Methyl groups of trimethylamine N-oxide orient away from hydrophobic interfaces

Laura B. Sagle, Katherine Cimatu, Vladislav A. Litosh, Yi Liu, Sarah C. Flores, Xin Chen, Bin Yu, Paul S. Cremer

Research output: Contribution to journalArticle

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Abstract

The molecular orientation of trimethylamine N-oxide (TMAO), a powerful protein stabilizer, was explored at aqueous/hydrophobic interfaces using vibrational sum frequency spectroscopy (VSFS). The systems studied included the octadecyltrichlorosilane (OTS)/water interface, which represents an aqueous solution in direct contact with a hydrophobic medium. Surprisingly, the measurements revealed that the methyl groups of TMAO pointed into the aqueous phase and away from the OTS. This orientation may arise from the more hydrophilic nature of methyl groups attached to a strongly electron-withdrawing atom such as a quaternary nitrogen. Additional studies were performed at the air/water interface. This interface showed a high degree of TMAO alignment, but the dangling OH from water was present even at 5 M TAMO. Moreover, the addition of this osmolyte modestly increased the surface tension of the interface. This meant that this species was somewhat depleted at the interface compared to the bulk solution. These findings may have implications for the stabilizing effect of TMAO on proteins. Specifically, the strong hydration required for the methyl groups as well as the oxide moiety should be responsible for the osmolyte's depletion from hydrophobic/aqueous interfaces. Such depletion effects should help stabilize proteins in their folded and native conformations on entropic grounds, although orientational effects may play an additional role.

Original languageEnglish (US)
Pages (from-to)18707-18712
Number of pages6
JournalJournal of the American Chemical Society
Volume133
Issue number46
DOIs
StatePublished - Nov 23 2011

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Oxides
Water
Proteins
Surface Tension
Molecular orientation
Vibrational spectra
Spectrum Analysis
Nitrogen
Hydration
Contacts (fluid mechanics)
Air
Surface tension
Electrons
Conformations
trimethyloxamine
Spectroscopy
Atoms
octadecyltrichlorosilane
14-thioglycolamido-7,8-dihydromorphinone

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Sagle, Laura B. ; Cimatu, Katherine ; Litosh, Vladislav A. ; Liu, Yi ; Flores, Sarah C. ; Chen, Xin ; Yu, Bin ; Cremer, Paul S. / Methyl groups of trimethylamine N-oxide orient away from hydrophobic interfaces. In: Journal of the American Chemical Society. 2011 ; Vol. 133, No. 46. pp. 18707-18712.
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Sagle, LB, Cimatu, K, Litosh, VA, Liu, Y, Flores, SC, Chen, X, Yu, B & Cremer, PS 2011, 'Methyl groups of trimethylamine N-oxide orient away from hydrophobic interfaces', Journal of the American Chemical Society, vol. 133, no. 46, pp. 18707-18712. https://doi.org/10.1021/ja205106e

Methyl groups of trimethylamine N-oxide orient away from hydrophobic interfaces. / Sagle, Laura B.; Cimatu, Katherine; Litosh, Vladislav A.; Liu, Yi; Flores, Sarah C.; Chen, Xin; Yu, Bin; Cremer, Paul S.

In: Journal of the American Chemical Society, Vol. 133, No. 46, 23.11.2011, p. 18707-18712.

Research output: Contribution to journalArticle

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AU - Sagle, Laura B.

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AU - Litosh, Vladislav A.

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AU - Chen, Xin

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