Palacios A G, Goldsmith T H, Bernard G D
Department of Biology, Yale University, New Haven, CT 06520-8103, USA.
Vis Neurosci. 1996 May-Jun;13(3):411-21. doi: 10.1017/s0952523800008099.
Photocurrents of cones in the retinas of a small fish, Danio aequipinnatus (Cyprinidae) were recorded with suction pipette electrodes. Spectral sensitivity was measured between 277 and 697 nm. Four spectral classes of cone were found, with lambdamax at 560, 480, 408, and 358 nm. For the latter, we provide the first complete characterization of spectral sensitivity of a vertebrate ultraviolet (UV) photoreceptor. All cones responded with similar kinetics, except for a subset of the 560-nm cones, which were distinctly faster. The alpha-bands of the three cones absorbing maximally in the visible have the same bandwidth when log sensitivity is plotted versus normalized frequency, and in this respect they are indistinguishable from primate cones ("Mansfield's rule"). An eighth-degree polynomial in lambdamax/lambda based on this combined data set (fish, primate) is presented as a template that is likely to have predictive value in describing cone spectra from other vertebrates. The alpha-band of the UV cone, however, is somewhat narrower than predicted by this function, is similar to other UV visual pigments, and an eighth-degree polynomial that describes its shape is also presented. These measurements also provide information on the beta-band (i.e. cis peak region), difficult to obtain by microspectrophotometry. The beta-band of cone pigments is found at longer wavelengths as the alpha-band shifts toward the red. A secondary rise in cone sensitivity around 280 nm indicates that photons absorbed by aromatic amino acids in the opsin (gamma-band) excite the transduction cascade, but the quantum efficiency is not as high as when absorption occurs in the retinal-protein chromophore.
用吸管电极记录了一种小鱼——斑马鱼（鲤科）视网膜中视锥细胞的光电流。在277至697纳米之间测量了光谱敏感性。发现了四类视锥细胞，其最大吸收波长分别为560、480、408和358纳米。对于后者，我们首次完整地描述了脊椎动物紫外光感受器的光谱敏感性特征。除了一部分560纳米视锥细胞反应明显更快外，所有视锥细胞的反应动力学相似。当绘制对数敏感性与归一化频率的关系图时，在可见光中最大吸收的三种视锥细胞的α波段具有相同的带宽，在这方面它们与灵长类视锥细胞无法区分（“曼斯菲尔德规则”）。基于这个综合数据集（鱼类、灵长类），给出了一个以最大吸收波长/波长为变量的八次多项式作为模板，它可能在描述其他脊椎动物的视锥光谱方面具有预测价值。然而，紫外视锥细胞的α波段比该函数预测的要窄一些，与其他紫外视觉色素相似，并且还给出了一个描述其形状的八次多项式。这些测量还提供了关于β波段（即顺式峰区域）的信息，这是通过显微分光光度法难以获得的。随着α波段向红色移动，视锥色素的β波段出现在更长的波长处。视锥细胞在280纳米左右的二次敏感性上升表明，视蛋白中芳香族氨基酸吸收的光子（γ波段）激发了转导级联反应，但量子效率不如在视网膜 - 蛋白质发色团中吸收时高。
