Hydrocarbon chain extended length

No. of C atoms in hydrocarbon chain Extended chain length (nm) A o / o 25 /25 Max. aggregation number... 

The c axis corresponds to both the short axis of the crystal and the axis along the molecular chain. The observed repeat distance in the c direction is what would be expected between successive substituents on a fully extended hydrocarbon chain with normal bond lengths and angles (see Sec. 1.2). 

In the synthesis of fatty acids the acetyl irnits are condensed and then are reduced to form straight hydrocarbon chains. In the oxo-acid chain elongation mechanism, the acetyl unit is introduced but is later decarboxylated. Tlius, the chain is increased in length by one carbon atom at a time. These two mechanisms account for a great deal of the biosynthesis by chain extension. However, there are other variations. For example, glycine (a carboxylated methylamine), under the influence of pyridoxal phosphate and with accompanying decarboxylation, condenses with succinyl-CoA (Eq. 14-32) to extend the carbon chain and at the same time to introduce an amino group. Likewise, serine (a carboxylated ethanolamine) condenses with... 

The phase behavior of a synthetic lecithin, dipalmitoyllecithin, as analyzed by Chapman and co-workers (5), is diagrammed in Figure 3. The main features are the same as in the phase diagram of egg lecithin a mixture of numerous homologs. As a consequence of the variation in fatty acid chain length, the chain melting point is lowered which means that the critical temperature for formation of liquid crystalline phases is reduced. This temperature is about 42 °C for dipalmitoyllecithin, and, if the lamellar liquid crystal is cooled below this temperature, a so-called gel phase is formed. The hydrocarbon chains in the lipid bilayers of this phase are extended, and they can be regarded as crystalline. The gel phase and the transitions between ordered and disordered chains are considered separately. 

The results of this study show that ultrasonic absorption techniques, when used in conjunction with other aggregate properties, provide important kinetic information about the partitioning process of alcohols tetween ionic micelles and the bulk phase. The effect of hydrocarbon chain length of the alcohol on the exit rates of monomer surfactant and alcohol components from the mixed micelles, aggregate size distribution, and the electrostatic stabilization of the head group region of the micelles will be considered. As well, previously unreported data for water- 1-butoxyethanol-DTAB will be used to extend conclusions based on previous work [2,3]. 

Then, since the radius of a spherical micelle cannot exceed a certain critical length, 4, roughly equal to but less than the fully extended length of the hydrocarbon chain, it is apparent from eqn (5.1) that once vjaolc > i, spherical micelles will not be able to form unless the surface area a > Oq. This gives a critical condition for the formation of spheres ... 

The value obtained for the maximally extended hydrocarbon length of 17.5 A is more difficult to compare with experimental values. In section 5 we found that 80-100 % of the fully extended hydrocarbon chain appears to be a reasonable estimate of 4 of saturated chains (see also Tanford Since egg PC is mainly... 

In the TSA and substrate-based inhibitor complexes, the sn-1 and 5m-2 hydrocarbon chains lie in a hydrophobic channel that extends from the active site to the surface of the enzyme. If the lengths of the hydrocarbon moieties were increased from the 7 to 8 carbons present in the model compounds to that of natural substrates (commonly 14 to 18 carbons long), they would protrude from the enzyme surface. It is probably safe to assume that these hydrophobic tails remain imbedded in the membrane during interfacial catalysis in order to minimize the energetic costs of substrate transfer. Thus the adsorption surface chosen by Scott et al. (1990a), which envelops the hydrophobic channel, is the most likely surface to contact the bulk phase lipid directly. 

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