We have studied the collision induced dissociation reactions of proton-bound diastereomeric adducts of S-1-phenylethanol and enantiomers of three different amino acids (tryptophan, phenylalanine, methionine). In all cases, the loss of S-1-phenylethanol from the adduct ion is the only observed process, and the relative abundance is found to be independent of the chirality of the amino acid. This is in contrast to earlier experiments on the dissociation of protonated tryptophan-2-butanol adducts, where chirality affected the results. Results obtained from quantum chemical computations support and provide a rationale for the experimental observations and highlight temperature as a possible factor of importance for the chiral effect in these types of systems. [GRAPHICS] .

This thesis comprises the research related to interactions of enantiopure amino acids with chiral and achiral molecules in gas phase. The investigation of the mechanism responsible for chiral discrimination is of the special interest in this work. An electrospray ion source platform (Stockholm University), quadrupole time-of-flight mass spectrometer (University of Oslo) and Fourier-transform ion cyclotron resonance mass spectrometer in combination with OPO laser (Centre Laser Infrarouge d'Orsay (CLIO), France)  have been used in our studies. Results of experiments on collisions of enantiopure amino acids, namely phenylalanine (Phe), tryptophan (Trp), and methionine (Met) with chiral and achiral targets in high and low energy regimes are presented. The fragmentation process is discussed in detail and compared with generally accepted models of amino acid fragmentation. Formation of proton bound diastereomeric adducts of amino acid and chiral alcohols (2-butanol and 1-phenylethanol) in single collisions is reported. The emphasis was given to reveal stereochemical effects in above mentioned reactions. The structure and vibrational properties of diastereomeric dimers of tryptophan studied using infrared multiphoton dissociation (IRMPD) spectrometry are presented. Structures and energies of most stable conformers obtained with quantum chemical calculations are described and compared to the experimental data. The stereo-dependent features are underlined and the chiral discrimination using IRMPD is addressed.

In this work we report the stereo-dependent collision-induced dissociation (CID) of proton-bound complexes of tryptophan and 2-butanol. The dissociation efficiency was measured as a function of collision energy in single collision mode. The homochiral complex was found to be less stable against CID than a heterochiral one. Additional gas dependence measurements were performed with diastereomeric complexes that confirm the findings.

Here we report on the gas-phase interactions between protonated enantiopure amino acids (l- and d-enantiomers of Met, Phe, and Trp) and chiral target gases [(R)- and (S)-2-butanol, and (S)-1-phenylethanol] in 0.1-10.0 eV low-energy collisions. Two major processes are seen to occur over this collision energy regime, collision-induced dissociation and ion-molecule complex formation. Both processes were found to be independent of the stereo-chemical composition of the interacting ions and targets. These data shed light on the currently debated mechanisms of gas-phase chiral selectivity by demonstrating the inapplicability of the three-point model to these interactions, at least under single collision conditions.

This thesis is based on experimental studies of chiral ions in gas-phase. Electrospray ion source platform (Stockholm University) and commercially available Quadrupole Time-of-Flight mass spectrometer have been used in our studies.

Using the advantages of tandem mass spectrometry, we have investigated interactions between protonated amino acids, namely phenylalanine (Phe), tryptophan (Trp), and methionine (Met) and Trp containing diastereomeric complexes with chiral 2-butanol, and achiral (argon) targets. In high energy collisions of 1 keV in the center-of-mass (c.o.m.) frame, collision induced dissociation (CID) via multiple channels independent on the chirality of either projectile or target was observed. The fragmentation via loss of H₂O + CO and NH₃ were found to be the main reaction channels for all studied amino acids. The energy gained in collisions was found to be sufficient to initiate fragmentation via various competitive reaction pathways.

Chiral recognition in CID of the diastereomeric proton-bound complexes of tryptophan and 2-butanol as a function of collision energy was studied. Stereo dependent dissociation of complexes was observed, and for the first time an energy dependence has been measured for such a complex. Where possible, the comparison with previously reported results have been performed.

We have studied the fragmentation of the singly protonated L- and D-forms of enantiomerically pure phenylalanine (Phe), tryptophan (Trp), and methionine (Met) in high-energy collisions with chiral and achiral gas targets. (S)-(+)-2-butanol, racemic (+/-)-2-butanol, and argon were used as target gases. At center-of-mass frame collision energy of I key, it was found that all of the ions exhibit common fragmentation pathways which are independent of target chirality. For all projectile ions, the elimination of NH3 and H2O + CO were found to be the main reaction channels. The observed fragmentation patterns were dominated by statistically driven processes. The energy deposited into the ions was found to be sufficient to yield multiple fragment ions, which arise from decomposition via various competitive reaction pathways.

We have studied the collision induced dissociation reactions of proton-bound diastereomeric adducts of S-(-)-1-phenylethanol and enantiomers of three different amino acids (tryptophan, phenylalanine, methionine) with argon at a collision energy of 0.5 eV in the center-of-mass frame. At this energy, fragmentation into the alcohol and the protonated amino acid was the only observed product channel. Contrary to anticipation, the fragmentation was found to be insensitive to the chirality of the constituents. The results obtained from quantum chemical calculations show that the hetero-chiral adducts are more stable than the homo-chiral forms. However, given the experimental conditions in the ion source, it is likely that multiple conformers which lie close in energy to the ground-state configuration are populated, limiting the experimental sensitivity to observe the predicted differences.