Delipidation

Both intact carotenoids and their apolar metabolites (retinyl esters) are secreted into the lymphatic system associated with CMs. In the blood circulation, CM particles undergo lipolysis, catalyzed by a lipoprotein lipase, resulting in the formation of CM remnants that are quickly taken up by the liver. In the liver, the remnant-associated carotenoid can be either (1) metabolized into vitamin A and other metabolites, (2) stored, (3) secreted with the bile, or (4) repackaged and released with VLDL particles. In the bloodstream, VLDLs are transformed to LDLs, and then HDLs by delipidation and the carotenoids associated with the lipoprotein particles are finally distributed to extrahepatic tissues (Figure 3.2.2). Time-course studies focusing on carotenoid appearances in different lipoprotein fractions after ingestion showed that CM carotenoid levels peak early (4 to 8 hr) whereas LDL and HDL carotenoid levels reach peaks later (16 to 24 hr). 

The binding of apo(a) to apo Bl00 is mediated by one disulfide bridge, endowing Lp(a) with specific chemical and physical properties e.g., delipidated apo-Bl00-apo(a) complex is freely soluble in water at pH values above 6.4, in contrast to delipidated apo Bt00 alone, which is only soluble at alkaline pH (FI 1,... 

High-density lipoproteins (HDL) and very low-density lipoproteins (VLDL) are synthesized in the liver. LDL is produced in the blood stream as VLDL particles are partially delipidated by lipoprotein lipase, a triglyceride hydrolysing enzyme located on the luminal surface of vessels in sites such adipose tissue. 

The substrate for the LPL is the triglyceride contained within the oily core of VLDL particles and chylomicrons. The fatty acids and monoglycerides liberated from triglyceride hydrolysis are taken into the adipocytes and reformed into neutral fat for calorie storage (Figure 9.11). The ultimate result of the delipidation of VLDL and chylomicrons to the formation of low-density lipoproteins (LDL) as described in Section 5.5. 

Berardesca E, Herbst R, Maibach H. 1993. Plastic occlusion stress test as a model to investigate the effects of skin delipidization on the stratum comeum water holding capacity in vivo. Dermatology 187 91-94. 

The cytokine-inducing active fraction (QM-A) was prepared from E, hirae ATCC 9790 cells as described [9]. Briefly, the bacterial cells (922 g) were delipidated and extracted with hot phenol-water, and the crude extract was digested with RNase and DNase, to give crude LTA fractions. The crude LTA was subjected to two successive chromatography, hydrophobic interaction... 

I Delipidation I Hot phenol-water extraction I Digestion with RNase-DNase... 

The purpose of the techniques described here is to obtain a protein, completely free of lipids and in its native state. Neither of these goals is readily achieved. Delipidation is usually incomplete the delipidated protein ordinarily contains 1-3% lipid by weight. In terms of conformation, the delipidated apoprotein exhibits some spectral differences from its parent complex. Such spectral changes between lipidated and delipidated apoproteins, however, have been proved to be reversible when the apoproteins are appropriately reexposed to lipids (88, 89). 

Since the early delipidation procedure was applied initially to the whole serum (815) and later to the isolated serum lipoproteins (818), many other methods of delipidation have been reported [see reference (816) for review], employing mixtures of organic solvents (ethanol-ethyl ether chloroform-methanol, acetone, etc.) or detergents (sodium dodecyl or decyl sulfate, Triton X-100, Nonidet, etc.). Techniques for delipidation have not been standardized, nor is there a comprehensive comparative assessment of the various proposed methods presently avail-... 

The delipidated serum lipoprotein proteins exhibit solubility differences in aqueous media. The polypeptides of HDL and the D polypeptides of VLDL are readily soluble in aqueous media, particularly in slightly alkaline low-ionic strength buffers (S28, S30). In contrast, the LDL protein does not dissolve in such buffers and, like many other water-insoluble proteins, requires denaturing agents, detergents, or suitable chemical modification. The many techniques for the solubilization of apo LDL have been reviewed recently (G15). A thorough assessment of such techniques is not possible since not all the solubilized products have been characterized. The choice of the method presently depends on the investigator s preference and experimental needs. 

