- 學位論文
氣態蛋白質構形和蛋白質與輔基間的鍵能探討
A Combined Study with FTICR Mass Spectrometry and IR Laser Spectroscopy: Dissociation of Heme from Gaseous Myoglobin Ions
並列摘要
Detachment of heme prosthetic groups from gaseous myoglobin and hemoglobin ions by Collision-Induced Dissociation (CID) and InfraRed MultiPhoton Dissociation (IRMPD) has been investigated by Fourier-Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry. Multiply charged holomyoglobin (hMb) or holohemoglobin (hHb) ions were generated by electrospray ionization and transferred into the ICR cell, where the ions of interest (hMb10+, for example) were isolated, excited translationally and collided with pulsed Ar gas or heated with IR laser, producing apomyoglobin (aMb) or apohemoglobin (aHb) ions. Dissociation energies of ~0.9 eV and ~0.7 eV were determined for myogloin and hemoglobin. Multiply charged hemoglobins were applied to IRMPD, such that the OPO laser was fired into the ICR cell and heated up the myoglobin to the point of dissociation. The dissociation energy of myoglobin from IRMPD is thus measured. Two techniques, IRMPD and CID, which have a similar nature of ion activation, are applied on hemoproteins and compared on a collateral level. The measured results concur with the previous Blackbody Infrared Radiative Dissociation method. Tunable OPO laser is directed on the myoglobin ions in the ICR cell and generates the first myoglobin spectroscopy in the gas phase. From the spectroscopy, the charge dependant hemoprotein unfolding process was suggested, displaying the C-H and free N-H bonds. The infrared spectroscopic evidence of gaseous myoglobin is thus presented for the first time.