N. Gadjev

Homodimeric monomethine cyanine dyes as fluorescent probes of biopolymers

The fluorescence properties of newly synthesized homodimeric monomethine cyanine dyes in the presence of biopolymers are investigated. They do not fluoresce in TE buffer and bidistilled water but become strongly fluorescent (Q(F)=0.3-0.9) in the region 530-650 nm when bound to dsDNA and ssDNA. The detection limit of dsDNA is about 1.7 ng/ml. Some of dyes studied are able to distinguish between dsDNA and ssDNA, RNA, BSA in solution and gel electrophoresis. The influence of different factors (temperature, pH and viscosity of the medium, presence of histone) on the formation of the dye-biopolymer complexes is investigated. The results of steady-state and dynamic fluorescence measurements concerning the different types of binding between dyes and biopolymers show that the new dyes are applicable in molecular biology as highly sensitive fluorescence labels.

Diazotization of 2-amino-6-methoxybenzothiazole at elevated temperature

Abstract The diazotization at elevated temperature of the weakly basic heterocyclic amine 2-amino-6-methoxybenzothiazole, which is used in the production of basic dyes was investigated. The results showed that the yields and purity of the dyes, produced by this method were comparable with those reported in the literature. The conclusion is drawn that the diazotization of 2-amino-6-methoxybenzothiazole at elevated temperature can result in technological improvement and simplification of the process.

Near-infrared absorbing pyrylium trimethinecyanine dyes

Abstract The synthesis of some new xanthene intermediates and derived near-infrared absorbing pyrylium trimethinecyanine dyes is described. The dyes absorb in the region from 700 to 860 nm. The structure of the compounds was confirmed by elemental analysis, electronic absorbtion spectra and in some cases by IR and 1 H-NMR spectroscopy.

Near-infrared absorbing asymmetrical trimethinecyanine dyes

Abstract The synthesis of some novel asymmetrical trimethinecyanine dyes containing pyrylium and heterocyclic rings as end groups is described. The absorption maxima of the dyes is within the range 687–793 nm.

Styryl dyes containing the benz[c,d]indolium heterocycle

Abstract The synthesis of some new styryl benz[c,d]indolium heterocycle dyes is described. The dyes absorb in the region from 636 to 686 nm. The structure of the compounds was confirmed by elemental analysis, electronic absorption spectra, IR and in some cases by 1 H-NMR spectroscopy.

Symmetric Meso-Chloro-Substituted Pentamethine Cyanine Dyes Containing Benzothiazolyl/Benzoselenazolyl Chromophores Novel Synthetic Approach and Studies on Photophysical Properties upon Interaction with bio-Objects

A series of symmetric pentamethine cyanine dyes derived from various N-substituted benzothiazolium/benzoselenazolium salts, and a conjugated bis-aniline derivative containing a chlorine atom at meso-position with respect to the polymethine chain, were synthesized using a novel improved synthetic approach under mild conditions at room temperature. The reaction procedure was held by grinding the starting compounds for relative short times. The novel method is reliable and highly reproducible. Some photophysical characteristics were recorded in various solvents, including absorption, and fluorescence quantum yields using Cy-5 as a reference. Additional studies on interactions with several bio-objects such as liposomes, DNA, and proteins have been investigated in the present work.

Near-infrared absorbing asymmetric trimethinecyanine dyes containing benz[c,d]indolium and pyrylium end groups

Abstract The synthesis of some new asymmetric trimethinecyanine dyes containing benz[ c,d ]indolium and pyrylium end groups is described. The dyes absorb in the region of 724 to 793 nm and have high molar absorption coefficients. The structure of the compounds was confirmed by elemental analysis, electronic absorption spectra and 1 H-NMR spectroscopy.

Preparation of 2-(N-alkyl-N-arylamino) ethyl trimethylammonium salts

Abstract The N-alkylation of 2-(N-arylamino)ethyl trimethylammonium salts with allyl chloride, benzyl chloride, epichlorohydrin, ethylene chlorohydrin and acrylonitrile was studied and the preparation of 2-(N-allyl-, -benzyl-, -2-hydroxyethyl-, 3-chloro-2-hydroxypropyl-and 2-cyanoethyl-N-arylamino)-ethyl trimethylammonium salts is described. A method is proposed for obtaining a series of differently N-substituted derivatives of these salts from the same 2-(N-arylamino)ethyl trimethylammonium salts.

Monomethine cyanine dyes containing benz[c,d]indole and pyrylium end-groups

Abstract Asymmetric monomethine cyanine dyes with benz[c,d]indole and pyrylium end-groups were prepared. The dyes absorb in the region 633–688 nm and are among the most deeply coloured monomethine cyanine dyes containing nitrogen heterocycles synthesized so far. Quantum-chemical considerations show that electronic excitation to the first-singlet-excited state is localized in the polymethine fragment and is connected with a considerable decrease in electronic polarizability.

Method for quaternization of nitrogen-containing heterocyclic azo dyes

Abstract A method is described for the quaternization of nitrogen-containing heterocyclic azo dyes using dimethyl sulphate and arylsulphonic acid methyl esters as alkylation agents in a two-phase liquid medium. The method is distinguished by fully competed quaternization at high reaction rates and moderate reaction temperatures.