Electron photodetachment dissociation of DNA anions with covalently or noncovalently bound chromophores
Electron photodetachment dissociation of DNA anions with covalently or noncovalently bound chromophores
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DOI：
10.1016/j.jasms.2007.08.007
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发表时间：
2007-11-01
影响因子：
3.2
通讯作者：
Dugourd, Philippe
中科院分区：
文献类型：
--
作者：
Gabelica, Valerie;Rosu, Frederic;Dugourd, Philippe
将双链DNA多电荷阴离子偶联到发色团上，进行UV-Vis光活化。在四极离子陷阱质谱仪中。生色团包括非共价结合的小沟槽粘结剂(在近紫外光下激活)，非共价结合的插层剂(在可见光下激活)，以及共价连接的荧光团和猝灭剂(在其最大吸收波长激活)。我们发现，只有具有较长荧光寿命的发色团的激活确实会导致有效的电子从DNA复合体中分离出来。在500 nm激发的乙锭-dsDNA复合体中，光剥离是一个多光子过程。比较了波长为260 nm的光剥离(DNA激发)和波长为300 nm的光剥离(生色团激发)产生的自由基的MS3断裂。激进分子没有记住他们是如何产生的。一种弱结合的非共价配体(间苯丙氨酸)允许在实验上探测到电子内能的一部分被转化为振动内能。这个碎裂通道被用来证明猝灭剂DABSYL的激发导致了内部转换，不同于荧光团6-FAM。总之，DNA络合物在生色团激发下的光剥离可以用以下机制来解释：(1)具有足够长激发态寿命的配体通过共振双光子激发达到DNA激发态的水平，然后(2)激发态必须与DNA激发态耦合才能发生光剥离。我们的实验也为通过Forster共振能量转移(FRET)在气相中实现生物分子构象的光解离探针铺平了道路。
Double stranded DNA multiply charged anions coupled to chromophores were subjected to UV-Vis photoactivation. in a quadrupole ion trap mass spectrometer. The chromophores included noncovalently bound minor groove binders (activated in the near UV), noncovalently bound intercalators (activated with visible light), and covalently linked fluorophores and quenchers (activated at their maximum absorption wavelength). We found that the activation of only chromophores having long fluorescence lifetimes did result in efficient electron photodetachment from the DNA complexes. In the case of ethidium-dsDNA complex excited at 500 nm, photodetachment is a multiphoton process. The MS3 fragmentation of radicals produced by photodetachment at lambda = 260 nm (DNA excitation) and by photodetachment at lambda > 300 nm (chromophore excitation) were compared. The radicals keep no memory of the way they were produced. A weakly bound noncovalent ligand (m-amsacrine) allowed probing experimentally that a fraction of the electronic internal energy was converted into vibrational internal energy. This fragmentation channel was used to demonstrate that excitation of the quencher DABSYL resulted in internal conversion, unlike the fluorophore 6-FAM. Altogether, photodetachment of the DNA complexes upon chromophore excitation can be interpreted by the following mechanism: (1) ligands with sufficiently long excited-state lifetime undergo resonant two-photon excitation to reach the level of the DNA excited states, then (2) the excited-state must be coupled to the DNA excited states for photodetachment to occur. Our experiments also pave the way towards photodissociation probes of biomolecule conformation in the gas-phase by Forster resonance energy transfer (FRET).