Lipid-like molecules

HRVs are non-enveloped viruses of icosahedral overall shape [44]. Located on the exterior of the viral capsid are three structural proteins (VPl, VP2 and VP3), each consisting of an eight-stranded antiparallel -barrel. VP4 is found at the interface with the RNA inside the virus. A pocket factor is usually bound to a hydrophobic canyon binding site within the VPl -barrel. This lipid-like molecule is important for the stability of the capsid and has been... 

Lipids with a suitable hydrophilic-lipophilic balance (HLB) are known to spread on the surface of water to form monolayer films. It is obvious that if the lipid-like molecule is highly soluble in water, it will disappear into the bulk phase (as observed for SDS). Thus, the criteria for a monolayer formation are that it exhibits very low solubility in water. The alkyl part of the lipid points away from the water surface. The polar group is attracted to the water molecules and is inside this phase at the surface. This means that the solid crystal, when placed on the surface of water, is in equilibrium with the him spread on the surface. A detailed analysis of this equilibrium has been given in the literature (Gaines, 1966 Adamson and Gast, 1997 Birdi, 2009). The thermodynamics allows one to obtain extensive physical data on this system. It is thus apparent that, by studying only one monolayer of the substance, the effect of temperature can be very evident. 

A certain type of lipid (or lipid-like) molecules are found that when dispersed in water tend to make self-assembly structures (Figure 4.13). Detergents were shown to aggregate to spherical or large cylindrical-shaped micelles. It is known that if egg phosphatidylethanolamine (egg lecithin) is dispersed in water at 25°C, it forms a self-assembly structure, which is called liposome or vesicle. 

Body cells have a membrane that is quite complicated but it ean be represented by a double layer of lipids or lipids attached to proteins. Thus the behavior of lipids and lipid-like molecules becomes very important in un-... 

Another insight to be gained by understanding the lipid layer around a cell membrane deals with problems associated with pesticides or other lipid-like molecules that get into places other than those intended. The problems arise because many pesticides are lipid-like and may change the way the cell membrane behaves. 

Bile salts readily form mixed micelles with lipid-like molecules such as lecithins or fatty acids. These mixed micelles are structurally very different from the simple micelles and generally have a much greater solubilizing capacity for hydrophobic molecules, both biological and synthetic. The solubility of DDT, a non-polar, water insoluble molecule, for example, in bile salt micellar solution can be increased to a far greater extent by the addition of unsaturated long chain fatty acids, probably because of mixed micelle formation. 

Figure 3.21. Monte Carlo surface pressure Isotherms for lipid-like molecules having 10 different conformational states available. 10.000 chains anchoring groups not specified. The filled circles are computed drawn lines are guides for the eye. Model parameters mimic dlpalmltoyl phosphatidyl choline (DPPC) monolayers. (Redrawn from Mouritsen et al. (1989).)...

In addition to lipid-like molecules, polymers can also form self-assembling particulates [8]. As expected, the amphiphilic polymers do form polymeric micelles with polar part orienting towards the surface of the particle and the hydrophobic part orienting towards the core of the particle. Also, in this case, different complicated self-assembled structures can be tailored by using block copolymers with regular blocks of monomer units but, only the simpler ones have been investigated so far in the context of drug delivery. 

Ketone bodies Small lipid-like molecules, usually produced from partial fatty-acid metabolism by the liver. They can be used for energy by most tissues, including the brain. 

The adsorption of lipid-like molecules onto metal single-crystal electrodes has been studied by electrochemical techniques and was recently reviewed [48]. Electrochemistry provides a very sensitive measure of the quality of an adsorbed film, and in addition enables control over the surface energetics of the metal/so-lution (M S) interface. This control allows for the investigation of a large range of stable and metastable arrangements of the adsorbed molecule on the metal electrode surface. 

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