A multi-method approach toward de novo glycan characterization: a Man-5 case study.

Regulatory agencies' expectations for biotherapeutic approval are becoming more stringent with regard to product characterization, where minor species as low as 0.1% of a given profile are typically identified. The mission of this manuscript is to demonstrate a multi-method approach toward de novo glycan characterization and quantitation, including minor species at or approaching the 0.1% benchmark. Recently, unexpected isomers of the Man(5)GlcNAc(2) (M(5)) were reported (Prien JM, Ashline DJ, Lapadula AJ, Zhang H, Reinhold VN. 2009. The high mannose glycans from bovine ribonuclease B isomer characterization by ion trap mass spectrometry (MS). J Am Soc Mass Spectrom. 20:539-556). In the current study, quantitative analysis of these isomers found in commercial M(5) standard demonstrated that they are in low abundance (<1% of the total) and therefore an exemplary "litmus test" for minor species characterization. A simple workflow devised around three core well-established analytical procedures: (1) fluorescence derivatization; (2) online rapid resolution reversed-phase separation coupled with negative-mode sequential mass spectrometry (RRRP-(-)-MS(n)); and (3) permethylation derivatization with nanospray sequential mass spectrometry (NSI-MS(n)) provides comprehensive glycan structural determination. All methods have limitations; however, a multi-method workflow is an at-line stopgap/solution which mitigates each method's individual shortcoming(s) providing greater opportunity for more comprehensive characterization. This manuscript is the first to demonstrate quantitative chromatographic separation of the M(5) isomers and the use of a commercially available stable isotope variant of 2-aminobenzoic acid to detect and chromatographically resolve multiple M(5) isomers in bovine ribonuclease B. With this multi-method approach, we have the capabilities to comprehensively characterize a biotherapeutic's glycan array in a de novo manner, including structural isomers at >/=0.1% of the total chromatographic peak area.

Mass spectrometric-based stable isotopic 2-aminobenzoic acid glycan mapping for rapid glycan screening of biotherapeutics.

Fast, sensitive, robust methods for "high-level" glycan screening are necessary during various stages of a biotherapeutic product's lifecycle, including clone selection, process changes, and quality control for lot release testing. Traditional glycan screening involves chromatographic or electrophoretic separation-based methods, and, although reproducible, these methods can be time-consuming. Even ultrahigh-performance chromatographic and microfluidic integrated LC/MS systems, which work on the tens of minute time scale, become lengthy when hundreds of samples are to be analyzed. Comparatively, a direct infusion mass spectrometry (MS)-based glycan screening method acquires data on a millisecond time scale, exhibits exquisite sensitivity and reproducibility, and is amenable to automated peak annotation. In addition, characterization of glycan species via sequential mass spectrometry can be performed simultaneously. Here, we demonstrate a quantitative high-throughput MS-based mapping approach using stable isotope 2-aminobenzoic acid (2-AA) for rapid "high-level" glycan screening.

Differentiating N-linked glycan structural isomers in metastatic and nonmetastatic tumor cells using sequential mass spectrometry.

In an effort to understand the role of molecular glycosylation in cancer a murine model has been used to characterize and fingerprint malignancies in established cell lines that manifest all the hallmarks of metastatic disease: spontaneous development, local invasion, intravasation, immune system survival, extravasation, and secondary tumor formation involving liver, kidney, spleen, lung, and brain. Using astrocyte cell controls, we compared N-linked glycosylation from a nonmetastatic brain tumor cell line and two different metastatic brain tumor cells. Selected ions in each profile were disassembled by ion trap mass spectrometry (MS(n)) which exhibited multiple structural differences between each tissue. These unique structures were identified within isomeric compositions as pendant nonreducing termini of di- and trisaccharide fragments, probably transparent to a tandem MS approach but distinctively not to sequential ion trap MS(n) detection.

The high mannose glycans from bovine ribonuclease B isomer characterization by ion trap MS.

Thirteen high mannose isomers have been structurally characterized within three glycomers, Man(5)GlcNAc(2), Man(7)GlcNAc(2), and Man(8)GlcNAc(2) released from bovine ribonuclease B, six previously unreported. The study was carried out with a single ion trap instrument involving no chromatography. Three previously characterized isomers from Man(7) and Man(8) (three each) have been identified plus one unreported Man(7) isomer. Incomplete alpha-glucosidase activity on the Man(6) and Man(7) glycoproteins appears to account for two additional isomeric structures. The preeminence of ion traps for detail analysis was further demonstrated by resolving three new isomers within the Man(5) glycomer summing to the six previously unreported structures in this glycoprotein. All reported structures represent a distribution of Golgi processing remnants that fall within the Man(9)GlcNAc(2) footprint. Topologies were defined by ion compositions along a disassembly pathway while linkage and branching were aided by spectral identity in a small oligomer fragment library. Isomers from this glycoprotein appear to represent a distribution of Golgi processing remnants, and an alphanumeric classification scheme has been devised to identify all products. Although numerous analytical strategies have been introduced to identify selected components of structure, it has been the continued focus of this and previous reports to only build upon protocols that can be integrated into a high throughput strategy consistent with automation. Duplication of these and results from comparable standards could bring an important analytical focus to carbohydrate sequencing that is greatly lacking.