68852-66-4Relevant academic research and scientific papers
Optically trapping confocal Raman microscopy of individual lipid vesicles: Kinetics of phospholipase A2-catalyzed hydrolysis of phospholipids in the membrane bilayer
Cherney, Daniel P.,Myers, Grant A.,Horton, Robert A.,Harris, Joel M.
, p. 6928 - 6935 (2006)
Phospholipase A2 (PLA2)-catalyzed hydrolysis at the sn-2 position of 1,2-dimyristoyl-sn-glycero-3-phosphocholine in optically trapped liposomes is monitored in situ using confocal Raman microscopy. Individual optically trapped liposomes (0.6 μm in diameter) are exposed to PLA2 isolated from cobra (Naja naja naja) venom at varying enzyme concentrations. The relative Raman scattering intensities of C-C stretching vibrations from the trans and gauche conformers of the acyl chains are correlated directly with the extent of hydrolysis, allowing the progress of the reaction to be monitored in situ on a single vesicle. In dilute vesicle dispersions, the technique allows the much higher local concentration of lipid molecules in a single vesicle to be detected free of interferences from the surrounding solution. Observing the local composition of an optically trapped vesicle also allows one to determine whether the products of enzyme-catalyzed hydrolysis remain associated with the vesicle or dissolve into solution. The observed reaction kinetics exhibited a time lag prior to the rapid hydrolysis. The lag time varied inversely with the enzyme concentration, which is consistent with the products of enzyme-catalyzed lipid hydrolysis reaching a critical concentration that allows the enzyme to react at a much faster rate. The turnover rate of membrane-bound enzyme determined by Raman microscopy during the rapid, burst-phase kinetics was 1200 s-1. Based on previous measurements of the equilibrium for PLA2 binding to lipid membranes, the average number of enzyme molecules responsible for catalyzing the hydrolysis of lipid on a single optically trapped vesicle is quite small, only two PLA2 molecules at the lowest enzyme concentration studied.
γ-Ray irradiation of liposomes of polymerizable phospholipids containing octadeca-2,4-dienoyl groups and characterization of the irradiated liposomes
Akama, Kazuhiro,Yano, Yoshihiro,Tokuyama, Satoru,Hosoi, Fumio,Omichi, Hideki
, p. 1047 - 1059 (2007/10/03)
The synthesis of a variety of polymerizable phospholipids containing the octadeca-2,4-dienoyl moiety on 2-acyl chains and the characteristics of liposomes containing those phospholipids of the γ-irradiation are described. We synthesized three different polymerizable phosphocholines that have different 1-acyl chain lengths with the octadeca-2,4-dienoyl moiety on the 2- acyl chain: myristoyl (MODPC), palmitoyl (PODPC) and stearoyl (SODPC). The liposomes were prepared by extrusion through polycarbonate filters with a pore size of 0.2 μm, and were polymerized by γ-irradiation with various dose rates. The polymerization rate increased in the order SODPC>MODPC>PODPC. The mechanism of the polymerization of SODPC was the same as that of 1,2-bis- [(E,E)-octadeca-2,4-dienoyl]-sn-glycero-3-phosphocholine (DODPC), but differed from that of MODPC and PODPC. Freeze-thaw testing was used to evaluate the stability of the polymerizable liposomes. The MODPC liposome was more stable than other monofunctional liposomes. For similar irradiation, the polymerization behavior of the liposomes was significantly affected by the 1- acyl length.
Studies of the topography of biomembranes: the four-step synthesis of a photoactivatable transmembrane phospholipidic probe and its dideuterated analogue
Yamamoto, Masakuni,Dolle, Valerie,Warnock, William,Diyizou, Yvonne,Yamada, Masashi,et al.
, p. 317 - 329 (2007/10/02)
A convenient method for the synthesis of a dipolar transmembrane phospholipid 1a, which would be a useful photolabelling probe for the study of the topography of sterols of proteins in biomembranes, is described.Starting from 4,4'-dihydroxybenzophenone 13, 1a was synthesized in 4 steps in 31percent total yield.The final, key step, acylation of lysophosphatidylcholine-cadmium chloride complex (4), was achieved using cesium fluoride as a catalyst in DMF.The preparation of the dideuterated 1b or diiodinated 1c analogues is also described.The reaction scheme presented here can also be used for the synthesis of a spin label, a fluorescence label, or a label carrying a high specific radioactivity.Keywords: photolabelling / transmembrane probe / topography / biomembrane / phospholipid bilayer
