Interaction of urea with fluorophores bound to cyclodextrins. Fluorescence of p-toluidino naphthalene sulphonate

✍ Scribed by Nilmoni Sarkar; Kaustav Das; Debnarayan Nath; Kankan Bhattacharyya

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 500 KB
• Volume: 196
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(92)85726-q

✦ Synopsis

The effect of urea on the fluorescence properties of p-toluidino naphthalene sulphonate (TNS) bound to a-and l3-cyclodextrin (CDx) has been studied by steady-state and time-resolved emission spectroscopy. From the observed emission yield, lifetime and emission maxima the polarity of the a-CDx and P_CDx environment is estimated. Addition of urea to aqueous CDx solutions decreases the fluorescence yield and lifetime of TNS. The effect is more pronounced for a-CDx and less for /3-CDx. The results are interpreted in terms of the model that urea increases the local polarity of the CDx surface and, in the case of a-CDx, displaces TNS molecules form the cyclodextrin interface. The TNS molecules are easily accessed by the urea molecule in the smallest a-CDx where a major part of the bound TNS molecule is projected outside the cavity. In PCDx two kinds of TNS: &CDx complexes ( 1: 1 and 1: 2) are formed. Addition of urea causes removal of TNS molecules bound to CDx in the 1: 1 complex, but TNS in the 1: 2 complex remains more or less unaffected because urea cannot approach it.