ABSTRACT
A large number of techniques have been applied to monitor the function of free metal ions in biological systems. Fluorescent ion probes have evolved into an extremely useful tool for contemporary experimentalists. Polycarboxylate indicators are widely used in the determination of metal ion concentrations, especially due to their cell membrane permeability. The design of these probes required detailed knowledge in related fields of medicine, biology, and chemistry, and their preparation demanded the expertise of organic synthesis. In this review, the basic rationale for the selection of particular chemical structures are analyzed, synthetic pathways leading to the desired structures are presented, often via a retrosynthetic approach, and properties and relative advantages of the use of these probes are described. References to specific applications are limited, given the large number of reviews on related subjects. Topics such as those related to dextran conjugates that are broad enough to be the subject of a different review are not included, and leakage resistance and near-membrane probes are mentioned briefly in separate sections, although these are chemically similar to typical polycarboxylate dyes. While reference to topics mentioned in related reviews is unavoidable, presentation of material in this review is from the point of view of a medicinal chemist rather than that of the many experts using these pioneering techniques.
Subject(s)
Carboxylic Acids/chemistry , Fluorescent Dyes/chemistry , Ions/analysisABSTRACT
A series of iminocoumarin-based fluorescent Ca2+ indicators were synthesized and the spectral profiles of their free and Ca2+ bound forms were studied. The newly-synthesized compounds incorporate the Ca2+ chelating structure of BAPTA. The chromophore moieties are iminocoumarins substituted at the 3-position with benzothiazolyl, benzoxazolyl and benzimidazolyl groups. These compounds are excited with visible light and their Ca2+ dissociation constants range from 5.4 to 27.5 microM. Fluorescence spectra studies of these probes indicated a clear shift in their excitation wavelength maxima upon Ca2+ binding along with changes in fluorescence intensity that enable the compounds to be used as low Ca2+ affinity, visible excitable probes.
Subject(s)
Calcium/analysis , Coumarins/radiation effects , Egtazic Acid/analogs & derivatives , Fluorescent Dyes/radiation effects , Chelating Agents/chemistry , Coumarins/chemical synthesis , Egtazic Acid/chemistry , Fluorescent Dyes/chemical synthesis , Light , Molecular StructureABSTRACT
In order to develop a reliable, laser-induced, fluorescence-guided, angioplasty system, fluorescence spectra were recorded during exposure of normal and atherosclerotic cadaveric aortic tissue to argon ion laser irradiation. A characteristic increase in the fluorescence signal in the 520-560 nm spectral region for atheromatous tissue was observed after treatment of the samples with a tetracarboxylate ion dye (BTC). This allowed the development of a simple algorithm (based on the intensity difference) and a subsequent index of discrimination between normal and atheromatous tissue. Our results suggest that monitoring of this index through the catheter could enhance selective ablation.
Subject(s)
Aorta, Abdominal/pathology , Arteriosclerosis/pathology , Calcinosis/pathology , Algorithms , Autopsy , Cadaver , Carboxylic Acids , Fluorescent Dyes , Humans , Muscle, Smooth, Vascular/pathology , Reference Values , Spectrometry, Fluorescence/instrumentation , Spectrometry, Fluorescence/methodsABSTRACT
Four new potential fluorescent probes for Ca2+ using the coumarin moiety as a fluorophore have been synthesized and their spectral properties and binding affinities for Ca2+ determined. The most promising derivative for intracellular use, BTC, exhibits an excitation wavelength shift from 462 nm to 401 nm on binding Ca2+, with an emission wavelength of 530 nm. The quantum yield of this probe increases from 0.07 as the free indicator to 0.12 on binding Ca2+. BTC, loaded as its tetraacetoxymethyl ester (AM ester) into mouse myeloma P3X cells, responded only when cytoplasmic Ca2+ exceeded typical intracellular calcium concentrations. The dye, therefore, appears to be useful in excitatory cells or extracellular spaces with intracellular calcium concentrations high enough to saturate typical excitation ratio Ca2+ indicators such as Fura-2.