Wilson Jeffrey J, Brodbelt Jennifer S
Department of Chemistry and Biochemistry, 1 University Station A5300, University of Texas at Austin, Austin, Texas 78712, USA.
Anal Chem. 2007 Mar 1;79(5):2067-77. doi: 10.1021/ac061946f. Epub 2007 Jan 24.
Noncovalent duplex DNA/drug complexes formed between one of three 14-base pair non-self-complementary duplexes with variable GC content and one of eight different DNA-interactive drugs are characterized by infrared multiphoton dissociation (IRMPD), and the resulting spectra are compared to conventional collisionally activated dissociation (CAD) mass spectra in a quadrupole ion trap mass spectrometer. IRMPD yielded comparable information to previously reported CAD results in which strand separation pathways dominate for complexes containing the more AT-rich sequences and/or minor groove binding drugs, whereas drug ejection pathways are prominent for complexes containing intercalating drugs and/or duplexes with higher GC base content. The large photoabsorptive cross section of the phosphate backbone at 10.6 mum promotes highly efficient dissociation within short irradiation times (<2 ms at 50 W) or using lower laser powers and longer irradiation times (<15 W at 15 ms), activation times on par with or shorter than standard CAD experiments. This large photoabsorptivity leads to a controllable ion activation method which can be used to produce qualitatively similar spectra to CAD while minimizing uninformative base loss dissociation pathways or instead be tuned to yield a high degree of secondary fragmentation. Additionally, the low-mass cutoff associated with conventional CAD plays no role in IRMPD, resulting in richer MS/MS information in the low m/z region. IRMPD is also used for multiadduct dissociation in order to increase MS/MS sensitivity, and a two-stage IRMPD/IRMPD method is demonstrated as a means to give specific DNA sequence information that would be useful when screening drug binding by mixtures of duplexes.
由三种具有不同GC含量的14碱基对非自互补双链体之一与八种不同的DNA相互作用药物之一形成的非共价双链DNA/药物复合物，通过红外多光子解离（IRMPD）进行表征，并将所得光谱与四极杆离子阱质谱仪中的传统碰撞激活解离（CAD）质谱进行比较。IRMPD产生的信息与先前报道的CAD结果相当，在先前的结果中，对于含有较多富含AT序列和/或小沟结合药物的复合物，链分离途径占主导，而对于含有嵌入药物和/或具有较高GC碱基含量的双链体的复合物，药物喷射途径则很突出。磷酸主链在10.6μm处的大光吸收截面促进了在短照射时间内（50W时<2ms）或使用较低激光功率和较长照射时间（15ms时<15W）的高效解离，激活时间与标准CAD实验相当或更短。这种大的光吸收性导致了一种可控的离子激活方法，该方法可用于产生与CAD定性相似的光谱，同时最小化无信息的碱基损失解离途径，或者调整以产生高度的二级碎片化。此外，与传统CAD相关的低质量截止在IRMPD中不起作用，从而在低m/z区域产生更丰富的MS/MS信息。IRMPD还用于多加合物解离以提高MS/MS灵敏度，并且展示了一种两级IRMPD/IRMPD方法，作为给出特定DNA序列信息的手段，这在筛选双链体混合物的药物结合时将是有用的。
