Phosphatide cations

Baeza, L, Wong, C., Mondragon, R., etal. (1994). Transbilayer diffusion of divalent cations into liposomes mediated by lipidic particles of phosphatidate, / Mol. EvoL, 39, 560-8. 

Cochleates can also be used for plasmid delivery. A negatively charged phospholipid such as phosphatidylserine, phosphatidic acid or phosphatidyl glycerol, in the absence or presence of cholesterol, are utilized to produce a suspension of multilamellar vesicles containing plasmids, which are then converted to small unilamellar vesicles by sonication. These vesicles are dialyzed against buffered divalent cations (e.g. calcium chloride) to produce an insoluble precipitate referred to as cochleates. Cochleates have been shown to encapsulate plasmid and enhance plasmid stability and transfection efficiency. 

Peroxide Value, Fats and Oils (PV) (Cd 8-53) determines all substances, in terms of milliequivalents of peroxide per 1000 g of sample, that oxidize potassium iodide (KI). These substances generally are assumed to be peroxides or products of fat oxidation. Phosphorus in Oils (Ca 13-55) estimates the phospholipid content of crude, degummed, and refined vegetable oils in terms of phosphorus. Refineries often use induction coupled plasma (ICP) spectrographs to analyze divalent cations rapidly in aspirated crude oil. The calcium and magnesium measured are mainly responsible for nonhydratable phosphatides (NHP) and are determined directly. An AOCS method for analysis by ICP is being developed. 

Several classes of lipids common for the biomembranes can form inverted nonlamellar phases under physiologic conditions (4). The principle ones are phosphatidylethanolamines and monogalactosyldiglycerides. Also, cardiolipins and phos-phatidic acids can form inverted phases in the presence of divalent cations, and phosphatidylserines and phosphatidic acids both form inverted phases at low pH. Moreover, biomembrane lipid extracts and membrane-mimicking lipid compositions form nonlamellar phases if heated above physiologic temperatures, dehydrated, or treated with divalent cations (5-7). 

In the soft-degumming process, a chelating agent (EDTA) is added to the oil to remove the cations from the nonhydratable phosphatides, thereby making them hydratable again (Table 4.11) [4]. 

Besides choline, the cationic character of phosphatides is created also by 2-aminoethanol, sphingosine and other aminoalcohols. Phosphatides with two hydrocarbon chains attached to the same head group are more lipophilic amphiphiles characterised by vesicular (liposomal) aggregation in water contrary to single-chain surfactants that typically form micelles. Synthetic monoalkylphosphorylcholines are essentially water-soluble zwitter-ionic surfactants [120] the distinction of which consist in the hindered compatibility with anionics in view of the end position of the cationic betaine group. 

Among phospholipids, phosphatidylcholine (lecithin) is certainly the less reactive, whereas anionic phospholipids such as phosphatidylglycerol, phosphatidylserine, and phosphahdic acid are of course sensitive to cations (e.g., Ca , Mg phosphatidic acid is sensitive to too), to polyamines (spermine, spermidine, etc.), or basic proteins. Fatty... 

The enzymes responsible are found in the albatross salt gland (Hokin and Hokin, 1960), erythrocyte membranes (Holdn and Hokin, 1961), and brain microsomes (Hokin and Hokin, 1959b). Mcllwain (1963) has criticized the scheme on quantitative grounds, making the point among others that the observed rates for the enzymatic reactions involved in cerebral tissue are about 0.02% of tiie rates of cation transport. It is still not proved, in fact, whether the increased exchange of phosphate with phosphatidic acid in membranous systems in the presence of acetylcholine is a secondary result of an action of the drug on some other system. 

Since ouabain decreased cation transport and yet stimulated phosphate exchange in phosphatidic acid over a short period, any relationship of this particular lipid to cation transport would be difficult to explain. Digitoxin also enhanced the uptake of labeled phosphate into the phospholipids of rat heart in vivo (Marinetti et al., 1%1) the effect was greatest with ethanolamine phospholipids, but in these experiments the possibility of an increased permeability of the tissue to phosphate was not eliminated. Recent studies have strongly suggested that ouabain inhibits the sodium- and potassimn-activated adenosinetriphosphatase (Chamock and Post, 1963). It may well do this by specifically inhibiting the potassium-dependent phosphorolysis reaction which leads to the release of orthophosphate (see also, McIIwain, 1963). 

A bottom layer consisting mainly of lutoid particles and also including other particulate components with a density greater than that of serum. Lutoid particles amount to 15 to 20% of latex volume. Their negatively charged tonoplast membrane, rich in phosphatidic acid, encloses a fluid serum known as B-serum. The vacuolar medium is acidic and positively charged. It includes cations, basic amino acids and a whole... 

In Fig. 13 similar cation spectra of three other phosphate colloids (two different fractions of soya bean phosphatides and sodium nucleate) are given. 

The alkali cations form transition series with the two phosphatides (see text). 

Phosphatides are extremely difficult to obtain in a pure state. The phosphatide preparations used must be considered as mixtures of pure phosphatides (ampholytes) and phosphatidic acid, the latter giving the phosphatide preparation the character of a colloid of acidic nature . The purer the preparation the higher the reciprocal hexol-number, the higher also the LE.P. and as shown in the figure the lower the reversal of charge concentrations for polyvalent cations (e.g., Ca). 

The number of cations in this figure is reduced to the minimum which suffices to bring out the phosphate colloid character of the phosphatides. This figure shows that the higher the reciprocal hexol number (i.e. the closer the phosphatide preparation approximates to pure phosphatide) the lower the reversal of charge concentrations come out (for the rest this displacement does not make its appearance with Na and K) (see further text). 

The sequence of the organic cations is from left to right quinine — strychnine — procaine — guadinine, except with alcohol soluble soya bean phosphatide where the reversal of charge points of procaine and guanidine are interchanged (the -4 -5 -2... 

Fig. 27. Reversal of charge spectrum of alcohol soluble soya bean phosphatide (R.H.N = 3800) with substituted ammonium cations.

If the salts behave additively C ji must amount to 5S% of C//. The experimentally determined points must then lie on the lowest dotted horizontal line drawn at an ordinate value of log C li/Cu = log 0.58 = 0.76 — 1. The combination LiCl + NaCl practically satisfies this with this phosphatide. With the other combinations antagonism occurs, i.e., the deviations from the additive behaviour are so great that the points even lie higher than the highest dotted horizontal line drawn at an ordinate value log C li/Cii = 0, i.e. C li/Cii — 1.00 or 100%. The large complex cations (which on account of their size can no longer exert a polarising action) occupy a position apart. 

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