Search results for "Fluorescence"
showing 10 items of 2463 documents
Nanomolar pyrophosphate detection in water and in a self-assembled hydrogel of a simple terpyridine-Zn2+ complex.
2014
A simple terpyridine-Zn(II) complex is shown to act as an efficient and highly selective fluorescent sensor for pyrophosphate in water at physiological pH. The sensor complex showed an unprecedented fluorescence response (∼500 fold increase) and a record nanomolar sensitivity (detectable fluorescent response at 20 nM and LOD ∼ 0.8 nM). It has successfully been used to stain and record confocal fluorescence microscopy images of HeLa cells. Moreover, the complex was found to self-assemble into a hydrogel which was subsequently used to coat disposable paper strips for easy, low-cost detection of pyrophosphate.
Ķīmisko elementu satura izvērtējums Madonas novada ābolos
2015
Ķīmisko elementu satura izvērtējums Madonas novada ābolos. Reinerte S., zinātniskais vadītājs Dr. ķīm., doc. Rudoviča V. Bakalaura darbs, 39 lpp., 14 attēli, 8 tabulas, 28 literatūras avoti, 9 pielikumi, latviešu valodā. Darbā veikta ķīmisko elementu kvantitatīvā analīze Madonas novadā ievāktajos ābolos. Izvērtēts elementu (Ca, K, Cu, Fe, Mg, P, Cd, Pb) saturs ābolos, atkarībā no paraugu ņemšanas vietas urbanizācijas. Elementu kvantitatīvā satura analīze veikta izmantojot viļņu dispersijas rentgenfluorescences spektrometrijas, liesmas un elektrotermālās atomabsorbcijas spektrometrijas un liesmas fotometrijas metodes.
Determination of ultratrace bismuth in milk samples by atomic fluorescence spectrometry.
2003
Abstract A sensitive procedure was developed for determination of bismuth (Bi) in milk samples by hydride generation atomic fluorescence spectrometry (HG–AFS) after microwave-assisted sample digestion with HNO3 and H2O2. The method provides a sensitivity of 1832 fluorescence units (ng/mL) with a detection limit of 0.01 ng/mL, which corresponds to 20 pg absolute limit of detection, equivalent to 0.50 ng/g in the original sample. Application of the methodology to cow milk samples from the Spanish market showed the presence of Bi at a concentration of 11.8–28.8 ng/g, which compared well with data obtained after dry ashing of samples and with data obtained by inductively coupled plasma–mass spe…
Fit-for-purpose chromatographic method for the determination of amikacin in human plasma for the dosage control of patients
2015
In this paper, a simple, rapid and sensitive method based on liquid chromatography with fluorimetric detection (HPLC-FLD) for the determination of amikacin (AMK) in human plasma is developed. Determination is performed by pre-column derivatization of AMK with ortho-phtalaldehyde (OPA) in presence of N-acetyl-L-cysteine (NAC) at pH 9.5 for 5 min at 80 °C. In our knowledge, this is the first time that NAC has been used in AMK derivatization. Derivatization conditions (pH, AMK/OPA/NAC molar ratios, temperature and reaction time) are optimized to obtain a single and stable, at room temperature, derivative. Separation of the derivative is achieved on a reversed phase LC column (Kromasil C18, 5 μ…
Absence Ochratoxin A in soy sauce
2004
A method is described for the determination of ochratoxin A (OTA) in soy sauce using phosphate-buffered saline (PBS) extraction, an immunoaffinity clean-up, a liquid chromatographic determination with fluorescence detection (LC-FD) and confirmation with LC-FD after methylation of OTA. Recoveries of OTA spiked to soy sauce samples at 0.25 ng/ml level were 90% with relative standard deviations of 4%. The limit of detection was 0.01 ng/ml for OTA using the proposed method. Furthermore, the proposed method was applied to 60 soy sauce samples from China and Japan and none of them were found to contain OTA.
Optimization of fluorescence enhancement for silicon-based microarrays
2008
An optical technique for the enhancement of fluorescence detection sensitivity on planar samples is presented. Such a technique is based on the simultaneous optimization of excitation and light collection by properly combining interference and reflectance from the sample holder. Comparative tests have been performed in microarray applications, by evaluating the proposed solution against commercial glass-based devices, using popular labeling dyes, such as Cy3 and Cy5. The proposed technique is implemented on a substrate built with standard silicon technology and is therefore well suited for integrated micro total analysis systems (microTAS) applications.
Single-molecule FRET studies of counterion effects on the free energy landscape of human mitochondrial lysine tRNA.
2011
The folding energy landscape of RNA is greatly affected by interactions between the RNA and counterions that neutralize the backbone negative charges and may also participate in tertiary contacts. Valence, size, coordination number, and electron shell structure can all contribute to the energetic stabilization of specific RNA conformations. Using single-molecule fluorescence resonance energy transfer (smFRET), we have examined the folding properties of the RNA transcript of human mitochondrial tRNA(Lys), which possesses two different folded states in addition to the unfolded one under conditions of thermodynamic equilibrium. We have quantitatively analyzed the degree of RNA tertiary structu…
Determination of the relative quantum yields of the conformational species of autoassociating polypeptide gramicidin A in organic solvent using combi…
1987
Abstract A simple, novel method is proposed for the accurate determination of the relative quantum yields of each of the interconverting conformational species of the autoassociating polypeptide gramicidin A in organic solution. The method is based on fitting the experimental results obtained independently from fluorescence emission spectroscopy and high performance liquid chromatography. The fluorescence parameters obtained are discussed in terms of the structural features of the individual conformational species. The advantages of this approach and its possible application to other different organic solvents or to other autoassociating polypeptides are also considered.
Alkoxy-styryl DCDHF fluorophores
2010
A photostable dicyanomethylenedihydrofuran fluorophore which contains electron-donating alkoxy groups is described. This chromophore is highly environmentally-sensitive, which is a remarkable property for a fluorescent reporter. Its light excitation also enables, in low viscous solvents, the formation of dark states whose radical or triplet nature is ruled out.
Spectral hole burning study of protoporphyrin IX substituted myoglobin.
1992
Protoporphyrin IX substituted myoglobin reveals excellent hole burning properties. We investigated the frequency shift of persistent spectral holes under isotropic pressure conditions in a range from 0 to 2.4 MPa. In this range, the protein behaves like an elastic solid. The shift of the holes under pressure shows a remarkable frequency dependence from which the compressibility of the protein can be determined. The compressibility, in turn, allows for an estimation of the equilibrium volume fluctuations. Within the frame of the model used to interpret the pressure data, it is possible to determine the absorption frequency of the isolated chromophore and the associated solvent shift in the p…