O'Malley S M, McDonald M J
Department of Chemistry, University of Massachusetts at Lowell 01854.
Biochem Biophys Res Commun. 1994 Apr 15;200(1):384-8. doi: 10.1006/bbrc.1994.1460.
A nonfluorescent reagent, 4-phenylazophenylmaleimide [4-PAPM], was attached to the sole cysteine residue [104(G11)] of alpha apohemoglobin (alpha degree) and served as an energy acceptor for the single intrinsic tryptophanyl [14(A12)] donor. This novel fluorescence system provided a transmolecular vehicle by which the overall structure of alpha degree could be monitored in 0.05 M potassium phosphate buffer at 5(0) C. Ratio of the emission intensities at 335 nm for monomeric solutions (5 x 10(-6) M) of both alpha degree and alpha degree [4-PAPM] furnished a measure of the efficiency of energy transfer and average distance of separation (r). An apparent increase in the value of r was observed from pH 6.5 to 8.5, suggesting that the conformation (the structural relationship of the A and G helical segments) of alpha degree is responsive to its electrostatic environment.
一种非荧光试剂，4-苯基偶氮苯马来酰亚胺[4-PAPM]，连接到α-脱辅基血红蛋白（α°）唯一的半胱氨酸残基[104(G11)]上，并作为单个内在色氨酸残基[14(A12)]供体的能量受体。这个新型荧光系统提供了一种跨分子载体，通过它可以在5(0)℃的0.05M磷酸钾缓冲液中监测α°的整体结构。α°和α°[4-PAPM]的单体溶液（5×10(-6)M）在335nm处的发射强度比提供了能量转移效率和平均分离距离（r）的度量。从pH 6.5到8.5观察到r值明显增加，这表明α°的构象（A和G螺旋段的结构关系）对其静电环境有响应。
