Search results for "Fluorescence"
showing 10 items of 2463 documents
Fluorescence, Browning Index, and Color in Infant Formulas during Storage
2005
Free and total fluorescent compounds, browning index, and color formation were measured in milk-based powdered infant formulas (IF) during 2 years of storage at 20 and 37 degrees C. The excitation spectra from 415 nm emission show three peaks (ex lambda1 = 270 nm, lambda2 = 325/315 nm, lambda3 = 350 nm) and from 347 nm excitation two emission peaks (415 and 520 nm), and no wavelength shifts were observed. Temperature and time of storage exert in general no significant effect on the development of fluorescence emission intensity and browning index. However, an important increase in pentodilysine was recorded-probably because of the iron and ascorbic acid contents of the samples-as well as in…
Comparison of quantum dot-binding protein tags: Affinity determination by ultracentrifugation and FRET
2013
Abstract Background Hybrid complexes of proteins and colloidal semiconductor nanocrystals (quantum dots, QDs) are of increasing interest in various fields of biochemistry and biomedicine, for instance for biolabeling or drug transport. The usefulness of protein–QD complexes for such applications is dependent on the binding specificity and strength of the components. Often the binding properties of these components are difficult and time consuming to assess. Methods In this work we characterized the interaction between recombinant light harvesting chlorophyll a / b complex (LHCII) and CdTe/CdSe/ZnS QDs by using ultracentrifugation and fluorescence resonance energy transfer (FRET) assay exper…
High resolution spectroscopy and potential determination of the (3)1Pi state of NaCs.
2006
The (3)(1)Pi state of the NaCs molecule was studied by high resolution Fourier-transform spectroscopy. The (3)(1)Pi--X (1)Sigma(+) laser induced fluorescence was excited by an Ar(+) ion laser or by a single-mode frequency-doubled cw Nd:YAG laser. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the (3)(1)Pi state term values, as well as to observe Lambda splittings in a wide range of vibrational (v(')) and rotational (J(')) quantum numbers. The data field includes about 820 energy levels of (3)(1)Pi NaCs in the range from v(')=0 to 37 and from J(')=3 to 190, which corresponds to ca. 95% of the potential well depth. Direct fit o…
Double Laser LIBS and micro-XRF spectroscopy applied to characterize materials coming from the Greek-Roman theater of Taormina
2009
The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown, in recent years, its great potential for rapid qualitative analysis of materials. The possibility to implement a portable instrument that perform LIBS analysis makes this technique particularly useful for in situ analysis in the field of cultural heritages. The aim of this work is to compare the results, obtained by LIBS measurements with X-Ray Fluorescence (XRF) ones, on calcareous and refractory materials coming from the Greek-Roman theater of Taormina. Calibration curves for LIBS and XRF were obtained by measuring certified reference materials and using them as standards. LIBS measurements we…
A Boron Dipyrromethene (BODIPY)-Based Cu(II) -Bipyridine Complex for Highly Selective NO Detection.
2015
[EN] A BODIPY-containing Cu-II-bipyridine complex for the simple selective fluorogenic detection of NO in air and in live cells is reported. The detection mechanism is based on NO-promoted Cu-II to Cu-I reduction, followed by demetallation of the complex, which results in the clearly enhanced emission of the boron dipyrromethene (BODIPY) unit.
Alkyloxy modified pyrene fluorophores with tunable photophysical and crystalline properties
2019
Novel alkyloxy modified 2,7-di-tert-butyl-4,5,9,10-tetra(arylethynyl)pyrenes were prepared through a straightforward Sonogashira coupling approach. Optical properties such as quantum yields and absorption/emission spectra of the fluorophores were investigated by UV/Vis and fluorescence measurements. Aggregation induced excimer formation of the chromophores in polar solvents and in the solid state was proved by the presence of a characteristic bathochromically shifted emission band and a decrease of the emission capability. These results strongly indicate the unexpected observation that the excimer formation of adjacent pyrene rings is not prevented by the introduction of bulky tert-butyl su…
Confocal microscopy of single molecules of the green fluorescent protein
1998
Single molecule detection has been extended into life sciences by use of strongly fluorescent labels. The green fluorescent protein (GFP) as a self-fluorescent biomolecule has attracted considerable attention. Here, single molecules of the GFP-mutant Glu222Gln are immobilized in a polyvinylalcohol matrix and detected by confocal fluorescence microscopy. Although this mutant stabilizes one of both conformers of the wild-type GFP, the investigation of its fluorescence dynamics reveals strong signal fluctuations. This fluorescence behaviour is—at least partly—caused by reversible photochemical changes of the protein framework, that can relax into the fluorescent state on different timescales. …
Dendrimers with peripheral stilbene chromophores
2006
Abstract Two types of dendritic nanoparticles were prepared, which contain ( E )-stilbene chromophores in the terminal positions of the dendrons. The compounds showed a highly efficient photoreactivity in the course of which statistical CC bond formations led to a crosslinking of the particles. Finally, all stilbene chromophores reacted and the typical ( E )-stilbene absorption and fluorescence disappeared completely.
Poly(propylene imine) dendrimers functionalized with stilbene or 1,4-distyrylbenzene chromophores
2007
Abstract Two generations of dendritic nanoparticles were prepared, which contain ( E )-stilbene or ( E , E )-1,4-distyrylbenzene chromophores in the 4 or 8 terminal positions of the propylene imine dendrons. The compounds show a highly efficient photoreactivity. On prolonged irradiation all stilbenoid chromophores were destroyed by oligomerization (crosslinking) and the typical absorption and fluorescence of the chromophores disappeared completely.
ChemInform Abstract: Poly(propylene imine) Dendrimers Functionalized with Stilbene or 1,4-Distyrylbenzene Chromophores.
2008
Abstract Two generations of dendritic nanoparticles were prepared, which contain ( E )-stilbene or ( E , E )-1,4-distyrylbenzene chromophores in the 4 or 8 terminal positions of the propylene imine dendrons. The compounds show a highly efficient photoreactivity. On prolonged irradiation all stilbenoid chromophores were destroyed by oligomerization (crosslinking) and the typical absorption and fluorescence of the chromophores disappeared completely.