Biomedical Engineering Reference
In-Depth Information
k
cant
k
eq
k
samp
n k
bond
Single bond
Multiple bonds
Complex bond
FIGURE 5.4
Spring model for interactions between the functionalized AFM tip and the
biological sample. In a series-parallel spring model, a complicate system of molecular inter-
actions is considered as a sophisticated assembly of connected springs. Each “simple” single
bond is modeled by a single spring. If an interaction involves multiple bonds, then this interac-
tion can be represented by multiple parallel springs, and so on. Accordingly, the rupture force
F
rupt
is a function of the number of parallel bonds,
n
and
F
rupt
=
nF
1
where
F
1
is the rupture
force of a single bond. Hypothetically, the modeled spring constant of the biological sample
k
samp
=
nk
bond
where
k
bond
is the spring constant of a single bond corresponding to individual
interaction.
effective loading rates of each event will be extracted from FD curves, it is not neces-
sary in this specific approach to especially target nominal loading rates by combining
well-defined
k
cant
with specific piezo speed values.
5.6 DETECTING RUPTURE EVENTS
FD curves contain a set of data representing distance on the x-axis and cantilever
deflection on the y-axis. These discrete curves are too complicated to be straightfor-
wardly analyzed without prior processing. Small cumulative errors in the analysis
lead to erroneous quantification of the energy landscape parameters (Bjornham &
Schedin, 2009).
The first step in FD curve processing is to import an often proprietary-owned
formatted file. Therefore, a conversion into a human-readable (ASCII) format is often
required as file formats may change from one software version to another (as it is
often seen). A standardization of such intermediate ASCII files is essential so that FD
data sets could be exchanged more easily as suggested in the COST Action TD1002
(COST Action TD1002, 2011).
The second step deals with the calibration of FD curves. For accurate interpre-
tation, it is necessary to recalibrate the Y-axis of FD curves such that the approach
Search WWH ::
Custom Search