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Interaction of the iron(II) mono- and bis-clathrochelates with bovine serum albumin (BSA), β-lactoglobulin, lysozyme and insulin was studied by the steady-state and time-resolved fluorescent spectroscopies. These cage complexes do not make significant impact on fluorescent properties of β-lactoglobulin, lysozyme and insulin. At the same time, the monoclathrochelates strongly quench a fluorescence intensity of BSA and substantially decrease its excited state lifetime due to their binding to this protein. This occurs due to the excitation energy transfer from a tryptophan residue to a cage molecule or/and to the change of the tryptophan nearest environment caused by either clathrochelate binding or an alteration of the BSA conformation. The effect of the iron(II) bis-clathrochelate on BSA fluorescence is much weaker as compared to its monomacrobicyclic analogs as a result of an increase in its size.

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]

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]

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]