Abstract
Matrix-assisted laser desorption/ionization (MALDI) with time-of-flight (TOF) mass spectrometry is a very powerful technique for the analysis of peptides and proteins. Fragmentation reactions of the protonated analyte molecule, [M+H]+ ions, that occur in the field-free region of the spectrometer, can be detected with the reflectron by using post-source focusing technique. This work presented here focuses on the fragmentation reactions of the hormone bradykinin and analogues, [D-Phe7]-bradykinin and hyp3-bradykinin (hyp stands for 4-hydroxyproline), using MALDI-TOF mass spectrometry. We observe that replacement of prolines at positions 3 and 7 of bradykinin affects the abundance of y-type cleavage significantly but have little influence on the b-type ion formation. The abundance of internal fragment ions in the PSD spectrum of [D-Phe7]-bradykinin is significantly less than that of bradykinin. A similar effect is observed in the fragmentation of hyp3 bradykinin. The primary study of solvent effect of methanol/water, methanol/acetonitrile and methanol/butanol systems on the bradykinin fragmentation is also shown here. It appears that addition of water to methanol increases the abundance of PSD fragment ions and the use of trifluoroacetic acid (TFA) in the sample preparation also increases fragment ion abundance. The total b-type and y-type fragment ions decreases for sample preparation using acetonitrile relative to that in methanol/water system. The fragment ion abundance of methanol/butanol is between that of methanol/water and methanol/acetonitrile. Butanol has a greater influence on the fragment ion abundances of bradykinin when TFA is absent than when 1% TFA is present.
Wei, Xiaona (1996). A postsource decay study of bradykinin by Matrix-assisted laser desorption ionization mass spectrometry. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -W453.