Morrow J S, Keim P, Visscher R B, Marshall R C, Gurd F R
Proc Natl Acad Sci U S A. 1973 May;70(5):1414-8. doi: 10.1073/pnas.70.5.1414.
Formation of (13)C-resonances attributable to carbamino derivatives has been observed in human erythrocyte hemolysate preparations equilibrated with (13)CO(2) at 33 degrees . Carbamino formation is most marked in deoxyhemoglobin and at alkaline pH, and is very largely inhibited by the addition of 2,3-diphosphoglycerate or conversion to oxyhemoglobin. The prominent carbamino resonance at 30.0 ppm upfield of CS(2) is visible in the spectrum of packed, deoxygenated erythrocytes equilibrated in (13)CO(2). This chemical shift falls close to that observed with sperm-whale myoglobin and within 2 ppm upfield of that seen with simple amino acids and peptides. The bicarbonate-carbonate resonance near 33 ppm is broad in the hemoglobin preparations, which always contain some carbonic anhydrase, but becomes narrow in the presence of the carbonic anhydrase inhibitor, acetazolamide. The nuclear magnetic resonance condition of intermediate exchange rate with dissolved CO(2) (68.4 ppm) obtains in the absence of inhibitor. The process has marked consequences in reducing the spin-lattice relaxation time, T(1), of the bicarbonate resonance by more than 10 times. The deoxyhemoglobin carbamino resonance has a T(1) value of 700 msec, indistinguishable from that of the protein carbonyl resonance envelope.
在33摄氏度下用(^{13}CO_2)平衡的人红细胞溶血制剂中,已观察到归因于氨基甲酰衍生物的(^{13}C)共振的形成。氨基甲酰的形成在脱氧血红蛋白和碱性pH条件下最为明显,并且通过添加2,3 - 二磷酸甘油酸或转化为氧合血红蛋白在很大程度上受到抑制。在(^{13}CO_2)中平衡的去氧红细胞堆积物的光谱中,可以看到在(CS_2)高场30.0 ppm处的突出氨基甲酰共振。这种化学位移接近在抹香鲸肌红蛋白中观察到的位移,并且在简单氨基酸和肽的高场2 ppm范围内。在血红蛋白制剂中,靠近33 ppm的碳酸氢盐 - 碳酸盐共振很宽,因为血红蛋白制剂中总是含有一些碳酸酐酶,但在碳酸酐酶抑制剂乙酰唑胺存在下会变窄。在没有抑制剂的情况下,与溶解的(CO_2)(68.4 ppm)处于中间交换速率的核磁共振条件得以实现。该过程在将碳酸氢盐共振的自旋 - 晶格弛豫时间(T_1)缩短10倍以上方面具有显著影响。脱氧血红蛋白氨基甲酰共振的(T_1)值为700毫秒,与蛋白质羰基共振包络的(T_1)值无法区分。