Fig. 6.

Deimination of Arg49 coupled with racemization of Asp48 in MBP from controls (●) and multiple sclerosis (MS) patients suffering from SPMS (○) PPMS (◊) and RRMS (▽). a For the L-Asp version (FFGGD(Cit)GAPK), no statistically significant difference was found in the levels of citrulline between controls and multiple sclerosis patients, but linear regression analysis revealed a significant increase in the amount of citrulline with age in control samples (R ² = 0.664, p = 0.004). b Conversion of L-Asp48 to the other Asp isomers in the tryptic peptide deiminated at Arg49 (FFGGD(Cit)GAPK). An increase in racemization of Asp48 in the deiminated peptide was seen in multiple sclerosis patients (p < 0.001, Mann–Whitney-U). Racemization in this case refers to combined D-Asp, D-isoAsp and L-isoAsp, since the isomers were not separated under these conditions. The percentage of modification was determined by the ion intensities of (FFGGD(Cit)GAPK))/(FFGGD(Cit)GAPK + FFGGD(Cit)GAPK) × 100. Controls n = 10; multiple sclerosis patients n = 8