Pazos Ileana M, Ahmed Ismail A, Berríos Mariana I León, Gai Feng
Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA.
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Anal Biochem. 2015 Aug 15;483:21-6. doi: 10.1016/j.ab.2015.04.026. Epub 2015 Apr 29.
We expand the spectroscopic utility of a well-known infrared and fluorescence probe, p-cyanophenylalanine, by showing that it can also serve as a pH sensor. This new application is based on the notion that the fluorescence quantum yield of this unnatural amino acid, when placed at or near the N-terminal end of a polypeptide, depends on the protonation status of the N-terminal amino group of the peptide. Using this pH sensor, we are able to determine the N-terminal pKa values of nine tripeptides and also the membrane penetration kinetics of a cell-penetrating peptide. Taken together, these examples demonstrate the applicability of using this unnatural amino acid fluorophore to study pH-dependent biological processes or events that accompany a pH change.
我们通过证明一种著名的红外和荧光探针对氰基苯丙氨酸还可作为pH传感器，拓展了其光谱学用途。这一新应用基于这样一种观念，即这种非天然氨基酸置于多肽N端或其附近时，其荧光量子产率取决于肽N端氨基的质子化状态。利用这种pH传感器，我们能够测定9种三肽的N端pKa值以及一种细胞穿透肽的膜穿透动力学。综上所述，这些例子证明了使用这种非天然氨基酸荧光团来研究pH依赖性生物过程或伴随pH变化的事件的适用性。
