No abstract

We report on a novel strategy for identification of specific sulfation motifs in chondroitin/dermatan sulfate (CS/DS) chain derived from decorin (Dcn), based on enzyme cleavage and multistage MS (MS(n)). Released CS/DS chains were digested with chondroitin B and in parallel with AC I lyases to obtain oligosaccharides of known hexuronic acid (HexA) epimerization. The depolymerized chains were separated by gel filtration, and collected di- and hexasaccharides were analyzed by ESI MS(n). MS(2) on bisulfated 4,5-Delta-HexAGalNAc revealed an additional sulfate ester group at 4,5-Delta-HexA. MS(2) data provided evidence upon GlcA sulfation in Dcn due to the fact that 4,5-Delta-HexA derived from GlcA after chondroitin AC I lyase treatment. Hexasaccharide screening in the MS(1) mode indicated direct correlation between the sulfate distribution and HexA epimerization. MS(n) performed on ions that, according to mass calculation, correspond to pentasulfated [4,5-Delta-HexAGalNAc(GlcAGalNAc)(2)], trisulfated [4,5-Delta-HexAGalNAc(GlcAGalNAc)(2)] with IdoA-derived 4,5-Delta-HexA at the nonreducing end, tetrasulfated [4,5-Delta-HexAGalNAc(IdoAGalNAc)(2)] and monosulfated [4,5-Delta-HexAGalNAc(IdoAGalNAc)(2)] with GlcA-derived 4,5-Delta-HexA at the nonreducing end rendered fragmentation patterns confirming the presence of over-, regular, and under-sulfated regions as well as structural motifs having both types of HexA sulfated within Dcn CS/DS.

A sturdy home-built sheathless CE/ESI-QTOF-MS system was developed and optimized for carbohydrate analysis. The interface and employed methodology provided a simple analytical solution to laborious CE/MS interfacing methods and to problems in characterization of complex carbohydrate mixtures that require high-resolution separation of the components. The CE/ESI interface, feasible in any MS laboratory, consists of a one-piece CE column having the CE terminus in-laboratory shaped as a microsprayer and coated with copper. The CE microsprayer was inserted into an in-house made stainless steel clenching device and the whole assembly was mounted onto a quadrupole TOF mass spectrometer. The analytical potential of the interface in terms of suitability, microsprayer performance, copper coat durability, ionization efficiency, spray stability, and sensitivity was tested first on a simple mixture of standard saccharides, which were separated, resolved, and detected with high separation efficiency. The approach was next assessed for the screening of a biological sample, a complex mixture of O-glycosylated sialylated amino acids from urine of a patient suffering from Schindler disease. Preliminary data allow this method to be considered as one of general applicability in structural glycobiology and glycomics and easy to be implemented for proteomic surveys as well.

RATIONALE The assignment of correct structures for isomers with similar mass spectra (e.g. polyhalogenated aromatic compounds) is not always successful when spectral libraries alone are employed or, even worse, when the compounds are not present in commercial spectral libraries. METHODS We present a computational method based on differential mass spectrometry (Diff‐MS) for the validation of formation enthalpy (ΔfH) series calculated using quantum chemistry for the fragments produced in electron ionization (EI)‐MS. The method simulates the chemical structure identification (CSI) of isomers with similar mass spectra using differential mass spectra and ΔfH series. The best ΔfH values were those from which the correct structures could be derived. RESULTS We have used six tetrachlorinated biphenyl isomers (TeCBs 44, 46, 52, 66, 74, 77). Their EI mass spectra were acquired at 70 eV and, for the principal ions, five series of ΔfH values were computed by the semi‐empirical methods, AM1, MINDO3, MNDO, PM3, and RM1. The generation of differential mass spectra and the correlation with the ΔfH series for the calculation of probabilities from the list of structural assignments were carried out with the ordering algorithm (ORD) of the CSI‐Diff‐MS Data Analysis 3.1.1 program. CONCLUSIONS Intelligent software, used for structural elucidation based on MS and QCC, was employed to select the best values of the formation enthalpies of TeCBs. The advantages and disadvantages of the semi‐empirical methods for the calculation of ΔfH values for different TeCB ions are critically presented. The best semi‐empirical methods were RM1, AM1 and MINDO3, which can be used to calculate the ΔfH database necessary to identify TeCB isomers. This approach allowed the correct assignment of structures for isomers with very similar mass spectra and demonstrated the reliability of the correlation between differential mass spectra and the formation enthalpies of the fragment ions. Copyright © 2012 John Wiley & Sons, Ltd.

A variety of carbohydrates, in particular polysaccharides can be subjected to chemical modification to obtain derivatives with amphiphilic properties, which enable biochemical or biological reactions at the polymer surface. In the present work, a polydisperse maltodextrin mixture of average molecular weight 3000 was coupled with 1,6-hexamethylenediamine (HMD) via reductive amination reaction. Resulting products were characterized by thermal analysis and positive nanoelectrospray quadrupole time-of-flight (Q-TOF) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Both thermal analysis and MS screening confirmed the formation of the HMD-polysaccharide coupling products. Moreover, HMD-linked polysaccharide chains containing 2 to 26 glucose building blocks were identified by nanoESI Q-TOF MS. MS/MS fragmentation using collision-induced dissociation (CID) at low ion acceleration energies provided strong evidence for HMD-maltodextrin linkage formation and the set of sequence ions diagnostic for the composition and structure of a HMD-linked chain containing 18 glucose residues.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.