The modification of mammalian membrane polyunsaturated fatty acid composition in relation to membrane fluidity and function

Primary cultures of adult rat hepatocytes were treated in the presence or absence of extracellular calcium with ten different membrane-active toxins. In all cases more than half the cells were killed in 1 to 6 hours in the presence but not in the absence of extracellular calcium. An effect of calcium on the primary mechanism of membrane injury by any of the agents cannot be implicated. Viability, as determined by trypan blue exclusion correlated well with other indices of viability such as plating efficiency and the hydrolysis of fluorescein diacetate. It is concluded that the cells are killed by processes that involve at least two steps. In each type of injury, disruption of the integrity of the plasma membrane by widely differing mechanisms is followed by a common functional consequence involving extracellular calcium, and most likely representing an influx of calcium across the damaged plasma membrane and down a steep concentration gradient. This later step represents, or at least initiates, a final common pathway for the toxic death of these cells.

https://science.sciencemag.org/content/sci/206/4419/700.full.pdf

Calcium dependence of toxic cell death: a final common pathway

Membranes are the most common cellular structures in both plants and animals. They are now recognized as being involved in almost all aspects of cellular activity ranging from motility and food entrapment in simple unicellular organisms, to energy transduction, immunorecognition, nerve conduction and biosynthesis in plants and higher organisms. This functional diversity is reflected in the wide variety of lipids and particularly of proteins that compose different membranes. An understanding of the physical principles that govern the molecular organization of membranes is essential for an understanding of their physiological roles since structure and function are much more interdependent in membranes than in, say, simple chemical reactions in solution. We must recognize, however, that the word ‘understanding’ means different things in different disciplines, and nowhere is this more apparent than in this multidisciplinary area where biology, chemistry and physics meet.

/pdf/physical-principles-of-membrane-organization-2enzb9mlqb.pdf

Physical principles of membrane organization.

The function of sterols in membranes.

http://www.bio21.bas.bg/ibf/PC_review.pdf

Phases and phase transitions of the phosphatidylcholines

Application of laser Raman and infrared spectroscopy to the analysis of membrane structure.

We have examined the Raman scattering from erythrocyte ghosts at 2700 to 3000 cm-1 (CH-stretching region). Plots of the intensity (I) of the 2930 cm-1 band relative to the intensity of the thermally stable 2850 cm-1 band, i.e., the [I2930/I2850] ratio, as a function of temperature reveal a sharp discontinuity, which at pH 7.4 has a lower limit of 38 degrees and is irreversible above 42 degrees. [I2930/I2850] is stable between pH 7.0 and pH 7.4, but increases or decreases sharply below pH 7.0 or above pH 7.5, respectively. Reduction of pH to 6.5 lowers the transition temperature by about 16 degrees, and a shift to pH 6.0 drops the transition range to 0 to 7 degrees. The above effects of temperature and pH on Raman scattering closely correspond to those detected by studies on the interaction of membrane protein fluorophores and lipid-soluble fluorescence quenchers [Bieri, V. and Wallach, D.F.H. (1975) Biochim. Biophys. Acta 406, 415-423]. Taken together, these results suggest that the transitions represent concerted process, involving hydrophobic amino acid residues and lipid chains at apolar protein-lipid boundaries.

Surendra P. Verma

Papers

Application of laser Raman and infrared spectroscopy to the analysis of membrane structure.

Erythrocyte membranes undergo cooperative, pH-sensitive state transitions in the physiological temperature range: evidence from Raman spectroscopy.

Multiple thermotropic state transitions in erythrocyte membranes a Laser-Raman study of the CH-stretching and acoustical regions

Raman spectra of some saturated, unsaturated and deuterated C18 fatty acids in the HCH-deformation and CH-stretching regions.

Raman analysis of the thermotropic behavior of lecithin-fatty acid systems and of their interaction with proteolipid apoprotein