Solvation dynamics of DCM in a DPPC vesicle entrapped in a sodium silicate derived sol-gel matrix

Abstract

Solvation dynamics of 4-(dicyanomethylene)-2-methyl-6(p-dimethylaminostyryl) 4H-pyran (DCM) has been studied in a dipalmitoyl-phosphatidylcholine (DPPC) vesicle entrapped in a sodium silicate derived sol-gel glass. Solvation dynamics in DPPC in a sol-gel glass is described by two components of 350 ± 50 ps (50%) and 2300 ± 200 ps (50%) with a total dynamic Stokes shift of 1300 cm. The fast component (350 ps) is similar to the fast component in a DPPC vesicle in bulk water (320 ± 50 ps). This component may be ascribed to the dynamics of the water molecules inside the water pool of the vesicle. However, the slow component (2300 ± 200 ps) is about 2.5 times slower compared to the slow component of solvation dynamics of DCM in a DPPC vesicle in bulk solvent (900 ± 100 ps). The anisotropy decay of DCM in a DPPC vesicle both in sol-gel glass and in bulk water exhibits a very fast initial decay with a large residual anisotropy, which does not decay in 10 ns. The time scale of anisotropy decay is very different from that of solvation dynamics.