光探測法之單粒子質譜學

Abstract

生物大分子，如細菌或病毒，其尺度分別界於0.1微米∼5微米和0.02微米∼0.3微米之間，對於質譜學的探測而言，是一個很大的挑戰。在首章中，我們對傳統的游離型探測器、電荷感應型偵測器、熱感應型偵測器給一回顧性的介紹，說明其在探測生物大分子時所遭遇到的困難。本論文

Detection of macroions represents a challenge in the field of mass spectrometry. The biological macroions discussed in this thesis, say bacterial or viral particles, having sizes ranging from 0.1 um to 5 um and 0.02 um to 0.3 um respectively are very difficult to detect by conventional mass spectrometry detection methods. In chapter I, we give an overview why the conventional detection methods including ionization-based detectors, charge-sensitive detectors, energy-sensitive detectors failed to detect such large particles in general. In this thesis, we propose using photon-sensitive detectors to detect macroions, by either elastic light scattering (ELS) or laser-induced fluorescence (LIF). In chapter II, we start to detect single particle in a three dimensional quadrupole ion trap by ELS method and precisely measure its mass based on the single particle’s motion. This method opens up new opportunities for high-precision mass measurement of single microbial particles and constitutes a top-down approach for rapid identification of microorganisms. In chapter III, we scan along the stability diagram and detect microparticles outside the trap with ELS method. The single particle mass spectra reveal its capability to detect particles with size greater than 100 nm. When the particle size is smaller than 100 nm, according to Rayleigh-Debye theory, it is very difficult to be detected by ELS. The advances has been made in the detection of single fluorescent molecules in condense phase. This enables us to detect dye labeled particles with ion trap mass spectrometry. As we have demonstrated in this thesis, by coupling a new ion trap to the first ion trap mass spectrometer, the second trap can play a role to confine the ejected particles from the first ion trap, and thereby the detection of the LIF signal is made possible. In chapter IV, we show the mass spectra of 27 nm and 110 nm polystyrene nanoparticles. Finally, in chapter V, we discuss the possibility to obtain the mass spectra of viral particles. According to the observation from TEM study of HSV1 and Swinepox viruses, we have found their size distribution to be very narrow as compared to the bacterial samples. We propose to make a transparent ion trap to increase the optical collection efficiency. This transparent ion trap is a kind of an objective lens. Therefore, the conventional confocal optical path design and single molecule detection techniques can thus be applied to this new setup. With the aid of labeling fluorescent dye molecules or quantum dots (QDs), the single viral particle mass spectrometry with LIF detection may become a reality.