Phospholipid phase transitions

Mouritsen, O. G. (1991). Theoretical models of phospholipid phase transitions, Chem. Phys. Lipids, 57, 179-194. 

I agree with Professor McConnell that phospholipid phase transitions may play a role in controlling the activity of a membrane-bound enzyme. However, the case cited is somewhat ambiguous, since porcine phospholipase A2 is a soluble enzyme acting on a phospholipid surface. The major effect of the phase transition in this case is to alter the nature of the substrate rather than the intrinsic catalytic activity of the enzyme. 

The effects of small organic molecules such as n-alkanes, n-alkanols, fatty acids, and charged alkyl compounds on phase transition behavior of various phospholipids have been studied and reviewed by Lohner [29]. Although they are located differently in the membrane, all of these different molecules have been shown to induce similar effects on phospholipid phase transition. 

Not all NMR-active nuclei may therefore be suitable for the study of phase separation in phospholipids. Limited information can be gained on phospholipid phase transformation from 1H- and UC-NMR because of problems in resolution. Only some signals, for example the choline methyl groups of phospholipids in the outer and inner leaflets of unilamellar bilayers, can be identified by 1H- and 13C-NMR when chemical shift reagents are used. However, 13C-NMR can be applied to the study of phospholipid phase transition when the lipid is specifically enriched at the sn-2, carbonyl position [91]. 

Mantsch, H. H. and McElhaney, M. J. Phospholipid phase transitions in model and biological membranes as studied by infrared spectroscopy. Chemistry and Physics of Lipids 57(2-3) 2l3-226, 1991. 

Pringle, M. J. and Miller, K. W. Differential effects on phospholipid phase transitions produced by stmcturally related long-chain alcohols. Biochemistry 78 3314-3320, 1979. 

Laggner P, Kriechbaum M, Rapp G.Structural intermediates in phospholipid phase-transitions. J. Appl. Crystallogr. 1991 24 836-842. 

Kinnunen P, Laggner P, eds. Phospholipid phase transitions 1991 57. Chem. Phys. Lipids. Entire issue. 

IV.2 In Bx and Band III In B2) (14). The C transition exhibits many of the characteristics of a phospholipid phase transition, and D has been assigned to a protein denaturation process (13). Thus the membrane Is resolved Into a number of "domains," and one can probe the Interactions of a polymeric solute with each of these structures. 

The feasibility of phospholipid phase transition phenomena in the propagation of nerve impulse as well as in information transfer in biological systems in general has been noted earlier. The phase transition of model and biomembranes exhibits considerable hysteresis.The possible role of fast and slow hysteresis phenomena in biomembranes for information storage was put forward by Trauble. " ... 

The 2e leaves the CT band and enters SMOS. Upon removal of the electron pair from the CT band the CT couple dissociates and the phospholipid starts to undergo a phase transition from induced liquid crystalline state to crystalline state preconditioned by the unscreened, protonated phosphatidylserines. Concomitantly with the initiation of phospholipid phase transition the energy level of the holes in the CT band is elevated and the removed 2e cannot return to... 

Phase transitions may be detected through changes in specific IR parameters. The more commonly used parameters are the frequency and the half-bandwidths of the individual vibrational modes. These parameters have the advantage of relating to specific phenomena at the molecular level and can be used to discriminate between different motions of the absorbing groups. Specific examples of phospholipid phase transitions as seen by IR spectroscopy will be shown in Section 9.1.5. 

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