Laboratoire Modélisation et Simulation Multi Échelle, Université Paris-Est, MSME UMR 8208 CNRS, UPEM, 5 bd Descartes, 77454 Marne-la-Vallée, France.
Molecules. 2019 Apr 20;24(8):1565. doi: 10.3390/molecules24081565.
The emitted color in fireflies' bioluminescent systems depends on the beetle species the system is extracted from and on different external factors (pH, temperature…) among others. Controlling the energy of the emitted light (i.e., color) is of crucial interest for the use of such bioluminescent systems. For instance, in the biomedical field, red emitted light is desirable because of its larger tissue penetration and lower energies. In order to investigate the influence of the protein environment and the AMP protonation state on the emitted color, the emission spectra of the phenolate-keto and phenolate-enol oxyluciferin forms have been simulated by means of MD simulations and QM/MM calculations, considering: two different protein conformations (with an open or closed C-terminal domain with respect to the N-terminal) and two protonation states of AMP. The results show that the emission spectra when considering the protein characterized by a closed conformation are blue-shifted compared to the open conformation. Moreover, the complete deprotonation of AMP phosphate group (AMP) can also lead to a blue-shift of the emission spectra but only when considering the closed protein conformation (open form is not sensitive to changes of AMP protonation state). These findings can be reasoned by the different interactions (hydrogen-bonds) found between oxyluciferin and the surrounding (protein, AMP and water molecules). This study gets partial insight into the possible origin of the emitted color modulation by changes of the pH or luciferase conformations.
萤火虫生物发光系统的发射颜色取决于该系统提取的甲虫种类以及其他外部因素（pH 值、温度等）。控制发射光的能量（即颜色）对于此类生物发光系统的应用至关重要。例如，在生物医学领域，由于红色发射光具有更大的组织穿透性和更低的能量，因此是理想的选择。为了研究蛋白质环境和 AMP 质子化状态对发射颜色的影响，通过 MD 模拟和 QM/MM 计算模拟了酚酮-酮和酚醇氧黄素形式的发射光谱，考虑了两种不同的蛋白质构象（相对于 N 端具有开放或关闭的 C 端结构域）和 AMP 的两种质子化状态。结果表明，考虑到具有封闭构象的蛋白质，发射光谱发生蓝移。此外，AMP 磷酸盐基团（AMP）的完全去质子化也会导致发射光谱蓝移，但仅当考虑封闭的蛋白质构象时（开放形式对 AMP 质子化状态的变化不敏感）。这些发现可以通过氧黄素与周围（蛋白质、AMP 和水分子）之间的不同相互作用（氢键）来解释。这项研究初步了解了 pH 值或荧光素酶构象变化引起的发射颜色调制的可能原因。
