5. Operating the INFINITE M1000 PRO
2011-09
Instructions for Use for INFINITE M1000 PRO No. 30064852 Rev. No. 1.0
67
5.6 Optimize
AlphaScreen/AlphaLISA
5.6.1 Excitation
Time
The excitation time defines the duration of the sample illumination by the laser.
Optimizing the excitation time for AlphaScreen and AlphaLISA assays may help
to minimize sample bleaching and improve the signal-to-noise ratio.
The excitation time for AlphaScreen/AlphaLISA is selectable from 10 - 1000 ms;
a longer excitation time will increase the total read time of the plate.
5.6.2 Integration
Time
At very low light levels, a PMT does not yield a continuous output current, which
is necessary for reliable analog to digital conversion, but instead a sequence of
pulses are produced, the average rate of which can be measured using a
counter. The advantage of using the photon counting technique at such low light
levels is that pulse height selection criteria allow much of the electronic noise to
be filtered out.
At very low light levels, the measured counts per second are proportional to the
light intensity. An increase in measurement time per well yields more accurate
values because of the irregular photon impact (photon statistics). The photonic
noise (shot noise) cannot be reduced technically.
The integration time for AlphaScreen/AlphaLISA is selectable from
100 - 20,000 ms; a longer integration time will increase the total read time of the
plate.
Note
The relevant signal to (shot) noise ratio can be improved by a factor
when measurement time is multiplied with the square of the desired
factor.
Note
The results of AlphaScreen/AlphaLISA measurements
are always displayed in counts per second, regardless of the integration
time used.
