Mass Measurement of Intact Bacterial and Viral Macroions
1Department of physics, National Dong Hwa University, Hualien, Taiwan
2Institute of Atomic and Molecular Sciences, Academia Sinica, Nankang, Taiwan
3Institute of Molecular Biology, Academia Sinica, Nankang, Taiwan
* presenting author:Shao-Yu Liang,
A novel and simple method was developed to measure the masses of intact single bacterial and viral macroions using a laser-induced RF plasma (LIRFP) coupled with a charge detection quadrupole ion trap mass spectrometer (CD QIT-MS). The LIRFP ion source was designed to enhance the charge number of bioparticles up to a few thousand with charge exchange reactions. This method allowed the mass and charge measurement of bioparticles with sizes from 300 nm to 3µm. The mass distributions of polystyrene particles with a diameter of 0.3, 0.4, 0.5, 0.75 and 2 μm measured (7.0±2.5)Χ10^9, (1.8±0.7)Χ10^10, (3.9±1.8)Χ10^10, (1.3±0.7)Χ10^11, and (2.1±0.9)Χ10^12, respectively, which were in good agreement with the calculated masses of (6.5±0.3)Χ10^9, (2.1±0.1)Χ10^10, (4.1±0.1)Χ10^11, (1.4±0.65)Χ10^11 and (2.1±0.2)Χ10^12 Da. The average charge of polystyrene particles of 0.3, 0.4, 0.5, 0.75 and 2 μm were 1437, 1631, 853, 675 and 571, respectively. The average charge of Escherichia coli EC11303, Escherichia coli strain W, Staphylococcus Aureus are measured 1343, 1463, 1304 with m/z range from 10^7 to 10^8 and the average masses are 6.1×10^10 Da, 8.8×10^10 Da, and 7.6×10^10 Da. The average mass and charge of vaccinia virus are ~8.4×10^9 Da and ~673 with an m/z of ~ 10^7. The measured masses of bacteria and virus were consistent with those measured by optical microscopy and cantilever resonators. The LIRFP ion source allowed soft ionization of bioparticles without fragmentation and the measuring speed of LIRFP CD QIT-MS was very fast with only few seconds to acquire one mass spectrum and 20 minutes to finish the measurement of one sample.

Keywords: Laser-induced RF plasma, charge exchange reaction, bacterial and viral particles, charge detection quadrupole ion trap, mass calibration