Temperature shift, fatty acid

Recently, the use of Hpase enzymes to iateresterify oils has been described (23). In principle, if a 1,3-speciftc Hpase is used, the fatty acid ia the 2 position should remain unchanged and the randomization occur at the terminal positions. However, higher temperatures, needed to melt soHd fats, may cause a 1,2-acyl shift and fatty acids are scrambled over all positions. 

A shift in temperature from 38 to 22 °C leads to desaturation of fatty acids in Anabaena variabilis [110], resulting in control of the fluidity of the plasma membrane. Mutants have been isolated in Synechocystis PCC 6803 that were defective in desaturation of fatty acids, and the growth rate of one of these mutants was much lower than that of the wild-type at 22 °C [112]. It turned out that the mutant strain had a mutation in the gene desA, and when the wild-type allele was introduced into the chilling-sensitive cyanobacterium Anacystis nidulans, it resulted in increasing the tolerance of that strain to low temperature [113]. These experiments nicely demonstrate the existence of a mechanism of adaptation to low temperature in a chilling-tolerant cyanobacterium. 

Comparson of the transitions observed by differential scanning calorimetry in membranes of M. laidlawii and in water dispersions of the lipids from the membranes support the concept that most of the lipids exist as a smectic mesophase in the membranes. The evidence for a bilayer structure is straightforward in this case. Lipid transition temperatures are a function of fatty acid composition and correlate well with biological properties. The calorimeter possesses advantages over high resolution NMR for M. laidlawii, and perhaps in many other systems, because the data can be interpreted less ambiguously. In M. laidlawii membranes the bilayer appears to be compatible with the same physical properties observed in other membranes—a red-shifted ORD, lack of ft structure in the infrared, reversible dissociation by detergents, and poorly... 

Cells regulate the lipid compositions of their plasma membrane so that a reasonable membrane fluidity is main-tained. They do this by controlling fatty acid biosynthesis so as to vary the lengths of the fatty acid chains and the ratio of unsaturated to saturated fatty acids (see chapter 19). If cells are grown at low temperatures, their phospholipids contain more unsaturated fatty acids or fatty acids with shorter chains or both. These adjustments shift the Tm to lower temperatures, with the result that (to the extent that the melting transition is sharp enough to be measureable) the Tm re-... 

The shift to the lower temperature would decrease fluidity by enhancing packing of the hydrophobic chains by van der Waals interaction. To prevent this, new phospholipids would be synthesized having shorter chains and a greater number of cis double bonds. The shorter chains would reduce the amount of van der Waals interaction, and the cis double bonds, causing the kink in structure, would prevent packing of the fatty acid tails of the phospholipids. 

Sturz and DoUe measured the temperature dependent dipolar spin-lattice relaxation rates and cross-correlation rates between the dipolar and the chemical-shift anisotropy relaxation mechanisms for different nuclei in toluene. They found that the reorientation about the axis in the molecular plane is approximately 2 to 3 times slower than the one perpendicular to the C-2 axis. Suchanski et al measured spin-lattice relaxation times Ti and NOE factors of chemically non-equivalent carbons in meta-fluoroanihne. The analysis showed that the correlation function describing molecular dynamics could be well described in terms of an asymmetric distribution of correlation times predicted by the Cole-Davidson model. In a comprehensive simulation study of neat formic acid Minary et al found good agreement with NMR relaxation time experiments in the liquid phase. Iwahashi et al measured self-diffusion coefficients and spin-lattice relaxation times to study the dynamical conformation of n-saturated and unsaturated fatty acids. 

Although trans- and saturated fats have beneficial attributes from the standpoint of food formulation (firmness, reduction of oil migration, and leakage), they have also been linked to detrimental health effects. As a result, the World Health Organization recommends that fat consumption should be shifted toward unsaturated fatty acids as opposed to saturated and trans-fats. However, fat sources higher in unsaturated fatty acids, such as edible oils, lack structure at room temperature. As a consequence, they can produce adverse effects in food products, which often result in a reduction in... 

Phospholipid/fatty acid DMPC, DPPC, DSPC, egg PC/ oleic acid, linoleic acid. T c 2800-3000 cis-unsaturated fatty acids split the transition. Main broadens and shifts to lower temperatures. Linoleic acid most effective Verma effl/. (1980a)... 

Acid anhydrides are prepared by interacting fatty acids or, better, acid chlorides with acetic anhydride at reflux temperature. The least-volatile component of the equilibrium mixture (acetic add or acetyl chloride) is continuously removed by distillation to shift the equilibrium in the desired direction. 

Some bacterial cells contain mono-unsaturated fatty acids with a rran -confuguration as acyl components of membrane phospholipids. We found the temperature-dependent alteration in levels of a rran -mono-unsaturated fatty acid, 16 l(9t), in a psychrophilic bacterium, Vibrio sp. strain ABE-1 [1]. Morita et al. [2] presented the evidence for the direct in vivo isomerization between 16 l(9c) and 16 l(9t) in cells of this bacterium using stable isotope tracers, namely, [2,2-%2]16 l(9c) and [2,2-%2]16 l(9t). This isomerization is quite unique because of configurational isomerization of a double bond without shifting of the double bond position. In this article, we decribe purification and characterization of cis-trans isomerase from a psychrotrophic bacterium. Pseudomonas sp. strain E-3 Pseudomonas E-3), another organism that contains 16 l(9t) [1], and the possible physiological roles of rran -mono-unsaturated fatty acid in this bacterium. 

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