Substituent Effects on the Sensitivity of a Quinoline Photoremovable Protecting Group to One- and Two-Photon Excitation
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- 作者：M. Jarrett Davis ; Christopher H. Kragor ; Khalilah G. Reddie ; Hunter C. Wilson ; Yue Zhu ; Timothy M. Dore*
- 刊名：Journal of Organic Chemistry
- 出版年：2009
- 出版时间：February 20, 2009
- 年：2009
- 卷：74
- 期：4
- 页码：1721-1729
- 全文大小：382K
- 年卷期：v.74,no.4(February 20, 2009)
- ISSN：1520-6904
文摘
Photoremovable protecting groups that can reveal biologically important functional groups through one- and two-photon excitation (1PE and 2PE, respectively) have promise in regulating physiological function in a temporally and spatially restricted manner. Only a few chromophores have sufficient sensitivity to 2PE suitable for use as “caging groups” in physiology experiments. It would be useful to develop structure−property relationships of chromophores, so that chromophores with high two-photon uncaging action cross-sections (δu) can be designed. The 8-bromo-7-hydroxyquinolinyl chromophore (BHQ) releases a variety of functional groups through 1PE and 2PE. Swapping the bromine substituent for a nitro (NHQ), cyano (CyHQ), or chloro (CHQ) or exchanging the hydroxy for dimethylamino (DMAQ and DMAQ-Cl) or sulfhydryl (TQ) significantly alters the photochemical and photophysical properties of the quinoline chromophore. CyHQ-OAc demonstrated a 3-fold increase in sensitivity for acetate release, whereas NHQ-OAc was photochemically insensitive. The quantum efficiencies (Qu) of the amino and sulfhydryl derivatives were about an order of magnitude lower than that of BHQ-OAc. All of the chromophores showed diminished sensitivity to 2PE compared to BHQ-OAc, but the CyHQ, DMAQ, and DMAQ-Cl chromophores are sufficiently sensitive for physiological use. The high sensitivity of CyHQ to 1PE will be useful in biological applications requiring short exposure with low light intensity.