Armbrecht H J, Gunter T E, Puskin J S, Terepka A R
Biochim Biophys Acta. 1976 Mar 19;426(3):557-69. doi: 10.1016/0005-2736(76)90399-0.
Mn2+ uptake in the chick chorioallantoic membrane, an embryonic epithelial tissue which transports Ca2+ in vivo was studied using electron paramagnetic resonance (EPR). Mn2+ was used as a paramagnetic analog for Ca2+, since there is evidence that Mn2+ is accumulated by the Ca2+ transport mechanism. After 1.5 h of uptake the EPR spectrum of the Mn2+ in the membrane indicated that 89% of the Mn2+ was in a spin-exchange form, indicating close packing of Mn2+. The Mn2+ spacing was estimated from the line width to be about 4.7 A. The remaining Mn2+ was very likely Mn2+ hexahydrate. At pH 7.4 the spin-exchange spectrum tended to broaden when uptake was inhibited, while at pH 5.0 the spin-exchange spectrum was completely abolished in the presence of inhibitors. The EPR spectrum of Mn2+ in the chorioallantoic membrane had a broader line width than that of Mn2+ in isolated mitochondria, suggesting that in this tissue mitochondria are not directly involved in divalent cation transport. These EPR studies support the concept that divalent cations are sequestered in high concentrations from the rest of the cell contents during transcellular active transport.
利用电子顺磁共振（EPR）研究了鸡绒毛尿囊膜（一种在体内转运Ca2+的胚胎上皮组织）对Mn2+的摄取。由于有证据表明Mn2+是通过Ca2+转运机制积累的，因此Mn2+被用作Ca2+的顺磁类似物。摄取1.5小时后，膜中Mn2+的EPR光谱表明，89%的Mn2+处于自旋交换形式，这表明Mn2+紧密堆积。根据线宽估计Mn2+间距约为4.7埃。其余的Mn2+很可能是六水合Mn2+。在pH 7.4时，摄取受到抑制时自旋交换光谱趋于变宽，而在pH 5.0时，在存在抑制剂的情况下自旋交换光谱完全消失。绒毛尿囊膜中Mn2+的EPR光谱的线宽比分离的线粒体中Mn2+的线宽大，这表明在该组织中线粒体不直接参与二价阳离子转运。这些EPR研究支持了这样一种概念，即在跨细胞主动转运过程中，二价阳离子从细胞内容物的其余部分中被高浓度隔离。
