Fig. 4.

Newborn screening of various MPS disorders. A portion of a newborn bloodspot sample was immersed in a solution of Pronase and incubated overnight to solubilize GAGs. The GAGs were then purified by anion exchange chromatography using DEAE-Sepharose, washing away contaminants with 0.2 M NaCl. The GAGs were eluted with1 M NaCl. After desalting, the GAG chains were enzymatically depolymerized with heparan lyases and the released component residues including both NRE and internal unsaturated disaccharides were derivatized with [¹²C₆]aniline. The derivatized samples were mixed with standards NRE biomarkers labeled with [¹³C₆]aniline to distinguish them from the NRE residues present in the biological samples. The mixed samples were next analyzed by LC/MS and based on the biomarker profile a tentative diagnosis was determined using the logic mapped out in the decision tree shown in Fig. 3.