Glycerol headgroup

A number of experiments have been conducted to establish various aspects of structure-activity relationships (SAR) of substrates. Although the greatest emphasis has been upon the nature and orientation of the side chains on the glycerol backbone, variations in the phosphate headgroup have also been explored. 

Figure 1. Phosphoiylation, dephosphorylation and cleavage of Ptdlns. PI3-K phosphorylates the inositol ring at D3, while PTEN dephosphotylates it at the same position. SHIP dephosphotylates 5-phosphotylated Ptdlns, PLOy hydrolyses the phosphodiester bond between the glycerol backbone and the inositol headgroup of Ptdlns (3,4)/ 2> releasing IP3.

Glycerophosphollpid a complex lipid based on glycerol, containing two fatty acids, and a polar headgroup an important constituent of biological membranes. 

The phospholipid monolayers examined in this study were all saturated, symmetric, 1,2-diacyl-j -glycero-3-phosphate-based lipids. Four different lipid headgroups attached to the phosphate were examined choline, ethanolamine, glycerol and serine. Each lipid features a glycerol backbone, two saturated fatty acid chains and a phosphatidyl headgroup. 

The pattern of thermotropic phase behavior exhibited by an aqueous dispersion of any lipid molecular species will vary considerably, depending on the length and structure of the hydrocarbon chains, the structure and charge of the polar headgroup, the nature of the link (ester or ether) of the hydrocarbon chains to the glycerol or sphingosine backbone, and other chemical features of the lipid under study. Also, the degree of hydration and the pH and ionic composition of the aqueous phase can affect lipid thermotropic phase behavior profoundly. However, even a cursory discussion of this topic is beyond the scope of this article, and the reader is referred to recent reviews for more detailed information (16-18). 

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