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Interactions of algal spores and diatoms with mixed synthetic peptide SAMs.

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Interactions of algal spores and diatoms with mixed synthetic peptide SAMs.
Interactions of algal spores and diatoms
with mixed synthetic peptide SAMs.
T. Ederth*, P. Nygren, T. Ekblad,
M. Östblom, B. Liedberg
Division of Molecular Physics, Department of Physics,
chemistry and biology, Linköpings Universitet,
SE-581 83 Linköping, Sweden, * [email protected]
M. E. Pettitt, M. E. Callow, J. A. Callow
The University of Birmingham, School of Biosciences,
Birmingham B15 2TT, UK
Advanced nanostructured surfaces
for the control of biofouling
http://www.ambio.bham.ac.uk/
The problem – marine biofouling
Marine biofouling incurs additional costs and
environmental impact on the operation of vessels,
heat exchangers, fishing equipment, desalination
plants and many other facilities, by reduced
efficency and increased fuel consumption.
There are about 2500 fouling marine organisms,
using a broad range of settlement strategies and
bioadhesives. We study the interactions between
surfaces and marine organisms in terms of
physicochemical cues, in order to understand
settlement behaviour and ultimately to improve
anti-fouling properties of surfaces.
Mixed peptide SAMs
A synthetic cationic arginine-rich peptide is used to form
mixed SAMs on gold substrates (via a thiol linker), with a
shorter spacer molecule. IRAS, wetting and ellipsometry data
demonstrate that the peptides form organised monolayers.
Mol-%
ArgTyr
Thickness
(Å)
Contact
angles (θ
θa)
0%
13.1
41°
5%
16.5
46°
H2N
ArgTyr
O
20%
16.8
47°
50%
21.5
51°
75%
23.3
52°
100%
26.2
44°
O
H
N
H2 N
O
HS
NH
O
H
N
N
H
O
N
H
H2 N
O
H
N
N
H
H2N
HS
H2N
O
O
H
N
N
H
O
H
N
O
N
H
HO
O
H
N
NH
HN
O
HO
O
Gly3 spacer
NH
HN
O
HO
Thiol ”anchor”
NH
HN
( θr < 10 for all mixtures )
Biological tests
H2N
HN
N
H
O
H
N
O
N
H
1
Normalized peak area
Absorbance
We have studied the attachment of a major ship
fouling alga (Ulva) and a diatom (Navicula) to
the mixed peptide SAMs.
Solution
Mol-%
ArgTyr
100%
75%
50%
20%
5%
0.8
0.6
0.4
0.2
0%
1800
Spores
Ulva linza
Navicula perminuta
Ulva plants release spores which swim with the aid
of flagella. As a suitable surface for settlement is
located, a physiological change into a plant is
started. Ulva spores lack cell walls, and expose the
plasma membrane to the environment, while the
Navicula cells are encased within a silica cell wall.
The peptide SAMs were incubated in Ulva spores
or Navicula cells for 1 h, whereupon the density of
settled (attached) cells was determined.
Incubation assay
-2
Spores (mm )
2000
ArgTyr
Arg
Tyr
Gly
1500
1000
500
0
0
20
40
60
80
100
Peptide concentration (µM)
Up to 20 µM, free
ArgTyr peptides in
solution stimulate the
settlement of Ulva
spores. Above 20µM,
spores lysed (died).
No such effects were
observed for the free
amino acids of which
the ArgTyr peptide is
composed.
0
1000
0
20
40
60
80
100
% ArgTyr in solution
FTIR data for mixed ArgTyr/spacer SAMs. Peak areas within the
shaded region were used to estimate the surface fraction of the
ArgTyr peptide for different solution fractions (right).
Settlement results
The density of settled Ulva spores increases with bound ArgTyr
content but many of the 'settled' spores retained their flagella
indicating that they had not gone through the normal settlement
process; these spores probably died. Navicula cells, however,
are unaffected by the presence of the ArgTyr peptide; cell
attachment is not altered and no cells died. This difference is
probably due to the diatom cell wall preventing the bound ArgTyr
peptide from contacting the plasma membrane.
300
Spores per mm2
Plant
1600 1400 1200
Wavenumber (cm-1)
Total Ulva spores
250
5 µm
With flagella
200
Dead spores
150
100
50
0
0
5
20
50
75
Mol-% ArgTyr on surface
100
Normally settled (A) and
‘stuck’ (B) spores, with
flagella still attached.
Summary: The ArgTyr peptide interacts specifically with Ulva cell membranes, promoting adhesion to a surface,
but also preventing it from going through its normal settlement physiology, and ultimately causing cell death.
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