Phase transitions in lipids. Possible switch processes in biological membranes

Temperature dependence of the light-induced spectral shift of carotenolds in Cyanidium caldarium and higher plant leaves. Evidence for an effect of the physical phase of chloroplast membrane lipids on the permeability of the membrane to ions

Nonlinear Effect of Sucrose on Lamellar-Hexagonal Phase Transition Kinetics

Phase Transitions in Lipids in Relation to the Structure of Membranes

Influence of fatty acid and sterol composition on the lipid phase transition and activity of membrane-bound enzymes in Acholeplasma laidlawii

The temperature dependence of the yield of in vivo prompt and delayed chiorophyll fluorescence was investigated in maize and barley leaves. In the chilling-sensitive maize, delayed fluorescence at steady-state level showed a maximum near the temperature at which thylakoid membrane lipids undergo a phase transition as revealed by differential scanning calorimetry measurements. In the chilling-resistant barley, no phase transition was detected above 0°C and the delayed light emission varied in a monotonic fashion. It was shown that measurements of delayed luminescence intensity in vivo can provide a rapid and sensitive method for detecting the phase change of membrane lipids in intact leaves of chilling-sensitive plant species such as tomato, cotton, cucumber, castor bean or avocado. In contrast, the use of steady-state prompt chlorophyll fluorescence as an indicator of membrane fluidity change was not successful.

Temperature dependence of the delayed fluorescence of chlorophyll a in blue-green algae

Apolipophorin III (apoLp-III) from Manduca sexta has a molecular weight of 18,100. Based on its hydrodynamic properties (sedimentation and diffusion coefficients, frictional ratio, intrinsic viscosity) and its behavior during gel permeation chromatography, we concluded that apoLp-III is a prolate ellipsoid with an axial ratio of about 3. The circular dichroic spectrum of apoLp-III suggests that the protein contains approximately 50% alpha-helix. At the air-water interface, apoLp-III forms a monolayer which is gaseous at surface pressures less than or equal to 1 dyne/cm. The isotherm of this phase yields an excluded molecular area of 3800 A2/molecule (23 A2/amino acid). At a surface pressure of 22.1 dynes/cm, the monolayer undergoes a phase transition reminiscent of a first-order phase transition of pure lipids. The monolayer can be compressed in this surface pressure range to an area per molecule of 480 A2 (2.9 A2/amino acid). Since a globular protein of molecular weight 18,100 could occupy an area of only about 2000 A2 when bound to a surface, it is suggested that in the expanded state, apoLp-III must unfold on the surface, whereas in the compressed state, the molecule is oriented with its minor axis parallel to the water surface. ApoLp-III binds with high affinity (Kd = 1.9 X 10(-7)M) to both phosphatidylcholine- and diacylglycerol-coated polystyrene beads. All of these results are consistent with the proposal that apoLp-III plays a key role in increasing the capacity of the insect lipoprotein, lipophorin, to transport diacylglycerol by stabilizing the increment of lipid-water interface that results from diacylglycerol uptake.

Cooperativity of the phase transition in single- and multibilayer lipid vesicles

Characterization of Low-Temperature (i.e., <65° C) Lipid Transitions in Human Stratum Corneum

Lipid and protein composition and thermotropic lipid phase transitions in fatty acid-homogeneous membranes of Acholeplasma laidlawii B

We have studied the interaction of melittin with lecithin bilayer membranes. Fluorescence polarisation measurements were performed beside the use of excimer forming pyrene derivatives.1. Diphenyl hexatriene, a fluorescence polarisation probe, was used to investigate the lipid phase transition. Addition of melittin leads to an increase of the transition temperature. Characteristic breaks were obtained plotting Tu as a function of the melittin concentration. The change in the width of the phase transition gives an indication of phase separation phenomenon.2. Pure pyrene lecithin membranes were agitated by melittin. A dramatic decrease in the excimer to monomer ratio was observed showing the same characteristic breaks.3. No change in the lipid phase transition temperature was obtained using pyrene decanoic acid and pyrene lecithin as probe molecules. Pyrene lecithin is involved in the lipid‐protein‐complex and therefore prevented from undergoing the lipid phase transition. Rigid patches surrounding the peptide molecule were formed. The pyrene decanoic acid is squeezed out from these regions leading to an increase of the excimer yield in the bulk lipid.4. High melittin concentration (c &gt; 10 mole‐%) leads to a membrane disruption followed by the formation of a stable melittin micell furnished with lipids.

