Forster probe

Finally, it should be mentioned that small magnetic fields, down to approximately 0.1 mOe, can be measured conveniently with a Forster probe [For55]. Its principal of operation will be explained with the help of Fig. 10.9. The probe consists of a pair of ferromagnetic cores (Kj and K2), each surrounded by a primary and a secondary coil. A sinoidal alternating current with a frequency of 20 kHz is sent... 

Eddy currents The examination of non-ferrous tubing using external coils is a well-tried and successful inspection technique, owing mainly to the pioneering work of Forster in Germany. The adoption of this method for in-situ inspection of condenser tubes, by mounting eddy-current coils in probes (or bobbins) that can be inserted in condenser tubes, was a logical development of the technique. Suitable apparatus was developed in the immediate post-war period more or less independently by several oil and chemical companies. The principle of operation has been described in the literature... 

The lifetime of the excited state of fluorophores may be altered by physical and biochemical properties of its environment. Fluorescence lifetime imaging microscopy (FLIM) is thus a powerful analytical tool for the quantitative mapping of fluorescent molecules that reports, for instance, on local ion concentration, pH, and viscosity, the fluorescence lifetime of a donor fluorophore, Forster resonance energy transfer can be also imaged by FLIM. This provides a robust method for mapping protein-protein interactions and for probing the complexity of molecular interaction networks. 

The protocol for modifying DNA probes with photobiotin can be found in Chapter 27, Section 2.3. It is based on the method of Forster et al. (1985). The following method is a suggested protocol for the modification of proteins using a photoreactive biotin derivative. Some optimization may be necessary to obtain the best incorporation levels. 

Forster, A.C., Mclnnes, J.L., Skingle, D.C., and Symons, R.H. (1985) Non-radioactive hybridization probes prepared by the chemical labeling of DNA and RNA with a novel reagent, photobiotin. Nucleic Acid Res. 13, 745-761. 

Murphy CB, Zhang Y, Troxler T, Ferry V, Martin JJ, Jones WE Jr (2004) Probing Forster and Dexter energy-transfer mechanisms in fluorescent conjugated polymer chemosensors. J Phys Chem B 108 1537-1543... 

Moon SH, Chiche A, Forster AM, Zhang WH, Stafford CM (2005) Evaluation of temperature-dependent adhesive performance via combinatorial probe tack measurements. Rev Sci lustrum 76 062210... 

The values of /labs were determined from the experimentally measured absorption anisotropy with Eq. 6. In viscous polyTHF, the rotational movement of dye molecules on a lOOps time scale is assumed to be negligible, and thus, does not reduce the limiting value of anisotropy. For the concentrated fluorene solutions (5 x 10 M, 1 mm cuvette), the anisotropy Tabs was not affected by FOrster depolarization mechanisms [13] due to the short time delay, tD, between probe and pump pulses when td/ti 1 [35]. 

Additional work by the Forster group, making use of transient emission spectroscopy, probed the rate of photoinduced electron transfer between metal centers within a novel trimeric complex [Os(II)(bpy)2(bpe)2 ] [Os(II) (bpy)2Cl]2 4+, where bpy is 2,2/-bipyridyl and bpe is fra s-l,2-bis-(4-pyridyl) ethylene. Transient emission experiments on the trimer, and on [Os(bpy)2(bpe)2]2+ in which the [Os(bpy)2Cl]+ quenching moieties are absent, reveal that the rate of photoinduced electron transfer (PET) across the bpe bridge is 1.3 0.1 x 108s-1. The electron transfer is believed to be from the peripheral Os(II)Cl metal centers to the [Os(bpy)2(bpe)2]2+ chro-mophore. Comparison to rate constants for reduction of monolayers at a Pt electrode reveals that the photoinduced process is significantly faster [39]. 

The elucidation of the structure, dynamics and self assembly of biopolymers has been the subject of many experimental, theoretical and computational studies over the last several decades. [1, 2] More recently, powerful singlemolecule (SM) techniques have emerged which make it possible to explore those questions with an unprecedented level of detail. [3-55] SM fluorescence resonance energy transfer (FRET), [56-60] in particular, has been established as a unique probe of conformational structure and dynamics. [26-55] In those SM-FRET experiments, one measures the efficiency of energy transfer between a donor dye molecule and an acceptor dye molecule, which label specific sites of a macromolecule. The rate constant for FRET from donor to acceptor is assumed to be given by the Forster theory, namely [59,61-64]... 

The spectroscopic characteristics of actinide and lanthanide luminescent probes are sensitive to numerous parameters, such as modifications of solvent composition, addition of supporting electrolytes, temperature changes etc. Therefore, TRES appears as an interesting tool for the chemist, because it provides sensitive experimental data. However, the interactions between the probe and the surrounding medium (in a wide sense) appear to be intricate and difficult to handle. In this sense, attempts to describe lifetime variations as a function of a unique parameter, the hydration sphere number, have shown their limitations. On the other hand, the open questions related to Forster s mechanism are a vivid and still not fully explored field. 

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