Perrella M, Benazzi L, Ripamonti M, Rossi-Bernardi L
Dipartimento di Scienze e Tecnologie Biomediche, Università di Milano, Italy.
Biochemistry. 1994 Aug 30;33(34):10358-66. doi: 10.1021/bi00200a016.
The Bohr protons released by oxygen exposure of the unliganded subunits of intermediates (alpha +CN-beta) (alpha +CN-beta) and (alpha beta +CN-) (alpha beta +CN-) were obtained by titrations of concentrated solutions of these species. The Bohr protons released by oxygen exposure of the other intermediates were obtained from titrations of equilibrium mixtures of two parental species, (alpha beta) (alpha beta), (alpha +CN-beta) (alpha +CN-beta), (alpha beta +CN-) (alpha beta +CN-), and (alpha +CN-beta +CN-) (alpha +CN-beta +CN-), in which the concentration of the hybrid intermediate was determined by cryogenic electrophoretic techniques. The Bohr effect of the intermediates was calculated by subtracting the Bohr protons released by oxygen exposure of the intermediates from the total Bohr protons of deoxyhemoglobin at the same pH. The Bohr effects of intermediates (alpha +CN-beta) (alpha beta) and (alpha beta +CN-) (alpha beta) were similar and vanished at pH 8 where the total Bohr effect of deoxyhemoglobin is still significant. This suggests that the Bohr effect in these intermediates is tertiary in the quaternary T structure. The curve of the Bohr effect of intermediate (alpha +CN-beta +CN-) (alpha beta), which was close to the curve obtained by adding the Bohr effects of the two monoliganded intermediates at acidic and physiological pH values, was significantly different from the curve obtained by adding the Bohr effects of one liganded subunit of intermediate (alpha +CN-beta) (alpha +CN-beta) and one liganded subunit of intermediate (alpha beta +CN-) (alpha beta +CN-).(ABSTRACT TRUNCATED AT 250 WORDS)
通过对中间体（α+CN-β）（α+CN-β）和（αβ+CN-）（αβ+CN-）未结合亚基进行氧暴露所释放的玻尔质子，是通过对这些物种的浓溶液进行滴定获得的。其他中间体进行氧暴露所释放的玻尔质子，则是从两种亲本物种（αβ）（αβ）、（α+CN-β）（α+CN-β）、（αβ+CN-）（αβ+CN-）和（α+CN-β+CN-）（α+CN-β+CN-）的平衡混合物滴定中获得的，其中杂合中间体的浓度通过低温电泳技术测定。中间体的玻尔效应是通过在相同pH值下，从脱氧血红蛋白的总玻尔质子中减去中间体进行氧暴露所释放的玻尔质子来计算的。中间体（α+CN-β）（αβ）和（αβ+CN-）（αβ）的玻尔效应相似，且在pH 8时消失，而此时脱氧血红蛋白的总玻尔效应仍然显著。这表明这些中间体中的玻尔效应在四级T结构中是三级的。中间体（α+CN-β+CN-）（αβ）的玻尔效应曲线，在酸性和生理pH值下接近通过将两种单配体中间体的玻尔效应相加得到的曲线，但与通过将中间体（α+CN-β）（α+CN-β）的一个配体亚基和中间体（αβ+CN-）（αβ）的一个配体亚基的玻尔效应相加得到的曲线显著不同。（摘要截断于250字）
