Two-Dimensional Infrared Spectroscopy of Photoswitchable Peptides

Abstract

We present a detailed discussion of the complimentary fields of the application of two-dimensional infrared (2D-IR) spectroscopy in comparison with two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy. Transient 2D-IR (T2D-IR) spectroscopy of nonequilibrium ensembles is probably one of the most promising strengths of 2D-IR spectroscopy, as the possibilities of 2D-NMR spectroscopy are limited in this regime. T2D-IR spectroscopy uniquely combines ultrafast time resolution with microscopic structural resolution. In this article we summarize our recent efforts to investigate the ultrafast structural dynamics of small peptides, such as the unfolding of peptide secondary structure motifs. The work requires two ingredients: 2D-IR spectroscopy and the possibility of triggering a structural transition of a peptide on an ultrafast timescale using embedded or intrinsic photoswitches. Several photoswitches have been tested, and we discuss our progress in merging these two pathways of research. AbstractWe present a detailed discussion of the complimentary fields of the application of two-dimensional infrared (2D-IR) spectroscopy in comparison with two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy. Transient 2D-IR (T2D-IR) spectroscopy of nonequilibrium ensembles is probably one of the most promising strengths of 2D-IR spectroscopy, as the possibilities of 2D-NMR spectroscopy are limited in this regime. T2D-IR spectroscopy uniquely combines ultrafast time resolution with microscopic structural resolution. In this article we summarize our recent efforts to investigate the ultrafast structural dynamics of small peptides, such as the unfolding of peptide secondary structure motifs. The work requires two ingredients: 2D-IR spectroscopy and the possibility of triggering a structural transition of a peptide on an ultrafast timescale using embedded or intrinsic photoswitches. Several photoswitches have been tested, and we discuss our progress in merging these two pathways of research.

Direct observation of ground-state lactam–lactim tautomerization using temperature-jump transient 2D IR spectroscopy

“…Nevertheless, the time window for these experiments is limited to the vibrational lifetime of the systems, typically a few picoseconds. To circumvent this limitation, one can perform transient 2D IR (t-2D IR) experiments that follow reequilibration after an abrupt perturbation (25)(26)(27)(28)(29)(30). Our strategy to monitor ground-state reactivity is to perform t-2D IR triggered by a nanosecond T-jump and observe the tautomeric interconversion in real time during the reequilibration.…”

Communication: Probing non-equilibrium vibrational relaxation pathways of highly excited C≡N stretching modes following ultrafast back-electron transfer

“…[7][8][9][10][11][12] Recently, transient two-dimensional infrared spectroscopy has been used to probe vibrational dynamics following electronic excitation in chemical, biological, and material systems. [13][14][15][16][17][18][19][20] Nonlinear IR probes are ideally suited to study energy transfer among coupled vibrational modes in ultrafast charge transfer processes. Cyano-bridged transition metal mixed valence complexes serve as very interesting model systems for probing relaxation dynamics among highly excited vibrational modes populated in <200 fs by ultrafast backelectron transfer (BET).…”

Fast infrared spectroscopy of protein dynamics: advancing sensitivity and selectivity

“…In such an experiment, an actinic pump pulse triggers a non-equilibrium process and a transient 2D IR pulse sequence is used at a later delay time to explore the response of the sample (see Refs. [35][36][37][38] for reviews). Examples include studies of the folding/unfolding of small peptides after the photoreaction of an artificially incorporated molecular group [6, 39,40] or after a temperature jump [9,10].…”