**7. Conclusion**

In current work the approach based on the simultaneous use of nonlinear laser fluorimetry, spectrophotometry and conventional fluorimetry methods has been applied for investigation of the photophysical properties of the protein molecules of different complexity. The full set of photophysical parameters of the fluorophores (tryptophan residues) of human and bovine serum albumins has been determined. The photophysical processes in the spectral forms of the red FP mRFP1 under UV (266 nm) and visible (532 nm) irradiation are described quantitatively. The individual photophysical parameters of the new mutants of the mRFP1 protein (a single substitution at the 66 amino acid position) were determined. It was shown that the individual extinction coefficient of the red chromopore of the proteins correlate positively with the volume of the substituted amino acid residue at position 66 (for polar substitution). A similar correlation has been described for the position of the maximum of the absorption, fluorescence excitation and emission spectra: the position of the maximum moves to the red with increasing the volume of the residue. In addition, the partial concentration of the fluorescent spectral form in the resultant solution of each FP variant has been determined.