Permeability of mitochondria to sucrose induced by hydrostatic pressure

Excitable membranes can be induced to show an increase in conductivity such as that encountered in the “action potential.” We suggest that this transient condition may be the result of heating of the sites through which the ions pass. The heat could be generated by an adiabatic phase transition of the membrane lipids. Equations derived on the basis of these ideas give good agreement with voltage clamped current measurements in algae and perfused squid axon.

A detailed temperature dependence study of a well-defined plant ion channel, the Ca(2+)-activated K+ channel of Chara corallina, was performed over the temperature range of their habitats, 5-36 degrees C, at 1 degree C resolution. The temperature dependence of the channel unitary conductance at 50 mV shows discontinuities at 15 and 30 degrees C. These temperatures limit the range within which ion diffusion is characterized by the lowest activation energy (Ea = 8.0 +/- 1.6 kJ/mol) as compared to the regions below 15 degrees C and above 30 degrees C. Upon reversing membrane voltage polarity from 50 to -50 mV the pattern of temperature dependence switched from discontinuous to linear with Ea = 13.6 +/- 0.5 kJ/mol. The temperature dependence of the effective number of open channels at 50 mV showed a decrease with increasing temperature, with a local minimum at 28 degrees C. The mean open time exhibited a similar behavior. Changing the sign of membrane potential from 50 to -50 mV abolished the minima in both temperature dependencies. These data are discussed in the light of higher order phase transitions of the Characean membrane lipids and corresponding change in the lipid-protein interaction, and their modulation by transmembrane voltage.

We investigated the response of chilling-sensitive plants of cucumber (Cucumis sativus L.) to prolonged permanent (6 days) (PLT) and short-term (3 h) daily exposures to low non-freezing temperatures (9 and 12°С) (DROP) lying on different sides of the critical value (10°С) corresponding to a phase transition of membrane lipids in chilling-sensitive plants from a liquid-crystalline to a solid gel structure. Effects and aftereffects of DROP treatments at temperatures of 9 and 12°С (DROP9 and DROP12, respectively) were identical. They caused a reduction in linear dimensions of plants (as compared with control plants) and enhanced chilling tolerance of leaves but did not influence photosynthetic activity and water relations. However, when exposure to these temperatures was permanent (PLT9 and PLT12), their effects on plants were different. PLT9 almost entirely suppressed plant growth and development, inactivated photosynthetic apparatus (PSA), increased relative electrolite leakage (REL), and boosted lipid peroxidation (LPO). PLT12 also considerably reduced plant height and leaf area and suppressed (but did not inactivate) PSA; it did not boost POL or increased REL. It is important that, after the termination of chilling, PLT9 plants (unlike PLT12 plants) could not quickly resume growth and restore photosynthetic activity. Thus, considerable differences in plant responses to various patterns of chilling (long permanent or short-term daily) are probably due to the fact that, in the case of DROP treatments, relatively short-term (3 h) chilling of plants is followed in the diurnal cycle by a prolonged period (21 h) of optimal temperature when possible deviations and/or disturbances of PSA are restored and toxic substances that could accumulate in the course of chilling metabolized and/or neutralized. Pronounced differences in plant response to permanent exposure to temperatures of 9 and 12°С probably depend on the fact that these temperatures lie on different sides of a critical value (10°С) below which chilling-sensitive plants suffer grave physiological disturbances due to cooling. In addition, we showed that different responses of plants to PLT and DROP treatments are not determined by a usual dose-effect relationship but depend in many respects on the pattern of temperature influence (prolonged or short-term, single or recurring). As a result, the number of DROP spans experienced by plants in the experiments proved to be more important than their duration (at least, within a time interval from 2 to 12 h).