2D UV spectroscopy: A new tool for the investigation of ultrafast processes in biomolecules – Femto-2DNA

Femtosecond two-dimensional electronic spectroscopy (2DES) is a novel nonlinear optics technique holding promises to track the interactions in a multichromophoric systems with unprecedented time and spectral resolution. By spreading the information content of the nonlinear signal on two frequency axes, it provides, in analogy to two-dimensional NMR, much more information than its one-dimensional (1D) counterpart. For the time being two-dimensional spectroscopy has been mainly implemented in the IR domain (probing vibrational transitions) and the visible range (limited to probe visible-light absorbing chromophores) . Here we propose to extend 2DES to the UV regime (280 – 400 nm, 2DUV) where multichromophoric biomolecular systems, such as DNA and proteins, display strong absorption bands. We will develop the theoretical and the experimental tools for the investigation of ground state structural heterogeneity and excited state dynamical processes in DNA, proteins and their aggregates, including interactions with exogenous chromophoric systems. 2DUV then goes far beyond the limitations of NMR (little time resolution), or 1D techniques such as Circular Dichroism (CD) and IR spectroscopy (inhomogeneous broadening) or time-resolved fluorescence (missing quantitative link between kinetics and structure). The tools developed within this project, if successful, will pave the way to an unprecedented insight and improved understanding of the molecular properties and activity of in vitro biosystems in general, going far beyond the specific molecular systems targeted in this project.
FEMTO-2DNA is a 4-year project situated in the rapidly evolving area of ultrafast molecular sciences, where 2D femtosecond and 1D attosecond spectroscopies are the recent most important developments. 2DES and 2DUV are under very active development in academic labs in particular for molecular systems with interacting chromophores. But, to the best of our knowledge, 2DUV is not being developed in France. Today, it is also evident that these new spectroscopies require an accurate and complete theoretical treatment in order for the 2D spectra to be correctly interpreted and exploited. FEMTO-2DNA will explore the ultimate frontiers in ultrafast spectroscopy and advance our fundamental understanding on multi-chromophoric (biological) systems by going beyond the current limitations of experimental and computational tools and protocols.
This joint project will involve three partners with distinct and complementary contributions and know-how: i) development of the experimental setup for 2DUV with sub-20fs excitation pulses and broadband probing (S. Haacke, Strasbourg, coordinator), ii) new electronic structure methods to model larger molecular systems and their 2D electronic spectra (X. Assfeld, Nancy) and iii) the simulation tools to predict and extract all the relevant information from the 2D electronic spectra (M. Garavelli, Lyon).