Fandom

VroniPlag Wiki

Ry/062

< Ry

31.385Seiten in
diesem Wiki
Seite hinzufügen
Diskussion0 Teilen

Störung durch Adblocker erkannt!


Wikia ist eine gebührenfreie Seite, die sich durch Werbung finanziert. Benutzer, die Adblocker einsetzen, haben eine modifizierte Ansicht der Seite.

Wikia ist nicht verfügbar, wenn du weitere Modifikationen in dem Adblocker-Programm gemacht hast. Wenn du sie entfernst, dann wird die Seite ohne Probleme geladen.

Permeation of Organometallic Compounds through Phospholipid Membranes

von Dr. Raycho Yonchev

vorherige Seite | zur Übersichtsseite | folgende Seite
Statistik und Sichtungsnachweis dieser Seite findet sich am Artikelende
[1.] Ry/Fragment 062 01 - Diskussion
Zuletzt bearbeitet: 2016-01-12 21:58:09 WiseWoman
Anézo 2003, Fragment, Gesichtet, KomplettPlagiat, Ry, SMWFragment, Schutzlevel sysop

Typus
KomplettPlagiat
Bearbeiter
Klgn
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 62, Zeilen: 1 ff. (entire page)
Quelle: Anézo 2003
Seite(n): 142, 143, Zeilen: 142:17-32; 143:1ff
[By passing through such hydrated defects, the permeating molecule can avoid the high-energy barrier associated with partitioning into the hydrophobic] membrane interior. Transport through transient pores seems to be the dominant mechanism for the permeation of ions through lipid bilayers. In the case of small polar molecules, it is plausible that both mechanisms, the partitioning and pore mechanisms, operate in parallel [67].

Water wires extending across a lipid bilayer are thermodynamically unstable, so that they form infrequently and their lifetime is limited. Owing to their transient character, they are particularly hard to detect experimentally, which makes their existence doubtful. However, it should be noted that the hydrophobic core of the membrane is not impenetrable to water and, just as organic liquids, has a measurable miscibility with water. Water is thought to exist at a millimolar concentration within the hydrocarbon core. Subczynski and co-workers determined the hydrophobicity profile across PC bilayer membranes using an ESR spin-labeling method and showed that the water penetration into the membrane is extensive up to the depth of the carbon atom C8 [70]. Membrane permeability to hydrophilic solutes could be therefore facilitated by penetration of water into the hydrophobic region of the membrane.

II.4. Simulation of permeation processes

As already mentioned in the introduction, the time required for a penetrating molecule to permeate through the membrane is much longer than can be simulated. To get some statistical information on permeation processes, simulations on the order of microseconds are indeed necessary. Equilibrium MD simulations can still be performed to follow the trajectory of the penetrant in time within the membrane. But, in order to get a full description of the permeation process across the whole membrane, non-equilibrium MD simulations using indirect methods have to be carried out.

II.4.1 Equilibrium MD simulations

“Conventional” equilibrium MD simulations, starting with solute molecules located at various depths within the membrane (e.g. hydrophobic core, interface, water layer), [directly provide the average distribution of the solute in the membrane.]


67. Weaver, J. C.; Powell, K. T.; Mintzer, R. A. Bioelectrochem. Bioenerg. 1984, 12, 405.

70. Subczynski, W. K.; Wisniewska, A.; Yin, J. J.; Hyde, J. S.; Kusumi, A. Biochemistry 1994, 33, 7670.

[page 142]

By passing through such hydrated defects, the permeating molecule can avoid the high-energy barrier associated with partitioning into the hydrophobic membrane interior. Transport through transient pores seems to be the dominant mechanism for the permeation of ions through lipid bilayers [173]. In the case of small polar molecules, it is plausible that both mechanisms, the partitioning and pore mechanisms, operate in parallel [170].

Water wires extending across a lipid bilayer are thermodynamically unstable, so that they form infrequently and their lifetime is limited. Owing to their transient character, they are particularly hard to detect experimentally, which makes their existence doubtful. However, it should be noted that the hydrophobic core of the membrane is not impenetrable to water and, just as organic liquids, has a measurable miscibility with water. Water is thought to exist at a millimolar concentration within the hydrocarbon core [174]. Subczynski and co-workers determined the hydrophobicity profile across PC bilayer membranes using an ESR spin-labeling method and showed that the water penetration into the membrane is extensive up to the depth of the carbon atom C8 [175]. Membrane permeability to hydrophilic solutes could be therefore facilitated by penetration of water into the hydrophobic region of the membrane.

[page 143]

5.2.2 Simulation of permeation processes

As already mentioned in the introduction, the time required for a penetrating molecule to permeate through the membrane is much longer than can be simulated. To get some statistical information on permeation processes, simulations on the order of microseconds are indeed necessary. Equilibrium MD simulations can still be performed to follow the trajectory of the penetrant in time within the membrane. But, in order to get a full description of the permeation process across the whole membrane, non-equilibrium MD simulations using indirect methods have to be carried out. In the present study, the umbrella sampling method as well as the average force method on constrained particle have been employed and are described below.

5.2.2.1 Equilibrium MD simulations

“Conventional” equilibrium MD simulations, starting with solute molecules located at various depths within the membrane (e.g. hydrophobic core, interface, water layer), directly provide the average distribution of the solute in the membrane.


[170] J. C. Weaver, K. T. Powell, and R. A. Mintzer. Bioelectrochem. Bioenerg., 12:405–412, 1984.

[173] S. Paula, A. G. Volkov, A. N. van Hoek, T. H. Haines, and D. W. Deamer. Biophys. J., 70:339–348, 1996.

[174] T. R. Stouch. Prog. Colloid. Polym. Sci., 103:116–120, 1997.

[175] W. K. Subczynski, A.Wisniewska, J.-J. Yin, J. S. Hyde, and A. Kusumi. Biochemistry, 33:7670–7681, 1994.

Anmerkungen

The source is not given.

Sichter
(Klgn), WiseWoman


vorherige Seite | zur Übersichtsseite | folgende Seite
Letzte Bearbeitung dieser Seite: durch Benutzer:WiseWoman, Zeitstempel: 20160112215909

Auch bei Fandom

Zufälliges Wiki