Sensing metabolites using donor-acceptor nanodistributions in fluorescence resonance energy transfer

Before fluorescence sensing techniques can be applied to media as delicate and complicated as human tissue, an adequate interpretation of the measured observables is required, i.e., an inverse problem needs to be solved. Recently we have solved the inverse problem relating to the kinetics of fluorescence resonance energy transfer (FRET), which clears the way for the determination of the donor-acceptor distribution function in FRET assays. In this letter this approach to monitoring metabolic processes is highlighted and the application to glucose sensing demonstrated

Characterisation of phosphate coacervates for potential biomedical applications

In this study, amorphous (Na2O)x(CaO)0.50−x(P2O5)0.50·yH2O (where x = ∼0.15 and y = ∼3) samples were prepared by a coacervate method. Thermal analysis showed that two types of water molecules were present in the coacervate structures: one type loosely bound and the other part of the phosphate structure. Structural studies using Fourier transform infrared spectroscopy (FTIR) and X-ray total diffraction revealed the samples to have very similar structures to melt-quenched glasses of comparable composition. Furthermore, no significant structural differences were observed between samples prepared using calcium nitrate as the calcium source or those prepared from calcium chloride. A sample containing ∼1 mol% Ag2O was prepared to test the hypothesis that calcium phosphate coacervate materials could be used as delivery agents for antibacterial ions. This sample exhibited significant antibacterial activity against the bacterium Psuedomonas aeruginosa. FTIR data revealed the silver-doped sample to be structurally akin to the analogous silver-free sample

Photoproduction of D∗±D^{*\pm} mesons associated with a leading neutron

The photoproduction of $D^{*\pm} (2010)$ mesons associated with a leading neutron has been observed with the ZEUS detector in $ep$ collisions at HERA using an integrated luminosity of 80 pb$^{-1}$. The neutron carries a large fraction, {$x_L>0.2$}, of the incoming proton beam energy and is detected at very small production angles, {$\theta_n<0.8$ mrad}, an indication of peripheral scattering. The $D^*$ meson is centrally produced with pseudorapidity {$|\eta| 1.9$ GeV}, which is large compared to the average transverse momentum of the neutron of 0.22 GeV. The ratio of neutron-tagged to inclusive $D^*$ production is $8.85\pm 0.93({\rm stat.})^{+0.48}_{-0.61}({\rm syst.})\%$ in the photon-proton center-of-mass energy range {$130 <W<280$ GeV}. The data suggest that the presence of a hard scale enhances the fraction of events with a leading neutron in the final state.Comment: 28 pages, 4 figures, 2 table

EUROPEAN ACHIEVEMENTS IN SENSOR RESEARCH DEDICATED TO IN VIVO MONITORING - (a) Glucose

International audienceMembers of the EC Concerted Action on Chemical Sensors for In Vivo Monitoring, and invited workshop participants, were sent a questionnaire which sought to record details of in vivo and ex vivo glucose sensors under development in Europe. One workshop..

A new approach to fluorescence lifetime sensing based on molecular distributions

Fluorescence resonance energy transfer (FRET) from donor to acceptor molecules is one of the most powerful techniques for monitoring structure and dynamics. This is because FRET has a strong spatial dependence with angstroms resolution. This dependence includes the simplest case of a random distribution of acceptors for which an analytical solution exists for the fluorescence impulse response I(t). However, in general the acceptor distribution function p(r) is not random and a unique solution cannot be found for I(t). In many important applications of FRET eg in proteins, the simple random treatment is quite inappropriate and yet the information concerning conformation changes is preserved in p(r). One approach, which as been applied to the problem of determining p(r), is to make some assumptions as to its form eg Gaussian and then try to use this to describe I(t)

Near-infrared assay for glucose determination

A new glucose sensing system based on near infra-red fluorescence resonance energy transfer (FRET) from CocanavalinA-allophycocyanin to dextran labelled malachite green is demonstrated. Single-photon timing fluorescence lifetime measurements have enabled us to investigate and understand the quenching kinetics in terms of the dimensionality of energy transfer

A time-resolved near-infrared fluorescence assay for glucose: opportunities for trans-dermal sensing

We report a time-resolved near-infrared fluorescence assay for glucose detection that incorporates pulsed diode laser excitation. Reduction in fluorescence resonance energy transfer to a malachite green-Dextran complex from allophycocyanin bound to concanavalin A (ConA) due to displacement of the complex by glucose from ConA provides the basis of the assay. The fluorescence quenching kinetics are analysed and discussed in detail. The change in fluorescence decay kinetics in the presence of glucose is found from dimensionality studies to be brought about by a change in the distribution of malachite green-Dextran acceptors. Glucose concentrations are measured in solution to within ±10% over the range 0-30 mM