Effect of heparin modification on its circular dichroism spectrum

Area of Science:

• Biochemistry
• Carbohydrate Chemistry
• Molecular Biology

Background:

• Heparin's high affinity for antithrombin III is crucial for its anticoagulant properties.
• Understanding how chemical modifications affect heparin's structure-activity relationship is essential for drug development.

Purpose of the Study:

• To investigate the impact of carboxyl group modifications on high-affinity heparin's binding affinity to antithrombin III.
• To analyze the structural changes induced by these modifications using circular dichroism (CD) spectroscopy.

Main Methods:

• Chemical modification of heparin's carboxyl groups, including esterification and glycine ester conjugation.
• Assessment of antithrombin III binding affinity using established assays.
• Circular dichroism (CD) spectroscopy to analyze conformational changes.

Main Results:

• Binding affinity to antithrombin III decreased in the order: Heparin > Heparin Methyl Ester > Heparinylglycine > Heparinylglycine Methyl Ester.
• Esterification of carboxyl groups (heparin methyl ester) did not alter the CD profile at 210 nm.
• Introduction of glycine methyl ester (heparinylglycine methyl ester) induced a significant CD band at 235 nm.

Conclusions:

• Carboxyl group modification significantly impacts heparin's binding affinity to antithrombin III.
• The observed spectral changes in heparinylglycine methyl ester suggest a conformational change in the uronic acid moiety.
• These findings provide insights into the structural requirements for heparin-antithrombin III interaction.