SANDERS R T, GIESE A C
J Gen Physiol. 1959 Jan 20;42(3):589-607. doi: 10.1085/jgp.42.3.589.
The Na(+) and K(+) content of non-metabolizing yeast cells was determined before and after monochromatic ultraviolet (UV) irradiation. UV facilitated the uptake of Na(+) into and the loss of K(+) from the cells (net ion flux); the effect is greatest for the shortest wavelength employed (239 mmicro) and is partly dependent upon the presence of oxygen. The UV effect on net ion flux persists for at least 90 minutes during which tests were made and it occurs following dosages which are without measurable effect on colony formation. The UV effect on net ion flux is decreased by acidity and promoted by alkalinity. Addition of calcium ions in sufficient amount prevents the usual net ion flux changes observed in irradiated yeast. Increase in concentration gradient between the inside and the outside of the cell increases the net ion flux of irradiated yeast, Na(+) uptake leading K(+) loss in all cases. UV appears to act by disorganizing the constituents of the cell surface, permitting K(+) to leave the cell in exchange for Na(+). At low intensities of UV this ionic exchange approaches equivalence, but at higher intensities more Na(+) is taken up than K(+) is lost. Some evidence suggests that the Na(+) in excess over that exchanged for K(+) is adsorbed to charged groups produced by the photochemical effect of UV on the cell surface.
在单色紫外线（UV）照射前后，测定了非代谢酵母细胞的钠（Na⁺）和钾（K⁺）含量。紫外线促进了细胞对Na⁺的摄取以及K⁺从细胞中的流失（净离子通量）；对于所使用的最短波长（239微米），这种效应最为显著，并且部分依赖于氧气的存在。在进行测试的至少90分钟内，紫外线对净离子通量的影响持续存在，并且在对菌落形成没有可测量影响的剂量之后也会发生这种情况。紫外线对净离子通量的影响在酸性条件下会降低，而在碱性条件下会增强。加入足够量的钙离子可防止在辐照酵母中观察到的通常的净离子通量变化。细胞内外浓度梯度的增加会增加辐照酵母的净离子通量，在所有情况下都是Na⁺的摄取导致K⁺的流失。紫外线似乎是通过破坏细胞表面的成分起作用的，使K⁺离开细胞以交换Na⁺。在低强度紫外线照射下，这种离子交换接近等价，但在较高强度下，摄取的Na⁺比流失的K⁺更多。一些证据表明，超过与K⁺交换量的过量Na⁺被吸附到紫外线对细胞表面的光化学作用产生的带电基团上。
