Biomedical subjects

Robert D Jenkins

Publications and source records attributed to Robert D Jenkins.

3 recordsLinked to original sources

PubMed2004

Quantum pathways for resonance energy transfer.

A quantum electrodynamical calculation is presented that focuses individually on the two quantum pathways or time orderings for resonance energy transfer. Conventional mathematical procedures necessitate summing the quantum pathway amplitudes at an early stage in the calculations. Here it is shown, by the adoption of a different strategy that allows deferral of the amplitude summation, that it is possible to elicit key information regarding the relative significance of the two pathways and their distinct distance dependences. A special function integration method delivers equations that also afford new insights into the behavior of virtual photons. It is explicitly demonstrated that both time-ordered pathways are effective at short distances, while in the far field the dissipation of virtual traits favors one pathway. Hitherto unknown features are exhibited in the oblique asymptotic behavior of the time-ordered contributions and their quantum interference. Consistency with the rate equations of resonance energy transfer is demonstrated and results are presented graphically.

Journal Article↗

PubMed2003

Biexciton resonance energy transfer in a model photosystem.

The absorption of two photons by a concentrated assembly of identical chromophores can lead to formation of a biexciton. This work concerns the transfer of biexcitonic energy from a ring to a central donor, with a particular focus on rates and geometric effects. Quantum amplitudes are expressed in terms of orientation factors with a clear physical significance and detailed calculations are performed on an idealised, three-fold symmetric photosystem-a structural motif common in a variety of natural and artificial light-harvesting systems.

Energy Transfer↗

PubMed2003

Exciton resonance energy transfer: effects of geometry and transition moment orientation in model photosystems.

When a photon is absorbed by a group of identical chromophores the excited state may be described as an exciton. Such excitons play a significant role in the energetics of many photoactive systems, and in particular the photosynthetic unit. This work concerns the transfer of excitonic energy to a donor, focussing on the effects of geometry. To facilitate the analysis, calculated quantum amplitudes are expressed in terms of orientation factors with clear physical significance. In detailed calculations on an idealised, three-fold symmetric photosystem it is shown that intermolecular vectors and relative transition dipole moment orientations directly affect transfer rates, and the detailed form of that dependence is determined. Differences in the linear combinations which form the excitonic states are fully investigated and various configurations exclusively exhibiting excitonic behaviour are identified.

Journal Article↗