The Synthesis of Photoaffinity Neoglycolipid Probes as Tools for Studying Membrane Lectins

Abstract

A method for the synthesis of photoaffinity neoglycolipid probes with a highly efficient carbene-generating diazocyclopentadien-2-ylcarbonyl (Dcp) label, which can be radioiodinated under standard oxidation conditions, was developed. The probes are intended for incorporation into the lipid bilayer. They are lipophilic glycoconjugates on the basis of an amphiphilic aglycone built up from a diacylglycerol and a polyethylene glycol spacer (with a polymerization degree of 9-16) bearing the Dcp label at the terminal unit. The location of the label in the aglycone provides the possibility of one-step preparation of a wide range of probes using various carbohydrate synthons. We have synthesized photoaffinity neoglycoconjugates containing the oligosaccharides: sialyl LewisX tetrasaccharide and A trisaccharide, which is specific to some tumor cells. A probe containing an inactive pentaol (aminodeoxyglucitol) was also synthesized to detect nonspecific binding. The Dcp label is bound to the probe molecule by ester bond; its lability under alkaline conditions facilitates the analysis of cross-linked products after photoaffinity labeling. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 2; see also http://www.maik.ru.

Enhanced transient recombinant protein production in CHO cells through the co‐transfection of the product gene withBcl‐xL

“…Radiolabelled 125 I‐diazocyclopentadien‐2‐ylcarbonyl (Dcp) GM1 derivatives such as 37 (Scheme ) have been prepared by Molotkovsky and co‐workers and successfully used for the photolabelling of the integral protein haemagglutinin in a well‐characterised influenza model,81 as well as for investigations into the binding site of GM1 with IL‐4 82. This work builds on the group's previous studies of the synthesis of GM1 derivatives bearing Dcp groups;83 the use of the 125 I‐Dcp photoactive group has subsequently been extended to the synthesis of photoaffinity neoglycoconjugates containing the oligosaccharides SLe X and Le A trisaccharide 84. Other gangliosides, such as 125 I‐labelled 12[(4‐azidosalicyl)amino]dodecanoic acid acylated derivatives of GM3, GD3 and GM1 gangliosides such as 38 and sialyl paragloboside (SPG) have also been prepared by Pacuszka and Panasiewicz and used for the photolabelling of erythrocyte membrane proteins,85 whereas Hatanaka and Yasumaru prepared biotinylated diazirinyl ceramide GM1 derivative 39 86 and determined that it was a substrate for Pseudomonas sp.…”