文献类型：期刊文献

英文题名：Ultrafast internal conversion dynamics of bilirubin bound to UnaG and its N57A mutant

作者：Cao, Xiaodan[1];Zhang, Changcheng[5];Gao, Ziheng[5];Liu, Yangyi[1];Zhao, Yuzheng[5];Yang, Yi[5];Chen, Jinquan[1,6];Jimenez, Ralph[2,3,4];Xu, Jianhua[1,6]

机构：[1]East China Normal Univ, State Key Lab Precis Spect, Shanghai, Peoples R China;[2]NIST, JILA, Boulder, CO 80309 USA;[3]Univ Colorado, Boulder, CO 80309 USA;[4]Univ Colorado, Dept Chem & Biochem, Campus Box 215, Boulder, CO 80309 USA;[5]East China Univ Sci & Technol, Sch Pharm, Shanghai, Peoples R China;[6]Shanxi Univ, Collaborat Innovat Ctr Extreme Opt, Taiyuan 030006, Shanxi, Peoples R China

年份：2019

卷号：21

期号：5

起止页码：2365

外文期刊名：PHYSICAL CHEMISTRY CHEMICAL PHYSICS

收录：;EI(收录号：20201708550032);WOS:【SCI-EXPANDED(收录号:WOS:000461667900010)】；

基金：This study was funded by National Natural Science Foundation of China (No. 11674101, 21873030 and 91850202 to J. C.) and the National Science Foundation Physics Frontier Center at JILA (NSF PHY 1734006 to R. J.). Supported by the 111 Project (B12024). R. J. is a staff member in the Quantum Physics Division of NIST. Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

语种：英文

外文关键词：Hydrogen bonds - Crystal structure - Chromophores - Proteins - Excited states

摘要：Fluorescent proteins (FPs) have become fundamental tools for live cell imaging. Most FPs currently used are members of the green fluorescent protein super-family, but new fluorophores such as bilin-FPs are being developed and optimized. In particular, the UnaG FP incorporates bilirubin (BR) as a chromophore, enhancing its fluorescence quantum yield by three orders of magnitude relative to that in solution. To investigate the mechanism of this dramatic enhancement and provide a basis for further engineering of UnaG and other tetrapyrrole-based fluorophores, we performed picosecond fluorescence and femtosecond transient absorption measurements of BR bound to UnaG and its N57A site-directed mutant. The dynamics of wt-UnaG, which has a fluorescence QY of 0.51, are largely homogeneous, showing an excited state relaxation of approximate to 200 ps, and a 2.2 ns excited-state lifetime decay with a kinetic isotope effect (KIE) of 1.1 for D2O vs. H2O buffer. In contrast, for UnaG N57A (fluorescence QY 0.01) the results show a large spectral inhomogeneity with excited state decay timescales of 47 and 200 ps and a KIE of 1.4. The non-radiative deactivation of the excited state is limited by proton transfer. The loss of direct hydrogen bonds to the endo-vinyl dipyrrinone moiety of BR leads to high flexibility and structural heterogeneity of UnaG N57A, as seen in the X-ray crystal structure.