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Concept: Fluorometer

165

Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger.

Concepts: Fluorescence, Fluorescence spectroscopy, Diode, Ocean, Transducer, Infrared, Pulse oximeter, Fluorometer

26

The interaction of acid (PTCA) with cetyltrimethylammonium bromide (CTAB) has been studied by fluorescence spectroscopy. The fluorescence of PTCA can be greatly enhanced by the addition of CTAB, due to the formation a fluorescent supramolecular compound. Under optimum conditions, the enhancement intensity of fluorescence was proportional to the concentration of CTAB over a range of 0-4.5 µmol L(-1) . Its detection limit was 0.057 µmol L(-1) , which was lower than reported previously. Compared with other methods that have been reported to determine CTAB, this method has high sensitivity, stability and wide linear range and it can be used satisfactorily for the determination of CTAB in aqueous samples. Copyright © 2014 John Wiley & Sons, Ltd.

Concepts: Fluorescence, Spectroscopy, Oxygen, Function, Light, Fluorescence spectroscopy, Chemistry, Fluorometer

0

The lipid organization of microbubbles is important in many applications. By monitoring the photoselection and emission spectrum of the fluorescent probe Laurdan in perfluorobutane gas-filled DPPC microbubbles with a two-photon laser scanning microscope, we observed a transition to a more rigid lipid organization in 30 minutes to several hours.

Concepts: Fluorescence, Ultraviolet, Optics, Light, Spectrum, Fluorescence microscope, Fluorometer, Emission

0

To understand drug-protein dynamics, it is necessary to account for drug molecular flexibility and binding site plasticity. Herein, we exploit fluorescence from a tyrosine kinase inhibitor, AG1478, as a reporter of its conformation and binding-site environment when complexed with its cognate kinase. Water-soluble kinases, aminoglycoside phosphotransferase APH(3`)-Ia and mitogen activated protein kinase 14 (MAPK 14), were chosen for this study. Based on our prior work, the AG1478 conformation (planar or twisted) was inferred from the fluorescence excitation spectrum, the polarity of the AG1478 binding site was deduced from the fluorescence emission spectrum, while red-edge excitation shift (REES) probed the heterogeneity of the binding site (protein conformation and hydration) distributions in the protein conformational ensemble. In the AG1478-APH(3`)-Ia complex both twisted (or partially-twisted) and planar AG1478 conformations were evidenced from emission wavelength-dependent excitation spectra. The binding site environment provided by the APH(3`)-Ia was moderately polar (λmax= 480nm) with evidence for considerable heterogeneity (REES= 34nm). In contrast, in the AG1478-MAPK14 complex, AG1478 was in a predominantly planar conformation with a lower degree of conformational heterogeneity. The binding site environment provided by the MAPK14 protein was of relatively low polarity (λmax= 430nm) with a smaller-degree of heterogeneity (REES= 11nm). The results are compared with available literature x-ray data and discussed in the context of our current understanding of TKI conformation and protein conformational ensembles.

Concepts: Fluorescence, Spectroscopy, Signal transduction, Fluorescence spectroscopy, Tertiary structure, Protein kinase, Fluorometer, Electromagnetic spectroscopy

0

Two mitochondria-targeted colorimetric and ratiometric fluorescent probes for SO2derivatives were constructed based on the SO2derivatives-triggered Michael addition reaction. The probes exhibit high specificity toward HSO3-/SO32-by interrupting their conjugation system resulting in a large ratiometric blue shift of 46-121nm in their emission spectrum. The two well-resolved emission bands can ensure accurate detection of HSO3-. The detection limits were calculated to be 1.09 and 1.35μM. Importantly, probe 1 and probe 2 were successfully used to fluorescence ratiometric imaging of endogenous HSO3-in BT-474 cells.

Concepts: Fluorescence, Light, Measurement, Luminescence, Nucleophilic addition, Fluorometer, Astronomical spectroscopy

0

Expanded calixpyrrole-type macrocycles, calix[2]benzo[4]-pyrroles, bearing fluorescent moieties attached via conjugated vinyl spacer were synthesized from the corresponding formyl-derivatives using Knoevenagel condensation. The anion-binding properties of the resulting fluorescent macrocycles were studied using NMR, UV-vis and fluorescence spectroscopy. The main interest was devoted to dicarboxylates matching the size of the binding cavity of the calix[2]benzo[4]pyrrole skeleton. The observed anion binding properties were compared with the regular calix[4]pyrroles bearing identical fluorophores. Surprisingly, the parent calix[4]pyrroles appear to be equally if not more efficient sensors for anions, including dicarboxylates. The recorded affinity constants for various anions and dianions show the sensors S1-S5 to be highly cross-reactive. The cross-reactivity of the sensors was utilized in the microchip based array sensor, which showed perfect (100%) classification of 18 analytes utilizing only 5 sensors. Finally, the same array was used to perform quantitative analysis of dicarboxylates such as oxalate and malonate whereas the data from the array were subjected to linear regression to distinguish varying concentrations of dianions with low error (<2%).

