烟草系统素多肽的质谱裂解规律研究

烟草系统素多肽是烟叶植物中系统性防御反应的信号分子，调控烟草的生长、发育和防御等整个生命周期活动。本工作采用液相色谱 线性离子阱质谱（LC-LTQ-MS）联用技术，研究3种烟草系统素多肽的质谱裂解规律。结果表明：烟草系统素多肽的准分子离子均带3~4个电荷；多肽准分子离子峰在18~25 V的碰撞电压下，主要产生b型和y型碎片离子；在离子化过程中，烟草系统素Ⅱ（TobSys Ⅱ）最强准分子离子［M+4H］⁴⁺的最优碰撞电压为20 V；烟草系统素Ⅰ（TobSys Ⅰ）和烟草系统素Ⅲ（TobSys Ⅲ）最强准分子离子峰［M+3H］³⁺的最优碰撞电压为22 V；在最优碰撞电压下，烟草系统素多肽的离子碎片信息丰富，特征离子碎片的峰强度最大，且主要在亮氨酸、羟脯氨酸和脯氨酸的氨基端进行断裂。该质谱裂解规律可为检测植物样品中的系统素提供科学依据。

Study on Mass Spectrometric Fragmentation Mechanism of Tobacco Systemin Polypeptides

Polypeptide hormones of tobacco systemin are systemic wound signal, which regulate tobacco growth, development, defense and other activities in the whole life cycle. Therefore it has been desired to develop a sensitive and accurate determination method to find and monitor trace systemins in plants for better understanding molecular mechanisms of polypeptide hormones. In this work, a method of liquid chromatography coupled to linear quadrupole ion trap orbitrap mass spectrometry equipped with an electrospray ionization source (LC-ESI-LTQ Orbitrap-MS) was developed to investigate the fragmentation mechanism of tobacco systemins. The results show that the three-to four-fold protonated systemin ions are observed, and b- and y-type fragment ions are generated at 18-25 V of collision voltages. The optimal collision voltage for ［M+4H］⁴⁺ is found to be 20 V for TobSys Ⅱ, and ［M+3H］³⁺ to be 22 V for TobSys Ⅰ and TobSys Ⅲ. Under the optimized collision voltage, tobacoo systemins have abundant fragment ions and the strongest intensity of the typical fragment ions are b5 (m/z 512.295 3) for TobSys Ⅰ, y12 （m/z 432.218 5） for TobSys Ⅱ, and y8 （m/z 443.712 3） for TobSys Ⅲ, respectively. In addition, the amide of tobacco polypeptide bond to leucine, hydroxyproline and proline are easily cleaved. The method is sensitive and accurate, which is suitable for fragmentation mechanism and qualitative analysis of tobacco polypeptide hormones in tobaccos.