Cephalin

Kelvin scale See absolute temperature. kephaUn See cephalins. 

The identity of the moiety (other than glycerol) esterified to the phosphoric group determines the specific phosphoHpid compound. The three most common phosphoHpids in commercial oils are phosphatidylcholine or lecithin [8002-45-5] (3a), phosphatidylethanolamine or cephalin [4537-76-2] (3b), and phosphatidjlinositol [28154-49-7] (3c). These materials are important constituents of plant and animal membranes. The phosphoHpid content of oils varies widely. Laurie oils, such as coconut and palm kernel, contain a few hundredths of a percent. Most oils contain 0.1 to 0.5%. Com and cottonseed oils contain almost 1% whereas soybean oil can vary from 1 to 3% phosphoHpid. Some phosphoHpids, such as dipaLmitoylphosphatidylcholine (R = R = palmitic R" = choline), form bilayer stmetures known as vesicles or Hposomes. The bdayer stmeture can microencapsulate solutes and transport them through systems where they would normally be degraded. This property allows their use in dmg deHvery systems (qv) (8). 

Amphiphilic Molecules. In just about all cases of lyotropic Hquid crystals, the important component of the system is a molecule with two very different parts, one that is hydrophobic and one that is hydrophilic. These molecules are called amphiphilic because when possible they migrate to the iaterface between a polar and nonpolar Hquid. Soaps such as sodium laurate and phosphoHpids such as a-cephalin [5681-36-7] (phosphatidylethanolamine) (2) are important examples of amphiphilic molecules which form Hquid crystal phases (see Lecithin Soap). 

Dilauroyl-sn-glycero-3-phosphoethanolamine ( -dilauroyl-a-cephalin, 3-sn-phosphat-idylethanolamine 1,2-didodecanoyl) [59752-57-7] M 579.8, m 210 , pKes,(d (PO4H), PKes,(2) 10.5 (NH2). Recrystd from EtOH or tetrahydrofuran. [Bevan and Malkin J Chem Soc 2667 /95/ IR Bellamy and Beecher7 Chem Soc 728 1953.]... 

Phosphatidylethanolamine (cephalin) and ph os-phatidylserine (found in most tissues) differ from phosphatidylcholine only in that ethanolamine or serine, respectively, replaces choline (Figure 14-8). 

On the other hand, changes of subphase pH have no considerable influence on the shape of then -A curves of lecithins, since they do not contain movable protons. This is different in the case of cephalins (e.g. (7)), where the isotherms at high pH s are considerably broadened (34). 

Phosphatidyl ethanolamines —ch2ch2nh3 Large amounts in animals, plants and microorganisms Old trivial name is cephalin. Methyl and dimethyl ethanolamine derivatives also occur... 

Phosphatidylcholine (lecithin) is the most abundant phospholipid in membranes. Phosphatidylethanolamine (cephalin) has an ethanolamine residue instead of choline, and phosphatidylserine has a serine residue. In phosphatidylinositol, phosphatidate is esterified with the sugarlike cyclic polyalcohol myo-inositol. A doubly phosphorylated derivative of this phospholipid, phosphatidylinositol 4,5-bisphosphate, is a special component of membranes, which, by enzymatic cleavage, can give rise to two second messengers, diacylglycerol (DAG) and inositol l,4,5trisphosphate (InsPsi see p.386). 

Other chemicals which inhibit milk lipase include hydrogen peroxide, animal cephalin, sodium arsenite, diisopropyl fluorophosphate, 2,4 din-itro-l-fluorobenzene, p-hydroxymercuribenzoate, potassium dichromate, lauryl dimethyl benzyl ammonium chloride, aureomycin, penicillin, streptomycin, and terramycin (Schwartz 1974). 

The cationic lipid (20, n = 12), the natural lipid (23) and the zwitterionic diacetylenic lecithin (18, n = 12) were mixed with naturally occurring lecithins, cephalins, and cholesterol. 

Prepare lipid sample solution and calibration standard solutions as described (see Basic Protocol, steps 2 and 3) but include dihexadecanoyl cephalin in the standard solution. 

Dihexadecanoyl lecithin is used to represent all individual phospholipids except phosphatidyl ethanolamine, which is calibrated by dihexadecanoyl cephalin. 

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