This review is motivated by the exciting new area of radiation therapy using a phenomenon termed FLASH in which oxygen is thought to have a central role. Well-established principles of radiation biology and physics suggest that if oxygen has a strong role, it should be the level at the DNA. The key aspect discussed is the rate of oxygen diffusion. If oxygen freely diffuses into cells and rapidly equilibrates, then measurements in the extracellular compartment would enable FLASH to be investigated using existing methodologies that can readily measure oxygen in the extracellular compartment. EPR spin-label oximetry allows evaluation of the oxygen permeability coefficient across lipid bilayer membranes. It is established that simple fluid-phase lipid bilayers are not barriers to oxygen transport. However, further investigations indicate that many physical and chemical (compositional) factor can significantly decrease this permeation. In biological cell plasma membranes, the lipid bilayer forms the matrix in which integral membrane proteins are immersed, changing organization and properties of the lipid matrix. To evaluate oxygen permeability coefficients across these complex membranes, oxygen permeation across all membrane domains and components must be considered. In this review, we consider many of the factors that affect (decrease) oxygen permeation across cell plasma membranes. Finally, we address the question, can the plasma membrane of the cell form a barrier to the free diffusion of oxygen into the cell interior? If there is a barrier then this must be considered in the investigations of the role of oxygen in FLASH.

这篇综述的动机是放射治疗这一令人兴奋的新领域，该领域使用一种称为 FLASH 的现象，其中氧气被认为具有核心作用。公认的辐射生物学和物理学原理表明，如果氧气有很强的作用，那么它应该是 DNA 的水平。讨论的关键方面是氧扩散的速率。如果氧气自由扩散到细胞中并迅速平衡，那么细胞外隔室中的测量将使 FLASH 能够使用现有的方法来研究，这些方法可以很容易地测量细胞外隔室中的氧气。EPR 自旋标签血氧饱和度允许评估跨脂质双层膜的氧气渗透系数。已经确定简单的液相脂质双层不是氧气运输的障碍。然而，进一步的研究表明，许多物理和化学（组成）因素可以显着降低这种渗透。在生物细胞质膜中，脂质双分子层形成基质，整合膜蛋白浸入其中，从而改变脂质基质的组织和性质。为了评估这些复杂膜的氧渗透系数，必须考虑所有膜域和组件的氧渗透。在这篇综述中，我们考虑了许多影响（减少）细胞质膜氧渗透的因素。最后，我们要解决这个问题，细胞的质膜能否形成阻碍氧气自由扩散到细胞内部的屏障？如果存在障碍，那么在研究氧气在 FLASH 中的作用时必须考虑这一点。