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PRO_689_sm_SuppinfoFig1.doc869KSupporting Information Figure 1. Analysis of an in-house generated aldonic acid standard (Glc4GlcA) generated by chemical oxidation of cellooligosaccharides. Note that the efficiency of the oxidation reaction is less than 100% and that some components partially co-elute in the subsequent purification step. Consequently, the Glc4GlcA sample also contains minor amounts of other compounds such as Glc5, Glc6 and Glc5GlnA. (A) Verification of the oxidized oligosaccharide by MALDI-TOF analysis. The mass spectrum shows the K and Na adducts of the lactone (Glc4GlcLA), aldonic acid (Glc4GlcA) and the native oligosaccharide (Glc5). Additionally, the K and Na adducts of the K and Na aldonic acid salts are observed. A distribution of ions representing the oxidized hexameric cellooligosaccharide (Glc5GlcLA/ Glc5GlcA/ Glc6) can also be observed. (B) HPAEC analysis. The picture shows an overlay of a chromatogram for the chemically oxidized oligosaccharide (dotted line) with a chromatogram for products generated by CelS2 action on Avicel (solid line). The chromatogram of the pentameric standard shows the same species as detected by MS analysis: the aldonic acid, the lactone and native form (Nb. Formally, the peak labeled Glc4GlcLA must be regarded as “unknown”; the peak was annotated as Glc4GlcLA by inference from the mass spectrum of panel A). The absence of the lactone form in the CelS2 product mix is due to the slow equilibrium between lactone and aldonic acid at the pH of the reaction (pH 6.5).

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