Structural modification and aggregation of mucin by chromium(III) complexes.

Area of Science:

• Biochemistry
• Materials Science
• Coordination Chemistry

Background:

• Metal ions binding to proteins can regulate protein function and induce structural modifications.
• Pig gastric mucin (PGM) is a complex glycoprotein involved in various physiological processes.

Purpose of the Study:

• To investigate the interaction and conformational changes of PGM upon binding with different chromium(III) complexes.
• To elucidate the distinct binding mechanisms and their effects on PGM's structural and rheological properties.

Main Methods:

• Steady-state fluorescence spectroscopy to monitor protein conformational changes.
• Viscosity measurements to assess changes in PGM's rheological behavior.
• Circular dichroism (CD) spectroscopy to determine secondary structure alterations.
• Histochemical analysis to support observations on macromolecular aggregation.

Main Results:

• Complexes 1 ([Cr(salen)(H2O)2](ClO4)) and 3 ([Cr(EDTA)(H2O)]Na) interact coordinately with PGM, decreasing viscosity due to flexible fiber formation.
• Complex 2 ([Cr(en)3]Cl3) binds via electrostatic interactions and hydrogen bonding, inducing sol-gel transition, increased viscosity, and significant alpha-helical structure formation in PGM.
• Fluorescence quenching/enhancement varied with complex concentration and type, indicating differential protein interactions.

Conclusions:

• Chromium(III) complexes exhibit distinct binding modes with PGM, leading to varied structural and functional outcomes.
• Complex 2 promotes PGM oligomerization and alpha-helical structuring, suggesting potential applications in biomaterials.
• The charge and ionic character of chromium(III) complexes significantly influence their interaction with PGM.