Recently, it has been shown that fraction V of apo HDL, closely resembling the D polypeptides of apo VLDL, is moderately soluble in aqueous solutions of ethanol, a fact to be taken into consideration in the delipidation of serum lipoproteins with extracting mixtures containing this organic solvent. The relevance to recovery problems was pointed out previously (Sll). 

After total delipidation of the Lp (a)-lipoprotein, only apo VLDL is soluble in 0.9% NaCl and detectable by immunochemical means (S28). It therefore seems unlikely that the specific antigenic determinant of the Lp (a)-lipoprotein is located on or is part of the apo VLDL protein moiety. At present, the nature of the antigenic determinant of Lp(a)-lipoprotein is not known. 

Scanu, A. M., and Edelstein, C., Solubility in aqueous ethanol of the small molecular weight peptides of very low-density and high-density lipoproteins relevance to the recovery problem during delipidation of serum lipoproteins. Anal. Biochem. 44, 576-588 (1971). 

Supercritical carbon dioxide was used for bone delipidation. It appeared that this technology is very efficient since supercritical CO2 is able to diffuse into microporous solids much better than liqnids and that it has a good solvent capacity for lipids. Moreover, it is safe since it involves no toxic chemical and is potentially usable with allografts as well as xenografts (Fages et al., 1994). 

The question of whether an enzyme is membrane bound or membrane associated is to some extent a matter of semantics. However, it is certainly true that some proteins are readily dissociated from membranes whereas others require quite drastic conditions before they can be dissociated from the membrane. As limiting cases, the former can be designated as membrane associated and the latter as membrane bound. Enzymes that are generally considered membrane bound are firmly embedded in the membrane structure. For example, the mitochondrial coupling factor is strongly coupled to the bilayer structure by hydrophobic polypeptides. The Na+-K+ ATPases that have been purified have a small patch of associated phospholipids when the enzyme is delipidated, enzymatic activity is lost. In fact, membrane-bound enzymes appear to be... 

In-vitro BA binding assay is performed to verify the association of TCDCA and CDCA with delipidated recombinant murine ILBP. A mixture of 400 pi of BA... 

Purified cotton consists of the fibers of different cultivated varieties of Gossypium sp. The material is freed from adhering impurities, deprived of fatty matter, bleached, and sterilized. The length of cotton fibers is up to about 5 cm, the diameter varies between 9 to 25 pm. A typical cotton fiber is cylindrical when young, but becomes flattened and twisted as it matures. The genuine cellulose wall of the cotton fiber is covered with a waxy cuticule. Delipidation is essential in order to transform the genuine fiber to absorbent cotton wool which is readily wetted by water. 

After drying and delipidation this biomass can be considered as a naturally immobilized enzyme (Fig, 3.). The hydrolytic activity measured on olive oil in di-isopropyl-ether is around 75 to 200 micromoles per g of dry mycelium and per mn. The chain length specificity spectrum is broad, as shown before (from C14 to C22). 

Lipid-free (Na+, K+)-ATPase is incapable of hydrolyzing ATP or p-nitrophenyl phosphate. The precise role of the lipid and the specificity for the lipid have not yet been determined. The addition of lipid to the delipidated enzyme brings about conformational changes, with phosphatase activity regenerated before ATPase activity.51 It seems evident that the lipid will affect the conformation of the enzyme and determine membrane fluidity, which is relevant to conformational change. 

The addition of zwitterionic or non-ionic detergents to SD buffers has three important functions. Detergents aim to disrupt membranes and consequently solubilize lipids and delipidate proteins, which are bound to membranes or vesicles. The use of SDS as a detergent will affect the overall net charge and so non-ionic or zwitterionic detergents such as Triton X-100 or CHAPS are used (Shaw and Riederer, 2003). Commonly used CHAPS, which will not affect the overall charge, can be added up to 4% in SD buffers to account for... 

Figure 8. Gel chromatography on Bio- Gel P2 of oligosaccharide preparations obtained after phage 28 B (A) and phage 36 (B) hydrolysis ofpartially delipidatedS. typhimurium LPS, and on Bio-Gel P6 of pooled fractions 50-60 (C). (A and B reproduced with permission from Ref. 36. Copyright 1979, J. VirolJ...

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