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The lack of apparent membrane binding of 2NH- and 3OH-methylated SM analogs and the failure to cause significant membrane permeabilization suggested that these analogs failed to support stable membrane association of StnII. Additionally, the phosphate moiety could be further stabilized by the cationic side chain of Arg51. Molecular docking of SM to the POC-binding site of StnII suggests that the phosphate oxygens interact with Tyr111 and Tyr136, while the 2NH and 3OH engage in electrostatic interactions with Tyr135. Besides being of great importance for the biophysical membrane properties of SM, 2NH and 3OH are also implicated in specific interactions with actinoporins’ residues.
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Also, sterol affinity for bilayers containing these methylated SM analogs was markedly lowered.
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Methylation of these groups has been shown to reduce SM gel-phase stability, suggesting that hydrogen-bonding involving the 2NH is important for SM–SM interlipid interactions ( Fig. These observations together suggest that both the POC head group and the hydrogen bonding interfacial groups in SM (the 2NH and the 3OH) ( Fig. 5), other SM regions in the lipid at the membrane surface must be involved in specific interactions with actinoporins which would explain functional differences.
Dmpc pro Pc#
Álvaro Martínez-del-Pozo, in Advances in Biomembranes and Lipid Self-Assembly, 2017 2.2 Implication of the Interfacial Hydrogen-Bonding Network of SM Moleculesīecause SM and PC share POC as head group ( Fig. PLA1 (variant of Thermomyces ( Humicola) lanuginosa lipase) was developed, expressed and purified by Novozymes (Novo Nordisk) and details on the procedure will be published elsewhere. Top layers are removed by ‘washing’ them off gently with fresh buffer solution. The sample was kept at 80 ✬ for 3 hours and in case the liquid cell can only contain a small amount of buffer, the buffer solution is refreshed every 30 minutes. The pH of this buffer solution was adjusted to 8 by adding sodium hydroxide. Just before measuring, the sample is hydrated by putting the mica sheets in a liquid cell holder and adding 10 mM Hepes buffer (Aldrich) that contains 150 mM sodium chloride (Sigma-Aldrich), 30 μM CaCl2 (Aldrich) and 10 μM EDTA (Sigma). The mica samples are then dried under vacuum for a few hours. Hofkens, in Handai Nanophotonics, 2007 2.1 Sample preparationĪ 10 mM POPC solution in CHCl 3 (obtained from Avanti Polar Lipids and used without further purification) that was labelled with 0.5% of 1,1'-didodecyl- 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiIC12 from Molecular Probes) is spin coated at a speed of 3000 rpm during 40 seconds on freshly cleaved sheet of mica with a thickness of approximately 70 to 100 μm. Both acyl groups of POPC are cleaved in 30 min and 37 ☌ with 1.0 N aqueous methanolic NaOH. 2228Įnzymatic hydrolysis of DPPC, DSPC, DOPC, or POPC with Crotalus adamanteus snake venom phospholipase gives exclusively the corresponding 2-lysophospholipids PHPC, 2134 SHPC, 2229 OHPC, 2230 and PHPC, 2230 whereas enzymatic hydrolysis of DPPC, POPC, DOPC, or DLPC with lipase from the mold Rhizopus arrhizus gives exclusively the corresponding 1-lysophospholipids HPPC, 2231 HOPC, 2232 HOPC, 2233 and HLPC, 2233 respectively. The Arrhenius plot shows a break at the gel-to-liquid phase transition temperature T m (42 ☌) with activation energy E a = 91 kJ/mol below the T m and 67 kJ/mol above it. 191 Hydrolysis of DPPC in acetate buffer at pH 4.0 follows pseudo-first-order kinetics ( k obs. = 1.0 × 10 - 2 day - 1 at 30 ☌).
Dmpc pro free#
Most, if not all, of the free choline is formed by hydrolysis of the glycerophosphocholine ( k = 0.069 h - 1) rather than the intact DPPC. Under milder conditions (0.2 N methanolic NaOH at 37 ☌), the first-order rate constant for the liberation of palmitic acid is 1.0 h - 1. Hydrolysis of DPPC with either HCl or NaOH in refluxing ethanol yields palmitic acid and a mixture of α- and β-glycerophosphoric acids owing to migration of the phosphate group. Frank, in Chemistry of Plant Phosphorus Compounds, 2013 Hydrolysis