Ultrafast internal rotational dynamics of the azido group in (4S)-azidoproline: Chemical exchange 2DIR spectroscopic investigations

Kyung Koo Lee, Kwang Hee Park, Cheonik Joo, Hyeok Jun Kwon, Hogyu Han, Jeong Hyon Ha, Sungnam Park, Minhaeng Cho

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


The azido group in 4-azidoproline (Azp) derivative, SA (Ac-(4S)-Azp-NHMe), can form an intramolecular electrostatic interaction with the backbone peptide in the s-trans and C γ-endo conformations of SA. As a result, the azido group exists as two forms, bound and free, which are defined by the presence and absence of such interaction, respectively. The bound and free azido forms are spectrally resolved in the azido IR spectrum of SA in CHCl 3. Using the two-dimensional infrared (2DIR) and polarization- controlled IR pump-probe methods, we investigated the internal rotational and orientational relaxation dynamics of the azido group and determined the internal rotational time constant of the azido group to be 5.1 ps. The internal rotational motion is found to be responsible for the early part of the orientational relaxation of the azido group in SA. Thus, the femtosecond 2DIR spectroscopy is shown to be an ideal tool for studying ultrafast conformational dynamics of SA.

Original languageEnglish
Pages (from-to)23-29
Number of pages7
JournalChemical Physics
Issue number1
Publication statusPublished - 2012 Mar 2

Bibliographical note

Funding Information:
This work was supported by the NRF Grant (No. 2010-0005020 ) to S.P., the NRF (No. 2009-0078897 and 2010-0020209) and KBSI (T31401) Grants to M.C., and the NRF (No. 2010-0022070) and KBSI (T31401) grants to H.H.


  • Azido stretch mode
  • Proline dynamics
  • Two-dimensional infrared spectroscopy

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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