Binding interaction of differently charged fluorescent probes with egg yolk phosphatidylcholine and the effect of β-cyclodextrin on the lipid-probe complexes: a fluorometric investigation

A fluorescence approach on the investigation of urea derivatives interaction with a non-PET based acridinedione dye-beta Cyclodextrin (β-CD) complex in water: Hydrogen-bonding interaction or hydrophobic influences or combined effect?

Photophysical studies of resorcinol based acridinedione dyes with beta Cyclodextrin (β-CD) in the presence of urea (U) and tetramethylurea (TMU) were carried out in water. A marked variation in the absorption spectra of dye-β-CD complex was found to be more significant in the case of U rather in TMU. Interestingly, the role of urea on the excited state behavior of dye-β-CD complex is found to be entirely different from that of TMU. The formation of urea-water hydrogen-bonding self assemblies and creation of microspheres of varying environment results in an effective displacement of dye from the hydrophobic nanocavity of β-CD. On the contrary, the dye prefers a more confined hydrophobic micro environment in the presence of TMU. The nature of urea derivative, hydrogen-bonding of urea-water assemblies and hydrophobic influences of methyl moieties in urea molecular framework governs the stability and also the dissociation of dye-β-CD complex. The displacement of dye from the environment of the sugar molecule by urea derivatives is established from fluorescence studies wherein the variation in the spectral behavior of non-PET based dye-β-CD complex is found to be entirely different from that of PET dye. Both hydrogen-bonding along with hydrophobic interactions influences the excited state properties of the both PET and non-PET based acridinedione dyes are elucidated through fluorescence spectral studies. The extent of binding and the microenvironment of the dye in the presence of β-CD and urea are established through molecular docking and fluorescence anisotropy studies.

Aggregation of Nile Red in Water: Prevention through Encapsulation in β-Cyclodextrin

The present work, based on various spectroscopic investigations, vividly demonstrates the self-association of Nile red (NR) in aqueous medium. The rapid decrease in the absorbance as well as emission of NR in water bears the signature of the aggregation process. Appearance of a new blue-shifted absorption band in addition to the original one and a drastic decrease in the emission intensity imply that the aggregation is of H-type. Poor solubility of NR in water, hydrophobic interaction, and the planar structure of the dye are ascribed to favor the formation of the aggregate in the aqueous medium. Absorption-based kinetic studies reveal the aggregation process to be second order, thereby establishing the aggregate to be a dimer. Similar kinetic profiles of the absorbance of NR in the presence and absence of light confirm that the aggregation process is not photoassisted. The presence of an isosbestic point in the absorbance spectra and an isoemissive point in the time-resolved area normalized emission spectra bears the evidence of equilibrium between the dimeric and the monomeric species of NR in the ground state as well as in the photoexcited state. Encapsulation of the monomer of NR within the hydrophobic cavity of β-cyclodextrin is demonstrated to prevent the aggregation process.

Exploration of the binding interaction of a potential nervous system stimulant with calf-thymus DNA and dissociation of the drug–DNA complex by detergent sequestration

The binding interaction of a potential nervous system stimulant with calf-thymus DNA has been divulged and dissociation of the drug–DNA complex has been achieved by the detergent sequestration method.