No abstract

One of the principal goals of glycoprotein research is to correlate glycan structure and function. Such correlation is necessary in order for one to understand the mechanisms whereby glycoprotein structure elaborates the functions of myriad proteins. The accurate comparison of glycoforms and quantification of glycosites are essential steps in this direction. Mass spectrometry has emerged as a powerful analytical technique in the field of glycoprotein characterization. Its sensitivity, high dynamic range, and mass accuracy provide both quantitative and se-

Proteomics data can be processed using simple speadsheet formula.

A Glycomics approach to detect disease is illustrated in the analyses of human tear fluid for rosacea. The diagnosis of ocular rosacea is particularly challenging in a subgroup of patients that do not present with typical facial skin findings but have ocular signs and symptoms. Indeed, up to 90% of patients with ocular rosacea may have neither obvious roseatic skin changes nor a previous diagnosis of rosacea. Tear fluid was collected from 37 subjects (21 controls and 16 patients with ocular rosacea) after conjunctival stimulation with filter (Schirmer) paper. O-linked oligosaccharides were released from tear fluid by beta-elimination and then purified using solid-phase extraction. Mass spectra were recorded on an external source HiResMALDI with a 7.0 T magnet. Mass spectra were obtained in both the positive and negative modes. However, signals were stronger in the negative mode. Tear fluid samples from rosacea patients yielded distinctive clusters of peaks that extend to higher masses. Patients with rosacea presented several oligomeric series that were not found in the controls. To discriminate the ocular rosacea cases from the normal controls, the sum of absolute intensities of 13 series corresponding to nearly 50 identified mass spectrum peaks was used. Thirty-six out of the 37 samples were correctly classified. This yields a sensitivity of 100% (95% CI 79.5-100) and specificity of 95.2% (95% CI 76.2-99.9). The high abundance of oligosaccharides in the tear fluid of patients with rosacea may lead to an objective diagnostic marker for the disease.