Aggregation phenomena in xanthene dyes
About: This article is published in Accounts of Chemical Research.The article was published on 1989-05-01. It has received 408 citations till now. The article focuses on the topics: Xanthene.
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2,459 citations
TL;DR: Although MRI, US, and x-ray CT are often listed as molecular imaging modalities, in truth, radionuclide and optical imaging are the most practical modalities for molecular imaging, because of their sensitivity and the specificity for target detection.
Abstract: In vivo medical imaging has made great progress due to advances in the engineering of imaging devices and developments in the chemistry of imaging probes Several modalities have been utilized for medical imaging, including X-ray radiography and computed tomography (x-ray CT), radionuclide imaging using single photons and positrons, magnetic resonance imaging (MRI), ultrasonography (US), and optical imaging In order to extract more information from imaging, “contrast agents” have been employed For example, organic iodine compounds have been used in X-ray radiography and computed tomography, superparamagnetic or paramagnetic metals have been used in MRI, and microbubbles have been used in ultrasonography Most of these, however, are non-targeted reagents
Molecular imaging is widely considered the future for medical imaging Molecular imaging has been defined as the in vivo characterization and measurement of biologic process at the cellular and molecular level1, or more broadly as a technique to directly or indirectly monitor and record the spatio-temporal distribution of molecular or cellular processes for biochemical, biologic, diagnostic, or therapeutic application2 Molecular imaging is the logical next step in the evolution of medical imaging after anatomic imaging (eg x-rays) and functional imaging (eg MRI) In order to attain truly targeted imaging of specific molecules which exist in relatively low concentrations in living tissues, the imaging techniques must be highly sensitive Although MRI, US, and x-ray CT are often listed as molecular imaging modalities, in truth, radionuclide and optical imaging are the most practical modalities, for molecular imaging, because of their sensitivity and the specificity for target detection
Radionuclide imaging, including gamma scintigraphy and positron emission tomography (PET), are highly sensitive, quantitative, and offer the potential for whole body scanning However, radionuclide imaging methods have the disadvantages of poor spatial and temporal resolution3 Additionally, they require radioactive compounds which have an intrinsically limited half life, and which expose the patient and practitioner to ionizing radiation and are therefore subject to a variety of stringent safety regulations which limit their repeated use4
Optical imaging, on the other hand, has comparable sensitivity to radionuclide imaging, and can be “targeted” if the emitting fluorophore is conjugated to a targeting ligand3 Optical imaging, by virtue of being “switchable”, can result in very high target to background ratios “Switchable” or activatable optical probes are unique in the field of molecular imaging since these agents can be turned on in specific environments but otherwise remain undetectable This improves the achievable target to background ratios, enabling the detection of small tumors against a dark background5,6 This advantage must be balanced against the lack of quantitation with optical imaging due to unpredictable light scattering and absorption, especially when the object of interest is deep within the tissue Visualization through the skin is limited to superficial tissues such as the breast7-9 or lymph nodes10,11 The fluorescence signal from the bright GFP-expressing tumors can be seen in the deep organ only in the nude mice 12,13 However, optical molecular imaging can also be employed during endoscopy14 or surgery 15,16
1,851 citations
TL;DR: Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution and how these complexes interact with each other and with solvent-free substrates is studied.
Abstract: Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution Roy N. Dsouza, Uwe Pischel,* and Werner M. Nau* School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany Centro de Investigaci on en Química Sostenible (CIQSO) and Departamento de Ingeniería Química, Química Física y Química Org anica, Universidad de Huelva, Campus de El Carmen s/n, E-21071 Huelva, Spain
897 citations
TL;DR: This work evaluated Alexa dyes compared with conventional dyes in applications using various conjugates, including those of goat anti-mouse IgG (GAM), streptavidin, wheat germ agglutinin (WGA), and concanavalin A (ConA).
