A study of moss (Marchantia polymorpha) thylakoid membrane lipids in monolayers.

Monolayers of seven fractions of natural lipids (phosphatidyl inositol, sulfoquinovosyl diacylglycerol, phosphatidylcholine, digalactosyl diacylglycerol, phosphatidyl glycerol, phosphatidylethanolamine, monogalactosyl diacylglycerol), isolated from the photoautotrophic cell culture of the moss Marchantia polymorpha grown under normal and light-stress conditions, have been prepared for the first time. We have shown that the high-intensity light affects the area occupied by the lipid molecule. In the case of digalactosyl diacylglycerol and phosphatidyl glycerol fractions, after the light stress the area significantly increased from 0.50 to 0.80 nm2 and from 0.47 to 0.63 nm2, respectively, and in the case of the sulfoquinovosyl diacylglycerol fraction, the area decreased from 0.40 to 0.32 nm2. These results are in agreement with our previous data on the redistribution of the double bonds in the aliphatic chains of these lipids and can be used to characterize the state of the lipid bilayer of the thylakoid membranes.

[Effect of surfactants on peroxidase activity. II. Effect of cationic surfactants]. / Vliianie poverkhnostno-aktivnykh veshchestv na aktivnost' peroxidazy. II. Vliianie kationnykh PAV.

The effect of various cationic surfactants on the initial rate of the 5-aminosalicylic acid peroxidation with horseradish peroxidase was studied. With increasing concentration of the surfactant, the rate first increased and then decreased. We attributed these changes to a primary activation of the enzyme and/or an increase in the concentration of the substrate in the region of the active site and to the subsequent inactivation of the protein with surfactant followed by its denaturing, respectively.

Mixed lipid-protein films of bacterial photosynthetic reaction centres. II. Mixed multilayers on solid supports.

Mixed lipid-protein multilayers composed of the reaction centre (RC) proteins from the Chloroflexus aurantiacus and Rhodobacter sphaeroides (wild type) photosynthetic bacteria and synthetic lipids were investigated. The optimal conditions for forming thin films on solid plates (approximately 100% transfer) were 30 mN/m surface pressure and transfer of the interfacial monolayers from the buffer/air interface onto the plates by the Langmuir-Schaefer method. The films transferred onto quartz and optical transparent current-conducting plates retained their optical and photoelectric properties. The preferential orientation of the protein of the interfacial surface depended on the type of lipid used. In RC-acryloylphosphatidylethanolamine films, the H subunit of the RC from Rhodobacter sphaeroides was oriented toward the water phase, in contrast to RC-diacetylenic acid films, in which the H-subunit was oriented toward the air phase. It is shown that RC can change their orientation in a monolayer, even to the opposite one, depending on the type of lipid matrix.

Polymer ultrathin films with immobilized photosynthetic reaction center proteins.

Mixed monolayers of lipids with photosynthetic reaction center proteins (RCs) from Rb. sphaeroides and C. aurantiacus were studied and the optimum conditions for stable films fabrication were determined. The following synthetic: ACPE, TDA, PDA, DODL and natural lipids: PE, PC were used. The rate of polymerization of the mixed ACPE-RC and TDA-RC monolayers is lower than those for pure lipid-like monomers on the air/water interface but high enough for the fast preparation of the polymer films. The optical and photoelectrical measurements provide evidence for an orientation of RCs (from Rb. sphaeroides) on interface. Hydrophilic H-subunit in the mixed ACPE-RCs and DODL-RCs monolayers is preferentially oriented towards water as in the pure RC monolayers. Opposite orientation was found with TDA-RCs and PDA-RCs films. No preferential orientation was found for lipid-RCs (C. aurantiacus) monolayers probably because of the low asymmetry of hydrophobic subunits (M and L) of these RCs.