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Summer Research Fellowship Programme of India's Science Academies

Investigation on complexation behavior of Zwitterionic SYPRO Orange with Beta Cyclodextrin and its Sulfobutylether derivative

P Zamandas Hundani

Sant Gadge Baba Amravati University, Amravati 444602

Sukhendu Nath

Scientific Officer, Radiation and Photochemistry Division, Babha Atomic Research Centre, Mumbai 400085

Abstract

The noncovalent interactions between biologically important Zwitterionic dye, SYPRO Orange (SO), β-cyclodextrin (β-CD) and sulfobutylether β-cyclodextrin (SBE-β-CD) have been evaluated and compared using photophysical techniques. The inclusion complex of SO and β-CD shows remarkably large enhancement (~120 fold) along with ~40 nm blue shift in its emission spectra. From the job’s plot and time resolved fluorescence measurements it has been shown that SO forms inclusion complex with two equivalents of β-CD. In comparison to β-CD complex, SO: SBE-β-CD (1:1) complex shows less emission enhancement and ~100 fold stronger binding. Stronger binding is due to the additional hydrophobicity offered by extended butylethers of SBE-β-CD and also from the attractive electrostatic interaction between positively charged stilbazolium and negatively charged SO3- portals at the end. Low enhancement is attributing to the difference in stoichiometry as well as a result of repulsive interaction of the sulfonate group of the dye with SO3- of host which leads to the fetching of alkyl ether chains away from the cavity. Increase in ionic strength OF SO: SBE-β-CD complex enhances the emission intensity but not up to the value of β-CD. It is understood that hydrophobic forces and ion-ion interactions both play key roles in determining the behavior of complexation of SO with macrocyclic hosts.

Keywords: beta cyclodextrin, Sulphobutylether beta cyclodextrin, Sulphated Cyclodextrin, Time Correlated Single Photon Counting, SYPRO Orange,

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