Dehydroergosterol (DHE, Δ^5,7,9(11),22-ergostatetraen-3β-ol) is a naturally occurring fluorescent analog of cholesterol found in yeast. Since DHE has been shown to faithfully mimic cholesterol in a large number of biophysical, biochemical, and cell biological studies, it is widely used to explore cholesterol organization, dynamics and trafficking in model and biological membranes. In this work, we show that DHE, in spite of its localization at the membrane interface, does not exhibit red edge excitation shift (REES) in model membranes, irrespective of the membrane phase. These results are reinforced by semi-empirical quantum chemical calculations of dipole moment changes of DHE in ground and excited states, which show a very small change in the dipole moment of DHE upon excitation. We conclude that DHE fluorescence exhibits lack of environmental sensitivity, despite its usefulness in monitoring cholesterol organization, dynamics and traffic in model and biological membranes.

脱氢麦角甾醇 (DHE, Δ ^5,7,9(11),22 -ergostatetraen-3 β -ol) 是酵母中发现的天然存在的胆固醇荧光类似物。由于 DHE 在大量生物物理、生物化学和细胞生物学研究中已被证明能够忠实地模拟胆固醇，因此它被广泛用于探索模型和生物膜中的胆固醇组织、动力学和运输。在这项工作中，我们表明，尽管 DHE 位于膜界面，但无论膜相如何，在模型膜中都不会表现出红边激发位移 (REES)。这些结果通过 DHE 在基态和激发态偶极矩变化的半经验量子化学计算得到了证实，计算表明 DHE 偶极矩在激发时的偶极矩变化非常小。我们得出的结论是，尽管 DHE 荧光可用于监测模型和生物膜中的胆固醇组织、动态和运输，但它缺乏环境敏感性。