Eneigy transfer

N. Lokan, M. N. Paddon-Row, T. A. Smith, M La Rosa, K P. Ghiggino, S. Speiser, Highly Efficient Through-Bond-Mediated Electronic Excitation Eneigy Transfer Taking Place Over 12 A , J. Am Chem Soc 1999,121,2917-2918. 

Under the condition when one can use FO perturbation approach in quantum and quasiclassical calculations, the classical mean square eneigy transfer can also be calculated in the FO classical perturbation theory. This again opens a possibility for comparison of FOD and FOA (now classical) approximations. Fig.4 shows the... 

The structural dimension at a water/DCE interface is d = 2.48, while short-range structural information about the interface obtained by the fluorescence dynamic anisotropy experiments suggests that the interface is three-dimensional-like. Taking the results obtained by molecular dynamics simulations into account, these results can be understood only by the fact that the water/DCE interface is thin ( 1 nm), but is rough with respect to the spatial resolution of the excitation eneigy transfer quenching method ( 7 nm), as shown in Figure 12.7. 

Electronic Structure and Eneigy Transfer in Solid a-Sexithienyl... 

If radiant eneigy transfer can be prevented, the following equation is used ... 

Figure 2. Energy level Scheme of Tm -Yb codoped oxyfluoride glass ceramic. The Dashed lines show the upconversion process to populate G4 level of Tm ions by eneigy transfer from Yb ions which are produced by using OPO laser at 975 nm. Solid line shows the optical gain transition.

Fi >. U. Eneigy transfer from a sensiiiser S to an activator A. Energy transfer is indicated by E.T. For further nouition, see Hg. 1.1... 

At higher temperatures the occupation of vibrational levels is no longer restricted to the zero-vibrational levels. The spectral bands broaden, and, as a consequence the spectral overlap may increase enough to make (thermally stimulated) eneigy transfer possible. We will now discuss several examples for illustration [7,10]. 

For example, the measured pressure exerted by an enclosed gas can be thought of as a time-averaged manifestation of the individual molecules random motions. When one considers an individual molecule, however, statistical thermodynamics would propose its random motion or pressure could be quite different from that measured by even the most sensitive gauge which acts to average a distribution of individual molecule pressures. The particulate nature of matter is fundamental to statistical thermodynamics as opposed to classical thermodynamics, which assumes matter is continuous. Further, these elementary particles and their complex substmctures exhibit wave properties even though intra- and interparticle eneigy transfers are quantized, ie, not continuous. Statistical thermodynamics holds that the impression of continuity of properties, and even the soUdity of matter is an effect of scale. 

Van Der Meer WB, Coker G, Chen SS-Y (1991) Resonance eneigy transfer. Wiley, New York... 

There are numerous additional reasons for measuring tune-resolved fluorescence. In the presence of eneigy transfer, the intensity decays reveal how acc tors are distributed in space around the donors. Time>resolved measurements reveal whether quenching is due to diffusion or to complex formatioD with the ground-state fluoro-phores. In Huorescence, much of the molecular informaticMi content is availaHe only from time-resolved measurements. 

Figure 13.2. Dependence of the eneigy transfer efficiency ( ) on distmce A, is the l%ister distance.

Energy transfer is widely useful in biochemistry even apart from its application for the measurement of distances. This is because energy transfer occurs independently of the linker joining the donor and acceptor and depends only on the D-A distance. Hence, any process bringing the donor and acceptor into close proximity will result in eneigy transfer. This includes biochemical association reactions, as will be illustrated below for protein subunits and DMA oligomers. 

There is considerable infcxmation in these time-resolved decays, and methods to recover this information are described in Chapter 15. In the more general case, the distance between donor and acceptor can vaiy both as a result of a range of distances and by difiusion. Both factors affect the rates of eneigy transfer and must be considered in any such analysis. 

Hoirocks.W.DeW..HolflM iilst.B..andNUlee.B.Ul975.Eneigy transfer between tetbinmQID and cobalt(II) in dtennolyna A new class of metal-aetal distance probes. Proc. Mut Acad Sci VSA. 72 4764-4768. 

E W e not immediatdy obvious, the extent of transfer from a tryptophan donor to an acceptor is expected to change upon association of foe acceptor-labeled monomers. This is because, upon dimerization, each tryptophan residue will be brou imo proximity df foe acceptor on the other subunit Hence, ea tryph ian will transfer to two accqnors, resulting in a arnoum of eneigy transfer and a lower donor quadinn yidd in foe dimeric state. 

In order to determine the eneigy transfer on the molecular formation, it is applied the principle of electronegativity equalization, EN5 Principle, such as ... 

A. Anders, Selective laser excitation of bases in nucleic acids. Appl. Phys. 20,257 (1979) A. Anders, Models of DNA-dye-complexes eneigy transfer tind molecular structure. Appl. Phys. 18,373 (1979) ... 

Markovitsi D, Gustavsson T, Talbot F (2(XJ7) Exdted states and eneigy transfer among DNA bases in double heUces. Photochem Photobiol Sd 6 717... 

Both the exciton/radical pair equilibrium model and the bipartite model predict formally the same kinetics and thus both give rise also to a biexponential fluorescence decay. However, the two models are fundamentally different. This difference consists in the entirely different meaning of the rate constants involved and thus in the entirely different origin of the two observed lifetimes. In the bipartite model the biexponentiality is due to the equilibration of the excitons between antenna and reaction center. Thus one of the lifetime components reflects an eneigy transfer process. In contrast to the exciton/radical pair equilibrium model the bipartite model basically describes a diffusion-limited kinetics. Despite the fact that it formaUy can describe correctly the observed kinetics, the application of the bipartite model on experimental data leads to physically unreasonable results. First it results in a charge separation time in the reaction centers which is by one to two orders of magnitude too high. 

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