Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)

Jimmy Bak, Jens Spanget-Larsen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl4 suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide-amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS2 and CCl4, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl4 solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425cm−1 (ν(N-H)), 1784cm−1 (ν(C&dbnd;O), lactone), 1688cm−1 (amide I), and 1494cm−1 (amide II) (CCl4).
Original languageEnglish
JournalVibrational Spectroscopy
Volume49
Issue number2
Pages (from-to)237-241
ISSN0924-2031
DOIs
Publication statusPublished - 2009

Keywords

  • N-Acyl-homoserine lactones (AHL)
  • Infrared spectroscopy
  • Molecular conformation
  • Intermolecular hydrogen bonding
  • Density functional theory (DFT)

Cite this

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title = "Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)",
abstract = "The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl4 suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide-amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS2 and CCl4, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl4 solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425cm−1 (ν(N-H)), 1784cm−1 (ν(C&dbnd;O), lactone), 1688cm−1 (amide I), and 1494cm−1 (amide II) (CCl4).",
keywords = "N-Acyl-homoserine lactones (AHL), Infrared spectroscopy, Molecular conformation, Intermolecular hydrogen bonding, Density functional theory (DFT)",
author = "Jimmy Bak and Jens Spanget-Larsen",
year = "2009",
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language = "English",
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pages = "237--241",
journal = "Vibrational Spectroscopy",
issn = "0924-2031",
publisher = "Elsevier",
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}

Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL). / Bak, Jimmy; Spanget-Larsen, Jens.

In: Vibrational Spectroscopy, Vol. 49, No. 2, 2009, p. 237-241.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Molecular and vibrational structure of the extracellular bacterial signal compound N-butyryl-homoserine lactone (C4-HSL)

AU - Bak, Jimmy

AU - Spanget-Larsen, Jens

PY - 2009

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N2 - The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl4 suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide-amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS2 and CCl4, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl4 solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425cm−1 (ν(N-H)), 1784cm−1 (ν(C&dbnd;O), lactone), 1688cm−1 (amide I), and 1494cm−1 (amide II) (CCl4).

AB - The molecular and vibrational structure of the title compound (C4-HSL) was studied by experimental and theoretical methods. The infrared (IR) absorption spectrum was measured in the solid state and in CCl4 suspension. The observed absorption bands were compared with transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT) calculations. Two stable molecular conformations were predicted, corresponding to an endo- and an exo-conformer with similar energies. Intermolecular amide-amide hydrogen bonding in the crystal state was approximated by a simple cluster model, leading to excellent agreement with the observed solid state IR spectrum. Due to the low solubility of C4-HSL in common solvents for IR spectroscopy, such as CS2 and CCl4, a liquid solution spectrum of pure, monomeric C4-HSL was not obtained. However, absorbance peaks observed in oversaturated CCl4 solution could be assigned to distinct contributions from suspended micro-crystalline aggregates and dissolved monomeric species. The key vibrational bands of the monomeric form of C4-HSL are reported here for the first time: 3425cm−1 (ν(N-H)), 1784cm−1 (ν(C&dbnd;O), lactone), 1688cm−1 (amide I), and 1494cm−1 (amide II) (CCl4).

KW - N-Acyl-homoserine lactones (AHL)

KW - Infrared spectroscopy

KW - Molecular conformation

KW - Intermolecular hydrogen bonding

KW - Density functional theory (DFT)

U2 - 10.1016/j.vibspec.2008.09.003

DO - 10.1016/j.vibspec.2008.09.003

M3 - Journal article

VL - 49

SP - 237

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SN - 0924-2031

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