Fluorescence

et al. 2015

J. Phys. Chem. Lett.

Self Cite

We have monitored the formation of toxic β-amyloid oligomers leading to Alzheimer's disease by detecting changes in the fluorescence decay of intrinsic tyrosine. A new approach based on the non-Debye model of fluorescence kinetics resolves the complexity of the underlying photophysics. The gradual disappearance of nonmonotonic fluorescence decay rates, at the early stages of aggregation as larger, tighter-packed oligomers are formed, is interpreted in terms of tyrosine-peptide dielectric relaxation influencing the decay. The results demonstrate the potential for a new type of fluorescence lifetime sensing based on dual excited-state/dielectric relaxation, with application across a broad range of biological molecules. The results also reconcile previously conflicting models of protein intrinsic fluorescence decay based on rotamers or dielectric relaxation by illustrating conditions under which both are manifest.

mentioning

confidence: 99%

Tyrosine Photophysics During the Early Stages of β-Amyloid Aggregation Leading to Alzheimer’s

Rolinski

Wellbrock

et al. 2015

J. Phys. Chem. Lett.

Self Cite

“…The key instrumentation components for employing fluorescence in surgical systems are largely based on proven technology and methodologies that are already in widespread use for fluorescence spectroscopy and microscopy [28,[98][99][100] and namely comprise of an excitation source, a fluorescent probe, excitation and emission filters and the fluorescence detector. Since the details on fluorescent probes have already been discussed in section 2, this section will focus on the requirements of excitation sources, filters and detectors as well as developments being made in these areas if applicable.…”

Section: Key Components In Fluorescence-based Surgical Systemsmentioning

confidence: 99%

Fluorescence Guided Surgery

Stewart

Methods Appl. Fluoresc.

2021

Fluorescence guided surgery (FGS) is an imaging technique that allows the surgeon to visualise different structures and types of tissue during a surgical procedure that may not be as visible under white light conditions. Due to the many potential advantages of fluorescence guided surgery compared to more traditional clinical imaging techniques such as its higher contrast and sensitivity, less subjective use, and ease of instrument operation, the research interest in fluorescence guided surgery continues to grow over various key aspects such as fluorescent probe development and surgical system development as well as its potential clinical applications. This review looks to summarise some of the emerging opportunities and developments that have already been made in fluorescence guided surgery in recent years while highlighting its advantages as well as limitations that need to be overcome in order to utilise the full potential of fluorescence within the surgical environment.

“…Time-correlated single-photon counting fluorescence decay measurements were performed using a HORIBA Jobin Yvon IBH DeltaFlex incorporating non-linear least-squares reconvolution analysis with DAS6 software and a χ2 goodness of fit criterion. 27,28 2 -4 exponential models were used as appropriate. Excitation was with a NanoLED laser diode at 437 nm, 1 MHz repetition rate and < 200 ps pulse width.…”

Section: Spectroscopy Measurementsmentioning

confidence: 99%

Probing pheomelanin synthesis using thioflavin T fluorescence

Davy

Reporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications XI

2019

The fluorescent rotor probe thioflavin T (ThT) is used to investigate the presence of sheet structures in pheomelanin by studying the formation and disassembly of pheomelanin synthesized from L-cysteine, L-DOPA and the enzyme tyrosinase. Brown/black eumelanin and red/yellow pheomelanin are the most common forms of melanin with the former more extensively studied. The conclusion of decades of research is that both melanins possess ill-defined polymeric structures, which are reflected in their complex photophysics. The structural integrity and coexistence of these two forms has significant bearing on their functionality and indeed their spectroscopy offers possibilities as a melanoma biomarker. Extrinsic fluorescence probes have been little used to study melanin, but the evidence from ThT fluorescence is consistent with other techniques in finding that eumelanin's constituent dihydroxyindoles form a stacked sheet structure akin to graphite. Whether or not such an equivalent sheet structure exists for pheomelanin's constituent benzothiazines and benzothiazoles is unresolved. On investigating this possibility we find a sigmoidal increase in ThT fluorescence during pheomelanin synthesis is similar to that observed for eumelanin, implying a sheet structure. A red spectral shift in ThT fluorescence in pheomelanin and the emergence of a fluorescence decay component of ~ 5.5 ns, much longer than that of ThT, are interpreted in terms of sites wherein ThT is coupled to pheomelanin's native structure. Such sites can act as fluorescent traps to which energy is funneled when melanin is excited and the composite fluorescence yield thus increased. However, we find the abundance of this decay component is significantly less for pheomelanin (6%) than eumelanin (11%), suggesting that ThT does not intercalate so readily in pheomelanin. This may reflect less sheet structure or tighter binding of pheomelanin's sheets, consistent with its low fluorescence quantum yield. Disassembling pheomelanin upon raising pH provides further spectroscopic evidence that ThT is trapped in sheet-like aggregates of smaller oligomeric forms.