Lipid residues degradation

The first example is the plasma-borne retinol-binding protein, RBP, which is a single polypeptide chain of 182 amino acid residues. This protein is responsible for transporting the lipid alcohol vitamin A (retinol) from its storage site in the liver to the various vitamin-A-dependent tissues. It is a disposable package in the sense that each RBP molecule transports only a single retinol molecule and is then degraded. 

Sterols are seldom detected in archaeological residues due to their low concentration and the tendency to undergo chemical degradation. In any case, the presence of sterols or of their oxidation products in a sample can help distinguish between animal and plant lipid materials cholesterol is the most abundant animal sterol, while campesterol and sitosterol are the two major plant ones. 

LAs are reported to bind in a charged form within the pore of sodium channels near the cytoplasmic surface of the plasma membrane (for review see Butterworth and Strichartz, 1990 Tetzlaff, 2000). Before binding LAs have to cross the lipid layer of the plasma membrane probably in an uncharged form. The common structure of LAs is a hydrophilic moiety (usually a tertiary amine) linked by a short alkyl chain and an ester or amide group to a hydrophobic moiety (usually an aromatic residue). The linkage is enzymatically degraded in the plasma. 

The stability of PenG residues in both meat and liver tissues was tested in water, 5% ethanol, 5% bicarbonate, and sunflower oil. Penicillin-G residues were stable at 65°C in water. The half-time of decay in water at 100°C and 5% ethanol was approximately 60 min. The concentration reduced to about 40 min in acidic buffer and to 15 min in 5% sodium bicarbonate at 100°C. The half-times in sunflower oil at 140°C and 180°C were 45 and 20 min, respectively. This suggested that PenG was less stable in an aqueous than in a lipid environment and indicated that the degradation was caused by acid-and-base-catalyzed hydrolysis (97). 

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