29 research outputs found
Quantum Yield Calculations for Strongly Absorbing Chromophores
This article demonstrates that a commonly-made assumption in quantum yield
calculations may produce errors of up to 25% in extreme cases and can be
corrected by a simple modification to the analysis.Comment: 3 pages, 2 figures. Accepted by Journal of Fluorescenc
Imaging of Flow Patterns with Fluorescent Molecular Rotors
Molecular rotors are a group of fluorescent molecules that form twisted intramolecular charge transfer states (TICT) upon photoexcitation. Some classes of molecular rotors, among them those that are built on the benzylidene malononitrile motif, return to the ground state either by nonradiative intramolecular rotation or by fluorescence emission. In low-viscosity solvents, intramolecular rotation dominates, and the fluorescence quantum yield is low. Higher solvent viscosities reduce the intramolecular rotation rate, thus increasing the quantum yield. We recently described a different mechanism whereby the fluorescence quantum yield of the molecular rotor also depends on the shear stress of the solvent. In this study, we examined a possible application for shear-sensitive molecular rotors for imaging flow patterns in fluidic chambers. Flow chambers with different geometries were constructed from polycarbonate or acrylic. Solutions of molecular rotors in ethylene glycol were injected into the chamber under controlled flow rates. LED-induced fluorescence (LIF) images of the flow chambers were taken with a digital camera, and the intensity difference between flow and no-flow images was visualized and compared to computed fluid dynamics (CFD) simulations. Intensity differences were detectable with average flow rates as low as 0.1 mm/s, and an exponential association between flow rate and intensity increase was found. Furthermore, a good qualitative match to computed fluid dynamics simulations was seen. On the other hand, prolonged exposure to light reduced the emission intensity. With its high sensitivity and high spatial and temporal resolution, imaging of flow patterns with molecular rotors may become a useful tool in microfluidics, flow measurement, and control
Non-invasive intravital imaging of cellular differentiation with a bright red-excitable fluorescent protein
A method for non-invasive visualization of genetically labelled cells in animal disease
models with micron-level resolution would greatly facilitate development of cell-based
therapies. Imaging of fluorescent proteins (FPs) using red excitation light in the âoptical
windowâ above 600 nm is one potential method for visualizing implanted cells. However,
previous efforts to engineer FPs with peak excitation beyond 600 nm have resulted in
undesirable reductions in brightness. Here we report three new red-excitable monomeric FPs obtained by structure-guided mutagenesis of mNeptune, previously the brightest monomeric FP when excited beyond 600 nm. Two of these, mNeptune2 and mNeptune2.5, demonstrate improved maturation and brighter fluorescence, while the third, mCardinal, has a red-shifted excitation spectrum without reduction in brightness. We show that mCardinal can be used to non-invasively and longitudinally visualize the differentiation of myoblasts and stem cells into myocytes in living mice with high anatomical detail
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Haemodynamics and Oxygenation of the Tumor Microcirculation
Abnormalities of the tumor vasculature and their consequences on the microenvironment of tumor cells impact on tumor progression and response to both blood-borne anti-cancer agents and radio-therapy, as well as making tumor blood vessels a target for therapy in their own right. Intravital microscopy of experimental tumors, most commonly grown in âwindowâ chambers, such as the dorsal skin fold chamber in mice and rats, enables investigations of tumor microcirculatory function. This is needed both to understand the molecular control of tumor vascular function and to measure the response of the vasculature to treatment. In particular, intravital microscopy enables parameters associated with blood supply, vascular permeability and oxygenation to be estimated, at high spatial and temporal resolution. In this chapter, methods used for measuring a range of these parameters, specific examples of their applications, the significance of findings and some of the limitations of the techniques are described
Mapping regional oxygenation and flow in pig hearts in vivo using near-infrared spectroscopic imaging
NRC publication: Ye
Assessment of optical path length in tissue using neodymium and water absorptions for application to near-infrared spectroscopy
NRC publication: Ye
Relative contributions of hemoglobin and myoglobin to near-infrared spectroscopic images of cardiac tissue
NRC publication: Ye
Detection of myocardial cell damage in isolated rat hearts in near-infrared spectroscopy
NRC publication: Ye