An isosbestic point
is detectable at 645 nm on the last Q band of the porphyrin (Figure 6(b)).
The above spectral changes also demonstrate an isosbestic point
which evidences that the molecule possesses two forms which transform to each other.
Fura-2 dye has two excitation (absorption) peaks (340 and 380 nm), an isosbestic point
at 360 nm and one emission peak at 510 nm.
The isosbestic point
230 nm was found to be satisfactory (Fig.
While in the presence of increasing concentration of CTAB in a fixed concentration of 5-FU, the signal at 206 nm showed increase in absorbance (hyperchromic effect) accompanied with red shift (bathochromic effect), generation of another signal at 296 nm and an isosbestic point
. In contrast, the signal at = 268 nm exhibited hypochromic effect (decrease in absorbance) when the concentration of CTAB was increased in a solution containing constant amount of 5-FU.
(6), we scanned the excitation spectra of the coproporphyrin calibrator and the real fecal samples from 340 to 450 nm, while monitoring the emission at 668 nm, the emission isosbestic point
for coproporphyrin and protoporphyrin.
The isosbestic point
158 may, presumably, be due to equal increase of DNA fragments by the probable DNA damage with the increasing in concentration of the compound- DNA complex.
The maximum absorbance is affected by temperature; however, temperature dependency can be avoided by making the absorbance measurements at a temperature isosbestic point
(near 1000 nm).
This difference is minimal at 610 nm, an isosbestic point
. Below 610 nm, however, the absorbance curves become very steep, indicating that a compromise using wavelengths between 610 and 625 nm, for example, may prove better.
The state of equilibrium between various protonated and deprotonated species was examined from the spectral changes like shifting of peaks and formation of isosbestic points
. The whole range of spectral data as shown in the Figure 5(a) was included in the calculations by nonlinear least square fitting program pHAb, which gave best fit for three species whose protonation constants agreed well with the potentiometric results.
Furthermore, spectroscopic titration studies for the interaction of these food additives with DNA showed that these dyes bind to calf thymus DNA and distinct isosbestic points
are observed clearly suggesting binding of the dyes to DNA.
The retina is illuminated through the pupil, preferably at isosbestic points
for oxy- and deoxyhemoglobin, using several discrete visible/NIR light bands while the reflected light from vessels overlying the optic disk is analyzed.