Acyl chain composition membranes

The importance of investigating how cholesterol content and acyl chain composition alter the physical properties of membranes is highlighted by the functional deficits associated with 22 6n-3-deficient diets and the antisocial behavior associated with varied cholesterol levels. In the context of psychological disease and neurotransmitter receptor function, it is important to investigate how compositionally induced changes in membrane physical properties influence membrane-associated signaling processes. 

Gibson NJ, Brown MF. Lipid headgroup and acyl chain composition modulate the MI-MII equilibrium of rhodopsin in recombinant membranes. Biochemistry 1993 32 2438-2454. 

Once host lipid or lipid constituents are acquired, both organisms respond in a similar fashion—modification of the gross lipid composition and, in some cases, the fatty acyl chain composition of complex lipids. In most cases it is unknown why these changes are needed. The malaria parasite may be attempting to alter the permeability of the parasitized cell to allow more facile entry of nutrients. A significant part of the African typanosomes lipid metabolism is directed toward synthesis of not only membrane lipid, but supply of the glycolipid anchor of its unique surface coat. 

Because the DHA content of membrane phospholipids affects the hydration and water permeabUily of membranes (38), it is conceivable that the decrease in the proportion of DHA and other n-3 PUFA contributes to the altered phase angle we have documented in children with SCD. Our results seem to point to a link between the phase angle of an individual and the n-3 PUFA acyl chain composition of their membrane phospholipids. 

Apparently the only stable component is the genetically determined protein. One plausible explanation for the control by this protein of lipid polar head composition, and for an apparent lack of control over acyl chain composition is that structurally important protein/lipid interactions occur mainly through the polar heads of the membrane lipids (Vandenheuvel, 1966). 

Without change in the composition of local lipid precursor pools the lipid composition of the membrane should remain unaltered. On the other hand, a change in acyl chain composition in the acyl chain... 

Major determinants of membrane fluidity may be grouped within two categories [53] (1) intrinsic determinants, i.e., those quantifying the membrane composition and phase behavior, and (2) extrinsic determinants, i.e., environmental factors (Table 1). In general, any manipulation that induces an increase in the molal volume of the lipids, e.g., increase in temperature or increase in the fraction of unsaturated acyl chains, will lead to an increase in membrane fluidity. In addition, several intrinsic and extrinsic factors presented in Table 1 determine the temperature at which the lipid molecules undergo a transition from the gel state to liquid crystalline state, a transition associated with a large increase in bilayer fluidity. 

Schneiter, R. Brugger, B. Sandhoff, R. Zellnig, G. Leber, A. Lampl, M. Athenstaedt, K. Hrastnik, C. Eder, S. Daum, G. Paltauf, F. Wieland, F. T. Kohlwein, S. D. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of the lipid molecular species composition of yeast subcellular membranes reveals acyl chain-based sorting/remodeling of distinct molecular species en route to the plasma membrane. J. Cell Biol. 1999,146,741-754. 

Recently, the effect of the lipid composition on the permeability in PAMPA was investigated [129], By varying the phosphate head group and the saturation degree of the acyl chain, differences in transport were observed for a set of five model compounds, which was due to changes in membrane fluidity and ion pairing [129],... 

Lipids in a biological membrane can exist in liquid-ordered or liquid-disordered states in the latter state, thermal motion of acyl chains makes the interior of the bilayer fluid. Fluidity is affected by temperature, fatty acid composition, and sterol content. 

Several studies have been performed to analyze the effect of membrane composition on accumulation and transport of antineoplastic drugs. In particular, the role of anionic lipids in transport and passive diffusion, as well as on the binding of doxorubicin and its effect on the degree of order of lipid acyl chains was investigated. Using 2H-NMR spectroscopy the effect of doxorubicin on mixed bilayers of DOPS, DOPA, dioleoylphosphatidylcholine (DOPC), and DOPE was studied. It was found that doxorubicin does not affect acyl chain order of pure zwitterionic phospholipids but dramatically influences that of anionic lipids [112]. At 25 °C, in bilayers consisting of 67... 

A second important feature worth emphasizing is that the proton leak is affected by the lipid composition of the inner mitochondrial membrane. In general, the fatty acyl chains of phospholipid components of membranes can vary in their degree of unsaturation. The proton leak increases with the incorporation of polyunsaturated fatty acids (FAs) the greater the number of double bonds, the greater the proton leak (Hulbert and Else, 2000). As we shall note in the chapter on temperature relations, fatty acyl composition of membranes, including the inner mitochondrial membranes, changes in various... 

One of the commonest relationships noted in adaptation of membranes to temperature is a decrease in acyl chain saturation during acclimation to reduced temperature. Hazel (1988) has reviewed changes in molecular species composition during acclimation in bacteria, plants, and animals. As a broad generalization, a decrease in acclimation temperature of 20° C is accompanied by a decrease of approximately 19% in the percentage of fully saturated acyl... 

Synthetic phospholipids are commercially available and they contain polar heads occurring in nature and and the same type of fatty acid in both, 9 -l and sn-2 sites. The acyl chains may be mainly myristoyl (C14 0), palmitoyl (C16 0), olcoyl (C16 l) or stearoyl (C18 0) residues. The physicochemical characteristics of the lipidic bilayers that are prepared from synthetic phospholipids are well defined. The lipid composition influences many physical properties of model membranes and it has been shown that single synthetic lipids or mixtures of short and long fatty acid chains can produce stable lipidic bilayers and liposomes. 

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