Global Analysis of Fluorescence and Anisotropy decays [1, 2, 4] can be done by either MLE with Poissonian statistics of the noise
or Least-Squares methods [3].
Deconvolution via Instrumental response function:
Deconvolution via one-exponential Reference compound:
where:
I(t) is impulse response function of
the sample;
g(t) is measured Instrumental response
function (IRF);
fref(t)
is measured one-exponential reference
compound;
B(t)
is measured background;
D denotes the
time shift between sample
decay and IRF;
b is time-uncorrelated
background in the IRF or Reference compound;
g
is background multiplication factor;
c is time-uncorrelated background in
the sample decay;
n is
scattered light coefficient;
tref
is decay time of reference compound;
are fit parameters and
d(t)
is Dirac delta-function.
Complete deconvolution for analysis of multi-excitation decays is also
supported.
The detailed protocol of the global analysis, programmed in TRFA Data Processor, is published in [4].
- Multi-exponential
model for fluorescence decays
- Multi-exponential
model for anisotropy decays
The form of the multi-exponential model depends on the model
property Fluor Parameters Type, which can be either “Amplitudes
and decay times” or “Contributions and decay times” or “Ratio
and decay times”.
Switching between amplitudes and contributions is controlled by
Normalization property of the multi-exponential model and can
be done independently for positive and negative pre-exponential
factors.
-
Associative and
non-associative models for anisotropy
Two approaches for performing of anisotropy analysis are supported:
1. Two stage anisotropy analysis based on a sequential fit of the measured
sample total fluorescence decay and the measured sample parallel and
perpendicular polarization components to the
multi-exponential model.
2. The anisotropy analysis based on a direct global fit of the sample parallel
and perpendicular polarization components.
This approach also supports an associative anisotropy analysis. The
fluorescence decay is calculated accordingly to the following equation:
where A is the normalization parameter;
aj and
tj are, respectively, contributions and decay times of
the corresponding fluorescence exponents;
Q is the polarization angle,
bk and
jk are, respectively, the amplitudes and rotational
correlation times of the corresponding anisotropy exponents and Tjk
controls the associations.
- Two compartmental
models
Fit parameters:
D
- the normalization parameter;
ci
- the emission weighting factor of species i* (i=1,2);
bi
- the concentration of species i* (i=1,2) at time zero;
k0i -
the composite rate constant of species i* (i=1,2);
k12 -
first-order rate constant for dissociation of 2* into 1* and
co-reactant;
k21 -
second-order rate constant for the association of 1* and co-reactant
to 2*.
-
Three compartmental
models
Fit parameters:
D
- the normalization parameter;
ci
- the emission weighting factor of species i* (i=1,…,3);
bi
- the concentration of species i* (i=1,…,3) at time zero;
k0i -
the composite rate constant of species i* (i=1,…,3);
k1i -
first-order rate constant for dissociation of i* (i=2,3) into 1* and co-reactant;
ki1 -
second-order rate constant for the association of 1* and co-reactant to i* (i=2,3).
k23 -
interconversion rate constant from state 3* to 2*;
k32 -
interconversion rate constant from state 2* to 3*.
- Poisson distribution
of decay rates model
Fit parameters:
A
- the normalization parameter;
l1 -
the inverted decay time of first fluorescence component in
absence of energy transfer or other quenching;
b1 -
quenching efficiency of first fluorescence component;
m
- average number of quenchers;
e
- rate of quenching for a
probe interacting with one quencher;
a
- the relative contribution
of second fluorescence component;
l2 -
the inverted decay time of second fluorescence component in
absence of energy transfer or other quenching.
- Gaussian distribution
of decay rates model
Fit parameters:
A
- the normalization parameter;
s
- standard deviation on decay rate;
m
- average decay rate; k0
- minimum decay rate;
a
- the relative contribution of second
fluorescence component;
l2 -
the inverted decay time of second fluorescence component.
Modular object-oriented architecture
allows for easy extension
of the model library
|