Identifying Ca2+-binding sites in proteins by liquid chromatography-mass spectrometry using Ca2+-directed dissociations.

Here we describe a new method to identify calcium-binding sites in proteins using high-resolution liquid chromatography-mass spectrometry in concert with calcium-directed collision-induced dissociations. Our method does not require any modifications to the liquid chromatography-mass spectrometry apparatus, uses standard digestion protocols, and can be applied to existing high-resolution MS data files. In contrast to NMR, our method is applicable to very small amounts of complex protein mixtures (femtomole level).

Complexation of divalent metal ions with diols in the presence of anion auxiliary ligands: zinc-induced oxidation of ethylene glycol to glycolaldehyde by consecutive hydride ion and proton shifts.

Ternary complexes of the type AH•••M(2+)•••L(-) (AH = diol, including diethylene and triethylene glycol, M = Ca, Mn, Fe, Co, Ni, Cu and Zn and auxiliary anion ligand L(-)  = CH(3)COO(-), HCOO(-) and Cl(-)) have been generated in the gas phase by MALDI and ESI, and their dissociation characteristics have been obtained. Use of the auxiliary ligands enables the complexation of AH with the divalent metal ion without AH becoming deprotonated, although A(-)•••M(2+) is often also generated in the ion source or after MS/MS. For M = Ca, dissociation occurs to AH + M(2+)•••L(-) and/or to A(-)•••M(2+) + LH, the latter being produced from the H-shifted isomer A(-) •••M(2+)•••LH.

Structure and dissociation characteristics of metal chloride anion clusters containing redox-active metal ions studied by laser desorption and electrospray ionization mass spectrometry and ab initio calculations.

Copper chloride anion clusters with both copper oxidation states can be made by laser desorption of CuCl(2) crystals. We have used this method to study the dissociation characteristics of such cluster ions. The stability and the structure of the observed complexes were probed by ab initio calculations.

Metal ion attachment to the matrix meso-tetrakis(pentafluorophenyl)porphyrin, related matrices and analytes: an experimental and theoretical study.

In a previous study [van Kampen et al. Analytical Chemistry 2006; 78: 5403], we found that meso-tetrakis (pentafluorophenyl)porphyrin (F20TPP), in combination with lithium salts, provides an efficient matrix to cationize small molecules by Li+ attachment and that this combination can be successfully applied to the quantitative analysis of drugs, such as antiretroviral compounds using matrix-assisted laser desorption ionization in conjunction with a time-of-flight analyzer (MALDI-TOF). In the present study, we further explore the mechanism of metal ion attachment to F20TPP and analytes by MALDI-FTMS(/MS).