ABSTRACT
We prepared a pair with a visible-absorbing donor dye and a near-infrared fluorescing acceptor dye. The donor and the acceptor were covalently linked close enough for Förster resonance energy transfer to occur. Under cryogenic conditions at 1.7 K, we observed the fluorescence excitation spectra of the individual pairs in a water matrix. We tested one rhodamine, two Bodipy, and one carbopyronine derivatives as the donor. Among these donors, Bodipy derivatives show the narrowest spectral width of the individuals with respect to the ensemble width. Thus, Bodipy dyes were favorable as the donor for the spectral selection of individual pairs. At 1.7 K, from the several Bodipy-acceptor pairs in the diffraction-limited volume, an individual pair was selected by the fluorescence excitation spectrum of the donor. The spectrally selected pair was localized using the near-infrared fluorescence of the acceptor.
ABSTRACT
We have developed a spectroscopic optical coherence tomography (OCT) for imaging lipid distribution within blood vessel in order to detect coronary artery plaque. A 1.7-µm spectral-domain OCT with A-scan rate of 47 kHz is fabricated using a broadband light source based on super-luminescent diodes and spectrometers based on extended InGaAs line sensors. We demonstrate imaging of lipid distribution in an in vitro artery model with lipid. The sensitivity and specificity in the differentiation between artery and lipid are 87% and 90% in the training, respectively. The validation test also shows detection of lipid with an accuracy over 90%.
ABSTRACT
The visible fluorescence spectrum of single flavoprotein at a temperature of 1.5 K has been measured by one-photon excitation. The flavoprotein studied was a photoswitchable enzyme, photoactivated adenylyl cyclase. The time course of the spectrum revealed a structural change occurring at a rate of 10(-3) s(-1) around hydrogen bonds at the flavin cofactor binding site.
