Saikusa Kazumi, Asakawa Daiki, Fuchigami Sotaro, Akashi Satoko
Research Institute for Material and Chemical Measurement, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan.
Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
Mass Spectrom (Tokyo). 2023;12(1):A0131. doi: 10.5702/massspectrometry.A0131. Epub 2023 Oct 17.
Ion mobility spectrometry-mass spectrometry (IMS-MS) provides values and collision cross sections (CCSs) of gas-phase ions. In our previous study, an intrinsically disordered protein, the H2A-H2B dimer, was analyzed using IMS-MS, resulting in two conformational populations of CCS. Based on experimental and theoretical approaches, this resulted from a structural diversity of intrinsically disordered regions. We predicted that this phenomenon is related to ion heating in the IMS-MS instrument. In this study, to reveal the effect of ion heating from parameters in the IMS-MS instrument on the conformational population of the H2A-H2B dimer, we investigated the arrival time distributions of the H2A-H2B dimer by changing values of three instrumental parameters, namely, cone voltage located in the first vacuum chamber, trap collision energy (trap CE) for tandem mass spectrometry, and trap bias voltage for the entrance of IMS. These results revealed that the two populations observed for the H2A-H2B dimer were due to the trap bias voltage. Furthermore, to evaluate the internal energies of the analyte ions with respect to each parameter, benzylpyridinium derivatives were used as temperature-sensitive probes. The results showed that the trap CE voltage imparts greater internal energy to the ions than the trap bias voltage. In addition, this slight change in the internal energy caused by the trap bias voltage resulted in the structural diversity of the H2A-H2B dimer. Therefore, the trap bias voltage should be set with attention to the properties of the analytes, even if the effect of the trap bias voltage on the internal energy is negligible.
离子淌度质谱联用技术（IMS-MS）可提供气相离子的相关数值和碰撞截面积（CCS）。在我们之前的研究中，使用IMS-MS分析了一种内在无序蛋白——H2A-H2B二聚体，结果得到了两种CCS构象群体。基于实验和理论方法，这是由内在无序区域的结构多样性导致的。我们预测这种现象与IMS-MS仪器中的离子加热有关。在本研究中，为了揭示IMS-MS仪器中的参数所导致的离子加热对H2A-H2B二聚体构象群体的影响，我们通过改变三个仪器参数的值来研究H2A-H2B二聚体的到达时间分布，这三个参数分别是位于第一真空室的锥孔电压、串联质谱的阱碰撞能量（阱CE）以及IMS入口的阱偏置电压。这些结果表明，H2A-H2B二聚体观察到的两种群体是由阱偏置电压引起的。此外，为了评估分析物离子相对于每个参数的内能，使用苄基吡啶鎓衍生物作为温度敏感探针。结果表明，阱CE电压比阱偏置电压赋予离子更大的内能。此外，阱偏置电压引起的这种内能的轻微变化导致了H2A-H2B二聚体的结构多样性。因此，即使阱偏置电压对内能的影响可以忽略不计，也应根据分析物的性质谨慎设置阱偏置电压。
