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Morphology and molecular conformation in thin films of poly-gamma-methyl-L-glutamate at the air-water interface

Gillgren, H; Stenstam, Anna LU ; Ardhammar, M; Norden, B; Sparr, E and Ulvenlund, Stefan LU (2002) In Langmuir 18(2). p.462-469
Abstract
The behavior of poly-gamma-methyl-L-glutamate (pMeE) at the air-water interface has been studied with the surface film balance technique. In addition, Langmuir-Blodgett (LB) films of pMeE deposited on mica and quartz have been studied by atomic force microscopy (AFM) and circular and linear dichroism (CD and LD) spectroscopy. Depending on the spreading solvent, pMeE displays strikingly different compression isotherms. When spread from chloroform or trifluoroacetic acid (TFA) the surface pressure isotherms are consistent with that of a peptide in a-helix conformation. However, the latter solvent gives rise to isotherms with a considerably smaller apparent mean molecular area, A(0). When spread from pyridine, on the other hand, pMeE yields... (More)
The behavior of poly-gamma-methyl-L-glutamate (pMeE) at the air-water interface has been studied with the surface film balance technique. In addition, Langmuir-Blodgett (LB) films of pMeE deposited on mica and quartz have been studied by atomic force microscopy (AFM) and circular and linear dichroism (CD and LD) spectroscopy. Depending on the spreading solvent, pMeE displays strikingly different compression isotherms. When spread from chloroform or trifluoroacetic acid (TFA) the surface pressure isotherms are consistent with that of a peptide in a-helix conformation. However, the latter solvent gives rise to isotherms with a considerably smaller apparent mean molecular area, A(0). When spread from pyridine, on the other hand, pMeE yields an isotherm that is expanded and inconsistent with the presence of a monolayer consisting entirely of a-helical peptides. Isotherms and AFM images strongly suggest that peptide aggregation and solvent retention are the main factors behind the isotherm differences. When the water-soluble spreading solvent TFA is used, pMeE forms discrete wormlike aggregates embedded in a monolayer matrix. In the pyridine case, aggregation in the spreading solvent and retention of pyridine in the film result in a rough aggregate network coexisting with discrete aggregates. No aggregation takes place when chloroform is used as spreading solvent. CD and LD spectra of the LB films reveal a pronounced lateral orientation of the alpha-helices in films spread from chloroform and TFA, while spectra of films spread from pyridine are consistent with unordered peptide strands in beta-sheet conformation. In conclusion, the results show that if water-soluble and/or low-volatile solvents are used as spreading media, hydrophobic peptides cannot, a priori, be assumed to form proper monolayers. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
18
issue
2
pages
462 - 469
publisher
The American Chemical Society
external identifiers
  • wos:000173423700022
  • scopus:0037154484
ISSN
0743-7463
DOI
10.1021/la011143h
language
English
LU publication?
yes
id
a7b6cd0e-8624-4281-b679-39fe99455cd7 (old id 344394)
date added to LUP
2007-08-20 15:24:12
date last changed
2017-01-01 04:31:32
@article{a7b6cd0e-8624-4281-b679-39fe99455cd7,
  abstract     = {The behavior of poly-gamma-methyl-L-glutamate (pMeE) at the air-water interface has been studied with the surface film balance technique. In addition, Langmuir-Blodgett (LB) films of pMeE deposited on mica and quartz have been studied by atomic force microscopy (AFM) and circular and linear dichroism (CD and LD) spectroscopy. Depending on the spreading solvent, pMeE displays strikingly different compression isotherms. When spread from chloroform or trifluoroacetic acid (TFA) the surface pressure isotherms are consistent with that of a peptide in a-helix conformation. However, the latter solvent gives rise to isotherms with a considerably smaller apparent mean molecular area, A(0). When spread from pyridine, on the other hand, pMeE yields an isotherm that is expanded and inconsistent with the presence of a monolayer consisting entirely of a-helical peptides. Isotherms and AFM images strongly suggest that peptide aggregation and solvent retention are the main factors behind the isotherm differences. When the water-soluble spreading solvent TFA is used, pMeE forms discrete wormlike aggregates embedded in a monolayer matrix. In the pyridine case, aggregation in the spreading solvent and retention of pyridine in the film result in a rough aggregate network coexisting with discrete aggregates. No aggregation takes place when chloroform is used as spreading solvent. CD and LD spectra of the LB films reveal a pronounced lateral orientation of the alpha-helices in films spread from chloroform and TFA, while spectra of films spread from pyridine are consistent with unordered peptide strands in beta-sheet conformation. In conclusion, the results show that if water-soluble and/or low-volatile solvents are used as spreading media, hydrophobic peptides cannot, a priori, be assumed to form proper monolayers.},
  author       = {Gillgren, H and Stenstam, Anna and Ardhammar, M and Norden, B and Sparr, E and Ulvenlund, Stefan},
  issn         = {0743-7463},
  language     = {eng},
  number       = {2},
  pages        = {462--469},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Morphology and molecular conformation in thin films of poly-gamma-methyl-L-glutamate at the air-water interface},
  url          = {http://dx.doi.org/10.1021/la011143h},
  volume       = {18},
  year         = {2002},
}