生物分子加速器

Abstract

本研究旨在開發生物大分子加速器，並且推衍為廣用的質譜儀。第一章，將回顧加速器的發展沿革，以及質譜儀於量測大分子所遭遇之困頓；第二章，基於分段加速之概念，我們讓基質輔助雷射脫附游離產生的大分子離子，經由一連串同步調控的脈衝高電壓，使離子在前往偵測器的過程中，逐步累加能量轉而漸增速度，實驗結果顯示，加速效率接近預期，驗證了大分子可透過加速，俾使偵測效率提高；第三章，在加速器前端，整合了一個三維離子阱，作為不同質量離子的儲存與選擇，掃瞄頻率拋出至加速器，再針對不同質量各別加速，此裝置將質譜儀與加速器揉合，唯離子拋出時的廣泛時間分佈造成有效加速失利。故而，在第四章中，於三維離子阱之後，我們再增添一個二維線性離子阱，整個裝置成為二重離子阱質譜儀，將來自三維離子阱掃瞄拋出的離子，再次侷限於二維離子阱的交流電場中，俟離子儲存之後，再於端蓋電極施以平均約一千伏特之電壓推出離子，送至偵測器，此設計改善了離子分佈。不同質荷比之離子分次拋至線性離子阱而後量測，紀錄三維離子阱拋出頻率值與得到的離子訊號強度，將前者轉換為質量，便可展示出一張含有多重質量資訊的質譜圖。在末章中，做一簡短的結論，奠基於二重離子阱質譜儀與加速器的整合來提高偵測效率，我們克服了以往大分子於質譜儀上偵測效率低的瓶頸，並可應用於分析含複合物的樣品。此外，該儀器乃嶄新之大分子加速器，將加速器，由電子或原子領域跨入分子層級，無論是在物理學上的基礎研究，或是在生命科學上的應用，皆可望開拓新的科學領域。

This thesis is focused on the development of a novel instrument which produces biomolecular ions with high kinetic energy, and subsequently applied to mass spectrometry. We call this innovative device to generate high kinetic energy of biomolecular ions as “biomolecular ion accelerator (BIA).” This “accelerator” incorporates a soft ionization source, an acceleration region and a regular detection assembly. The attempt at developing BIA is to facilitate the detection efficiency in mass spectrometry or fragmentation efficiency in a collision process. The high energy molecular ion beam can possibly be used for biomolecular microscopy, disease diagnosis, disease treatment, detailed kinetic studies of biomolecular-ion collision process, etc. The thesis is divided into five parts. The first part introduces the brief history of accelerator development and its basic principle as well as the framework and basis of mass spectrometry. Furthermore, a soft ionization method, matrix-assisted laser desorption/ionization (MALDI), is also reviewed. In the second part, the effect of acceleration on ions with a high mass is discussed. Once the biomolecular ions are generated by MALDI, they are accelerated by a programmed series of pulsed electric fields on their way traveling toward the detector. As a result of an efficient gain of energy, ultra-heavy ions impinging upon the charge amplification detector can lead to the emission of more secondary electrons/ions than those without acceleration. Hence by monitoring the improvement of signal intensity, the effect of biomolecular ions carrying high energy can be confirmed. The third part describes the integration of an ion trap assembly with the acceleration device. Potential applications of this instrument are discussed. This is the first combination of ion trap and multi-stage ion accelerator assembly. The concept and results are examined in detail. In the fourth section, dual ion traps device are employed to serve as a new type of mass spectrometer. A linear ion trap (LIT) mounted next to the quadrupole ion trap (QIT) is used to capture ions ejected from QIT. With the use of frequency sweep or step scan, different types of ions can be stored inside of the QIT, ejected toward the LIT one by one and then captured inside of the LIT. Captured ions are then extracted, detected and produce a mass spectrum. Results show the capture efficiency reaches ~58 %. Furthermore, dual ion traps solve the problem of ejected ions from QIT with a wide time-spread while frequency sweep or step scan is adopted. In the last chapter, we describe the development of Biomolecular Ion Accelerator Mass Spectrometer (BIA-MS) in which dual-ion-traps is integrated with the accelerator to take advantages of both ion traps and accelerator. Ig G is first selected to demonstrate the application of dual traps-accelerator mass spectrometer. Results indicate the further application to other different biomolecules is also feasible. This home-built instrument serves as the first biomolecular-ion accelerator in the world with an appealing feature of a mass spectrometer for ultra-large biomolecules analysis.