Saleh Na'il, Suwaid Abdul Rahman Ba, Alhalabi Ahmad, Abuibaid Ahmed Z A, Maltsev Oleg V, Hintermann Lukas, Naumov Panče
Department of Chemistry, College of Science, United Arab Emirates University , P. O. Box 15551, Al Ain, United Arab Emirates.
Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85748 Garching bei München, Germany.
J Phys Chem B. 2016 Aug 11;120(31):7671-80. doi: 10.1021/acs.jpcb.6b06557. Epub 2016 Aug 2.
Fireflies generate flashes of visible light via luciferase-catalyzed chemiexcitation of the substrate (luciferin) to the first excited state of the emitter (oxyluciferin). Microenvironment effects are often invoked to explain the effects of the luciferase active pocket on the emission; however, the exceedingly complex spectrochemistry and synthetic burdens have precluded elucidation of the nature of these interactions. To decipher the effects of microenvironment on the light emission, here the hydrophobic interior of cucurbit[7]uril (CB7) is used to mimic the nonpolar active pocket of luciferase. The hydrophobic interior of CB7 induces shifts of the ground-state pKas by 1.9-2.5 units to higher values. Upon sequestration, the emission maxima of neutral firefly oxyluciferin and its conjugate monodeprotonated base are blue-shifted by 40 and 39 nm, respectively, resulting in visual color changes of the emitted light.
萤火虫通过荧光素酶催化底物（荧光素）化学激发至发射体（氧化荧光素）的第一激发态来产生可见光闪光。微环境效应常被用来解释荧光素酶活性口袋对发射的影响；然而，极其复杂的光谱化学和合成负担阻碍了对这些相互作用本质的阐明。为了解释微环境对发光的影响，本文使用葫芦[7]脲（CB7）的疏水内部来模拟荧光素酶的非极性活性口袋。CB7的疏水内部使基态pKa值向更高值移动1.9 - 2.5个单位。螯合后，中性萤火虫氧化荧光素及其共轭单去质子化碱的发射最大值分别蓝移40和39纳米，导致发射光的视觉颜色变化。
