Saturated fatty acids have no double bonds in the hydrocarbon chain, and the maximum amount of hydrogen.
While the addition of one double bond raises the melting temperature, research conducted by Xiaoguang Yang et.
The membrane phospholipids incorporate fatty acyl chains of varying length and saturation.
Lipids with shorter chains are less stiff and less viscous because they are more susceptible to changes in kinetic energy due to their smaller molecular size and they have less surface area to undergo stabilizing London forces with neighboring hydrophobic chains.
The fluidity of these membranes can be controlled by the lateral pressure applied, e.g. by the side walls of a box.
Atomic force microscopy experiments can measure fluidity on synthetic[6] or isolated patches of native membranes.
[7] Solid state deuterium nuclear magnetic resonance spectroscopy involves observing deuterated lipids.
[1] Fluorescent probes show varying degree of preference for being in an environment of restricted motion.
In deuterium nuclear magnetic resonance spectroscopy, the average carbon-deuterium bond orientation of the deuterated lipid gives rise to specific spectroscopic features.
Decreasing linewidth from 5th to 16th carbons represents increasing degree of motional freedom (fluidity gradient) from headgroup-side to methyl terminal in both native membranes and their aqueous lipid extract (a multilamellar liposomal structure, typical of lipid bilayer organization).
This pattern points at similarity of lipid bilayer organization in both native membranes and liposomes.
This is explainable as due to motional restricting effect at these positions, because of steric hindrance by large chlorophyll headgroups, specially so, in liposomes.
[1] The melting of charged lipid membranes, such as 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol, can take place over a wide range of temperature.
[4] Microorganisms subjected to thermal stress are known to alter the lipid composition of their cell membrane (see homeoviscous adaptation).
[11] Lateral diffusion (within the membrane matrix) of membrane-related enzymes can affect reaction rates.