Figure 4. Investigation of posttranslational modifications.

Immunoblot of Serpin A1 in a PDD-patient with and without neuraminidase-treatment (different exposures of times are shown to better visualize the individual spots, intensity of both blots were similar; exposure time for the immunoblot without neuraminidase-treatment  = 2 seconds, exposure time for the immunoblot with neuraminidase-treatment  = 10 seconds). Treatment with the enzyme leads to an isoform shift towards a more basic pI and thereby to the disappearance of the diagnostic relevant most acidic spots 1 and/or 2. “Untreated” means usage of a native CSF-sample without neuraminidase-digest.