Seidel C, Orth A, Greulich K O
Physikalisch-Chemisches Institut, Universität Heidelberg, Germany.
Photochem Photobiol. 1993 Aug;58(2):178-84. doi: 10.1111/j.1751-1097.1993.tb09546.x.
It is shown for a series of tyrosine-derivatives and tyrosine-containing peptides that the amide group in combination with electron-withdrawing substituents quenches the fluorescence of the phenol moiety. The ammonium group has the strongest electron-withdrawing effect and thus the largest influence on the quenching rate. The peptide group itself does not quench the fluorescence. In a series of peptides with an increasing number of alanines the decreasing quenching efficiency of the peptide group due to the greater distance of the ammonium group is demonstrated. In tyrosine-containing di- and tripeptides a linear correlation between the 13C-NMR chemical shift delta of the C alpha atom of various aliphatic amino acids and the fluorescence-quenching constant confirms the hypothesis that electron-withdrawing and -donating groups are modulating the fluorescence-quenching efficiency of the peptide group. In small peptides the fluorescence lifetime of tyrosine is characteristic for the neighboring amino acids. Using model substances the redox properties of a peptide group and the phenol ring were studied electrochemically. The highest occupied molecular orbital of the tyrosine (1.4 V vs saturated calomel electrode [SCE]) and the lowest unoccupied molecular orbital of the peptide group (-3.12 V vs SCE) have appropriate energies for a photoinduced electron transfer reaction. For solute-quenching experiments quencher molecules can be systematically selected.
一系列酪氨酸衍生物和含酪氨酸的肽表明，酰胺基团与吸电子取代基结合会淬灭酚部分的荧光。铵基团具有最强的吸电子作用，因此对淬灭速率的影响最大。肽基团本身不会淬灭荧光。在一系列丙氨酸数量增加的肽中，由于铵基团距离增大，肽基团的淬灭效率降低得到了证明。在含酪氨酸的二肽和三肽中，各种脂肪族氨基酸的Cα原子的13C-NMR化学位移δ与荧光淬灭常数之间的线性相关性证实了以下假设：吸电子和供电子基团正在调节肽基团的荧光淬灭效率。在小肽中，酪氨酸的荧光寿命是相邻氨基酸的特征。使用模型物质对肽基团和酚环的氧化还原性质进行了电化学研究。酪氨酸的最高占据分子轨道（相对于饱和甘汞电极[SCE]为1.4 V）和肽基团的最低未占据分子轨道（相对于SCE为-3.12 V）具有适合光诱导电子转移反应的能量。对于溶质淬灭实验，可以系统地选择淬灭剂分子。
