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Permeation of Organometallic Compounds through Phospholipid Membranes

von Dr. Raycho Yonchev

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[1.] Ry/Fragment 014 01 - Diskussion
Zuletzt bearbeitet: 2016-04-10 12:49:19 WiseWoman
Anézo 2003, Fragment, Gesichtet, KomplettPlagiat, Ry, SMWFragment, Schutzlevel sysop

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I.2.1 The hydrophobic effect

The hydrophobic effect is one of the most important concepts necessary for the understanding of membrane structure. The major driving force stabilizing hydrated phospholipid aggregates is the hydrophobic force, which is not an attractive force but rather a force representing the relative inability of water to accommodate non-polar species. The three other stabilizing factors are hydrogen bonding and electrostatic interactions between polar headgroups and between headgroups and water, and van der Waals dispersion forces between adjacent hydrocarbon chains, which are short-range and weak attractive forces resulting from interactions between induced dipoles. Compared to the hydrophobic force, however, they are relatively minor stabilizing factors.

The hydrophobic force is the thermodynamic drive for the system to adopt a conformation in which contact between the non-polar portions of the lipids and water is minimized [9]. This so-called “force” is entropic in origin. Hydrophobic molecules aggregate in water so as to maximize orientational and configurational entropy. The larger the surface area of the hydrophobic molecule, the larger the water cage that must be built around that molecule, and the larger the unfavorable entropy contribution to the transfer of that molecule into the water phase [10].

The hydrophobic effect drives phospholipids to aggregate into the fundamental structural element of biological membranes, the phospholipid bilayers.

I.2.2 Phase structures

Phospholipid molecules aggregate in an aqueous solution to form a variety of assemblies, which correspond to structurally distinct phases. Which phase predominates in a given system depends on environmental factors such as temperature, pressure, pH and ionic strength on the composition and water content of the system, and on the structure and conformation of the individual phospholipid components. The various morphologies of phospholipid assemblies are reviewed below (see also reference [11]). Each morphology is stabilized by a balance between favorable and unfavorable [interactions, resulting directly from an optimization of the hydrophobic effect with a variety of intramolecular and intermolecular interactions.]


9. Gennis, R. B. Biomembranes: Molecular Structure and Function; Springer-Verlag: Berlin, 1989.

10. Yeagle, P. L. The Membranes of Cells, 2nd ed.; Academic Press: San Diego, 1993.

11. Seddon, J. M.; Templer, R. H. Handbook of Biological Physics - Structure and Dynamics of Membranes: From Cells to Vesicles; Elsevier Science: Amsterdam, 1995; Vol. 1A.

[page 28]

1.2.1 The hydrophobic effect

The hydrophobic effect is one of the most important concepts necessary for the understanding of membrane structure. The major driving force stabilizing hydrated phospholipid aggregates is the hydrophobic force, which is not an attractive force but rather a force representing the relative inability of water to accommodate non-polar species. The three other stabilizing factors are hydrogen bonding and electrostatic interactions between polar headgroups and between headgroups and water, and van der Waals dispersion forces between adjacent hydrocarbon chains, which are short-range and weak attractive forces resulting from interactions between induced dipoles. Compared to the hydrophobic force, however, they are relatively minor stabilizing factors.

The hydrophobic force is the thermodynamic drive for the system to adopt a conformation in which contact between the non-polar portions of the lipids and water is minimized [19]. This so-called “force” is entropic in origin. Hydrophobic molecules aggregate in water so as to maximize orientational and configurational entropy. The larger the surface area of the hydrophobic molecule, the larger the water cage that must be built around that

[page 29]

molecule, and the larger the unfavorable entropy contribution to the transfer of that molecule into the water phase [2].

The hydrophobic effect drives phospholipids to aggregate into the fundamental structural element of biological membranes, the phospholipid bilayer.

1.2.2 Phase structures

Phospholipid molecules aggregate in an aqueous solution to form a variety of assemblies, which correspond to structurally distinct phases. Which phase predominates in a given system depends on environmental factors such as temperature, pressure, pH, and ionic strength, on the composition and water content of the system, and on the structure and conformation of the individual phospholipid components. The various morphologies of phospholipid assemblies are reviewed below (see also reference [20]). Each morphology is stabilized by a balance between favorable and unfavorable interactions, resulting directly from an optimization of the hydrophobic effect, with a variety of intramolecular and intermolecular interactions.


[2] P. L. Yeagle. The Membranes of Cells. Academic Press, San Diego, second edition, 1993.

[19] R. B. Gennis. Biomembranes: Molecular Structure and Function. Springer-Verlag, C. R. Cantor (Ed.), Berlin, 1989.

[20] J. M. Seddon and R. H. Templer. Polymorphism of Lipid-Water Systems. In: Handbook of Biological Physics - Structure and Dynamics of Membranes: From Cells to Vesicles, volume 1A. Elsevier Science, R. Lipowsky and E. Sackmann (Eds.), Amsterdam, 1995

Anmerkungen

No source is given.

Sichter
(Klgn), WiseWoman


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