MODELING OF COMPLEX BIOLOGICAL-SYSTEMS .2. EFFECT OF CHAIN-LENGTH ON THE PHASE-TRANSITIONS OBSERVED IN DIGLYCERIDE MONOLAYERS

Citation
Gh. Peters et al., MODELING OF COMPLEX BIOLOGICAL-SYSTEMS .2. EFFECT OF CHAIN-LENGTH ON THE PHASE-TRANSITIONS OBSERVED IN DIGLYCERIDE MONOLAYERS, Langmuir, 11(10), 1995, pp. 4072-4081
Citations number
82
Categorie Soggetti
Chemistry Physical
Journal title
ISSN journal
07437463
Volume
11
Issue
10
Year of publication
1995
Pages
4072 - 4081
Database
ISI
SICI code
0743-7463(1995)11:10<4072:MOCB.E>2.0.ZU;2-7
Abstract
We have performed molecular dynamics computer simulations to examine t he effect of chain length on the phase transitions observed in 1,2-sn- diglyceride monolayers. Simulations were performed for three different diglycerides of chain length 10, 16, and 22. The monolayers composed of molecules of chain lengths 16 and 22 exhibit complex phase transiti ons as a function of surface pressure. These two Langmuir films underg o two phase transitions, where the transition at low surface density i s associated with tilt. The high surface pressure transition is unique for the diglyceride molecules and is driven by a competition of hydro phobic/hydrophilic and intra-/intermolecular forces involving the two head groups. Increasing the chain length, on one hand, stabilizes the chains in the layer resulting in a lower percentage of gauche defects but, on the other hand, the low-pressure phase transition is shifted t o higher surface density. No tilt transition is observed in the 1,2-sn -didecanoylglycerol film due to the short length of the alkyl chains. This film is more mobile than the C16 and C22 layers, and the melting of the layer proceeds by creating gauche defects in the alkyl chains.