Abstract
Human IgG is a defence protein and quite reactive to dicarbonyls. In this study, methylglyoxal-induced modification of IgG was examined by various biochemical and biophysical methods. The methylglyoxal-induced changes in IgG were monitored by UV-visible and fluorescence spectroscopy, Fourier transform infrared spectroscopy, 1-anilinonaphthalene-8-sulfonic acid (ANS), and thermal denaturation studies. Aggregate formation was studied by Thioflavin T (ThT), Congo red (CR) and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Spectroscopic studies suggested gross changes in MGO-modified IgG. Fluorogenic AGEs appeared during modification and the MGO-modified IgG gained thermostability. The reaction produced oxidative stress in the medium because carbonyl content increased manifold and sulfhydryl groups decreased. Enhanced binding of the MGO-modified IgG by Congo red and Thioflavin T suggests crosslinking and aggregation. This was supported by SEM and TEM results.
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Abbreviations:
- IgG: Immunoglobulin G
- MGO: Methylglyoxal
- AGEs: Advanced glycation end products
- SEM: Scanning electron microscope
- TEM: Transmission electron microscope
- ANS: 8-anilinonaphthalene-1-sulfonic acid
- DNPH: Dinitrophenyl hydrazine
- FT-IR: Fourier transform infrared spectroscopy
- DTNB: 5,5’-dithiobis-(2-nitrobenzoic acid)
- NBT: Nitroblue tetrazolium
Acknowledgements
MAK is thankful to the CSIR, New Delhi for NET-Junior/Senior Research Fellowship awarded vide letter no. 09/112 (0506)/2013-EMR-I. Authors are thankful to the USIF of the AMU for SEM and TEM, as well as the instrument facility of the “DST-FIST” program of the department.