Formic acid and HEPES were obtained from Sigma-Aldrich (St. was purchased from Fluka Chemical (Milwaukee, WI, USA). Buffer-free SMART Digest answer was provided by Perfinity Biosciences (West Lafayette, IN, USA; currently supplied by Thermo Fisher Scientific). Formic acid and HEPES were obtained from Sigma-Aldrich (St. Louis, MO, USA). Axygen MaxyClear Snaplock microtubes, 1.5 ml, were obtained from Fisher Scientific (Pittsburgh, PA, USA). Acetonitrile, pH 3.00 buffer, pH 6.00 buffer, SMART Digest trypsin kit, and sodium hydroxide solution were purchased from Thermo Fisher Scientific. The NIST SBI-0206965 mAb was purchased from NIST. Purified water was produced from in-house Milli-Q systems. Answer preparation HEPES SMART Digest buffer was prepared as follows: buffer-free SMART Digest answer, 70 ml, and HEPES, 476 mg, were added to a 250 ml bottle and mixed until fully dissolved. The solution was adjusted to pH 7.7 using 5 N sodium hydroxide. Sample preparations Samples were prepared as explained. NIST mAb in HEPES SMART Digest buffer NIST mAb, 0.5 ml, was added to an Amicon 10K molecular weight cutoff filter and centrifuged at 14,000 for 15 min. An additional 0.3 ml NIST mAb was added to the retentate, and the sample was centrifuged at 14,000 for 15 min. HEPES SMART Digest buffer, 0.5 ml, was added, and the sample was centrifuged at 14,000 for 15 min. The buffer exchange was repeated twice more. The sample was collected at 1000 for 5 min and diluted to 1 1.6 ml using additional HEPES SMART Digest buffer. The SBI-0206965 final concentration of the sample was 1 mg mAb/200 l. NIST mAb glycopeptides NIST mAb in HEPES SMART Digest buffer, 200 l, was added to a microtiter well made up of resin-bound SMART Digest trypsin, 20 g enzyme. The resin was suspended in the sample, and the contents were transferred to another microtiter well made up of a fresh aliquot of resin-bound trypsin. The resin was suspended in the sample, and the contents were transferred to a third microtiter well made up of a fresh aliquot of resin-bound trypsin. This yielded a 3-fold increase in the trypsin available to digest the sample. The sample was digested on a digital shaking drybath at 70C for 3 h at 1400 rpm. The digest combination was diluted with 200 l acetonitrile and centrifuged at 21,100 for 15 min. The producing supernatant was collected for analysis. NIST mAb RapiFluor-labeled glycans Water, 15.3 l, was added to a 1.5 ml microcentrifuge tube. NIST mAb in HEPES SMART Digest buffer, 5 l, was also added followed by 8.5 l additional HEPES SMART Digest buffer. The combination was incubated at 90C for 3 min in a dry block bath. The sample was allowed to SBI-0206965 cool to Rabbit Polyclonal to TNF12 room heat. Rapid PNGase F, 1.2 l, was added to the sample, followed by incubation at 50C for 30 min at 600 rpm on a ThermoMixer R (Eppendorf, Hauppauge, NY, USA). glycopeptide are plotted. Good correlation exists between the quantification of glycopeptides and labeled glycans. Some of the anomalies may exist as a result of chromatography issues. The chromatography method did not fully handle some isobaric glycans, thereby complicating quantification. Multiple charge says for the same analyte are not summed. For the resin-bound SMART Digest, all of the mAb appear to be digested to yield the desired tryptic (glyco)peptide. The use of this type of digest presents several advantages, including reduced digestion time and dramatic lowering of miscleavages. This latter effect is likely, at least in part, a result of the resin-bound nature of the protease, lowering the possibility of trypsinCtrypsin interactions (Perfinity Biosciences; Application Note, http://www.perfinity.com/flash-digest-applications-by-type).14 Conversation In this work, we have demonstrated a highly efficient digestion method to produce predictable glycopeptides with no detected miscleavages. The designed resin-bound digestion method correlates SBI-0206965 well with the traditional method for glycan analysis PNGase F-released glycans. Efficient digestion of the protein at the site of glycosylation with minimal miscleavages allows the use of producing glycopeptides to quantify glycosylations in site-specific fashion. With the appropriate standards, this method could allow for site-specific absolute quantification of glycosylations on proteins. Whereas increase of the method sensitivity is usually ongoing, the current signal intensity is usually 1000-fold above the noise level and SBI-0206965 would limit miscleavage products, if they exist, to 0.1% in abundance relative to the desired tryptic peptide. This should allow for complete quantification of the glycosylation around the mAb with the appropriate standards. Any other glycoprotein, if it could be digested with comparable efficiency, could have its glycosylation quantified in a similar.