Vacuum ultraviolet postionization of aromatic groups covalently bound to peptides
Vacuum ultraviolet postionization of aromatic groups covalently bound to peptides
复制标题
DOI：
10.1021/ac0605997
复制
发表时间：
2006-08-15
影响因子：
7.4
通讯作者：
Hanley, Luke
中科院分区：
文献类型：
--
作者：
Edirisinghe, Praneeth D.;Moore, Jerry F.;Hanley, Luke
实验证明，在几个芳香族标记物中的一个作为生色团的化学衍生化之后，电离势大于7.87 eV的多肽可以在气相中用分子氟激光进行单光子电离。4-(二甲氨基)苯甲酸、1-萘乙酸和9-蒽甲酸(分别记为Benz、Naph和Anth)作为生色团，通过降低标记肽的IP来实现真空紫外光(VUV)激光的单光子电离。从底物上激光解吸并随后正位化的Anth标记的多肽产生以完整的自由基阳离子为主的质谱图，尽管也观察到质子化离子和碎裂物种。对Anth标记多肽的电子结构计算表明，除了降低电离势外，芳香族标记的存在还增加了环结构上的电荷局域化和离域，这可能稳定了自由基阳离子。对几个标记多肽的测量证实了这一计算，并表明标记的稳定作用按Benz<；naph<；Anth的顺序随着共轭体系的大小而增加。标记的六肽Anth-GAPKSC显示亲本离子，而Benz和Naph标记的多肽不显示亲本离子。这些结果得到了Anth标记的色氨酸和未标记的色氨酸的实验比较，进一步表明标记的高IP物种的VUV定位是扩展分子物种的质谱分析能力的一种有前途的方法。
Experiments demonstrate that peptides with ionization potentials (IPs) above 7.87 eV can be single-photon-ionized in the gas phase with a molecular fluorine laser following prior chemical derivatization with one of several aromatic tags acting as chromophores. 4-(Dimethylamino) benzoic acid, 1-naphthylacetic acid, and 9-anthracenecarboxylic acid (denoted Benz, Naph and Anth, respectively) behave as chromophores, allowing single-photon ionization for vacuum ultraviolet (VUV) laser light by lowering the IP of the tagged peptide. Anth-tagged peptides that are laser-desorbed from a substrate and subsequently postionized produce mass spectra dominated by the intact radical cation, although protonated ions and fragmented species are also observed. Electronic structure calculations on Anth-tagged peptides indicate that in addition to lowering the ionization potential, the presence of the aromatic tag increases charge localization on and delocalization across the ring structure, which presumably stabilizes the radical cation. Measurements on several tagged peptides confirm this calculation and show that the stabilizing effect of the tag increases with the size of the conjugated system in the order Benz < Naph < Anth. The tagged hexapeptide Anth-GAPKSC exhibits the parent ion, whereas the Benz- and Naph-tagged peptides do not. These results are supported by the experimental comparison of Anth-tagged vs untagged tryptophan, further suggesting that VUV postionization of tagged high-IP species is a promising method for expanding the capabilities of mass spectrometric analyses of molecular species.