Binding of cationic dyes to potassium alginate: A spectrophotometric and dichroic probe

✍ Scribed by Medini Kanta Pal; Nemai Mandal

• Book ID: 102764644
• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 527 KB
• Volume: 29
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360291205

✦ Synopsis

Acridine orange ( AO) binds to potassium alginate ( KAlg) stoichiometrically as is evidenced from conductometric and spectrofluorometric titrations. However, A 0 as well as methylene blue ( M B ) exhibits weak metachromasia and no induced dichroism a t any sensible polymer to dye ratio ( P / D ) . KAlg induces large blue shifts (by as much as 125 n m ) of the A, , , of the strongly aggregating dyes 1,9-dimethylmethyleneblue ( DMMB ) and pinacyanol at reasonable P / D values; KAlg also induces strong dichroism in these dyes. The signs of the induced CD spectra indicate KAlg to have a left-handed helical conformation. This polymer also induces red-shifted J band and dichroism in the dye N-N'-diethylpseudoisocyanine ( P I C ) a t high P / D under which condition the signs of CD spectra in DMMB reverse with drastic reduction in [ 01 values. This reversal of sign of CD or induction of J band in PIC a t only high KAlg concentrations does not involve any conformational change in the polymer as indicated by the insensitivity of the UV-CD spectrum of KAlg as a function of concentration.