have a means of evaluating CPL in materials in solid form like powder and film. We
herein introduce a method for measuring powder samples.
In the Nujol mull method, a powder sample is coated on a quartz plate, and the KBr
pellet method, commonly utilized in infrared spectroscopy, can be used. The CPL-300
is designed to detect transmitted fluorescence through samples. Thus, it can detect
fluorescence emitted from the back of a pellet while suppressing the effect of fluorescence anisotropy (Fig. 14.13). In the case of a solid sample containing a powder, the
spectrum may be affected by artifacts due to birefringence. To determine whether such
artifacts are present, it is necessary to measure enantiomers to obtain symmetrical
spectra. Furthermore, the confirmation of the isotropic CPL spectra by the sample
rotation to the optical axis of a light polarizer is necessary. Such measurements can be
g Abs(399 nm)
-0.0004
g lum(507 nm)
-0.0003
-0.001
0.001
-4
2
0
0.1
CD [mdeg]
g
abs
250
600
Wavelength [nm]
-0.001
0.001
g
lum
-4
2
CPL [mdeg]
0
1
300
400
500
CD/Abs
CPL/FL
Abs
FL [Arb Unit]
Fig. 14.11 CD, CPL, absorption, and fluorescence spectra of wild-type GFP
320
S. Suzuki