The phycocyanin content increased throughout the growth cycle, reaching
a maximum on day 65, and then began to decrease. Two-dimensional
correlation was calculated for the changes of phycocyanin content during
the growth cycle, and the synchronous and asynchronous two-dimensional
correlation fluorescence spectra of microalgae phycocyanin were
obtained. Figure 4.6(c) shows that there is only one autocorrelation
peak on the main diagonal, and there is no cross peak outside the main
diagonal. CQDs were used as probes to analyze the fluorescence changes
of phycocyanin content at different growth stages, and the excitation
wavelengths were all 370 nm, so no cross peak existed outside the main
diagonal because there was no obvious interference in the system. In
Figure 4.6(d), an asynchronous cross-peak appeared at 465 nm outside the
main diagonal. The asynchronous cross-peak appeared here reflected that
the excitation at 370 nm would get an emission peak at 465 nm, which was
consistent with the results shown in the previous 1D fluorescence
spectra, and the distribution of the algal cyanobacterial protein
content at different stages measured by the system was clear and well
correlated.
Figure 5 Variation of phycocyanin content in algal cells (a) (b); 2D
synchronous correlated fluorescence spectra (c); 2D asynchronous
correlated fluorescence spectra (d)
3.3
SOD content changes
As shown in Figure, SOD enzyme content showed an upward trend and
reached a maximum at 65 days. 2-D synchronous correlation fluorescence
spectra plots, it can be seen that there is only one autocorrelation
peak on the main diagonal, no cross peaks exist on the outside of the
main diagonal, the situation of the fluorescence change of SOD enzyme
content is probed by using CQDS as the probe, the excitation wavelength
is all 370 nm, the synchronous fluorescence change plot of SOD enzyme
all the peaks are synchronous changes; Since there was no significant
interference within the system, no cross peaks outside the main diagonal
existed. The asynchronous cross peak appears at 465 nm outside the main
diagonal, and the asynchronous cross peak presented here reflects that
excitation at 370 nm gives an emission peak at 465 nm, which is
consistent with the results shown in the previous one-dimensional
fluorescence spectrogram, and this system measures the SOD content
change at different growth stages, and the SOD enzyme content
distribution at different stages is clear and well correlated.