended phases, are appropriate tools to study this phenomenon. Equally important, this means that phase-transition studies performed on "model membranes" made from highly purified and commercially available lipids can be expected to yield useful information.…”