Combination of DSC and X-ray Diffraction

The thermodynamic and structural effects of diltiazem on lecithin (PC) liposomes have been studied by DSC and X-ray diffraction [154]. The authors found that at higher drug concentration the pretransition disappears, the main transition temperature decreases, and the lamellar thickness of the bilayer increases. The chains in the (3-conformation were packed in a hexagonal undistorted lattice. There was a complete agreement in the observed data all changes in the calorimetric and structural curves (X-ray) occurred at the same concentration, that is between 1(T2 and KT1 M. 

Drug (value of Kp) Drug concentration (mM) Tt (°C) AHcal (kcal/mol) A Hvh (CUb) 

The combination of X-ray and DSC has also been used to explore the effects of pindolol on model membranes. Changes in thermodynamic and structural parameters were observed. Depending on the temperature pindolol induced either a interdigitat-ed gel phase or, at high temperature, a lamellar phase. The data would seem to indicate that the non-polar moiety of pindolol penetrates deep into the bilayer interior while the hydrocarbon chains have to adopt a different conformation [156], 

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