Hofmeister anionic effects on hydration electric fields around water and peptide

Heejae Kim, Hochan Lee, Gayeon Lee, Haeyoung Kim, Minhaeng Cho

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Specific ion effects on water dynamics and local solvation structure around a peptide are important in understanding the Hofmeister series of ions and their effects on protein stability in aqueous solution. Water dynamics is essentially governed by local hydrogen-bonding interactions with surrounding water molecules producing hydration electric field on each water molecule. Here, we show that the hydration electric field on the OD bond of HOD molecule in water can be directly estimated by measuring its OD stretch infrared (IR) radiation frequency shift upon increasing ion concentration. For a variety of electrolyte solutions containing Hofmeister anions, we measured the OD stretch IR bands and estimated the hydration electric field on the OD bond to be about a hundred MVcm with standard deviation of tens of MVcm. As anion concentration increases from 1 to 6 M, the hydration electric field on the OD bond decreases by about 10, indicating that the local H-bond network is partially broken by dissolved ions. However, the measured hydration electric fields on the OD bond and its fluctuation amplitudes for varying anions are rather independent on whether the anion is a kosmotrope or a chaotrope. To further examine the Hofmeister effects on H-bond solvation structure around a peptide bond, we examined the amide I′ and II′ mode frequencies of N-methylacetamide in various electrolyte D 2O solutions. It is found that the two amide vibrational frequencies are not affected by ions, indicating that the H-bond solvation structure in the vicinity of a peptide remains the same irrespective of the concentration and character of ions. The present experimental results suggest that the Hofmeister anionic effects are not caused by direct electrostatic interactions of ions with peptide bond or water molecules in its first solvation shell. Furthermore, even though the H-bond network of water is affected by ions, thus induced change of local hydration electric field on the OD bond of HOD is not in good correlation with the well-known Hofmeister series. We anticipate that the present experimental results provide an important clue about the Hofmeister effect on protein structure and present a discussion on possible alternative mechanisms.

Original languageEnglish
Article number124501
JournalJournal of Chemical Physics
Volume136
Issue number12
DOIs
Publication statusPublished - 2012 Mar 28

Fingerprint

Hydration
peptides
hydration
Electric fields
Ions
Peptides
electric fields
Water
Solvation
solvation
water
Anions
ions
anions
Molecules
amides
molecules
Amides
Electrolytes
electrolytes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry
  • Medicine(all)

Cite this

Hofmeister anionic effects on hydration electric fields around water and peptide. / Kim, Heejae; Lee, Hochan; Lee, Gayeon; Kim, Haeyoung; Cho, Minhaeng.

In: Journal of Chemical Physics, Vol. 136, No. 12, 124501, 28.03.2012.

Research output: Contribution to journalArticle

Kim, Heejae ; Lee, Hochan ; Lee, Gayeon ; Kim, Haeyoung ; Cho, Minhaeng. / Hofmeister anionic effects on hydration electric fields around water and peptide. In: Journal of Chemical Physics. 2012 ; Vol. 136, No. 12.
@article{32bb6d27b94d481882826298ceaf974b,
title = "Hofmeister anionic effects on hydration electric fields around water and peptide",
abstract = "Specific ion effects on water dynamics and local solvation structure around a peptide are important in understanding the Hofmeister series of ions and their effects on protein stability in aqueous solution. Water dynamics is essentially governed by local hydrogen-bonding interactions with surrounding water molecules producing hydration electric field on each water molecule. Here, we show that the hydration electric field on the OD bond of HOD molecule in water can be directly estimated by measuring its OD stretch infrared (IR) radiation frequency shift upon increasing ion concentration. For a variety of electrolyte solutions containing Hofmeister anions, we measured the OD stretch IR bands and estimated the hydration electric field on the OD bond to be about a hundred MVcm with standard deviation of tens of MVcm. As anion concentration increases from 1 to 6 M, the hydration electric field on the OD bond decreases by about 10, indicating that the local H-bond network is partially broken by dissolved ions. However, the measured hydration electric fields on the OD bond and its fluctuation amplitudes for varying anions are rather independent on whether the anion is a kosmotrope or a chaotrope. To further examine the Hofmeister effects on H-bond solvation structure around a peptide bond, we examined the amide I′ and II′ mode frequencies of N-methylacetamide in various electrolyte D 2O solutions. It is found that the two amide vibrational frequencies are not affected by ions, indicating that the H-bond solvation structure in the vicinity of a peptide remains the same irrespective of the concentration and character of ions. The present experimental results suggest that the Hofmeister anionic effects are not caused by direct electrostatic interactions of ions with peptide bond or water molecules in its first solvation shell. Furthermore, even though the H-bond network of water is affected by ions, thus induced change of local hydration electric field on the OD bond of HOD is not in good correlation with the well-known Hofmeister series. We anticipate that the present experimental results provide an important clue about the Hofmeister effect on protein structure and present a discussion on possible alternative mechanisms.",
author = "Heejae Kim and Hochan Lee and Gayeon Lee and Haeyoung Kim and Minhaeng Cho",
year = "2012",
month = "3",
day = "28",
doi = "10.1063/1.3694036",
language = "English",
volume = "136",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "12",

