A Fluorescence Study on Binding Interaction of N-acetylated Dansylamide Conjugates with beta-cyclodextrin, Tween-20 and DPPC Lipid Bilayer Membrane

The present work describes the photophysical behavior of a saturated fatty acid (palmitic acid) containing N-acetylated dansylamide derivative (DAN-PA) into biologically important organized assembly such as beta-cyclodextrin (beta-CD), Tween-20 (T-20) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayer membrane. The results were compared by using another N-acetylated dansylamide conjugate having a short hydrophobic tail, DAN-ACYL. Long hydrophobic tail (saturated fatty acid) containing dansylamide conjugate (DAN-PA) shows more efficient binding interactions with the beta-CD as compared to the short tail containing dansylamide derivative (DAN-ACYL). The calculated binding constants values of DAN-PA and DAN-ACYL probes are 1.35 x 10(2) M (-1) and 0.31 x 10(2) M (-1) respectively. The DAP-PA is a sensitive fluorophore for understanding the micellization process in T-20, as compared to the DAN-ACYL because it shows a significant change in fluorescent properties (steady-state and time-resolved both) with changing in T-20 concentrations. The calculated CMC value for T-20 surfactant is 0.07 mM. While the DAN-ACYL does not show any change in the fluorescent properties while changing the T-20 concentrations. Fluorescent parameters like steady-state and time-resolved of DAN-PA are quite sensitive towards the thermo-tropic phase transitional changes into lipid bilayer membrane properties. And the calculated thermo-tropic phase transition temperature by using DAN-PA fluorophore is 42 A degrees C.