Characterization of methylglyoxal-modified human IgG by physicochemical methods

Area of Science:

• Biochemistry
• Biophysics
• Immunology

Background:

• Human immunoglobulin G (IgG) is a key defense protein.
• IgG exhibits reactivity towards dicarbonyl compounds.
• Dicarbonyl modifications can alter protein structure and function.

Purpose of the Study:

• To investigate the biochemical and biophysical effects of methylglyoxal (MGO) modification on human IgG.
• To characterize structural changes, aggregation, and oxidative stress induced by MGO.

Main Methods:

• UV-visible and fluorescence spectroscopy
• Fourier transform infrared spectroscopy (FTIR)
• 1-anilinonaphthalene-8-sulfonic acid (ANS) binding assays
• Thermal denaturation studies
• Thioflavin T (ThT) and Congo red (CR) binding assays
• Scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Main Results:

• MGO modification induced significant structural alterations in IgG, evidenced by spectroscopic changes.
• Formation of fluorogenic advanced glycation end-products (AGEs) and increased IgG thermostability were observed.
• Increased carbonyl content and decreased sulfhydryl groups indicated oxidative stress.
• Enhanced binding of ThT and CR, along with SEM/TEM data, confirmed MGO-induced crosslinking and aggregate formation.

Conclusions:

• Methylglyoxal modification leads to substantial structural changes and aggregation of human IgG.
• The modification results in increased protein thermostability and induces oxidative stress.
• These findings highlight the impact of dicarbonyls on IgG integrity and function.