Fandom

VroniPlag Wiki

Ry/Fragment 019 01

< Ry

31.371Seiten 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.


Typus
KomplettPlagiat
Bearbeiter
SleepyHollow02
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 19, Zeilen: 1 ff. (entire page)
Quelle: Anézo 2003
Seite(n): 31, 33, Zeilen: 31: last lines, 33: 1 ff.
Such non-lamellar phases are for instance observed as intermediate phases in common biological processes such as cell-cell adhesion and fusion.

I.2.3 Phase transitions

A phase transition is an abrupt change in the macroscopic properties of a system, involving a modification of the symmetry and/or topology of the system. Phase transitions are driven predominantly by two system variables, which are temperature and water content. There is thus a “natural” sequence in which the various possible phases occur. At low temperatures and hydration degrees, phospholipids tend to adopt an oriented conformation leading to crystalline or gel phases, while, at higher temperatures and hydration levels, fluid phases rather occur. At a given temperature and water content, transitions can be also induced by changes in the lipid composition or by additives. A study of the factors affecting or including a phase transition and of the changes taking place at the phase transition provides a very valuable method of characterizing the properties of the fluid state, which is the more relevant to biological membranes (see also reference [11]).

Effect of phospholipids hydration. The effect of water on the thermotropic behavior of phospholipid assemblies is complex. A certain amount of water molecules is bound to the polar headgroups and behaves differently from bulk water. Bound water appears to represent about 20% of the phospholipid-water system. Usually, the addition of water causes a general loosening of the lipid packing density, leading to a decrease of the transition temperature. The decrease in temperature can reach as much as 50OC. This can be explained by a growing mobility of all phospholipid molecules with increasing hydration, due to a diminishing intermolecular steric hindrance. More precisely, increasing hydration gives rise to a softening of the interfacial region, which enhances headgroup mobility. The enhanced headgroup mobility leads in turn to an increased mobility of the hydrocarbon chains.

Effect of phospholipids chemical structure. Within a particular class of phospholipids, the length of the hydrocarbon chains has a direct influence on the [transition temperature, e.g. from the gel state Lβ to the liquid crystalline state Lα.]


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.

Such non-lamellar phases are for instance observed as intermediate phases in common biological processes such as cell-cell adhesion and fusion.

[page 33:]

1.2.3 Phase transitions

A phase transition is an abrupt change in the macroscopic properties of a system, involving a modification of the symmetry and/or topology of the system. Phase transitions are driven predominantly by two system variables which are temperature and water content. There is thus a "natural" sequence in which the various possible phases occur. At low temperatures and hydration degrees, phospholipids tend to adopt an ordered conformation leading to crystalline or gel phases, while, at higher temperatures and hydration levels, fluid phases rather occur. At a given temperature and water content, transitions can be also induced by changes in the lipid composition or by additives. A study of the factors affecting or inducing a phase transition and of the changes taking place at the phase transition provides a very valuable method of characterizing the properties of the fluid state, which is the more relevant to biological membranes (see also reference [20]).

Effect of phospholipid hydration The effect of water on the thermotropic behavior of phospholipid assemblies is complex. A certain amount of water molecules is bound to the polar headgroups and behaves differently from bulk water. Bound water appears to represent about 20% of the phospholipid-water system. Usually, the addition of water causes a general loosening of the lipid packing density, leading to a decrease of the transition temperature. The decrease in temperature can reach as much as 50°C. This can be explained by a growing mobility of all phospholipid molecules with increasing hydration, due to a diminishing intermolecular steric hindrance. More precisely, increasing hydration gives rise to a softening of the interfacial region, which enhances headgroup mobility; the enhanced headgroup mobility leads in turn to an increased mobility of the hydrocarbon chains.

Effect of phospholipid chemical structure Within a particular class of phospholipids, the length of the hydrocarbon chains has a direct influence on the transition temperature, e.g. from the gel state Lβ to the liquid crystalline state Lα.


[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

The source is not mentioned.

Sichter
(SleepyHollow02), Klgn

Auch bei Fandom

Zufälliges Wiki