Fluorescence probes interface

In an effort to understand how actin-actin interactions might be affected by the binding of the myosin head, and in order to gain more insight into the nature of the actin-myosin interface, we have investigated the nature of the kinetic actin-myosin intermediates involved in the process of S)-induced polymerization of G-actin. For this purpose, a variety of fluorescent probes (e.g., pyrene, NBD, AEDANS) have been covalently attached to the C-terminus of G-actin to probe the G-actin-S] interaction under conditions of tightest binding, i.e., in the absence of ATP. 

Fluorescent probes are divided in two categories, i.e., intrinsic and extrinsic probes. Tryptophan is the most widely used intrinsic probe. The absorption spectrum, centered at 280 nm, displays two overlapping absorbance transitions. In contrast, the fluorescence emission spectrum is broad and is characterized by a large Stokes shift, which varies with the polarity of the environment. The fluorescence emission peak is at about 350 nm in water but the peak shifts to about 315 nm in nonpolar media, such as within the hydrophobic core of folded proteins. Vitamin A, located in milk fat globules, may be used as an intrinsic probe to follow, for example, the changes of triglyceride physical state as a function of temperature [20]. Extrinsic probes are used to characterize molecular events when intrinsic fluorophores are absent or are so numerous that the interpretation of the data becomes ambiguous. Extrinsic probes may also be used to obtain additional or complementary information from a specific macromolecular domain or from an oil water interface. 

The aim of this Chapter is to review a method by which fluorescence properties of organic dyes can, in general, be predicted and understood at a microscopic (nm scale) by interfacing quantum methods with classical molecular dynamics (MD) methods. Some review of our extensive applications [1] of this method to the widely exploited intrinsic fluorescence probe in proteins, the amino acid tryptophan (Trp) will be followed by a discussion of electrochromic membrane voltagesensing dyes. 

Fig. 21 In situ epifluorescence micrographs of (a) fluid racemic and (b) crystalline enantiomeric SSME monolayers at the air-water interface at 25°C. Lighter domains are fluorescing probe l-NBD PC darker domains are SSME. Total magnification is 5000x. Reprinted with permission from Harvey et al, 1989. Copyright 1989 American Chemical Society.

Chandar, P., P. Somasundaran, and N. J. Turro (1987), "Fluorescence Probe Studies on the Structure of the Adsorbed Layer of Dodecyl Sulfate at the Alumine Water Interface", J. Coll. Interf. Sci. 117, 31-46. 

A. P. Demchenko and N. V. Shcherbatska, Nanosecond dynamics of the charged fluorescent probes at the polar interface of the membrane phospholipid bilayer, Biophys. Chem. 22, 131-143 (1985). 

Based on these devices, different biomass estimation experiments were performed based on the culture fluorescence monitoring and feeding strategy studies were developed as well as bioreactor characterizations via mixing time experiments. During the next years smaller fluorescence probes were developed which could be interfaced with bioreactors via standard electrode ports. These open end detector systems measured the fluorescence fight in the backward di-... 

Fluorescence Probing of the Surfactant Assemblies in Solutions and at Solid-Liquid Interfaces... 

Keywords Fluorescence probing Hemimicelle Micellar fluidity Micelle Organized assemblies in solution and interfaces Polarity parameter Pyrene... 

Organizational characteristics of surface-active molecules have been studied by several researchers due to their applications in many areas such as personal care, polymerization, catalysis, drug delivery, separation and purification, enhanced oil recovery and lubrication. The structure of supramolecular organized assemblies formed in different solvents, when a critical concentration is exceeded, determines their properties such as solubilization [1-3], catalysis [1,4-6], adsorption [7-11] and flocculation [12,13]. As such, many techniques have been used to determine their structural properties. In this paper, the results obtained using fluorescence probing for properties of assemblies in solution and at solid-liquid interfaces are discussed in detail after a brief review of relevant assemblies formed by them. 

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... 

