Biopolym. Cell. 2022; 38(2):103-116.
http://dx.doi.org/10.7124/bc.000A75
Bioorganic Chemistry
N-alkyl functionalized squaraine dyes as fluorescent probes for the detection of serum albumins
1Syniugina A. T., 1, 2Chernii S. V., 1Losytskyy M. Yu., 3Ozkan H. G., 4Slominskii Yu. L., 1Syniugin A. R., 2Pekhnyo V., 3Mokhir A. A., 1Yarmoluk S. M.
  1. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03143
  2. Vernadsky Institute of General and Inorganic Chemistry, NAS of Ukraine
    32/34, prospekt Akademika Palladina, Kyiv, Ukraine, 03142
  3. Friedrich-Alexander-University of Erlangen-Nuremberg
    42, Henkestr, Erlangen, Germany, 91054
  4. Institute of Organic Chemistry, NAS of Ukraine
    5, Murmanska Str., Kyiv, Ukraine, 02660

Abstract

Aim. Here we synthesize a series of benzoindolium squaraine dyes with N-substituents (SQ) and examine these dyes as fluorescent probes to detect serum albumins. Methods. Organic synthesis, fluorescent spectroscopy, absorption spectroscopy, fluorescent microscopy. Results. The spectral-luminescent properties of SQ dyes in the aqueous solution and the presence of bovine serum albumin (BSA), human serum albumin (HSA), equine serum albumin (ESA), ovalbumin (OVA), beta-lactoglobulin (BLG) and lysozyme (LYS), and nucleic acids were investigated. The maxima of excitation spectra of the studied dyes in the buffer are located at 623-673 nm, with the fluorescence emission maxima lying between 635-690 nm. All these dyes showed a similar increase in fluorescence intensity with serum albumins and at the same time with the red shift up to 12 nm, which could point out the binding of the dyes to proteins. These dyes demonstrate noticeably lower fluorescence intensity in the presence of OVA, BLG, and LYS, which are structurally different from serum albumins. Studied dyes gave no significant fluorescent response upon the addition of nucleic acids. Equilibrium constants of dyes binding to BSA (K) were estimated as 3.0 ± 0.3x105 M-1 for SL-2411 and 2.4 ± 0.6x105 M-1 for SL-2412. Based on the relative values of K, we could suppose that the mechanism of dye-BSA binding is the interaction of the chromophore of the dye with the protein globule. It was shown that SL-2411 penetrates the cell membrane and distributes in the cytoplasm without co-localization with MitoTracker Green. Conclusion. These dyes could apply fluorescent spectroscopy for protein detection and potentially visualize cell components with minimum to no autofluorescence.
Keywords: squaraine dyes, serum albumins, fluorescent spectroscopy, absorptions spectroscopy, fluorescent detection, fluorescence microscopy
Full text: (PDF, in English)

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