Immobilization-dependent fluorescence of colchicine

Area of Science:

• Biochemistry
• Physical Chemistry

Background:

• Colchicine exhibits fluorescence when bound to tubulin, but not in simple solvents.
• The underlying mechanism of colchicine fluorescence has been a subject of investigation.

Purpose of the Study:

• To investigate the basis of colchicine fluorescence.
• To understand the role of solvent properties and molecular immobilization in modulating colchicine fluorescence.

Main Methods:

• Examined colchicine fluorescence in various solvents (alcohols, glycerol, dioxane, DMSO) with varying viscosity and polarity.
• Studied fluorescence of covalently attached desacetylcolchicine to macromolecules (thyroglobulin, albumin, lysozyme).
• Compared fluorescence properties of colchicine with its rigid analogue, imerubine.

Main Results:

• Colchicine fluorescence increases with solvent viscosity and chain length of alcohols, with glycerol enhancing efficiency and causing a blue shift.
• Fluorescence intensity correlates with viscosity, even in nonpolar solvents, and is also affected by solvent polarity.
• Immobilization via covalent attachment to proteins significantly enhances colchicine fluorescence.
• The rigid analogue imerubine fluoresces in water and is insensitive to viscosity.

Conclusions:

• Colchicine fluorescence is significantly contributed by immobilization within its binding site, influenced by its flexible nature.
• Immobilization-enhanced fluorescence is likely a broader phenomenon, observed in other flexible molecules like auramine O and flavines.