RESUMO
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an important analytical technique for biological macromolecules,such as proteins,peptides and nucleic acid, especially in the field of microbial identification. Based on previous study,a linear MALDI-TOF MS has been designed and assembled for biological applications. The instrument comprises a vacuum system,a vacuum fast sample introduction system, an optical system, a time-of-flight mass analyzer, an ion source, a data acquisition system and an electric control system. The ion source adopts two-stage source acceleration,delayed extraction and dynamic pulse focusing technology. The time-of-flight distance of field-free drift region is about 1 meter. The optical system adopts a solid laser with adjustable frequency of 1-2000 Hz and spots of 20-100 μm. The angle of incidence laser is controlled at 5 degrees. A series of experiments are carried out to further evaluate the instrument performances. It can not only analyze the samples more than 199 kDa, but also achieve isotope resolution at 1000-3000 Da and up to 900(FWHM) at 5000-17000 Da. The minimum detectable concentration of gramicidin is 10 amol/μL, absolute sensitivity can reach up to 2. 56 amol. Independent detection of saliva samples from different targets shows that the instrument has high reproducibility. We identified Escherichia Coli and Shigella spp,which are two common bacteria but difficult to be differentiated by mass spectrometry,showing its potential identification for clinical microorganism. In a summary,this instrument can play a role on clinical examination in the near future.