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

A detailed technical overview summarizes and discusses available evidence concerning the effects of fish oil n-3 polyunsaturated fatty acids (PUFA's) on reducing cardiovascular disease risks. Attention is given to: the characteristics and metabolism of n-6 and n-3 PUFA's and the effects of n-3 PUFA's on plasma lipid profiles; the role of n-3 PUFA's in reducing atherosclerosis risk; possible protection of n-3 PUFA's during myocardial infarction; the relative importance of eicosapentaenoic vs. docosahexaneoic acids; and appropriate intakes of n-3 PUFA's. The potential adverse health effects from ingesting fish oils also are discussed.(wz)

Cardiovascular effects of n-3 fatty acids

Structure of the inverted hexagonal (HII) phase, and non-lamellar phase transitions of lipids.

Chemistry and metabolism of lipids in the vertebrate retina

The essentiality of long chain n-3 fatty acids in relation to development and function of the brain and retina.

Interaction of rhodopsin with two unsaturated phosphatidylcholines: a deuterium nuclear magnetic resonance study.

CHAPTER 16 – THE ROLE OF DOCOSAHEXAENOIC ACID (22:6ω3) IN BIOLOGICAL MEMBRANES: EXAMPLES FROM PHOTORECEPTORS AND MODEL MEMBRANE BILAYERS1

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2881%2980061-0

Retinal rod outer segment lipids form bilayers in the presence and absence of rhodopsin: a 31P NMR study.

Deuterium nuclear magnetic resonance (2H NMR) spectra from aqueous dispersions of phosphatidylcholines in which perdeuterated palmitic acid is esterified at the sn-1 position have several very useful features. The powder spectra show six well-resolved 90 degree edges which correspond to the six positions closest to the methyl end of the acyl chain. The spectral overlap inherent in the multiple powder pattern line shape of these dispersions can be removed by using a "dePaking" procedure [Bloom, M., Davis, J.H., & Mackay, A. (1981) Chem. Phys. Lett. 80, 198-202] which calculates the spectra that would result if the lipid bilayers were oriented in the magnetic field. This procedure produces six well-resolved doublets whose NMR properties can be observed without interference from the resonances of other labeled positions. The presence of a single double bond in the sn-2 chain increases the order of the saturated 16:0 sn-1 chain at every position in the bilayer compared with a saturated sn-2 chain at the same reduced temperature. Surprisingly, addition of five more double bonds to the sn-2 chain only slightly reduces the order of the 16:0 sn-1 chain at many positions in the bilayer compared with the single double bond. Calculating oriented spectra from a spin-lattice (T1) relaxation series of powder spectra allows one to obtain the T1 relaxation times of six positions on the acyl chain simultaneously. As an example of the utility of these molecules, we demonstrate that the dependence of the spin-lattice (T1) relaxation rate as a function of orientational order for two unsaturated phospholipids differs significantly from the corresponding fully saturated analogue. Interpreting this difference using current models of acyl chain dynamics suggests that the bilayers containing either of the two unsaturated phospholipids are significantly more deformable than bilayers made from the fully saturated phospholipid.

Simultaneous observation of order and dynamics at several defined positions in a single acyl chain using 2H NMR of single acyl chain perdeuterated phosphatidylcholines.

Publisher Summary This chapter discusses the nuclear magnetic resonance (nmr) methods for the investigation of rhodopsin–lipid interactions in retinal rod outer segment (ROS) membranes. The rhodopsin-containing disk membranes of the retinal ROS represent an attractive model for the study of lipid–protein interactions in a native biological membrane system. The native ROS membrane phospholipid composition is well characterized, and a number of intriguing problems relating to the structural and functional role of the highly polyunsaturated ROS phospholipids are evident, which appear amenable to investigation using biophysical techniques. NMR spectra of good quality and resolution can be obtained from photoreceptor membrane preparations, so that their phospholipid organization and dynamic properties can be investigated in a manner quite analogous to nmr studies of simpler model lipid bilayer systems. NMR is a useful analytical tool for characterizing the isolated ROS membrane components.

Alan J. Deese

Papers

Interaction of rhodopsin with two unsaturated phosphatidylcholines: a deuterium nuclear magnetic resonance study.

CHAPTER 16 – THE ROLE OF DOCOSAHEXAENOIC ACID (22:6ω3) IN BIOLOGICAL MEMBRANES: EXAMPLES FROM PHOTORECEPTORS AND MODEL MEMBRANE BILAYERS1

Retinal rod outer segment lipids form bilayers in the presence and absence of rhodopsin: a 31P NMR study.

Simultaneous observation of order and dynamics at several defined positions in a single acyl chain using 2H NMR of single acyl chain perdeuterated phosphatidylcholines.

[96] Proton, carbon-13, and phosphorus-31 NMR methods for the investigation of rhodopsin-lipid interactions in retinal rod outer segment membranes