Applications of two-dimensional infrared spectroscopy

Abstract

Two-dimensional infrared (2D IR) spectroscopy has recently emerged as a powerful tool with applications in many areas of scientific research. The inherent high time resolution coupled with bond-specific spatial resolution of IR spectroscopy enable direct characterization of rapidly interconverting species and fast processes, even in complex systems found in chemistry and biology. In this minireview, we briefly outline the fundamental principles and experimental procedures of 2D IR spectroscopy. Using illustrative example studies, we explain the important features of 2D IR spectra and their capability to elucidate molecular structure and dynamics. Primarily, this minireview aims to convey the scope and potential of 2D IR spectroscopy by highlighting select examples of recent applications including the use of innate or introduced vibrational probes for the study of nucleic acids, peptides/proteins, and materials.

Figure 1

Simulated example 2D IR spectra and schematic illustrating 2D IR experimental pulse timing, geometry, and detection. Adapted with permission from Zheng et al. Accounts of Chemical Research, 2007, 40, 75–83. Copyright © 2007 American Chemical Society.

Figure 2

Polarization-dependent 2D IR spectra of an equimolar solution of Diels Alder substrate N-crotonyloxazolidinone and catalyst SnCl₄ (see text). Each of the red and green gridlines indicate bands due to a single species. The FTIR spectra are shown above the left panel for the mixture (black), the substrate (green), and the catalyst (red). The structures of the syn conformer of the substrate-catalyst complex and the anti conformer of the substrate are shown below. Adapted from Ref. with permission from the PCCP Owner Societies.

Figure 3

2D IR spectra of a solution of NaNCS and MgI₂ at several waiting times. Reprinted with permission from Sun et al. The Journal of Physical Chemistry B, 2013, 117, 12268 – 12275. Copyright © 2013 American Chemical Society.

Figure 4

2D IR spectra of solutions of sodium nitroprusside in ethylene glycol (upper panels) and water (lower panels) at several waiting times. Adapted with permission from Brookes et al. The Journal of Physical Chemistry A, 2013, 117, 6234 – 6243. Copyright © 2013 American Chemical Society.

Figure 5

Structure and 2D IR spectrum of PEG₄ with azido and succinimide ester reporter labels (T_w of 60 ps). To the left and above the axes of the 2D spectrum are the FTIR spectra of the labeled PEG₄ molecule (blue) and spectra of the laser pulses (green) used to pump and probe the molecule, respectively. Reprinted with permission from Lin, Z. and Rubtsov, I.V. Proceedings of the National Academy of Sciences of the United States of America, 2012, 109, 1413 – 1418.

Figure 6

FTIR spectra of oxythiamine taken at various temperatures (upper panel) and 2D IR spectrum taken at 10 °C (lower panel). Blue and green lines in the 2D spectrum are shown along the frequencies of the carbonyl modes of the two keto tautomers (X1a and X1b). The presence of a cross-band between a mode associated with a methyl vibration (X4) at 1525 cm⁻¹ and the X1a mode, and the absence of one with the X1b, is highlighted with a red ellipse. Reprinted with permission from Singh et al. ACS Chemical Biology, 2014, 9, 227 – 236. Copyright © 2014 American Chemical Society.

Figure 7

Structural model of γD-crystallin illustrating ¹³C-labeled N-terminal (yellow) and unlabeled C-terminal (blue) domains. 2D IR spectra of γD-crystallin labeled with ¹³C at the N-terminus are shown for (A) thermally-induced aggregates, (B) native, and (C) acid-induced aggregates. Reprinted with permission from Moran et al. Protein Science, 2014, 23, 321–331. Copyright © 2014 John Wiley and Sons.

Figure 8

Structural model of HP35 showing residues labeled with CNPhe and 2D IR spectra of CNPhe in folded (upper panels) and guanidium-denatured (lower panels) HP35 at different waiting times. Structural model: Reprinted with permission from Chung et al. The Journal of Physical Chemistry B, 2012, 116, 11024 – 11031. Copyright © 2012 American Chemical Society. 2D IR spectra: Reprinted with permission from Chung et al. Proceedings of the National Academy of Sciences of the United States of America, 2011, 108, 3578 – 3583.

Figure 9

Structural model of a metal-carbonyl vibrational probe attached to hen egg white lysozme and 2D IR spectrum of the metal-carbonyl frequency region. Reprinted with permission from King et al. Journal of the American Chemical Society, 2014, 136, 188 – 194. Copyright © 2014 American Chemical Society.

Figure 10

The structure of Re-carbonyl catalyst attached to a monolayer and example 2D IR spectrum. Rosenfeld et al. Science, 2011, 334, 634 – 639. Copyright © 2011 American Association for the Advancement of Science.