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Hydration of the Zwitterionic and Protonated Forms of Glycine Betaine Probed by Soft X-ray Emission Spectroscopy Coupled with Chemometrics

Ohsawa, Shohei ; Tokushima, Takashi LU and Okada, Kazumasa (2021) In Journal of Physical Chemistry B 125(7). p.1881-1887
Abstract

Soft X-ray absorption and emission spectra of glycine betaine (GB) have been measured at the O K-edge in neutral and strongly acidic solutions. The absorption spectra of the neutral solutions have a resonance peak at 532.6 eV, assigned to the transition to the π∗ orbital, whereas in the acidic solutions, the peak is shifted by -0.3 eV. The emission spectra taken as a function of the GB concentration have been analyzed by means of a modified classical least-squares regression method to obtain the hydration number of the solute. The analysis is successful when the emission spectra have been acquired at the energy of a slightly detuned resonance, giving 28 and 24 as the minimum values for the zwitterionic and protonated GB, respectively.... (More)

Soft X-ray absorption and emission spectra of glycine betaine (GB) have been measured at the O K-edge in neutral and strongly acidic solutions. The absorption spectra of the neutral solutions have a resonance peak at 532.6 eV, assigned to the transition to the π∗ orbital, whereas in the acidic solutions, the peak is shifted by -0.3 eV. The emission spectra taken as a function of the GB concentration have been analyzed by means of a modified classical least-squares regression method to obtain the hydration number of the solute. The analysis is successful when the emission spectra have been acquired at the energy of a slightly detuned resonance, giving 28 and 24 as the minimum values for the zwitterionic and protonated GB, respectively. The number of 28 accords with the reported values for the number of water molecules in the first hydration layer of the zwitterion and is greater than that obtained by other experimental techniques. The obtained numbers are used to discuss the hydration structure of GB with the aid of ab initio molecular orbital calculations. The hydration structure of the protonated form of GB is explored for the first time.

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author
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type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry B
volume
125
issue
7
pages
7 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85101639657
  • pmid:33570403
ISSN
1520-6106
DOI
10.1021/acs.jpcb.0c10712
language
English
LU publication?
no
id
b1bab541-d8cf-44d1-9cf5-cc1638d4e675
date added to LUP
2021-04-07 12:49:19
date last changed
2024-04-06 01:49:54
@article{b1bab541-d8cf-44d1-9cf5-cc1638d4e675,
  abstract     = {{<p>Soft X-ray absorption and emission spectra of glycine betaine (GB) have been measured at the O K-edge in neutral and strongly acidic solutions. The absorption spectra of the neutral solutions have a resonance peak at 532.6 eV, assigned to the transition to the π∗ orbital, whereas in the acidic solutions, the peak is shifted by -0.3 eV. The emission spectra taken as a function of the GB concentration have been analyzed by means of a modified classical least-squares regression method to obtain the hydration number of the solute. The analysis is successful when the emission spectra have been acquired at the energy of a slightly detuned resonance, giving 28 and 24 as the minimum values for the zwitterionic and protonated GB, respectively. The number of 28 accords with the reported values for the number of water molecules in the first hydration layer of the zwitterion and is greater than that obtained by other experimental techniques. The obtained numbers are used to discuss the hydration structure of GB with the aid of ab initio molecular orbital calculations. The hydration structure of the protonated form of GB is explored for the first time. </p>}},
  author       = {{Ohsawa, Shohei and Tokushima, Takashi and Okada, Kazumasa}},
  issn         = {{1520-6106}},
  language     = {{eng}},
  number       = {{7}},
  pages        = {{1881--1887}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of Physical Chemistry B}},
  title        = {{Hydration of the Zwitterionic and Protonated Forms of Glycine Betaine Probed by Soft X-ray Emission Spectroscopy Coupled with Chemometrics}},
  url          = {{http://dx.doi.org/10.1021/acs.jpcb.0c10712}},
  doi          = {{10.1021/acs.jpcb.0c10712}},
  volume       = {{125}},
  year         = {{2021}},
}