Molecular dynamics simulation of the cooperative adsorption of barley lipid transfer protein and cis-isocohumulone at the vacuum-water interface

S. R. Euston, P. Hughes, Md A. Naser, R. E. Westacott

Research output: Contribution to journalArticle

Abstract

Molecular dynamic simulations have been carried out on systems containing a mixture of barley lipid transfer protein (LTP) and cis-isocohumulone (a hop derived iso-a-acid) in one of its enol forms, in bulk water and at the vacuum-water interface. In solution, the cis-isocohumulone molecules bind to the surface of the LTP molecule. The mechanism of binding appears to be purely hydrophobic in nature via desolvation of the protein surface. Binding of hop acids to the LTP leads to a small change in the 3-D conformation of the protein, but no change in the proportion of secondary structure present in helices, even though there is a significant degree of hop acid binding to the helical regions. At the vacuum-water interface, cis-isocohumulone shows a high surface activity and adsorbs rapidly at the interface. LTP then shows a preference to bind to the preadsorbed hop acid layer at the interface rather than to the bare water-vacuum interface. The free energy of adsorption of LTP at the hop- vacuum-water interface is more favorable than for adsorption at the vacuum-water interface. Our results support the view that hop iso-a-acids promote beer foam stability by forming bridges between separate adsorbed protein molecules, thus strengthening the adsorbed protein layer and reducing foam breakdown by lamellar phase drainage. The results also suggest a second mechanism may also occur, whereby the concentration of protein at the interface is increased via enhanced protein adsorption to adsorbed hop acid layers. This too would increase foam stability through its effect on the stabilizing protein layer around the foam bubbles. © 2008 American Chemical Society.

Original languageEnglish
Pages (from-to)3024-3032
Number of pages9
JournalBiomacromolecules
Volume9
Issue number11
Early online date9 Oct 2008
DOIs
Publication statusPublished - 10 Nov 2008

Fingerprint

Humulus
Hordeum
Molecular Dynamics Simulation
Vacuum
Adsorption
Water
Acids
Proteins
Protein Conformation
isocohumulone
lipid transfer protein
Drainage
Membrane Proteins

Cite this

@article{ef57e5d391664b76bfcf131758bf136d,
title = "Molecular dynamics simulation of the cooperative adsorption of barley lipid transfer protein and cis-isocohumulone at the vacuum-water interface",
abstract = "Molecular dynamic simulations have been carried out on systems containing a mixture of barley lipid transfer protein (LTP) and cis-isocohumulone (a hop derived iso-a-acid) in one of its enol forms, in bulk water and at the vacuum-water interface. In solution, the cis-isocohumulone molecules bind to the surface of the LTP molecule. The mechanism of binding appears to be purely hydrophobic in nature via desolvation of the protein surface. Binding of hop acids to the LTP leads to a small change in the 3-D conformation of the protein, but no change in the proportion of secondary structure present in helices, even though there is a significant degree of hop acid binding to the helical regions. At the vacuum-water interface, cis-isocohumulone shows a high surface activity and adsorbs rapidly at the interface. LTP then shows a preference to bind to the preadsorbed hop acid layer at the interface rather than to the bare water-vacuum interface. The free energy of adsorption of LTP at the hop- vacuum-water interface is more favorable than for adsorption at the vacuum-water interface. Our results support the view that hop iso-a-acids promote beer foam stability by forming bridges between separate adsorbed protein molecules, thus strengthening the adsorbed protein layer and reducing foam breakdown by lamellar phase drainage. The results also suggest a second mechanism may also occur, whereby the concentration of protein at the interface is increased via enhanced protein adsorption to adsorbed hop acid layers. This too would increase foam stability through its effect on the stabilizing protein layer around the foam bubbles. {\circledC} 2008 American Chemical Society.",
author = "Euston, {S. R.} and P. Hughes and Naser, {Md A.} and Westacott, {R. E.}",
year = "2008",
month = "11",
day = "10",
doi = "10.1021/bm8004325",
language = "English",
volume = "9",
pages = "3024--3032",
journal = "Biomacromolecules",
issn = "1525-7797",
publisher = "American Chemical Society",
number = "11",

}

Molecular dynamics simulation of the cooperative adsorption of barley lipid transfer protein and cis-isocohumulone at the vacuum-water interface. / Euston, S. R.; Hughes, P.; Naser, Md A.; Westacott, R. E.