}

TY - JOUR

T1 - Hofmeister anionic effects on hydration electric fields around water and peptide

AU - Kim, Heejae

AU - Lee, Hochan

AU - Lee, Gayeon

AU - Kim, Haeyoung

AU - Cho, Minhaeng

PY - 2012/3/28

Y1 - 2012/3/28

N2 - Specific ion effects on water dynamics and local solvation structure around a peptide are important in understanding the Hofmeister series of ions and their effects on protein stability in aqueous solution. Water dynamics is essentially governed by local hydrogen-bonding interactions with surrounding water molecules producing hydration electric field on each water molecule. Here, we show that the hydration electric field on the OD bond of HOD molecule in water can be directly estimated by measuring its OD stretch infrared (IR) radiation frequency shift upon increasing ion concentration. For a variety of electrolyte solutions containing Hofmeister anions, we measured the OD stretch IR bands and estimated the hydration electric field on the OD bond to be about a hundred MVcm with standard deviation of tens of MVcm. As anion concentration increases from 1 to 6 M, the hydration electric field on the OD bond decreases by about 10, indicating that the local H-bond network is partially broken by dissolved ions. However, the measured hydration electric fields on the OD bond and its fluctuation amplitudes for varying anions are rather independent on whether the anion is a kosmotrope or a chaotrope. To further examine the Hofmeister effects on H-bond solvation structure around a peptide bond, we examined the amide I′ and II′ mode frequencies of N-methylacetamide in various electrolyte D 2O solutions. It is found that the two amide vibrational frequencies are not affected by ions, indicating that the H-bond solvation structure in the vicinity of a peptide remains the same irrespective of the concentration and character of ions. The present experimental results suggest that the Hofmeister anionic effects are not caused by direct electrostatic interactions of ions with peptide bond or water molecules in its first solvation shell. Furthermore, even though the H-bond network of water is affected by ions, thus induced change of local hydration electric field on the OD bond of HOD is not in good correlation with the well-known Hofmeister series. We anticipate that the present experimental results provide an important clue about the Hofmeister effect on protein structure and present a discussion on possible alternative mechanisms.

AB - Specific ion effects on water dynamics and local solvation structure around a peptide are important in understanding the Hofmeister series of ions and their effects on protein stability in aqueous solution. Water dynamics is essentially governed by local hydrogen-bonding interactions with surrounding water molecules producing hydration electric field on each water molecule. Here, we show that the hydration electric field on the OD bond of HOD molecule in water can be directly estimated by measuring its OD stretch infrared (IR) radiation frequency shift upon increasing ion concentration. For a variety of electrolyte solutions containing Hofmeister anions, we measured the OD stretch IR bands and estimated the hydration electric field on the OD bond to be about a hundred MVcm with standard deviation of tens of MVcm. As anion concentration increases from 1 to 6 M, the hydration electric field on the OD bond decreases by about 10, indicating that the local H-bond network is partially broken by dissolved ions. However, the measured hydration electric fields on the OD bond and its fluctuation amplitudes for varying anions are rather independent on whether the anion is a kosmotrope or a chaotrope. To further examine the Hofmeister effects on H-bond solvation structure around a peptide bond, we examined the amide I′ and II′ mode frequencies of N-methylacetamide in various electrolyte D 2O solutions. It is found that the two amide vibrational frequencies are not affected by ions, indicating that the H-bond solvation structure in the vicinity of a peptide remains the same irrespective of the concentration and character of ions. The present experimental results suggest that the Hofmeister anionic effects are not caused by direct electrostatic interactions of ions with peptide bond or water molecules in its first solvation shell. Furthermore, even though the H-bond network of water is affected by ions, thus induced change of local hydration electric field on the OD bond of HOD is not in good correlation with the well-known Hofmeister series. We anticipate that the present experimental results provide an important clue about the Hofmeister effect on protein structure and present a discussion on possible alternative mechanisms.

UR - http://www.scopus.com/inward/record.url?scp=84859545775&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84859545775&partnerID=8YFLogxK

U2 - 10.1063/1.3694036

DO - 10.1063/1.3694036

M3 - Article

C2 - 22462868

AN - SCOPUS:84859545775

VL - 136

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 12

M1 - 124501

ER -