Fragmentation behavior of multiple-metal-coordinated acidic oligosaccharides studied by matrix-assisted laser desorption ionization Fourier transform mass spectrometry

Using matrix-assisted laser desorption ionization we have been able to form gas-phase mixed metal complexes by doping acidic oligosaccharides simultaneously with two different alkali metals. Multiple metal coordination brings up several interesting points such as whether the alkali metals act like point charges by repelling one another, and whether the alkali metals bind to specific sites within the saccharide In this work we carried out collision induced dissociation (CID) on multiply coordinated oligosaccharides to gain insight into these questions. By using CID of the mixed metal complexes we find that different alkali metals show differing specificity for whether they bind to the sialic acid containing fragment, or the remaining oligosaccharide fragment. We also find that the sialic acid is not capable of solvating two small alkali metals simultaneously, but for larger alkali metals such as cesium this is not the case. Molecular modeling of acidic sugars show that there is not a defined binding site to which the different alkali metals bind, but many local minima exist. (C) 2000 Elsevier Science B.V.