Multidimensional identification of disaccharide isomers based on non-covalent complexes and tandem mass spectrometry.

Glycans are the most abundant organic polymers in nature. They are essential to living organisms and regulate a wide range of biological functions. However, mass spectrometry-based identification of glycan isomers remains challenging due to the complexity of their structures including their complex compositions, linkages, and anomeric configurations. In this study, two novel complex ions, the mononuclear copper-bound dimeric ions [(Cu2+)(A)(L-His)-H]+ and the mononuclear copper-bound quaternary ions [(Cu2+)(A)(L-Ser)3-H]+ (where A denotes a disaccharide, and L-Ser/His denotes l-serine/histidine), were designed for the collision-induced dissociation-based identification and relative quantification of 14 disaccharide isomers. When the unique fragmentation patterns of the above two types of complex ions were mapped into a three-dimensional vector, all the isomers were completely distinguished. Of note, the established method is able to identify mixtures of linkage isomers only using tandem mass spectrometry based on linkage-specific fragment ions of histidine-based complex ions. Finally, the method was successfully applied to the identification and relative quantification of two disaccharide isomers (lactose and sucrose) in dairy beverages. In conclusion, the established method is sensitive to subtle structural differences in disaccharide isomers and has the potential to be used for the differentiation of various glycans.

On the Rate of Interaction of Sodium Borohydride with Platinum (IV) Chloride Complexes in Alkaline Media.

In this work, sodium borohydride was used as a strong reductant of traces of platinum complex ions. The investigations of the kinetics of redox reaction between platinum(IV) chloride complex ions and sodium borohydride were carried out. For the first time, the kinetic experiments were carried out in a basic medium (pH~13), which prevents NaBH4 from decomposition and suppresses the release of hydrogen to the environment. The rate constants of Pt(IV) reduction to Pt(II) ions under different temperatures and concentrations of chloride ions conditions were determined. In alkaline solution (pH~13), the values of enthalpy and entropy of activation are 29.6 kJ/mol and -131 J/mol K. It was also found that oxygen dissolved in the solution strongly affects kinetics of the reduction process. Using collected results, the reduction mechanism was suggested. For the first time, the appearance of diborane as an intermediate product during Pt(IV) ions reduction was suggested. Moreover, the influence of oxygen present in the reacting solution on the rate of reduction reaction was also shown.

Synthesis, characterization, and stability of iron (III) complex ions possessing phenanthroline-based ligands.

It has previously been demonstrated that phenanthroline-based ligands used to make gold metallotherapuetics have the ability to exhibit cytotoxicity when not coordinated to the metal center. In an effort to help assess the mechanism by which these ligands may cause tumor cell death, iron binding and removal experiments have been considered. The close linkage between cell proliferation and intracellular iron concentrations suggest that iron deprivation strategies may be a mechanism involved in inhibiting tumor cell growth. With the creation of iron (III) phen complexes, the iron binding abilities of three polypyridal ligands [1,10-phenanthroline (phen), 2,9-dimethyl-1, 10-phenanthroline (methylphen), and 2,9-di-sec-butyl-1, 10-phenanthroline ( sec-butylphen)] can be tested via a competition reaction with a known iron chelator. Therefore, iron (III) complexes possessing all three ligands were synthesized. Initial mass spectrometric and infrared absorption data indicate that iron (III) tetrachloride complex ions with protonated phen ligands (RphenH+) were formed: [phenH][FeCl4], [methylphenH][FeCl4], [ sec-butylphenH][FeCl4]. UV-Vis spectroscopy was used to monitor the stability of the complex ions, and it was found that the sec-butylpheniron complex was more stable than the phen and methylphen analogues. This was based on the observation that free ligand was observed immediately upon the addition of EDTA to the [phenH][FeCl4] and [methylphenH] [FeCl4] complex ions.