Fluorescence spectral properties development

Module 1, Determination of Chemical and Structural Information on the Sample. The task of Module 1 is to provide non-chromato-graphic data for analytes prior to specification of the chromatographic method. Data bases have been developed for pK values of organic molecules, isoelectric points of proteins, and fluorescence spectral properties of organic molecules. 

Akiyama S, Akimoto H, Nakatsuji S, Nakashima K. Development and application of organic reagents for analysis VI. Synthesis and fluorescence spectral properties of 2-(4-substituted phenyl)benzofiirans. Bull Chem Soc Jpn 1985 58 2192-96. 

A series of amine-reactive, long-wavelength fluorescent labels 48a-48c was recently developed on the basis of a norsquaraine chromophore [97, 98], Importantly, norsquaraine dyes show shifted pK3 values as compared to norcyanines with the same heterocyclic end-groups by several pH units e.g., while the unsymmetri-cal norsquaraine 48b has a p/C, around 11.2, the norcyanine dye 47d carrying the same substituents has a p/sTa of 7.5 [118]. Due to this pATa-shift to the alkaline pH range, some of these norsquaraines are also useful as fluorescent labels as their spectral properties are not affected in the pH range below 7.5. 

Organic fluorescent dyes with the appropriate spectral properties also can be paired with lanthanide chelates in FRET systems. For instance, many rhodamine dyes and the cyanine dye Cy5 have ideal excitation wavelengths for receiving energy from a nearby europium chelate. The LeadSeeker assay system from GE Healthcare incorporates various Cy5-labeled antibodies for developing specific analyte assays. In addition, if using a terbium chelate as the donor, then a Cy3 fluorescent dye can be used in assays as the acceptor. 

DiCesare N, Lakowicz JR. Spectral properties of fluorophores combining the boronic acid group with electron donor or withdrawing groups implication in the development of fluorescence probes for saccharides. Journal of Physical Chemistry A 2001, 105, 6834—6840. 

Colorimetric pH sensing has a long tradition and numerous chromogenic sensors such as phenolphthalein, bromothymol blue, methyl red, and many others, have been developed. These indicators are involved in protonation-deprotonation equilibria between two (or more) forms of different spectral properties. Much higher sensitivity can be obtained with fluorescent proton sensors. Furthermore, this technique can be widely used in bioanalytical chemistry, cellular biology, and medicine. Application of fluorescence imaging techniques provides spatial information on pH. 

It is a serious limitation that all these optical techniques can only be used for reactions that are accompanied by significant chromophoric changes, ft is an additional limitation of all these techniques that optical spectra tend to be broad and often show considerable overlap. Therefore reactive species can often not be monitored individually, even in cases where all of them have distinct spectral properties. Optical methods also provide little structural information about the various species in the mixture. The use of traditional stopped-flow is dependent upon the availability of optical signals to monitor change in fluorescence, absorbance or CD that occur upon binding or chemical conversion of substrate to product. In order to overcome these limitations of traditional stopped-flow optical techniques, various detection methods have been developed, such as stopped-flow mass spectrometry (MS), stopped-flow NMR, and stopped-flow EPR. 

To maximize fluorophore excitation and increase the fluorescence quantum yield, the spectral properties of the metal nanoparticles need to be optimized. While spherical colloidal nanoparticles of noble metals have been well known for many years, it is only recently that there has been an explosion of reports on the preparation and properties of anisotropically-shaped materials. As will be discussed in the following sections, a wide range of morphologies can be produced, including triangular nanoplates (nanoprisms), cubes, octahedra, nanowires, nanorods and bi-pyramids. The last few years have also seen major developments in our understanding of the growth processes involved, so that now it is possible to prepare many types of shaped p>articles in a controlled fashion. 

The chemistry and spectral properties of dyes have been discussed in Sections 8.38.3.2 and 8.38.7.3. Intense research is underway to develop practical fluorescent labels and probes for bioanalytical applications <90JCR(S)308). The near-infrared fluorescing dyes are primary candidates for the development because of a negligible background interference from a biological medium in the near-infrared region. A large number of potential substrates for synthesis of polymethine near-infrared dyes can be found in the references listed in Section 8.38.3.2. 

Of the squaraine dyes N-succinimidyl ester-derivatized indolium-squaraine dyes have been specifically developed for conjugation to biomolecules, because this class of dyes has been shown to exhibit high photostability, a long fluorescence lifetime and spectral properties (absorption, emission, and fluorescence lifetime) which are... 

A new simple and reliable method for monitoring photoinduced acid generation in polymer films and in solutions of the kind used in 193 nm and deep-UV lithography was developed. By using N-(9-acridinyl)acetamide, a fluorescent acid-sensitive sensor, we have been able to study the effects of trifluoroacetic acid and photoacids generated from triphenylsulfonium hexafluoroantimonate on the spectral properties of the acid sensor in THF solution and in alicyclic polymer resist films exposed at 193 nm. In both cases a hypsochromic spectral shift and an increase in fluorescence intensity were observed upon protonation. This technique could find application in the study of diffiisional processes in thin polymer films. 

To determine the photophysical and photochemical properties of unsubstituted phthalocyanines (MPc, M = Mg, Al, ZrL, SiClj, V=0, 2H) in their aggregates su-pramolecular systems have been developed on the basis of protein (albumin), micelles, biocompatible hydrophihc polymers, and nanoscale silica. The ability of MPc in supramolecular systems to form aggregates of different types depends on the nature of the central metal ion and microenvironment. The dependence of the type of MPc photoactivity method on aggregation was shown. H-aggregates exhibit selective photoactivity in electron transfer to Oj to form ROS (triplet-triplet energy transfer and fluorescence are impossible). Monomers and J-aggregates of MPc fluoresce and may also participate in the triplet-triplet energy transfer with the formation of O. Spectral properties of J-correspond to the requirements of the photosensitizer. 

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