Lipid mixtures prepared with

M. W. De Jager, G. S. Gooris, M. Ponec, and J. A. Bouwstra. Lipid mixtures prepared with well-defined synthetic ceramides closely mimic the unique stratum corneum lipid phase behavior. J. Lipid Res. 46 2649-2656 (2005). 

In Vitro Lipid Organization of Lipid Mixtures Prepared with Isolated Ceramides... 

In the SC lipids form two crystalline lamellar phases.27 The mixture of both phases produces the optimal barrier to water loss from SC. The balance between the liquid crystalline and the solid crystal phases is determined by the degree of fatty acid unsaturation, the amount of water, and probably by other yet undiscovered factors. A pure liquid crystal system, produced by an all-unsaturated fatty acid mixture, allows a rapid water loss through the bilayers with a moderate barrier action. The solid system produced with an all-saturated fatty acid mixture causes an extreme water loss due to breaks in the solid crystal phase.6,23 Studies with mixtures prepared with isolated ceramides revealed that cholesterol and ceramides are very important for the formation of the lamellar phases, and the presence of ceramide 1 is crucial for the formation of the long-periodicity phase.27 The occurrence of dry skin associated with cold, dry weather for example, may result from an extensive, elevated level of skin lipids in the solid state. Therefore, a material that maintains a higher proportion of lipid in the liquid crystalline state may be an effective moisturizer.6... 

The lipid organization in stratum corneum is very unusual. Two lamellar phases are present with periodicities of approximately 6 and 13 nm. This lipid organization can be reproduced in vitro with mixtures prepared from either isolated ceramides (from pig and human stratum corneum) or synthetic ceramides. However, for the formation of the long periodicity phase the presence of acyl ceramides in the lipid mixtures is very crucial. The phase behavior of the lipid mixtures provides important information to explain the deviation in phase behavior in diseased skin. 

Prepare samples in PB to a final concentration of 50 pM and load 5 pL onto spots coated with either the POPC/POPS lipid mixture or PB alone. 

CRABP-GST is immobilized onto a glutathione-containing resin at a concentration that saturates the resin. A complex lipid mixture was prepared by combining a concentrated lipid extract derived from mouse tissue (brain) [5] (DMSO stock) with exogenously added retinoic acid (RA, positive control) and 13C-oleic acid (negative control). Analysis of this complex lipid mixture by LC-MS prior to incubation with immobilized CRABP demonstrated that the mixture contained RA (added), phospholipids, acylglycerols, cholesterol esters, and cholesterol. A portion of this mixture (corresponding to 1 nmol of RA) was added to PBS (DMSO concentration should not exceed 5%) and incubated with the CRABP-GST bound beads for 1 h. 

ER of adrenal, testis, ovary, liver and placenta. It is relatively unstable, being inactivated by freezing, even when pure. A phospholipid environment appears to be an important requirement since, when bovine adrenal microsomal preparations were treated with phospholipase A, 80-85% of phospholipids were hydrolysed with a concomitant loss of 80-90% of enzymic activity [84], Restoration of activity was achieved by adding back to the lipid-depleted membranes aqueous dispersions of microsomal total lipid mixtures [84],... 

Since lipases act on lipids at lipid-water interfaces, preparation of substrates in a suitable physical form for maximal lipase activity is very important. Preparation methods include emulsification with an emulsifying agent incorporation into a gel dissolution in a water-soluble organic solvent, such as 2-methoxyethanol or tetrahydrofuran, followed by addition to an aqueous reaction mixture sonication, with or without emulsifier and formation of a thin film or monolayer. 

Bicelles can be prepared with lipids with varying acyl chain lengths, such as 1,2-dilauroyl-.s -glycero-3-phosphocholinc (DLPC, 12 C) and dipalmitoyl-s -glycero-3-phosphocholine (DPPC, 16 C). It should, however, be noted that the morphology of such mixtures has not yet been fully characterized. 

The advantages of egg yolk antibodies with respect to the welfare of animals and to scientific and economic considerations are described in a recent review.50 Although antibodies issued from this source are mostly used in laboratories and for diagnostics, they must be extracted and purified from very complex mixtures. The presence of massive amount of insoluble material and lipids is the most important problem. The collected egg yolk must first be clarified and the lipid removed for a consistent chromatographic separation. Table 3 summarizes the most important characteristics of expression systems for antibody preparation with regards to the chromatographic separation. 

Finally, it should be mentioned that the temperature profile may indicate the po.ssible existence of heterogeneities or microdomains. Raman spectra have shown such phase separations in bilayers prepared with DHPC7DPPC mixtures and in lipids containing highly unsaturated sn2-acyl and completely saturated snl-acyl, such as POPC, PARC, and PDPC (Litman et al., 1991). 

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