Figure 11 [76-79]. In this system, Pe or DPA in the droplet acts as a fluorescence probe for the interfacial ET. Namely, fluorescence of Pe or DPA in the droplet is quenched by FeCp-X, but not by FeCp-X+ produced by the ET reaction. Therefore, the time course of the FeCp-X concentration in the oil droplet ([FeCp-X]0) during electrolysis of Fe(II) in water can be determined by that of the fluorescence intensity of the fluorescer (/F). Although fluorescence quenching by Fe(II) or Fe(III) is also expected to take place at the droplet/water interface, such a contribution is neglected compared to the quenching by FeCp-X in the droplet interior, owing to the short diffusion length of the excited singlet state Pe or DPA.

Figure 1. (Bottom) Diagram of the electrostatic potential adjacent to a membrane bearing a positive charge. The zeta potential is the potential at the hydrodynamic plane of shear, which should be about 2 A from the surface of the membrane. (Top) Schematic of the location of the probe molecules used to detect the potential produced by the adsorption of calcium and other alkaline earth cations to membranes formed from PC. The divalent cation cobalt and the amphipathic, anionic, fluorescent probe TNS will sense the potential at the interface. The non-actin-Rf complex will sense the potential in the center of the membrane.

The interactions of TDZ (6) with model membranes composed of different phospholipids were also studied by the same group [78]. Calorimetric studies demonstrated that TDZ (6) altered the thermotropic properties of negatively charged DMPC membranes to a larger extent than of zwitterionic phospholipids (PC and PE). The character of the drug-induced changes of the transition parameters of all studied lipids indicated that TDZ (6), similarly to other phenothiazine derivatives, was likely to be localized close to the po-lar/apolar interface of the bilayers. Experiments in which fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) was employed revealed that TDZ (6) reduced the mobility of lipid molecules in a concentration-dependent manner and thus decreased membrane fluidity. The influence of TDZ (6) on isolated... 

Chandar, P., Somasundaran, P., and Turro, N.J. (1987). Fluorescence probe studies on the structure of the adsorbed layer of dodecyl sulfate at the alumina-water interface. J. 

A demonstration of the single molecule detection at the liquid-liquid interface was reported for the fluorescent probe of l,l/-dioctadecyl-3,3,3/,. 3 -tetramethyI i ndoearboeyan i ne (Dil), which is a monovalent cation with two Cig alkyl chains. Thus, it has high adsorptivity at the dodecane-water interface. 

The FRAP method has been applied to the measurements of molecular lateral diffusion of molecules adsorbed at the interface of equilibrium common thin foam films and of black foam films [39-43], Initially Clark et al. reported FRAP measurement of surface diffusion of the fluorescence probe 5-N(octadecanoyl)aminofluorescein incorporated into foam films stabilised with NaDoS [39]. Then followed the measurements of protein-stabilised foam films where the protein was covalently labelled with fluorescein [40,41], Studies of FRAP measurements of surface lateral diffusion in equilibrium phospholipid common thin foam films and black foam films were also reported [42,43]. 

For TIR fluorescence spectroscopy on water/oil interfaces, the choice of a probe molecule is of primary importance. For example, the penetration depth (dp) of an incident evanescent wave at a 1,2-dichloroethane (DCE, refractive index (n) n = 1.44)/water (m2 = 1.33)interface is calculated to be 94nm on the basisofEquation(13),whereX = 580 nm and 0 = 80°. It has been reported that the thickness of a sharp water/oil interface represented by water/DCE is 1 nm [9], so that dp of the incident evanescent wave is thicker than the thickness of the interfacial layer, and the fluorescence characteristics of a probe molecule in the bulk phase are superimposed, more or less, on those at the interface [2]. Therefore, a probe molecule should be highly surface-active and adsorb on the interface, so as to exclude fluorescence of the probe molecule from the bulk phase. In the present experiments, we employed xanthene dyes as fluorescence probes throughout... 

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