Ion intensity and thermal proton transfer in ultraviolet matrix-assisted laser desorption/ionization.
The ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) was investigated by measuring the total cation intensity (not including sodiated and potasiated ions) as a function of analyte concentration (arginine, histidine, and glycine) in a matrix of 2,4,6-trihydroxyacetophenone (THAP). The total ion intensity increased up to 55 times near the laser fluence threshold as the arginine concentration increased from 0% to 1%. The increases were small for histidine, and a minimal increase occurred for glycine. Time-resolved fluorescence intensity was employed to investigate how analytes affected the energy pooling of the matrix. No detectable energy pooling was observed for pure THAP and THAP/analyte mixtures. The results can be described by using a thermal proton transfer model, which suggested that thermally induced proton transfer is crucial in the primary ion generation in UV-MALDI.
Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei 10617, Taiwan.
I-Chung
IC
Lu
Chuping
C
Lee
Hui-Yuan
HY
Chen
Hou-Yu
HY
Lin
Sheng-Wei
SW
Hung
Yuri A
YA
Dyakov
Kuo-Tung
KT
Hsu
Chih-Yu
CY
Liao
Yin-Yu
YY
Lee
Chien-Ming
CM
Tseng
Yuan-Tseh
YT
Lee
Chi-Kung
CK
Ni
D000098:Acetophenones / Q000737:chemistry*; D001120:Arginine / Q000032:analysis*; D005453:Fluorescence; D005998:Glycine / Q000032:analysis*; D006639:Histidine / Q000032:analysis*; D007477:Ions / Q000737:chemistry; D011522:Protons; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature
D000098:Acetophenones; D007477:Ions; D011522:Protons; D006639:Histidine; C107067:2,4,6-trihydroxyacetophenone; D001120:Arginine; D005998:Glycine