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The series of the β-ketoenoles (2 E ,5 Z ,7 E ,9 E )-2-(alkylamino)-6-hydroxy-10-phenyldeca-2,5,7,9-tetraen-4-ones with variation of the alkylamino tail groups was synthesized and studied as potential probes for the sensing of protein insoluble aggregates - amyloid fibrils. Depending on the structure of the alkylamino group, the dyes could increase their fluorescence intensity in the dozens of times in the presence of insulin fibrils. The compound with a 2-hydroxyethylamino substituent demonstrates the highest fluorescence response (up to 60 times) and good range of insulin fibril detection (1–50 μg/ml). In complexes with fibrils, the dyes possess fluorescence quantum yield values up to 15% and binding constant values of about 2 × 10 5 M −1 . The excitation and emission maxima of β-ketoenoles are located in the range 407–427 nm and 500–554 nm correspondingly. These compounds are weakly fluorescent when free and slightly sensitive to the native proteins insulin and bovine serum albumin. Thus β-ketoenoles are considered as prospective molecules for the fluorescent detection of amyloid aggregates of proteins. [ABSTRACT FROM AUTHOR]

Abstract: Photochemical processes (photoisomerization and generation of the triplet state) of the thiacarbocyanine dyes 3,3′,9-trimethylthiacarbocyanine iodide (Cyan 2), 3,3′-diethyl-9-methylthiacarbocyanine iodide (DMTC), and 3,3′,9-triethylthiacarbocyanine iodide (TETC) in complexes with biomacromolecules—DNA and chondroitin-4-sulfate—were studied by flash photolysis. It has been shown that, along with generation of the triplet state, enhancement of the photoisomer formation is observed for Cyan 2 and DMTC complexed with the biomolecules. This effect can be explained by the influence of the biopolymer matrix on the potential energy curves of the photoisomerization process. [Copyright &y& Elsevier]

Abstract: Three benzothiazole substituted squaraines bearing hydroxyethylamino, aminoethylamino and 3-iodobenzylamino substituents on the cyclobutane unit have been synthesized and characterized. The structure of the hydroxyethylamino substituted analogue was determined by X-ray crystallography. The fluorescent properties of the new dyes plus those of seven previously reported aza-substituted squaraines were studied in both pure solution as well as in the presence of human, bovine and horse serum albumins, and ovalbumin. All of the dyes demonstrated low fluorescence emission levels in pure solution, and fluorescence intensity increases of up to 400 times in the presence of albumins. Dyes with an aminoethylamino and N,N-dimethylhydrazino substituents demonstrated good emission intensities in complexes with albumins, with fluorescence quantum yields of the latter dye reaching 0.18. The aminoethylamino substituted dye demonstrated a wide human serum albumin detection range (1.5μg/mL to 20mg/mL of protein). Studies of the dyes in the presence of model sodium dodecyl sulphate and bovine serum albumin – sodium dodecyl sulphate systems have shown that these squaraines do not give a considerable fluorescent response in the presence of denatured proteins or surfactant, with the exception of the 2-sulfoethylamino aza-substituted dye. [Copyright &y& Elsevier]

In present paper series of trimethine cyanines modified in 5,5′- or 6,6′- position with hydroxy- or methoxy- substituents is studied for their ability to interact selectively with fibrillar formations. Processes of dye aggregation that accompany this interaction were also investigated. Meso-methyl trimethynecyanines with 5,5′- methoxy (7519) and hydroxy (7515) substituents strongly (up to 40 times) increase fluorescence intensity in the presence of fibrillar insulin, and also give noticeable fluorescent response on the presence of various aggregated proteins (lysozyme, β-lactoglobulin, α-synuclein A53T). 7519 and 7515 dyes can be used for fluorometric detection of fibrillar insulin at concentrations of approximately 1.5-120 microg/ml. For meso-ethyl substituted dye 7514 the ability to form H- and J-aggregates upon interaction with insulin fibrils was suggested. The model of the H- and J-aggregate packing in the protein fibrillar structure has been proposed. [ABSTRACT FROM AUTHOR]

Spectral-fluorescent properties of benzothiazole styryl monomer (Bos-3) and homodimer (DBos-21) dyes in presence of DNA were studied. The dyes enhance their fluorescence intensity in 2–3 orders of magnitude upon interaction with DNA. Studied styrylcyanines in DNA presence demonstrate rather high values of two-photon absorption (TPA) cross-section, which are comparable with the values of TPA cross section of the rhodamine dyes. An applicability of the styrylcyanines as probes for the fluorescence microscopy of living cells was studied. It was shown that both dyes are cell-permeable but homodimer dye DBos-21 produces noticeably brighter staining of HeLa cells comparing with monomer dye Bos-3. Molecules of DBos-21 initially bind to the nucleic acids- containing cell organelles (presumable mitochondria) and are able to penetrate into the cell nucleus. Thus, homodimer styryl DBos-21 dye is viewed as efficient stain for single-photon and two-photon excitation fluorescence imaging of living cells. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel, polymethine chalcone dye – 2-quinolone derivatives and their boron difluoride complexes were synthesized. The spectral-luminescence properties of a series of 2-quinolones and their coumarin analogues were characterized in the presence of a denaturing agent (sodium dodecyl sulfate), native bovine serum albumin as well as a combination of serum albumin and sodium dodecyl sulfate. A study of the influence of the BF2-ether group on the sensitivity of the polymethine dyes to proteins revealed that three of the dyes, namely two hydroxyquinoline dyes containing a 4-diethylamino-2-hydroxyphenyl substituent and a coumarine dye that contained an indolenine substituent, displayed high emission and bright fluorescence (quantum yield≤0.27) and thus offer promise for use in protein detection. [Copyright &y& Elsevier]

Abstract: The influence of methyl-, 2-hydroxyethyl-, dimethyl-, diethyl- and benzoyl-amino substituents in the 6,6′-positions of benzothiazole heterocycle of trimethine cyanines on their spectral-luminescent properties and behavior in presence of DNA, RNA and BSA was studied. It was shown that incorporation of 6,6′-substituents generally leads to the increase in dyes tendency to aggregation, resulting in the considerable decrease in the emission intensity of the disubstituted dyes as compared to the unsubstituted ones. Emission of the studied 6,6′-disubstited dyes in DNA presence is considerably more intensive than in presence of RNA, that points on the existing of DNA binding preference for the mentioned dyes. Insertion of benzoyl-amino groups into the 6,6′-positions permitted us to design the DNA-sensitive dyes on the basis of symmetric trimethine cyanines with unsubstituted polymethine chain, while typically such dyes slightly respond on the presence of biopolymers. 6,6′-Benzoyl-amino-disubstituted trimethine cyanines are proposed as efficient dyes for DNA detection. [Copyright &y& Elsevier]