Time：16:00-17:30, Thursday, May 18^th, 2023

Host: Prof. Hongfei Wang, PI of School of Science, Westlake University

Venue: E10-201, Yungu Campus, Westlake University

Prof. Hongmei Su,

Professor of Beijing Normal University.

NSFC Distinguished Young Scholar(2014)

E-mail:  hongmei@bnu.edu.cn

Speaker：

Prof. Hongmei Su obtained her B.S. degree in Shandong University and Ph.D. degree in the Institute of Chemistry, Chinese Academy of Sciences. She did her postdoctoral research at Columbia University from 1999 to 2004. She then obtained the support of the Hundred Talent Program of the Chinese Academy of Sciences and started her independent research in the Institute of Chemistry, Chinese Academy of Sciences from 2004. She was awarded the NSFC Distinguished Young Scholars in 2014. In 2015, Prof. Su moved to Beijing Normal University. Prof. Su serves as the editorial advisory board member of the Journal of Physical Chemistry A/B/C/Lett and International Review of Physical Chemistry. By ultrafast and time-resolved laser spectroscopic methods (transient IR, UV-vis, fluorescence), Prof. Su’s research aims to examine the spectroscopy and reaction dynamics of free radicals and excited states, which are highly reactive intermediates in many chemical and biological processes. The main research scopes include photochemical reaction dynamics of DNA/RNA, water-mediated chemical reactions of biomolecules, interaction of gold nanoparticles with excited state population dynamics, and photocatalytic chemistry.

Abstract:

Biological information is encoded into the nucleobase sequence of DNA and RNA. The nucleobases are the building blocks and chromophores accounting for the UV absorption of DNA and RNA at ~260 nm. Enhancing the UV sensitivity of the nucleobases is essential for the development of biocompatible sensitizers for photodynamic therapy (PDT) of cancer, which can accelerate DNA damage processes and cell death upon exposure to ionizing radiation or UV photolysis. Surprisingly, functionality-modified nucleobases such as thio-nucleobases (4-thiothymine and 6-thioguanine) introduce a longer-wavelength-absorbing chromophore (~ 350 nm) and can be incorporated into native DNA/RNA as a photosensitizer without affecting the biological function. They exhibit remarkable photoreactivity and can cause selective DNA damage of malignant cells or pathogens. However, single-functionality substitution confers only limited phototoxicity to DNA/RNA. To develop more potent tactics to boost the photolabile character of DNA/RNA, we integrate femtosecond and nanosecond time-resolved spectroscopy methods to follow the excited state reaction dynamics of double-functionality substituted nucleobases such as 5-bromo-4-thiouridine (5Br-4TUrd) or 6-methylthioguanine (me6-TG) upon UVA photoexcitation, allowing the capture of transient intermediates in unprecedented detail. In conjunction with high-level theoretical ab initio calculations, we decipher the dramatic and synergistic effects of double-functionality in shaping the excited state potential energy surface and opening multiple competing pathways in damaging DNA/RNA. Our mechanistic findings provide inspiration that thio-based double-substitution of natural nucleosides can be a powerful chemical modification strategy to be generalized toward various realistic applications in pharmacology, nucleic acid-based diagnostics and studies of nucleic acid/protein interactions.

Contact:

School of Science, Huang Li, Email: huangli10@westlake.edu.cn