Fluorescence solubility measurement

The formation of the complexes leads to significant changes of the solubility and reactivity of the guest molecules without any chemical modification. Thus, water insoluble molecules may become completely water soluble simply by mixing with an aqueous solution of native CD and CD derivatives, e.g. methylated (Me) or hydroxypropylated CD. The water solubility of these inclusion compounds enables detection of complex formation in solution by spectroscopic methods, such as NMR [16], UV, fluorescence, or circular dichroism spectroscopy, as well as by thermodynamic methods, e.g. microcalorimetry [17] or density [18,19], or by solubility measurements. Likewise, mass spectrometry was used [20],... 

Sensitivity of the instrument, which refers to the system response to small changes in concentration, is determined by the signal to noise ratio (SNR) of the measurement, as well as, the concentration slope. The SNR of each measurement may be considerably smaller than variation between measurements made on different occasions. Measurements of concentration from absolute fluorescent intensity (O) are possible provided that the calibration of the instrument remains unchanged. Reliable fluorescent intensity measurements across different instruments or from repeated measurements with the same instrument are possible only if the above factors can either be eradicated from consideration or be controlled with an experiment independent calibration coefficient. One effective solution proposed the development of a set of standard reference materials (SRMs) for use with identical instruments [9]. Thus, for a particular instrument, the concentration of a test solution can be expressed as a ratio of the fluorescent counts for the test and SRM. Subsequently, it was recommended that the concentration of the test solution could be expressed in molecular equivalent soluble fluorophore (MESF) units. This protocol was developed with respect to the use of flow c) tometers, which can be operated close to the ideal experimental conditions. Despite this, measurements of fluorescent intensity in terms of MESF units stiU have problems, as most fluorescence-based instruments cannot be guaranteed to operate under the same conditions from day to day. 

Atactic PSSA is soluble in water, methanol, and ethanol but insoluble in hydrocarbons. PSSA salts are insoluble in common organic solvents but soluble in water. Ultraviolet and fluorescence spectrometry measurements can yield information on features including local environment, neighboring groups, and tacticity. MHS values and solution properties are reviewed in Reference 56. Cross-linked PSSA has been used commercially as an ion-exchange resin and in heavy metal binding studies. Fractionated PSSA has been offered as a standard for aqueous gel-permeation chromatography... 

A red fluorescent coordination polymer (32) was obtained by our research group from a tpy-functionalized perylene bisimide chromophore by complexation with zinc triflate [85]. The polymer 32, which is readily soluble in chloroform/methanol mixtures and DMF, retains the excellent fluorescence properties of the free ligand and shows reversible binding, thus, the chain length decreases upon addition of an excess amount of Zn . The polymeric structure was estabhshed by NMR using a dimer model compound as reference as well as by DOSY NMR, UV/vis spectroscopy, fluorescence anisotropy measurements, and AFM [86]. Further superstructures were ob-... 

Robinson compared the behavior of a number of partitioning bi-dentate ligands in terms of reaction with Ni +(aq) in the presence of anionic micelles. More recently, Reinsborough and co-workers also studied in more detail the sub-cmc rate enhancement effects that are evident in surfactant solutions at concentrations near the cmc. It was concluded that, for the Ni VPADA reaction, nickel ion-surfactant aggregates could form below the normal cmc, and data from surface tension, dye solubility, and fluorescence probe measurements supported this interpretation. A more recent study has... 

Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

To measure a residence-time distribution, a pulse of tagged feed is inserted into a continuous mill and the effluent is sampled on a schedule. If it is a dry miU, a soluble tracer such as salt or dye may be used and the samples analyzed conductimetricaUy or colorimetricaUy. If it is a wet mill, the tracer must be a solid of similar density to the ore. Materials hke copper concentrate, chrome brick, or barites have been used as tracers and analyzed by X-ray fluorescence. To plot results in log-normal coordinates, the concentration data must first be normalized from the form of Fig. 20-15 to the form of cumulative percent discharged, as in Fig. 20-16. For this, one must either know the total amount of pulse fed or determine it by a simple numerical integration... 

As far as we know, this is the first molecular probe that includes two different types of reporter units activated upon on a specific stimulus. The other option to achieve dual detection would be to use two separate probes. However, in this case there could be a problem of competitive catalysis (circumstances in which the Km of the two substrate is not identical). In our probe, 6-aminoquinoline and 4-nitrophenol, detected by fluorescence and absorbance spectroscopy, respectively, were used as reporter units. Due to the synthetic flexibility of our approach, other reporter molecules with different types of functional groups, like amine or hydroxyl, can be linked to our molecular probe. The two assays must be orthogonal to each other, in order to prevent disturbances in the detection measurement. Another advantage of the probe is the aqueous solubility... 

The F/P ratio of the purified, labeled protein may be determined by measuring the absorbance at 345 and 280nm. Ratios between 0.3 and 0.8 usually produce labeled molecules having acceptable levels of fluorescent intensity and good retention of protein activity. AMCA-labeled proteins may be lyophilized without significant loss of fluorescence. The addition of bovine serum albumin (15mg/ml) or another such stabilizer is often necessary to retain solubility of the freeze-dried, labeled protein after reconstitution. 

In this respect, the solvatochromic approach developed by Kamlet, Taft and coworkers38 which defines four parameters n. a, ji and <5 (with the addition of others when the need arose), to evaluate the different solvent effects, was highly successful in describing the solvent effects on the rates of reactions, as well as in NMR chemical shifts, IR, UV and fluorescence spectra, sol vent-water partition coefficients etc.38. In addition to the polarity/polarizability of the solvent, measured by the solvatochromic parameter ir, the aptitude to donate a hydrogen atom to form a hydrogen bond, measured by a, or its tendency to provide a pair of electrons to such a bond, /, and the cavity effect (or Hildebrand solubility parameter), S, are integrated in a multi-parametric equation to rationalize the solvent effects. 

As a technique for selective surface illumination at liquid/solid interfaces, TIRF was first introduced by Hirschfeld(1) in 1965. Other important early applications were pioneered by Harrick and Loeb(2) in 1973 for detecting fluorescence from a surface coated with dansyl-labeled bovine serum allbumin, by Kronick and Little(3) in 1975 for measuring the equilibrium constant between soluble fluorescent-labeled antibodies and surface-immobilized antigens, and by Watkins and Robertson(4) in 1977 for measuring kinetics of protein adsorption following a concentration jump. Previous rcvicws(5 7) contain additional references to some important early work. Section 7.5 presents a literature review of recent work. 

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