Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2003 May 13;100(10):5601-6.
doi: 10.1073/pnas.0931292100. Epub 2003 Apr 22.

Dual-frequency 2D-IR spectroscopy heterodyned photon echo of the peptide bond

Igor V Rubtsov  1 , Jianping Wang, Robin M Hochstrasser
Affiliations

Dual-frequency 2D-IR spectroscopy heterodyned photon echo of the peptide bond

Igor V Rubtsov et al. Proc Natl Acad Sci U S A. .

Abstract

The structure fluctuations of the peptide bond interacting with solvent are examined through the coupling and correlations of the frequency distributions of amide I and amide II transitions. The fluctuations of the two modes are anticorrelated as a result of the solvent-induced changes in the mixing of the dominant valence-bond structures of the peptide. Significant anharmonic coupling of the two modes is seen. The results are the application of a new approach to two-dimensional infrared (2D-IR) spectroscopy in which the pulse sequences used to produce the vibrational echoes incorporate two frequencies. This dual-frequency arrangement greatly extends the capabilities of 2D-IR spectroscopy by allowing the coupling between widely separated modes to be characterized in analogy with heteronuclear NMR. The experiment exposes the cross peaks, representing the mode coupling, free of the interference of the strong diagonal peaks that typically dominate 2D-IR spectroscopy. The alignment and dephasing of coupled transitions, in this example the amide I and amide II transition dipoles, is also determined by these experiments.

PubMed Disclaimer

Figures

Figure 1
Figure 1
(Upper) Time sequence of the dual-frequency three-pulse photon-echo experiment. S (dashed line) is a typical signal envelope. LO denotes the local oscillator pulse. (Lower) The spatial arrangement of the three beams interacting with the sample. The pulse intervals used in the text are indicated. The signal envelope is observed in the k1 − k2 + k3 direction.
Figure 2
Figure 2
The linear spectrum on an optical density (OD) scale of NMA in DMSO. The laser spectra centered near ωI and ωII are shown also. LO, local oscillator pulse.
Figure 3
Figure 3
Liouville pathways contributing to the cross peak in the rephasing (R1 and R2) and nonrephasing (R3 and R4) IR-pulse sequences.
Figure 4
Figure 4
Absolute magnitude spectra of NMA in DMSO obtained for rephasing (a) and nonrephasing (b) dual-frequency 2D-IR spectroscopy. Symbols are as defined in Modeling the 2D-IR Spectra.
Figure 5
Figure 5
Real part of 2D-IR spectra of NMA for rephasing (a) and nonrephasing (b) sequences.
Figure 6
Figure 6
Absorptive dual-frequency 2D-IR spectra simulated to illustrate the effect of frequency correlations of the two vibrators included. The correlation factors are −1 (a), 0 (b), and +1 (c). The parameters for the vibrators are close to those of the amide I and amide II modes of NMA in DMSO.
Figure 7
Figure 7
Dual-frequency 2D-IR cross-peak spectra of NMA in DMSO: experiment (a) and simulated (b). The solid line is the diagonal of the 2D-IR spectrum (ωτ = ωt).
Figure 8
Figure 8
The diagonal 2D-IR spectra in the amide II region of NMA in DMSO. The solid line is ωτ = ωt.
Figure 9
Figure 9
The dominant valence-bond structures of NMA.
See this image and copyright information in PMC

References

    1. Hamm P, Lim M, Hochstrasser R M. J Phys Chem B. 1998;102:6123–6138.
    1. Asplund M C, Zanni M T, Hochstrasser R M. Proc Natl Acad Sci USA. 2000;97:8219–8224. - PMC - PubMed
    1. Hamm P, Lim M, DeGrado W F, Hochstrasser R M. J Chem Phys. 2000;112:1907–1916.
    1. Zanni M T, Asplund M C, Hochstrasser R M. J Chem Phys. 2001;114:4579–4590.
    1. Ge N-H, Hochstrasser R M. Phys Chem Commun. 2002;3:1–10.

Publication types

LinkOut - more resources