Fluorescent probe technique

Hasegawa M, Sugimura T, Shindo Y and Kitahara A 1996 Structure and properties of AOT reversed micelles as studied by the fluorescence probe technique Colloids Surf. A 109 305-18... 

Abstract Fluorescent molecules have been widely used as biomolecular labels, enzyme substrates, environmental indicators, and cellular stains and thus constitute indispensable tools in chemistry, physics, biology, and medicinal sciences. The large variation in the photophysics of the available fluorophores connected with chemical alterations give fluorescent probe techniques an almost unlimited scope for the detection of specific molecules and the investigation of intermolecular interactions on a molecular scale. 

Though y-CD was found to form complexes also with PEG, the yields were too small for their characterization. Thus, Harada et al. turned to two PEG deriva-tives-bis(3,5-dinitrobenzoyl)-PEG (PEG-DNB2) and bis(2,4-dinitrophenyl-amino)-PEG (PEG-DNP2)-, which were found to complex with this CD at high yields. Using a fluorescent probe technique the resulting complexes were shown to include four ethylene glycol units in one y-CD cavity. However, these PEG derivatives formed no complex with a-CD. This is attributable to the fact that their chains are too thick to enter the slim a-CD cavity. 

To obtain additional information PEG-DNB2 was allowed to complex with y-CD first by adding it to an aqueous solution of y-CD at the 2 1 stoichiometric ratio and then further adding the same amount of it to the mixture in total, 90% of the CD was consumed for complexation. The area of the H NMR peak for CD relative to that for PEG in the isolated complex was consistent with the above finding. It is interesting to compare this result with the complexation of a-CD with PEG, by the fluorescent probe technique. 

The evidence accumulated in the literature suggests that the structure of surfactant adsorbed layers is, in some respects, analogous to that of surfactant micelles. Fluorescence probing techniques - e.g., pyrene and dinaphtylpropane (DNP) fluorescence probes are used to investigate the structure of adsorbed layer of a surfactant - give information on the polarity of the microenvironment in the adsorbed... 

Initially, this mechanism was proposed on the basis of results obtained for zeta potential and flotation (Fig. 29). The formation of the hydrophobic aggregates at the interface was confirmed after the advent of the fluorescence probing technique. The adsorption isotherm is determined in the presence of pyrene as the fluorescent probe and the emission spectra of pyrene in both supernatant and slurries were analyzed after adsorption. The h/h of pyrene in solutions of SDS containing 0.1 M NaCl and in the slurry are shown in Figs. 30 and 31. In solution, the ratio remains at around 0.6 till the CMC (as determined by surface tension measurement) is attained. Above CMC, the value becomes 1.0 due to the solubilization of pyrene in micelles. In... 

Much remains to be learned, however, regarding the limits of applicability of the fluorescence probe technique to aggregates in non-polar media. A number of obvious experiments are conspicuous by their absence from the published literature. For example, 1-pyrene carboxaldehyde is a well known probe which has been used to measure the microscopic polarity of sodium dodecyl sulfate micelles in aqueous medium (5) there is, however, no account of its use in non-polar media. 

It is worthy of note that the micellar systems dealt with in this study differ from conventional "inverted micelles" in that they contain solubilized inorganic species in their cores. It was of additional interest to observe the response of such systems to the fluorescence probe technique. 

Zhao, C. L., M. A. Winnik, G. Riess, and M. D. Croucher. 1990. Fluorescence probe techniques used to study micelle formation in water-soluble block copolymekangmuir.6 514-516. 

Signal-amplified Fluorescent Probing Techniques Metallic nanoparticle enhancedfluorescence... 

Considering the wide-spread use of fluorescent probe techniques in biological studies, it is important that a full understanding of the photophysics of the bound and unbound probe is available to enable unambiguous interpretations of the fluorescence data. The most common probes used for fluorescence work are the anilino-naphtha-lene sulphonate derivatives, particularly l-anilino-8-naphthaiene sulphonate (ANS) (XIV) and 2-p-toluidinyl-6-naphthalene sulphonate (TNS) (XV). Changes in fluores-... 

