High pressure antagonism of alcohol effects on the main phase-transition temperature of phospholipid membranes: biphasic response

1991 ◽  
Vol 1066 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Katsuhiro Tamura ◽  
Yoshiroh Kaminoh ◽  
Hiroshi Kamaya ◽  
Issaku Ueda
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Main Phase ◽  
Phospholipid Membranes ◽  
Biphasic Response ◽  
Alcohol Effects

scholarly journals The Effect of Selected Anions on Dipalmitoylphosphatidylcholine Phase Transitions

2002 ◽  
Vol 57 (7-8) ◽  
pp. 712-716 ◽  
Author(s):  
Adriana Przyczyna ◽  
Bożenna Różycka-Roszk ◽  
Marek Langner
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Salt Concentration ◽  
Half Width ◽  
Main Phase ◽  
Interface Properties ◽  
Transition Enthalpy ◽  
Peak Half Width

The effect of three anions, Cl-, Br- and I-, on the phase transitions of dipalmitoylphosphatidylcholine (DPPC) was measured. Main phase transition was modestly affected by these anions in the salt concentration range 0.2 M. For Cl- and Br- the temperature of main phase transition was lower (by about 0.5 °C), its half-width modestly larger and enthalpy practically unchanged, all three parameters were altered to a much larger degree. Main phase transition temperature was 1.5 °C lower and the peak half-width significantly smaller. These changes were not accompanied by any alteration in main phase transition enthalpy. Iodide shifted the pretransition temperature toward lower values and increased its half-width to such an extent that at concentrations above 100 mm it was practically undetectable. Besides cations, the presence of anions also has a distinct effect on lipid bilayer interface properties.

A Semisynthetic 5-n-Alkylresorcinol Derivative and its Effect upon Biomembrane Properties

2007 ◽  
Vol 62 (11-12) ◽  
pp. 881-888 ◽  
Author(s):  
Maria Stasiuk ◽  
Dominika Bartosiewicz ◽  
Jerzy Gubernator ◽  
Katarzyna Cieslik-Boczula ◽  
Martin Hof ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Ph Value ◽  
Membrane Surface ◽  
Main Phase ◽  
Phospholipid Bilayer ◽  
Low Concentrations ◽  
Packing Defects ◽  
Semisynthetic Derivative

MSAR (1-sulfate-3-myristoyl-5-pentadecylbenzene) is a semisynthetic derivative of 5-npentadecylresorcinol (C15:0). MSAR exhibits hemolytic activity against sheep erythrocytes with a EH50 value of (35 ± 1.7) μm. At low concentrations MSAR also exhibits the ability to protect cells against their hypoosmotic lysis. This protective effect is significant as, at 0.1 μm of MSAR, the extent of osmotically induced cell lysis is reduced by approx. 20%. It was demonstrated that the 9-anthroyloxystearic acid signal was most intensively quenched by MSAR molecules, suggesting a relatively deep location of these molecules within the lipid bilayer. MSAR causes an increase of the fluorescence of the membrane potential sensitive probe. This indicates an alteration of the surface charge and a decrease of the local pH value at the membrane surface. At low bilayer content (1-4 mol%) this compound causes a significant increase of the phospholipid bilayer fluidity (both under and above the main phase transition temperature) of dipalmitoylphosphatidylcholine (DPPC) liposomes. At this low content MSAR slightly decreases the main phase transition temperature (Tc) value. The effects induced in the phospholipid bilayer by higher contents of MSAR molecules (5-10 mol%) make it impossible to determine the Tc value and to evaluate changes of the membrane fluidity by using pyrene-labeled lipid. MSAR also causes a decrease of the activity of membrane-bound enzymes-red blood cell acetylcholinesterase (AChE) and phospholipase A2 (PLA2). MSAR decreases the AChE activity by 40% at 100 μm. The presence of MSAR in the liposomal membrane induces a complete abolishment of the lag time of the PLA2 activity, indicating that these molecules induce the formation of packing defects in the bilayer which may result from imperfect mixing of phospholipids.

Mechanism of broadened phase transition temperature range in LaFeCoSiC compounds prepared upon high-pressure annealing

2020 ◽  
Vol 91 (1) ◽  
pp. 10601
Author(s):  
Zhengming Zhang
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Order Phase Transition ◽  
Magnetic Transition ◽  
Magnetic Refrigeration ◽  
Annealed Sample ◽  
Cooling Power ◽  
Temperature Range

The cobalt-carbon co-doped NaZn13-type compound LaFe10.95Co0.65Si1.4C0.15 (LFCSC) is one of the most promising candidates for room-temperature working substance in magnetic refrigerator due to its many excellent properties such as large reversible entropy, low cost, and short annealing time. However, owing to the narrow temperature regions of magnetic phase transition in LFCSC, the operation-temperature window for magnetic refrigeration is limited, which restricts its actual application to some extends. In this paper, it is shown that the application of high-pressure to LFCSC during annealing can tailor atomic environment and magnetic transition, which leads to a strongly expanded phase transition temperature range in LFCSC. This broadening behavior can be well understood by importing the magnetoelastic interaction of localized magnetic moments into a microscopic model. The refrigeration performance of the high-pressure annealed sample with wide phase transition temperature range is enhanced according to the relative cooling power (RCP). On the contrary, temperature averaged entropy change (TEC) exhibits a weakened value in the high-pressure annealed sample, which suggests that the magnetic cooling performance could not be effectively improved by simply expanding the phase transition temperature range in the second-order phase transition materials. However, high-pressure annealing would be helpful to the magnetic refrigeration performance for the first-order phase transition materials.

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