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Hydrophobic homopolymers of native α-L-amino acids at the air-water interface : A study by circular dichroism spectroscopy, atomic force microscopy, and surface balance experiments

Ulvenlund, Stefan LU ; Gillgren, Helen ; Stenstam, Anna LU ; Bäckman, Per and Sparr, Emma LU (2001) In Journal of Colloid and Interface Science 242(2). p.346-353
Abstract

Films of poly-L-leucine, poly-L-valine, and poly-L-isoleucine have been studied at the air-water interface by surface balance experiments. In addition, Langmuir-Blodgett (LB) films of these polypeptides deposited onto quartz and mica have been studied by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM) to elucidate the effects of polypeptide conformation and spreading agent (chloroform and trifluoroacetic acid, TFA) on film morphology and phase behavior. Monolayers of poly-L-leucine contain α-helical polypeptide strands. When spread from chloroform, the compression isotherm displays a collapse plateau and a limiting molecular area (A0) of 19 Å2 per amino acid residue. The corresponding LB... (More)

Films of poly-L-leucine, poly-L-valine, and poly-L-isoleucine have been studied at the air-water interface by surface balance experiments. In addition, Langmuir-Blodgett (LB) films of these polypeptides deposited onto quartz and mica have been studied by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM) to elucidate the effects of polypeptide conformation and spreading agent (chloroform and trifluoroacetic acid, TFA) on film morphology and phase behavior. Monolayers of poly-L-leucine contain α-helical polypeptide strands. When spread from chloroform, the compression isotherm displays a collapse plateau and a limiting molecular area (A0) of 19 Å2 per amino acid residue. The corresponding LB films are flat and featureless. When a water-soluble solvent (TFA) is used as a spreading agent, the AFM results reveal an extensive formation of polypeptide aggregates. The aggregation is accompanied by a substantial decrease in A0 but has little effect on polypeptide conformation, film compressibility, and phase behavior. According to CD spectroscopy, films of poly-L-valine and poly-L-isoleucine contain polypeptide strands in β-sheet conformation. The corresponding isotherms are steep and lack a collapse plateau. When TFA is used as a spreading agent, the limiting area decreases, but AFM data do not give direct evidence for any aggregation.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aggregation, Atomic force microscopy, CD spectroscopy, Circular dichroism, Compression isotherm, Langmuir-Blodgett film, Molecular monolayer, Poly-L-isoleucine, Poly-L-leucine, Poly-L-valine
in
Journal of Colloid and Interface Science
volume
242
issue
2
pages
8 pages
publisher
Elsevier
external identifiers
  • scopus:0035887834
ISSN
0021-9797
DOI
10.1006/jcis.2001.7789
language
English
LU publication?
yes
id
53fa7be6-4634-4759-b58f-6252e14f447f
date added to LUP
2023-12-07 14:56:08
date last changed
2023-12-08 14:45:39
@article{53fa7be6-4634-4759-b58f-6252e14f447f,
  abstract     = {{<p>Films of poly-L-leucine, poly-L-valine, and poly-L-isoleucine have been studied at the air-water interface by surface balance experiments. In addition, Langmuir-Blodgett (LB) films of these polypeptides deposited onto quartz and mica have been studied by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM) to elucidate the effects of polypeptide conformation and spreading agent (chloroform and trifluoroacetic acid, TFA) on film morphology and phase behavior. Monolayers of poly-L-leucine contain α-helical polypeptide strands. When spread from chloroform, the compression isotherm displays a collapse plateau and a limiting molecular area (A<sub>0</sub>) of 19 Å<sup>2</sup> per amino acid residue. The corresponding LB films are flat and featureless. When a water-soluble solvent (TFA) is used as a spreading agent, the AFM results reveal an extensive formation of polypeptide aggregates. The aggregation is accompanied by a substantial decrease in A<sub>0</sub> but has little effect on polypeptide conformation, film compressibility, and phase behavior. According to CD spectroscopy, films of poly-L-valine and poly-L-isoleucine contain polypeptide strands in β-sheet conformation. The corresponding isotherms are steep and lack a collapse plateau. When TFA is used as a spreading agent, the limiting area decreases, but AFM data do not give direct evidence for any aggregation.</p>}},
  author       = {{Ulvenlund, Stefan and Gillgren, Helen and Stenstam, Anna and Bäckman, Per and Sparr, Emma}},
  issn         = {{0021-9797}},
  keywords     = {{Aggregation; Atomic force microscopy; CD spectroscopy; Circular dichroism; Compression isotherm; Langmuir-Blodgett film; Molecular monolayer; Poly-L-isoleucine; Poly-L-leucine; Poly-L-valine}},
  language     = {{eng}},
  month        = {{10}},
  number       = {{2}},
  pages        = {{346--353}},
  publisher    = {{Elsevier}},
  series       = {{Journal of Colloid and Interface Science}},
  title        = {{Hydrophobic homopolymers of native α-L-amino acids at the air-water interface : A study by circular dichroism spectroscopy, atomic force microscopy, and surface balance experiments}},
  url          = {{http://dx.doi.org/10.1006/jcis.2001.7789}},
  doi          = {{10.1006/jcis.2001.7789}},
  volume       = {{242}},
  year         = {{2001}},
}