ISSN:
1435-1536
Keywords:
Key words Differential scanning microcalorimetry
;
hydrophobic mismatch
;
anchoring
;
sodium di-n-dodecyl phosphate
;
vesicle bilayers
;
hydrophobically modified poly(sodium acrylate)s
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Differential scanning microcalorimetric thermograms have been recorded for aqueous solutions containing vesicles formed by sodium di-n-dodecyl phosphate, in the presence of different concentrations of poly(sodium acrylate-co-n-alkyl methacrylate), where n-alkyl= C9H19, C12H25, C18H37. The mole fraction of hydrophobic moieties in the copolymer is 0.04. The main phase transition temperature (T m) is hardly affected by the presence of poly(sodium acrylate)s bearing n-dodecyl chains, whereas the anchoring of polymers bearing n-nonyl or n-octadecyl groups reduces the main phase transition temperature significantly from ca. 34 °C to ca. 32 °C. In parallel, the enthalpy of transition per mole of DDP monomer (Δm H int) is lowered upon adding polymer. Again, the polymer containing n-dodecyl moieties hardly affects Δm H int. These patterns are explained by the notion that the extent of the disruptive effect of alkyl chains incorporated into the bilayer depends on the extent of the mismatch between the chain lengths of the intruding alkyl chains and the hydrophobic moieties composing the vesicle bilayer. Added hydrophobically modified polymers increase the cooperativity of the melting process, as shown by the increase of n DDP. We suggest that the anchoring poly(sodium acrylate-co-n-alkyl methacrylate) relieves the strain in the curved outer monolayer of a pure DDP bilayer by allowing the presence of larger “patches” characterized by low curvature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003960050228
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