In: Biomacromolecules, Vol. 9, No. 11, 10.11.2008, p. 3024-3032.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Molecular dynamics simulation of the cooperative adsorption of barley lipid transfer protein and cis-isocohumulone at the vacuum-water interface

AU - Euston, S. R.

AU - Hughes, P.

AU - Naser, Md A.

AU - Westacott, R. E.

PY - 2008/11/10

Y1 - 2008/11/10

N2 - Molecular dynamic simulations have been carried out on systems containing a mixture of barley lipid transfer protein (LTP) and cis-isocohumulone (a hop derived iso-a-acid) in one of its enol forms, in bulk water and at the vacuum-water interface. In solution, the cis-isocohumulone molecules bind to the surface of the LTP molecule. The mechanism of binding appears to be purely hydrophobic in nature via desolvation of the protein surface. Binding of hop acids to the LTP leads to a small change in the 3-D conformation of the protein, but no change in the proportion of secondary structure present in helices, even though there is a significant degree of hop acid binding to the helical regions. At the vacuum-water interface, cis-isocohumulone shows a high surface activity and adsorbs rapidly at the interface. LTP then shows a preference to bind to the preadsorbed hop acid layer at the interface rather than to the bare water-vacuum interface. The free energy of adsorption of LTP at the hop- vacuum-water interface is more favorable than for adsorption at the vacuum-water interface. Our results support the view that hop iso-a-acids promote beer foam stability by forming bridges between separate adsorbed protein molecules, thus strengthening the adsorbed protein layer and reducing foam breakdown by lamellar phase drainage. The results also suggest a second mechanism may also occur, whereby the concentration of protein at the interface is increased via enhanced protein adsorption to adsorbed hop acid layers. This too would increase foam stability through its effect on the stabilizing protein layer around the foam bubbles. © 2008 American Chemical Society.

AB - Molecular dynamic simulations have been carried out on systems containing a mixture of barley lipid transfer protein (LTP) and cis-isocohumulone (a hop derived iso-a-acid) in one of its enol forms, in bulk water and at the vacuum-water interface. In solution, the cis-isocohumulone molecules bind to the surface of the LTP molecule. The mechanism of binding appears to be purely hydrophobic in nature via desolvation of the protein surface. Binding of hop acids to the LTP leads to a small change in the 3-D conformation of the protein, but no change in the proportion of secondary structure present in helices, even though there is a significant degree of hop acid binding to the helical regions. At the vacuum-water interface, cis-isocohumulone shows a high surface activity and adsorbs rapidly at the interface. LTP then shows a preference to bind to the preadsorbed hop acid layer at the interface rather than to the bare water-vacuum interface. The free energy of adsorption of LTP at the hop- vacuum-water interface is more favorable than for adsorption at the vacuum-water interface. Our results support the view that hop iso-a-acids promote beer foam stability by forming bridges between separate adsorbed protein molecules, thus strengthening the adsorbed protein layer and reducing foam breakdown by lamellar phase drainage. The results also suggest a second mechanism may also occur, whereby the concentration of protein at the interface is increased via enhanced protein adsorption to adsorbed hop acid layers. This too would increase foam stability through its effect on the stabilizing protein layer around the foam bubbles. © 2008 American Chemical Society.

UR - http://www.scopus.com/inward/record.url?scp=57049132826&partnerID=8YFLogxK

U2 - 10.1021/bm8004325

DO - 10.1021/bm8004325

M3 - Article

C2 - 18842056

VL - 9

SP - 3024

EP - 3032

JO - Biomacromolecules

JF - Biomacromolecules

SN - 1525-7797

IS - 11

ER -