Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay.
Adv Exp Med Biol. 2019;1127:3-19. doi: 10.1007/978-3-030-11488-6_1.
This chapter includes an overview of the structure of cell membranes and a review of the permeability of membranes to biologically relevant oxygen and nitrogen reactive species, namely oxygen, singlet oxygen, superoxide, hydrogen peroxide, hydroxyl radical, nitric oxide, nitrogen dioxide, peroxynitrite and also hydrogen sulfide. Physical interactions of these species with cellular membranes are discussed extensively, but also their relevance to chemical reactions such as lipid peroxidation. Most of these species are involved in different cellular redox processes ranging from physiological pathways to damaging reactions against biomolecules. Cell membranes separate and compartmentalize different processes, inside or outside cells, and in different organelles within cells. The permeability of these membranes to reactive species varies according to the physicochemical properties of each molecule. Some of them, such as nitric oxide and oxygen, are small and hydrophobic and can traverse cellular membranes virtually unhindered. Nitrogen dioxide and hydrogen sulfide find a slightly higher barrier to permeation, but still their diffusion is largely unimpeded by cellular membranes. In contrast, the permeability of cellular membranes to the more polar hydrogen peroxide, is up to five orders of magnitude lower, allowing the formation of concentration gradients, directionality and effective compartmentalization of its actions which can be further regulated by specific aquaporins that facilitate its diffusion through membranes. The compartmentalizing effect on anionic species such as superoxide and peroxynitrite is even more accentuated because of the large energetic barrier that the hydrophobic interior of membranes presents to ions that may be overcome by protonation or the use of anion channels. The large difference in cell membrane permeability for different reactive species indicates that compartmentalization is possible for some but not all of them.
这一章包括细胞膜结构的概述，以及对生物相关的氧气和氮气反应性物质（即氧气、单线态氧、超氧自由基、过氧化氢、羟自由基、一氧化氮、二氧化氮、过氧亚硝酸盐以及硫化氢）透过细胞膜的通透性的回顾。这些物质与细胞膜的物理相互作用被广泛讨论，但也讨论了它们与化学反应（如脂质过氧化）的相关性。这些物质中的大多数参与不同的细胞氧化还原过程，从生理途径到针对生物分子的破坏性反应。细胞膜将不同的过程分离和分隔在细胞内外以及细胞内的不同细胞器中。这些膜对反应性物质的通透性根据每个分子的物理化学性质而有所不同。其中一些物质，如一氧化氮和氧气，体积小且疏水性强，可以几乎不受阻碍地穿过细胞膜。二氧化氮和硫化氢的渗透稍高，但它们的扩散仍不受细胞膜的很大阻碍。相比之下，细胞膜对极性更强的过氧化氢的通透性要低 5 个数量级，这允许其形成浓度梯度、方向性和有效的分隔作用，其作用还可以通过促进其穿过膜扩散的特定水通道蛋白进一步调节。由于膜的疏水环境对阴离子（如超氧自由基和过氧亚硝酸盐）构成巨大的能量障碍，因此对阴离子的分隔作用更为明显，这种障碍可以通过质子化或使用阴离子通道来克服。不同反应性物质对细胞膜通透性的巨大差异表明，某些物质（但不是所有物质）可以实现分隔。