Abstract: Alexa 350, Alexa 430, Alexa 488, Alexa 532, Alexa 546, Alexa 568, and Alexa 594 dyes are a new series of fluorescent dyes with emission/excitation spectra similar to those of AMCA, Lucifer Yellow, fluorescein, rhodamine 6G, tetramethylrhodamine or Cy3, lissamine rhodamine B, and Texas Red, respectively (the numbers in the Alexa names indicate the approximate excitation wavelength maximum in nm). All Alexa dyes and their conjugates are more fluorescent and more photostable than their commonly used spectral analogues listed above. In addition, Alexa dyes are insensitive to pH in the 4-10 range. We evaluated Alexa dyes compared with conventional dyes in applications using various conjugates, including those of goat anti-mouse IgG (GAM), streptavidin, wheat germ agglutinin (WGA), and concanavalin A (ConA). Conjugates of Alexa 546 are at least twofold more fluorescent than Cy3 conjugates. Proteins labeled with the Alexa 568 or Alexa 594 dyes are several-fold brighter than the same proteins labeled with lissamine rhodamine B or Texas Red dyes, respectively. Alexa dye derivatives of phalloidin stain F-actin with high specificity. Hydrazide forms of the Alexa dyes are very bright, formaldehyde-fixable polar tracers. Conjugates of the Alexa 430 (ex 430 nm/em 520 nm) and Alexa 532 (ex 530 nm/em 548 nm) fluorochromes are spectrally unique fluorescent probes, with relatively high quantum yields in their excitation and emission wavelength ranges.
854 citations
TL;DR: This critical review provides an overview on the formation of pi-stacks of functional dyes in solution, aiming to acquaint young researchers with this topical research field and to stimulate further advance in supramolecular dye chemistry.
Abstract: This critical review provides an overview on the formation of π-stacks of functional dyes in solution, aiming to acquaint young researchers with this topical research field and to stimulate further advance in supramolecular dye chemistry. Different mathematical models that have been proposed and applied for the description of aggregation equilibria of π-systems in solution are discussed. The factors that have significant impact on the structural features of aggregates and the thermodynamics of π–π stacking such as electrostatic interactions, size and geometry of the dye molecules are covered in this review. A comparison of the binding strength is made for different classes of functional π-conjugated systems, from simple benzene to more extended polycyclic hydrocarbon molecules, including triphenylenes and hexabenzocoronenes, heteroaromatic porphyrins and phthalocyanines, quadrupolar naphthalene and perylene bisimides, dipolar or even zwitterionic merocyanines and squaraines, and some macrocyclic dyes. Solvent effects on binding constants are analysed by linear free energy relationships with various solvent polarity scales (98 references with multiple entries).
852 citations
References
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TL;DR: The literature contains numerous experiments designed to demonstrate the presence of excitation energy transfer, and the goal of theseresearches mightwell be not merely the demonstration of the presence, but a more detailed investigation designed to establish which available mechanism of energy transfer is operative.
Abstract: Energytransferphenomenacontinuetofascinatethebiologist, chemist, and physicist, and the literature contains numerous experiments designed to demonstrate the presence of excitation energy transfer. At the present stage of development of the theoryofsuchprocesses, thegoal oftheseresearchesmightwell be not merely the demonstration of the presence of energy transfer, but a more detailed investigation designed to establish which available mechanism of energy transfer is operative. The field of excitation energy transfer is replete with redundant and overlapping terms, whose multitude itself lends little order to the subject. Various authors quote, as energy transfer mechanisms, exciton transfer, resonance transfer, dipole-dipole transfer, inductive resonance, resonance force transfer, virtual photons, and diffuse excitation, among others. This paper will be devoted to the laying down of a further perspective for the discrimination and understanding of the main types of excitation energy transfer. A necessary
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TL;DR: In this article, the triplet oxygen quantum yield of 11 purified fluorescein derivatives was determined by reaction with singlet oxygen acceptors in aqueous and ethanolic solutions; in both solvents ϕ1o2 was enhanced with increasing halogenation.
Abstract: The singlet oxygen quantum yield (ϕ1o2) of 11 purified fluorescein derivatives was determined by reaction with singlet oxygen acceptors in aqueous and ethanolic solutions; in both solvents ϕ1o2 was enhanced with increasing halogenation. Tryptophan and 2,2,6,6-tetramethylpiperidone were found to be unadapted for the determination of ϕ1o2, in our systems; however, the use of 9.10-dipropionic anthracene acid andp-nitrosodimethylaniline in conjunction with imidazole derivatives was suitable for 1O2 detection in water. Both methods lead to results in excellent agreement. As in ethanol. ϕ1o2, was equal to the triplet state quantum yield (ϕT), the comparison between the two solvents showed that ϕT in water was greater than in ethanol. The comparison between our values obtained with polychromatic light with published data obtained with monochromatic light suggests that the triplet quantum yield of fluorescein derivatives is wavelength independent.
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