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1
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Expression, purification and functional characterization of recombinant human acyl-CoA-binding protein (ACBP) from erythroid cells

100%
Augoff K., Kolondra A., Chorzalska A., Lach A., Grabowski K., Sikorski A. F.
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2010
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vol. 57
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issue 4
533-540
EN
Fatty acyl-CoA esters are extremely important in cellular homeostasis. They are intermediates in both lipid metabolism and post-translational protein modifications. Among these modification events, protein palmitoylation seems to be unique by its reversibility which allows dynamic regulation of the protein hydrophobicity. The recent discovery of an enzyme family that catalyze protein palmitoylation has increased the understanding of the enzymology of the covalent attachment of fatty acids to proteins. Despite that, the molecular mechanism of supplying acyl-CoA esters to this reaction is yet to be established. Acyl-coenzyme A-binding proteins are known to bind long-chain acyl-CoA esters with very high affinity. Therefore, they play a significant role in intracellular acyl-CoA transport and pool formation. The purpose of this work is to explore the potential of one of the acyl-CoA-binding proteins to participate in the protein palmitoylation. In this study, a recombinant form of ACBP derived from human erythroid cells was expressed in E. coli, purified, and functionally characterized. We demonstrate that recombinant hACBP effectively binds palmitoyl-CoA in vitro, undergoing a shift from a monomeric to a dimeric state, and that this ligand-binding ability is involved in erythrocytic membrane phosphatidylcholine (PC) remodeling but not in protein acylation.
2
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Molecular dynamics simulation studies of lipid bilayer systems.

86%
Pasenkiewicz-Gierula M., Murzyn K., Róg T., Czaplewski C.
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2000
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vol. 47
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issue 3
601-611
EN
The main structural element of biological membranes is a liquid-crystalline lipid bilayer. Other constituents, i.e. proteins, sterols and peptides, either intercalate into or loosely attach to the bilayer. We applied a molecular dynamics simulation method to study membrane systems at various levels of compositional complexity. The studies were started from simple lipid bilayers containing a single type phosphatidylcholine (PC) and water molecules (PC bilayers). As a next step, cholesterol (Chol) molecules were introduced to the PC bilayers (PC-Chol bilayers). These studies provided detailed information about the structure and dynamics of the membrane/water interface and the hydrocarbon chain region in bilayers built of various types of PCs and Chol. This enabled studies of membrane systems of higher complexity. They included the investigation of an integral membrane protein in its natural environment of a PC bilayer, and the antibacterial activity of magainin-2. The latter study required the construction of a model bacterial membrane which consisted of two types of phospholipids and counter ions. Whenever published experimental data were available, the results of the simulations were compared with them.
3
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Physicochemical analysis of phosphatidylcholine-ceramide system in bilayer lipid membranes

86%
Naumowicz M., Petelska A. D., Figaszewski Z. A.
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2008
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vol. 55
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issue 4
721-730
EN
Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylcholine and ceramide were to be investigated, since they play an important biochemical role in cell membranes. The research on biolipid interaction was focused on quantitative description of processes that take part in a bilayer. Assumed models of interaction between amphiphilic molecules and the equilibria that take place there were described by mathematical equations for the studied system. The possibility of complex formation for two-component system forming bilayers was assumed that could explain the deviation from additivity rule. Equilibria were described by mathematical equations that were further verified experimentally. The determined values of parameters (stability constant, molecular area of complex, capacitance and conductance of the lipid membranes formed from molecules and complexes) were used for calculation of model curves. The comparison of model curves and experimental points verified the assumed model.
4
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Biophysical changes induced by cholesterol on phosphatidylcholine artificial biomembranes containing alamethicin oligomers

72%
Cernescu A., Luchian T.
Open Physics
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2006
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vol. 4
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issue 2
155-167
EN
Cholesterol is an important constituent of eukaryotic cell membranes, whose interaction with phospholipids leads to a broad range of biological roles, such as: maintenance of proper fluidity, formation of raft domains, reduction of passive permeability of various chemical species through the bilayer (e.g., glucose, glycerol, K+, Na+ and Cl− ions), and increased mechanical strength of the membrane. In this work we studied an interesting paradigm, as to whether cholesterol-containing phosphatidylcholine biomembranes influence the kinetics and transport features of alamethicin oligomers embedded into it. We demonstrate that moderate relative amounts of cholesterol increase the electrical conductance of various sub-conductance states of the alamethicin oligomer, caused probably by a non-monotonic change in the lumped dipole moment of the biomembrane. Our data suggest that biomembrane stiffness caused by cholesterol, visibly modifies the association-dissociation rates of alamethicin oligomerization in the biomembrane. Moreover, increasing concentrations of cholesterol seem to lead to more stable intermediate alamethicin oligomers. We show that in the presence of cholesterol, as the diameter of the alamethicin oligomer increases, so does the time of another monomer to get picked up. These results brings into focus the interesting issue of how oligomerization of proteins affects their interaction affinities for membrane-based lipids.
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