Model Sentetik Polimerlerin Ve Komplekslerinin Gaz Fazı Karakteristiklerinin İncelenmesi

Abstract

Mass spectrometry is the most convenient technique for obtaining useful information about the formation parameters of noncovalent complexes in both solution and gas phases with high accuracy and sensitivity. Ion mobility-mass spectrometry (IM-MS) additionally gives conformational data about the analyzed molecules. From the drift time data obtained from the IM-MS analyses, the collision cross sections (CCS) of ions can be determined, which is a size parameter related to the averaged momentum transfer impact area of the ions. At the beginning of the studies, poly-L-lysine (PLL) and polystyrene sulfonic acid (PSS) were analyzed using MALDI tandem time-of-flight (ToF/ToF) mass spectrometer. The end groups of their chains could be determined by evaluating data obtained from MALDI mass spectra. Mixtures of PLL and PSS were prepared in various molar ratios and the signals of their noncovalent complexes could be detected in the negative ion mode MALDI-MS analysis. The MALDI-MS/MS spectra confirmed the proposed stoichiometries of the observed noncovalent complexes of PLL and PSS. Noncovalent complexes of PLL and PSS could also be detected in both positive and negative ion mode using ESI-Q/ToF-MS with ion mobility capabilities. Complexes with various charge states and stoichiometries could be identified easily utilizing ion mobility separation. Most of the noncovalent complex ions obtained in positive and negative ion modes were fragmented upon collisionally activated dissociation in the transfer cell unit of the instrument. ESI-MS/MS spectra obtained for both positive and negative ion modes correlated well with the stoichiometry of the complexes. Another polyanion, polyacrylic acid (PAA) sample was analyzed by itself in detail and six different types of PAA series with various end groups were detected in the sample. It was determined that some of the series must have been present in the PAA sample solution while the other series were probably generated in gas phase during the MS experiment. CCS of PLL-PAA complex ions with different PAA series were derived separately for comparison of their compactness. The results prove that the sizes of end groups of each species affect the conformation of the noncovalent complex in the gas phase. When the poly-L-glutamic acid (PGA) was analyzed, it was determined that its sample contains linear and cyclic forms of PGA. A mixture of PLL and PGA was also analyzed in order to monitor the complexes formed between these polyelectrolytes. The CCS of polyelectrolyte ions were derived individually for comparing their compactness. It was obtained that the gas-phase conformations of the polyelectrolytes depend on the nature of functional groups located in their repeating unit. The CCS values of polyelectrolyte complex ions were also derived. Comparison of the CCS values of the complexes indicated that differences in complex ion formation may be caused by reducing repulsion forces between charged groups or forming more extended structures. Noncovalent complexes of lysozyme formed with PSS oligomers were also examined in the dissertation to determine how the CCS of protein changed with the stoichiometry of the PSS chains in the complex.