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Abstract: The macrocyclic compounds mono- and bis-iron(II) clathrochelates were firstly studied as potential anti-fibrillogenic agents using fluorescent inhibitory assay, atomic force microscopy and flow cytometry. It is shown that presence of the clathrochelates leads to the change in kinetics of insulin fibrillization reaction and reduces the amount of formed fibrils (up to 70%). The nature of ribbed substituent could determine the activity of clathrochelates—the higher inhibitory effect is observed for compounds containing carboxybenzenesulfide groups, while the inhibitory properties only slightly depend on the size of complex species. The mono- and bis-clathrochelate derivatives of meta-mercaptobenzoic acid have close values of IC50 namely 16±2 and 24±5μM, respectively. The presence of clathrochelates decreases the fibril diameter from 5-12nm for free insulin fibrils to 3–8nm for these formed in the clathrochelate presence, it also prevents the lateral aggregation of mature fibrils and formation of superfibrillar clusters. However the addition of clathrochelate results in more heterogeneous (both by size and structure) insulin aggregates population as compared to the free insulin. This way, cage complexes—iron(II) clathrochelates are proposed as efficient agents able to suppress the protein aggregation processes. [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]

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]