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Fluorescence quenching and time‐resolved fluorescence studies on Momordica Charantia (Bitter Gourd) seed lectin
Author(s) -
Padma P.,
Komath Sneha Sudha,
Swamy Musti J.
Publication year - 1998
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1002/iub.7510450509
Subject(s) - momordica , bitter gourd , fluorescence , lectin , quenching (fluorescence) , chemistry , biochemistry , traditional medicine , medicine , physics , optics
Chemical modification studies implicated tryptophan (Trp) residues in the sugar binding activity of Momordica charantia lectin (MCL) [Mazumdar, T., Gaur, N. & Surolia, A. (1981) Eur. J. Biochem. 113, 463–470]. In the present study, the accessibility and environment of Trp residues in MCL were investigated by intrinsic fluorescence quenching and time‐resolved fluorescence. The emission λ mm of native MCL in the absence as well as in the presence of 0.1 M lactose was around 335nm, which shifted to 365nm in the presence of 8 M urea, suggesting that the Trp residues which are predominantly buried in the hydrophobic core of the native lectin get exposed to the aqueous environment upon denaturation. At a quencher concentration of 0.5 M, the extent of quenching observed for the native MCL with acrylamide, I and Cs + was 46%, 17% and 12%, respectively. In the presence of 0.1 M lactose this quenching was smaller, suggesting that the sugar ligand provides a partial protection to the Trp residues. In time‐resolved fluorescence measurements, the decay curves could be fitted well to a biexponential function with the estimated life times 0.92 ns and 4.64 ns for the native protein and 1.15 ns and 5.1 ns in the presence of 0.1 M lactose. All these results are consistent with the involvement of Trp residues in the sugar‐binding activity of MCL.