Todor Deligeorgiev

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.

An improved method for the preparation of 2-aryl-, 2-hetaryl- and 2-styrylbenzothiazoles

Abstract An improved method for the preparation of 2-aryl-, 2-hetaryl- and 2-styrylbenzothiazoles by interaction of aryl aldehydes, heterocyclic aldehydes and cinnamaldehydes with 2-aminothiophenol in dimethyl sulphoxide with simultaneous removal of the volatile reaction products is described. The method offers a simple experimental procedure, higher yields and shorter reaction times.

DiOC6(3): a Useful Dye for Staining the Endoplasmic Reticulum

The present review discusses the fluorescent organelle probe, DiOC6(3), with reference to its structure, chemistry, availability, spectral properties, labeling procedures, vital staining characteristics, and major applications in cellular and molecular biology. The specificity of dye for endoplasmic reticulum is summarized. We examine the simplicity and advantages of the fluorescent dye system for evaluating structure and function of endoplasmic reticulum. Other significant uses of the dye are also discussed.

Preparation of intercalating dye thiazole orange and derivatives

An improved method for the preparation of asymmetric monomethine cyanines by the condensation of 6-substituted-2-iminobenzothiazolines and 1-alkyl-4-methylquinolinium salts is described. The preparation can be considered as being more environmentally friendly than the more usual method involving condensation of 2-methylthio-3-methylbenzothiazolium salts and 1-alkyl-4-methylquinolinium salts. The synthesis results in the important fluorogenic intercalating dye 1-methyl-4-[(3-methylbenzothiazoline-2-ylidene)methine]-quinolinium salts, or its derivatives with substituents at the 6-position in the benzothiazole nucleus. The starting materials are commercially available or can be easily synthesized. The procedure for the preparation of these biological non-covalent labels is simple and reliable.

Fluorescence spectral characteristics of novel asymmetric monomethine cyanine dyes in nucleic acid solutions.

Six new asymmetric monomethine cyanine dyes have been synthesized and their fluorescence characteristics in the presence of nucleic acids studied. The new dyes have no fluorescence of their own in water solutions upon excitation at 480 nm but they become strongly fluorescent in the presence of nucleic acids. The fluorescence maxima of the investigated dyes are found at 525–545 nm when bound to dsDNA and around 600 nm upon binding to RNA and ssDNA. Fluorescence quenching studies with increasing concentrations of NaCl indicate that the cyanine dyes have a mixed (intercalating and groove binding) type of interaction with dsDNA.

Photochromism of styryl cyanine dyes in solution

Abstract The photochemical and spectral behavior of two styryl cyanine dyes were studied in different solvents. The experimental results indicate that in solution the compounds exist in two forms—closed and open. The equilibrium is strongly shifted toward the closed form. From the absorption and luminescence properties, the conclusion can be made that absorbed energy can be lost through different channels:photochemical closed—open form and cis—trans isomerization and through photophysical processes such as fluorescence. The quantum yield of the process, closed—open form is measured. The reasons for the photochromic behavior of these compounds are discussed.

Novel Green Procedure for the Synthesis of 2-Arylbenzothiazoles Under Microwave Irradiation in Peg 200 Or Peg 400

An improved green procedure for the synthesis of 2-aryl- and 2-hetarylbenzothiazoles by condensation of equivalent amounts of 2,2′-diaminodiphenyldisulfides or 2-aminothiophenols and various aromatic aldehydes in PEG 200/400 under microwave irradiation has been developed. This method allows the synthesis of 2-arylbenzothiazoles in high yields and with high purity regardless of the state of the starting compounds (liquid or solid) or the nature of the substituents in the aromatic ring.

Near-membrane iminocoumarin-based low affinity fluorescent Ca2+ indicators

Two new potential near-membrane iminocoumarin-based fluorescent Ca(2+) indicators were synthesized and the spectral profiles of their free and Ca(2+) bound forms were studied. The probes incorporate in their BAPTA-related structures, the 3-(benzimidazolyl)iminocoumarin or the 3-(benzothiazolyl)iminocoumarin moiety, substituted at the imino nitrogen with an n-dodecyl lipophilic chain. The compounds are excited with visible light and have Ca(2+) dissociation constant values of 5.50 and 4.49 microM, respectively, the highest reported to date in the literature. Fluorescence spectra studies indicated a clear shift in their excitation wavelength maxima upon Ca(2+) binding along with changes in fluorescence intensity that enable the compounds to be used as ratiometric near-membrane, low Ca(2+) affinity probes.

Molecular Probes Based on Cyanine Dyes for Nucleic Acid Research

The development in the last several years of cyanine dyes as fluorescent labels is reviewed. The dyes are covering the spectrum from the blue to the near infrared region. The non-covalently binding labels have no tluorescence of their own, but a strong fluorescence enhancement is observed in the presence of nucleic acids. Monomeric, homodimerle and heterodimeric cyanine dyes with one to four positive charges are discussed. With the increasing number of positive charges in the dye molecule, the affinity to nucleic acids of such non-covalent labels is also increasing. Cyanine dyes (usually tri-, penta-, and heptamethine cyanines) with large molar absorptivity and high fluorescence quantum yield are suitable as covalent labels. Dyes with amine-reactive groups, such as isothiocyanates or succinimidyl esters, are used for covalent labelling of chemically modified nucleic acids. The efficient energy transfer from the donor cyanine dye to the acceptor fluorescent dye(s) by excitation of the single wavelength in donor-acceptor dye systems results in well separated emission maxima with enhanced fluorescence intensity both in the covalently and non-covalently binding nucleic acid labels.

Effect of some 2-arylbenzothiazoles on the photo-degradation of poly(vinyl chloride)

The action of some 2-phenyl-benzothiazoles (BT) as photo-sensitizers of the photo-degradation of poly(vinyl chloride) (PVC) is studied. On irradiation with unfiltered light in air, polyene sequences are formed. The initial dehydrochlorination of PVC as well as the development of polyene sequences strongly depend on the nature of the compounds. Complexes ((BTH)+ Cl−) formed from BT and HCl (liberated from the photo-dehydrochlorination of PVC) are observed. The role of these complexes is discussed and their effect on the physical and mechanical properties of PVC is considered. The data can be explained by the strong acceptor action of the excited states of BT.