Two-dimensional nuclear magnetic resonance structure determination module for introductory biochemistry: synthesis and structural characterization of lyso-glycerophospholipids

In this laboratory module, introductory biochemistry students are exposed to two-dimensional (1) H-nuclear magnetic resonance of glycerophospholipids (GPLs). Working in groups of three, students enzymatically synthesized and purified a variety of 2-acyl lyso GPLs. The structure of the 2-acyl lyso GPL was verified using (1) H-correlation spectroscopy. Students scored significantly higher on an assessment of NMR knowledge after having participated in this lab module and in comparison to a similar cohort who did not participate. Inaddition, student confidence in their NMR knowledge and abilities increased 62% following the module and correlated with their ability to apply their NMR knowledge. Based on these results, the laboratory module was very effective at providing students with a more extensive understanding of the underlying concepts of NMR as a tool for structural determination.

A new approach to phospholipid synthesis using tetrahydropyranyl glycerol: rapid access to phosphatidic acid and phosphatidylcholine, including mixed-chain glycerophospholipid derivatives

A new synthesis of phosphatidic acid and phosphatidylcholine is reported, relying on the preparation of 3-tetrahydropyranyl-sn-glycerol as the key intermediate for sequential introduction of the primary and secondary acyl functions to produce chiral diglycerides that are phosphorylated to obtain the target phospholipid compounds.

Glucosamine-glycerophospholipids that activate cell-matrix adhesion and migration

Two new analogues derived from the platelet activating factor (PAF), containing glucosamine instead of the acetyl group, were synthesized, and their effect on the human keratinocyte cell line HaCaT was evaluated with respect to cytotoxicity, proliferation, adhesion, and migration. Starting with (R)-1,2-isopropylideneglycerol (3), the glycosylation acceptor 1-O-octadecyl-3-O-tert-butyldimethylsilyl-sn-glycerol (6) was synthesized in three steps. Glycosylation of 6 with the already known O-(3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-beta-D-glycopyranosyl)trichloracetimidate gave 1-O-octadecyl-2-O-(3',4',6'-tri-O-acetyl-2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-3-O-tert-butyldimethylsilyl-sn-glycerol (7). After removing the (tert-butyldimethyl)silyl (TBDMS) group with FeCl3x6H2O, phosphoryl choline was introduced, yielding [1-O-octadecyl-2-O-(2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine (2) (glucosimide-PAF). pH controlled cleavage of the amino protection group gave [1-O-octadecyl-2-O-(2'-deoxy-2'-amino-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine hydrochloride (1) (glucosamine-PAF). 2 inhibited proliferation of HaCaT cells by 26% at nontoxic concentrations, while 1 increased the proliferation rate by 30% at low concentrations. At higher concentrations, both compounds showed cytotoxic properties with LD50 = 30 micromol/L (1) and LD50 = 5-6 micromol/L (2). Both 1 and 2 were potent promoters of cell adhesion and migration of HaCaT cells.

[Transdermal delivery of insulin]

A possibility is studied of the transdermal delivery of insulin by using a mixture of synthetic analogues of phosphoglycerides (SAP), as a potential activator of hormone diffusion, through the skin. Experimentally in vitro, it was proven that the diffusion of insulin through the skin of two types of transdermal therapeutic form (TTF)--matrix-type and matrix-hydrogel-type--is possible only in presence of activator SAP-M-99. The detected optimal composition of insulin matrix TTF with the area of 40 sq cm enabled a trandermal hormone diffusion speed of 0.26 UNITS/h, which is compatible with the secretion of insulin by the pancreas of an adult (0.25-1.5 UNITS/h). A change-over for the matrix-hydrogel system of insulin delivery based on a 40 sq cm collagenous sponge enabled to increase the insulin diffusion up to 0.54 UNITS/h.

Nonenzymatic synthesis of glycerolipids catalyzed by imidazole

Imidazole catalyzed acylations of lysolipids by acyl-CoAs in water at room temperature and at a pH close to neutrality. In the presence of oleoyl-CoA and either lysophosphatidylcholine, 1-palmitoyl-sn-glycero-3-phosphocholine (LPC); lysophosphatidylglycerol, monoacyl-sn-glycero-3-phosphoglycerol; lysophosphatidyl acid, 1-oleoyl-sn-glycero-3-phosphate; lysophosphatidylserine, monoacyl-sn-glycero-3-phosphoserin; or lysophosphatidylethanolamine, monoacyl-sn-glycero-3-phosphoethanolamine, the corresponding phospholipids were synthesized. Similarly, the use of lyso-platelet activating factor, an ether analog of LPC, yielded the formation of 1-O-alkyl-2-oleoyl-sn-glycero-3-phosphocholine. In the presence of LPC, an imidazole-catalyzed synthesis of phosphatidylcholine (PC) occurred when medium, long, and very long chain acyl-CoAs were added. With hydroxyacyl-CoA, a similar PC synthesis was obtained. The process described in the present paper appears to offer several potential applications of interest for the synthesis of glycerophospholipids and triglycerides with labeled and/or an unusual or fragile fatty acid, or when suitable acyltransferases have not yet been described in the literature and/or are not commercially available. The method described is very safe and simple since lipids can be synthesized in tubes containing 0.7% imidazole in water, and left for a few hours at room temperature on the bench.

Synthesis of enantiomerically pure, sn-1 modified sn-2-deoxy-2-amido-glycero-3-phospholipids

The synthesis of two types of enantiomerically pure sn-2-deoxy-2-amido-glycero-phospholipids differing in the connection of the alkyl chain at the sn-1-position is described. Both types of lipids were prepared from L-serine-methylester as the chiral starting material.

Nature of linkage between the cationic headgroup and cholesteryl skeleton controls gene transfection efficiency

Three novel cationic cholesterol derivatives with different modes of linkage between the cationic headgroup and the cholesteryl backbone have been synthesized and used as mixtures with 1, 2-dioleoyl-L-alpha-glycero-3-phosphatidyl ethanolamine (DOPE) for liposome-mediated gene transfection. A pronounced improvement in gene transfer efficiency was observed when the cationic center was appended to the cholesteryl backbone using an ether linkage as opposed to when the linkages were based on either ester or urethane groups. Amphiphiles with ether links such as cholest-5-en-3beta-oxyethane-N,N,N-trimethyl ammonium bromide (2) and cholest-5-en-3beta-oxyethane-N,N-dimethyl-N-2-hydroxyethyl ammonium bromide (3) showed transfection efficiencies considerably greater than commercially available gene transfer reagents. Notably, the transfection ability of 2 with DOPE in the presence of serum was significantly greater than Lipofectamine((R)) and Lipofectin((R)). Interestingly, 3 did not require the helper lipid DOPE for transfection. This suggests that these newly described cholesterol-based amphiphiles should be very promising in liposome-mediated gene transfection. The advantage that the ether linkage possesses would be important in the design of newer, more efficient cholesterol-based delivery reagents.