Search

[Display omitted] • Ultraviolet resonance Raman (UVRR) spectroscopy for molecular recognition of peptides/proteins. • Current limitations of UVRR application in real-life binding events in proteins and possible solutions. • UVRR spectroscopy of artificial ligands as selective carboxylate or lysine binders. • Prospects of Kerr gate-based UVRR for suppression of UV-excited fluorescence. Ultraviolet resonance Raman scattering (UVRR) has been frequently used for studying peptide and protein structure and dynamics, while applications in supramolecular chemistry are quite rare. Since UVRR offers the additional advantages of chromophore selectivity and high sensitivity compared with conventional non-resonant Raman scattering, it is ideally suited for label-free probing of relatively small artificial/supramolecular ligands exhibiting electronic resonances in the UV. In this perspective article, we first summarize results of UVRR spectroscopy in supramolecular chemistry in the context of peptide/protein recognition. We focus on selected artificial ligands which were rationally designed as selective carboxylate binders (guanidiniocarbonyl pyrrole, GCP, and guanidiniocarbonyl indole, GCI) and selective lysine binder (molecular tweezer, CLR01), respectively, via a combination of non-covalent interactions involving electrostatics, hydrogen bonding, and hydrophobic effects/van der Waals forces. Current limitations of applying UVRR as a universally applicable method for label-free and site-specific probing of molecular recognition between supramolecular ligands and proteins are highlighted. We then propose solutions to overcome these limitations for transforming UVRR spectroscopy into a generic tool in supramolecular chemistry on proteins, with an emphasis on mono- and multivalent GCP- and GCI-based ligands. Finally, we outline specific cases of supramolecular ligands such as molecular tweezers where alternative approaches such as laser-based mid-IR spectroscopy are required since UVRR can intrinsically not provide the required molecular information. [ABSTRACT FROM AUTHOR]

• A versatile ultraviolet resonance Raman spectroscopy setup. • Continuously tunable picosecond pulsed laser excitation source in 210–2600 nm range. • Triple stage-OPA based excitation source providing <15 cm−1 linewidth pulses. • UVRR excitation profile of artificial supramolecular ligand guanidiniocarbonyl pyrrole, GCP. We present a UVRR spectroscopy setup which is equipped with a picosecond pulsed laser excitation source continuously tunable in the 210–2600 nm wavelength range. This laser source is based on a three-stage optical parametric amplifier (OPA) pumped by a bandwidth-compressed second harmonic output of an amplified Yb:KGW laser. It provides <15 cm−1 linewidth pulses below 270 nm, which is sufficient for resolving Raman lines of samples in condensed phase studies. For demonstrating the capability of this tunable setup for UVRR spectroscopy we present its application to the artificial ligand guanidiniocarbonyl pyrrole (GCP), a carboxylate binder used in peptide and protein recognition. A UVRR excitation study in the range 244–310 nm was performed for identifying the optimum laser excitation wavelength for UVRR spectroscopy of this ligand (λ max = 298 nm) at submillimolar concentrations (400 µM) in aqueous solution. The optimum UVRR spectrum is observed for laser excitation with λ exc = 266 nm. Only in the relatively narrow range of λ exc = 266–275 nm UVRR spectra with a sufficiently high signal-to-noise ratio and without severe interference from autofluorescence (AF) were detectable. At longer excitation wavelengths the UVRR signal is masked by AF. At shorter excitation wavelengths the UVRR spectrum is sufficiently separated from the AF, but the resonance enhancement is not sufficient. The presented tunable UVRR setup provides the flexibility to also identify optimum conditions for other supramolecular ligands for peptide/protein recognition. [ABSTRACT FROM AUTHOR]