Matrix-assisted laser desorption/ionization (MALDI) mechanism revisited.
Although matrix-assisted laser desorption/ionization (MALDI) was developed more than a decade ago and broad applications have been successfully demonstrated, detailed mechanism of MALDI is still not well understood. Two major models; namely photochemical ionization (PI) and cluster ionization (CI) mechanisms have been proposed to explain many of experimental results. With the photochemical ionization model, analyte ions are considered to be produced from a protonation or deprotonation process involving an analyte molecule colliding with a matrix ion in the gas phase. With the cluster ionization model, charged particles are desorbed with a strong photoabsorption by matrix molecules. Analyte ions are subsequently produced by desolvation of matrix from cluster ions. Nevertheless, many observations still cannot be explained by these two models. In this work, we consider a pseudo proton transfer process during crystallization as a primary mechanism for producing analyte ions in MALDI. We propose an energy transfer induced disproportionation (ETID) model to explain the observation of an equal amount of positive and negative ions produced in MALDI for large biomolecules. Some experimental results are used for comparisons of various models.
Chang
Wei Chao
WC
Genomics Research Center, Academia Sinica, Taipei, Taiwan.
Huang
Ling Chu Lora
LC
Wang
Yi-Sheng
YS
Peng
Wen-Ping
WP
Chang
Huan Cheng
HC
Hsu
Nien Yeen
NY
Yang
Wen Bin
WB
Chen
Chung Hsuan
CH
D001483:Base Sequence; D001704:Biopolymers; D002412:Cations; D003460:Crystallization; D017931:DNA Primers; D010455:Peptides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D001704:Biopolymers; D002412:Cations; D017931:DNA Primers; D010455:Peptides; D011506:Proteins