In the last years, the fluorescence probe technique has become an increasingly importance in many fields of material science because this technique opens up the possibility to examine the microscopic environment of different materials. First, this method has been successfully applied in the field of polymer science to study the polymer building process [1], the relaxation behavior of linear [2] and crosslinked polymers [3], polymer blends [4], and the interaction between polymer chains and various solvents[5]. 

CONCLUSIONS This Study shows that fluorescence probing techniques are useful and powerful tools for investigation of conformational transitions of polyelectrolytes as induced by cationic surfactants, pH or other means. Studies on the interaction of cationic probes with polyelectrolytes provide useful information on the intermediates that lie between A states and B states. It is concluded that the conformational transition induced by pH is a progressive process over several pH units. Studies on the interaction of cationic surfactants with PMA at pH 8 show that the aggregates formed are large loose structures, while the interior of the aggregate has a hydrophobicity that is similar to that of a micelle. 

The specific fluorescent probe technique used in the present research is excimer formation between pyrene groups terminally attached to both ends of poly(ethylene glycol) (PEG) chains. Excimer formation in such a labeled polymer may result from both intramolecular and intermolecular interactions. A large body of literature over the past decade deals with intramolecular cyclization as detected by fluorescence techniques. This work has come largely from three groups. Cuniberti and Perico (24, 25) were the first to explore the possibility that excimer fluorescence could be used as a probe of end-to-end cyclization dynamics. Later, Horie and co-workers (26, 27) used triplet annihilation as a probe of cyclization in long chains. By... 

The CMC is the concentration of a copolymer above which the polymer self-assembles into nanoassemblies, and below which the copolymer exists in the solution as individual molecules (unimers). The CMC is a very important parameter, reflecting the stability of micelles in solution and the ability of copolymers to form micelles in solution. The fluorescence probe technique is the most used method to determine the CMC. Pyrene, whose fluorescent spectrum is environment sensitive, particularly its first and third peaks, is the first fluorescence dye used. The intensity ratio of the third and first peaks in its emission spectra has a sharp transition at CMC and thus can be used to determine the CMC (Figure 12). 

The structure of the microdomains which form in surfactant solutions is shown schematically in Fig. 5.1. Side chains and surfactant molecules combine to form aggregates resembling mixed micelles dispersed throughout the bulk aqueous network. The composition of these microdomains has been investigated using a fluorescence probe technique adapted from the surfactant literature [2]. Results are summarized in Table 5.1 and Fig. 5.2. The total aggregation number, Nj, of the clusters is equal to the sum of the number of surfactant molecules and alkyl side chains N and respectively) in each... 

Studies on a series of tactic PMMAs both by DSC and thermally stimulated current, TSC, show Til 0 strongest in iso-PMMA and next strongest in syndio-PMMA, with a broad minimum across Ae atactic region. TSC data also revealed a Tn in isotactic PS much stronger than in ar-PS and of about the same strength as in iso-PMMA (see Table VI of ref. 1). Loutfy and Teegarden, using a fluorescent probe technique, concluded that iso-PMMA is considerably stiffer than atactic or syndio-PMMA. 25 values as found in the Polymer Handbook confirm this conclusion. 

The fluorescent probe methods were used to determine miCToviscosity (T ,) of potassium A-acylalaninates and potassium A-acylvalinates micelles. The results obtained show that 11 on the micellar surface is larger in A-acylalaninates than in 7V-acylvalinates, whereas in the micellar core remains same in the micelles of the two surfactant series. The values of 11 of SDS, lithium dodecyl sulfate (LDS), CTACl, and CjjEg, determined at 15°C by monomer/excimer intensity ratio and excimer lifetime of dipyrenylpropane dissolved in micelles, are 19, 19, 39, and 57 cP, respectively. The fluorescent probe technique was used to determine r m values of SDS, CTABr, and CTACl micelles at different applied pressure. The derived values of SDS, CTABr, and CTACl micelles at 25°C and atmospheric pressure are 12,47, and 27 cP, respectively. The addition... 

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