Intramolecular Transfer of Electronic Energy in Dihydro Diphosphopyridine Nucleotide
Intramolecular Transfer of Electronic Energy in Dihydro Diphosphopyridine Nucleotide
复制标题
二氢二磷酸吡啶核苷酸中电子能的分子内转移
作者：
G. Weber
二氢二磷酸吡啶核苷酸显示蓝白色荧光（λmax. = 468 mµ）的水溶液1，在汞366 mµ辐射激发下的量子产率2为2%。几种还原的N-烷基烟酰胺的荧光光谱和量子产率与二氢二磷酸吡啶核苷酸的荧光光谱和量子产率几乎相同。这些还原的N-烷基烟酰胺的荧光激发光谱3（图1）显示，在探索的整个波长范围内（220-410 mµ），与分数吸收光谱完全一致。二氢二磷酸吡啶核苷酸水溶液在pH 7-9时的荧光激发光谱显示出另一个强带，最大值在260 mµ处，该区域80- 90%的吸收是由于分子的嘌呤部分。从这些观察结果可以看出，腺嘌呤吸收的30%的光子以烟酰胺荧光的形式出现。这种能量转移需要分子的完整性才能显示出来：在pH值为8.3的二氢二磷酸吡啶核苷酸溶液中，核苷酸焦磷酸酶4作用后，荧光激发光谱的260 mµ带消失，所得光谱变得与还原的N-烷基烟酰胺相似。该酶水解P-O-P键，使嘌呤和烟酰胺核苷酸成为独立的分子，在实验浓度为9 × 10−6 M的溶液中，它们的平均距离为300 A。彼此的关系。二氢二磷酸吡啶核苷酸在丙二醇中的溶液在荧光激发光谱中没有检测到260 mµ带，而在60%蔗糖水溶液中显示出260 mµ带，其强度是纯水中的五分之四。
DIHYDRO diphosphopyridine nucleotide shows blue-white fluorescence (λmax. = 468 mµ) in water solution1 with a quantum yield2 of 2 per cent on excitation by mercury 366 mµ radiation. Several reduced N-alkyl nicotinamides show fluorescence almost identical in spectrum and quantum yield with that of dihydro diphosphopyridine nucleotide. The excitation spectrum of the fluorescence3 of these reduced N-alkyl nicotinamides (Fig. 1) shows complete coincidence with the fractional absorption spectrum over the whole range of wave-lengths explored (220–410 mµ). The fluorescence-excitation spectrum of water solutions of dihydro diphosphopyridine nucleotide at pH 7–9 shows a further strong band with a maximum at 260 mµ, a region where 80–90 per cent of the absorption is due to the purine part of the molecule. From these observations it appears that 30 per cent of the photons absorbed by the adenine appear as nicotinamide fluorescence. The integrity of the molecule is required for this energy transfer to show itself: after a solution of dihydro diphosphopyridine nucleotide at pH 8.3 has been acted upon by nucleotide pyrophosphatase4 the 260 mµ band of the fluorescence-excitation spectrum disappears, the resulting spectrum becoming similar to that of the reduced N-alkyl nicotinamides. The enzyme hydrolyses the P—O—P linkage and causes the purine and nicotinamide nucleotides to become independent molecules, which in a 9 × 10−6 M solution, the concentration of the experiments, are at an average distance of 300 A. of each other. Solutions of dihydro diphosphopyridine nucleotide in propylene glycol show no detectable 260 mµ band in the fluorescence-excitation spectrum, while solutions in 60 per cent sucrose in water show a 260 mµ band the intensity of which is four-fifths of that in pure water.