Becker J F, Geacintov N E, Swenberg C E
Biochim Biophys Acta. 1978 Sep 7;503(3):545-54. doi: 10.1016/0005-2728(78)90152-4.
The photovoltage of suspensions of magnetically oriented chloroplasts using polarized light of 680 nm has been measured. The magnitude of the photo e.m.f. depends on the polarization of the light and on its direction of propagation with respect to the oriented thylakoid planes. This photo e.m.f. is qualitatively attributed to the Dember effect which arises when inhomogeneous light absorption gives rise to a gradient of positive and negative charges along x , where x is the direction defined by the propagation vector of the light and which is also the direction joining the two electrodes. The photovoltage obtained with the planes of the oriented thylakoids parallel to x depends on the plane of polarization of the incident light and shows that (1) the magnitude of the photovoltage depends on the absorption coefficient (which itself is polarization dependent) and thus on the magnitude of the charge gradient produced by the inhomogeneously absorbed light, and (2) a charge gradient within the planes of the thylakoids can give rise to the macroscopic photovoltage. While our experimental observations are basically in agreement with those previously reported (Fowler, C.F. and Kok, B.(1974) Biochim. Biophys. Acta 357, 308-318 and Witt, H.T. and Zickler, A. (1973) FEBS Lett. 37, 307-310) for unoriented chloroplasts, their interpretation of the origin of this effect in terms of a transmembrane potential must be modified in view of our results obtained with oriented chloroplasts. The macroscopically observed photovoltage of oriented chloroplasts is due to the creation of charge gradients either parallel or perpendicular to the thylakoid planes by a flash of light, the diffusion of these charges and to differences in the mobilities of the negative and positive charges. This interpretation in terms of the Dember effect is completely consistent with the existence of a transmembrane electric field as proposed by Fowler and Kok, as well as by Witt and Zickler. However, macroscopic measurements of the photovoltage using either oriented or unoriented chloroplast suspensions cannot prove that a transmembrane voltage exists, as previously claimed.
已测量了使用680nm偏振光时磁取向叶绿体悬浮液的光电压。光电动势的大小取决于光的偏振及其相对于取向类囊体平面的传播方向。这种光电动势定性地归因于当非均匀光吸收导致沿x方向产生正电荷和负电荷梯度时出现的丹伯效应，其中x是由光的传播矢量定义的方向，也是连接两个电极的方向。当取向类囊体的平面与x平行时获得的光电压取决于入射光的偏振平面，并表明：（1）光电压的大小取决于吸收系数（其本身取决于偏振），因此取决于由非均匀吸收光产生的电荷梯度的大小；（2）类囊体平面内存在电荷梯度可产生宏观光电压。虽然我们的实验观察结果与先前报道的未取向叶绿体的结果（Fowler，C.F.和Kok，B.（1974年）《生物化学与生物物理学报》357，308 - 318以及Witt，H.T.和Zickler，A.（1973年）《欧洲生物化学学会联合会快报》37，307 - 310）基本一致，但鉴于我们使用取向叶绿体获得的结果，他们关于这种效应起源的跨膜电位解释必须修改。取向叶绿体宏观上观察到的光电压是由于光脉冲在类囊体平面平行或垂直方向上产生电荷梯度、这些电荷的扩散以及正负电荷迁移率的差异。这种基于丹伯效应的解释与Fowler和Kok以及Witt和Zickler提出的跨膜电场的存在完全一致。然而，使用取向或未取向叶绿体悬浮液对光电压进行的宏观测量并不能像先前声称的那样证明存在跨膜电压。
