Far-red pentamethine cyanine dyes as fluorescent probes for the detection of serum albumins

Abstract

Benzothiazole based cyanine dyes with bridged groups in the pentamethine chain were studied as potential far-red fluorescent probes for protein detection. Spectral-luminescent properties were characterized for unbound dyes and in the presence of serum albumins (bovine (BSA), human (HSA), equine (ESA)), and globular proteins (β-lactoglobulin, ovalbumin). We have observed that the addition of albumins leads to a significant increase in dyes fluorescence intensity. However, the fluorescent response of dyes in the presence of other globular proteins was notably lower. The value of fluorescence quantum yield for dye bearing a sulfonate group complexed with HSA amounted to 42% compared with 0.2% for the free dye. The detection limit of HSA by this dye was greater than 0.004 mg ml −1 which indicates the high sensitivity of dye to low HSA concentrations. Modelling of structure of the dyes complexes with albumin molecules was performed by molecular docking. According to these data, dyes could bind to up to five sites on the HSA molecule; the most preferable are the haemin-binding site in subdomain IB and the dye-binding site in the pocket between subdomains IA, IIA and IIIA. This work confirms that pentamethine cyanine dyes could be proposed as powerful far-red fluorescent probes applicable for highly sensitive detection of albumins.

N-alkyl functionalized squaraine dyes as fluorescent probes for the detection of serum albumins

“…Previously we have studied a series of different classes of dyes, including benzothiazole aza-substituted squaraine dyes; they demonstrated an enhancement of emission intensity up to 400 times and the shift of excitation and emission maxima up to 60 nm in the presence of albumins [12,23]. In the present paper, a series of squaraine benzoindolium dyes are studied (Fig.…”

“…The equilibrium constant of the dyes Sl-2411 and Sl-2412 binding with BSA (binding constant, K) was estimated based on experimental measurements of the dependence of the fluorescence intensity of these dyes (5 μM) on BSA concentration in 0.05 M Tris-HCl buffer (pH 7.9) as described in [23]. Shortly, the calculation of K was performed, assuming that each protein globule has n sites for dye binding (and that the equilibrium constant of binding with different binding sites has equal values).…”

Trimethine Cyanine Dyes as NA-Sensitive Probes for Visualization of Cell Compartments in Fluorescence Microscopy

“…We have also shown that this dye in low concentration could stain RNA-rich nucleoli without a background in the cytoplasm and have reported highly specific green-emitted monomethine cyanine dyes to stain RNA-containing structures in cells . Besides this, our research group proposed near-infrared fluorescent probes among pentamethine cyanines and merocyanines as powerful far-red fluorescent probes applicable for the highly sensitive detection of albumins. , …”

“…19 Besides this, our research group proposed near-infrared fluorescent probes among pentamethine cyanines and merocyanines as powerful far-red fluorescent probes applicable for the highly sensitive detection of albumins. 20,21 Here we present our research of symmetrical cationic trimethine cyanine dyes with β-substituents in the polymethine chain based on substituted benzothiazole and benzoxazole heterocycles (ethyl group at the 3 positions and ethoxy group at the 6 positions for dye T-1, methyl group at the 3 positions for dyes T-2−T-5 with additional chloro-group at the 5 positions for dye T-5) as probes for nucleic acids detection and visualization by fluorescence microscopy (Figure 1).…”

“… 19 Besides this, our research group proposed near-infrared fluorescent probes among pentamethine cyanines and merocyanines as powerful far-red fluorescent probes applicable for the highly sensitive detection of albumins. 20 , 21 …”