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Tryptophan exposure and accessibility in the chitooligosaccharide-specific phloem exudate lectin from pumpkin (Cucurbita maxima). A fluorescence study

Paper ID Volume ID Publish Year Pages File Format Full-Text
31098 44542 2009 8 PDF Available
Title
Tryptophan exposure and accessibility in the chitooligosaccharide-specific phloem exudate lectin from pumpkin (Cucurbita maxima). A fluorescence study
Abstract

The exposure and accessibility of the tryptophan residues in the chitooligosaccharide-specific pumpkin (Cucurbita maxima) phloem exudate lectin (PPL) have been investigated by fluorescence spectroscopy. The emission λmax of native PPL, seen at 338 nm was red-shifted to 348 nm upon denaturation by 6 M Gdn.HCl in the presence of 10 mM β-mercaptoethanol, indicating near complete exposure of the tryptophan residues to the aqueous medium, whereas a blue-shift to 335 nm was observed in the presence of saturating concentrations of chitotriose, suggesting that ligand binding leads to a decrease in the solvent exposure of the tryptophan residues. The extent of quenching was maximum with the neutral molecule, acrylamide whereas the ionic species, iodide and Cs+ led to significantly lower quenching, which could be attributed to the presence of charged amino acid residues in close proximity to some of the tryptophan residues. The Stern–Volmer plot for acrylamide was linear for native PPL and upon ligand binding, but became upward curving upon denaturation, indicating that the quenching occurs via a combination of static and dynamic mechanisms. In time-resolved fluorescence experiments, the decay curves could be best fit to biexponential patterns, for native protein, in the presence of ligand and upon denaturation. In each case both lifetimes systematically decreased with increasing acrylamide concentrations, indicating that quenching occurs predominantly via a dynamic process.

Keywords
Chitooligosaccharide-specific lectin; Agglutinin; Carbohydrate binding protein; Fluorescence quenching; Acrylamide; Red-edge excitation shift
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Tryptophan exposure and accessibility in the chitooligosaccharide-specific phloem exudate lectin from pumpkin (Cucurbita maxima). A fluorescence study
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 97, Issue 1, 6 October 2009, Pages 40–47
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us