Biology Reference
In-Depth Information
The rates of mass change owing to the formation of the peptide
monolayer on the substrates were extracted using the Langmuir
isotherms [1]. The overall adsorption rate is influenced by both
association and dissociation processes. Figure 12.1 shows an
example concentration dependency of the adsorption rate that can
be estimated by a linear fit to determine both adsorption (slope)
and desorption (intercept) rates. Adsorption and desorption
values provide a quantitative measure of binding energetics, which
were used to evaluate the affinity of GBP1 to a given material. The
standard Gibbs free energy, estimated from the ratio of adsorption
to desorption rate, is a measure of the binding strength. Table 12.1
summarizes the parameters for adsorption kinetics of GBP1 on Pt
and Au surfaces.
was revealed to be double for Au
compared to that of Pt. The desorption coefficient
The adsorption constant
k
a
is about one
order of magnitude larger for GBP1 binding to Pt than binding to Au.
Therefore, GBP1 adsorption onto Au is much stronger, and desorption
from Au is much weaker compared to Pt. Furthermore, the standard
free energy values imply a significantly more stable interface for
the peptide binding to Au. Also, it was found that surface coverage
happens more rapidly for the Au substrate than the Pt substrate [1].
k
d
Table 12.1
Adsorption kinetics for GBP1 and metal substrates with the
equilibrium constant (
). Reproduced with permission
from Ref. [1]. Copyright Wiley-VCH Verlag GmbH & Co.
KGaA.
K
eq
Substrate
k
a
±
95% C.I. [M
-1
s
-1
]
k
d
±
95% C.I. [M
-1
s
-1
]
K
eq
[M
-1
]
±
×
10
3
±
×
−
4
±
×
10
7
Gold
(3.49
0.30)
(3.12
1.86)
10
(1.12
0.67)
±
×
10
3
±
×
−
3
±
×
10
6
Platinum
(1.65
0.41)
(1.57
0.35)
10
(1.05
0.35)
was chosen
to evaluate the direct assembly of GBP1 on Au, as compared to the
oxide surface. Selective adsorption onto various present substrate
materials is essential for applications such as nanostructure
assembly on different inorganic surfaces, molecularly functionalized
substrates, or direct immobilization. GBP1 was biotinylated (bio-
GBP1) before incubation on the substrate. Streptavidin-conjugated
light-emitting quantum dots (SAQDs), subsequently introduced to
A test pattern composed of microscale Au lines on SiO
2
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