Concepts: Fluorescence, Electron, Spectroscopy, Regression analysis, Fluorescence spectroscopy, Atom, Ion, Fluorometer

0

Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key parameter indicating the formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence parameters for signal detection and compared the results with conductometric and surface tension measurements. Based upon these results, requirements, advantages, and pitfalls of each method are discussed. Our study underlines the versatility of fluorometric methods that do not impose specific requirements on surfactants and are especially suited for the quantification of very low CMC values. Conductivity and surface tension measurements yield smaller uncertainties particularly for high CMC values, yet are more time- and substance consuming and not suitable for every surfactant.

Concepts: Fluorescence, Fluorescence spectroscopy, Hydrophobic effect, Surface tension, Surfactant, Micelle, Colloidal chemistry, Fluorometer

0

Two ESIPT-active benzimidazole derivatives (1 and 2) were synthesized by the acid-catalyzed intramolecular cyclization. The steady-state fluorescence spectrum in THF revealed that ring fused derivative 1 exhibits a dual emission, namely, the major emission from K* form (ESIPT emission) at 515 nm with a large Stokes shift of 11100 cm(-1) and the minor emission from E* form at below 400 nm. In contrast, the normal emission from E* form was dominant and the fluorescence quantum yield was very low (Φ ~ 0.01) for non-fused derivative 2. The time-resolved fluorescence spectroscopy of 1 suggested that ESIPT effectively occurs due to the restricted conformational transition to the S1-TICT state, and the averaged radiative and non-radiative decay rate constants were estimated as = 0.15 and = 0.60 ns(-1), respectively. The fluorescence emission of 1 was influenced by the measurement condition such as solvent polarity and basicity as well as the presence of Lewis base. These ESIPT process and solvatochromic behavior were nicely reproduced by the DFT/TDDFT calculation using the PCM model. In the single crystal fluorescent spectra, the ESIPT emissions were exclusively observed for both fused and non-fused compounds as a result of hydrogen bonding interactions.

Concepts: Fluorescence, Spectroscopy, Oxygen, Optics, Fluorescence spectroscopy, Solvent, Stokes shift, Fluorometer

0

The aqueous suspension of fluorescent nanoparticles were prepared by using 9-anthradehdye derivative (AH). The nanoparticles (AHNPs) were characterized using DLS-zeta sizer and SEM techniques. The photo physical properties of nanoparticles and precursor were measured and compared using UV-absorption spectroscopy, fluorescence spectroscopy and fluorescence lifetime studies. The significant overlap between fluorescence spectrum of AHNPs and excitation spectrum of Riboflavin (RF) led us to explore Fluorescence Resonance Energy Transfer (FRET) studies between AHNPs and RF in aqueous medium. The mechanism of FRET from AHNPs to RF discussed on spectral observations, thermodynamic parameters and changes produces in fluorescence lifetime in absence and presence of different concentrations of RF to AHNPs. The limit of detection for RF (0.071 µM) is considerably low compared with reported methods. Thus, we explore AHNPs as novel nano probe for quantitative determination of RF in pharmaceutical samples based on FRET study. In addition with this, AHNPs has excellent antibacterial activity than the bulk material for two different bacteria culture viz. E. coli and Bacillus sps. Graphical Abstract 9-anthradehdye based fluorescent nanoparticles (AHNPs) explores as nano probe to detect Riboflavin (RF) in aqueous medium based on Fluorescence Resonance Energy Transfer (FRET) studies. The proposed analytical method successfully applied for quantitative determination of RF in pharmaceutical samples. In addition, with this, AHNPs has excellent antibacterial activity than the bulk material for two different bacteria culture suspension viz. E. coli and Bacillus sps.

Concepts: Fluorescence, Spectroscopy, Bacteria, Microbiology, Fluorescence spectroscopy, Förster resonance energy transfer, Fluorometer, Electromagnetic spectroscopy

0

In this study, a novel fluorescent detection system for biological sensing of human albumin (HA) was developed on the basis of the pseudo-esterase activity and substrate preference of HA. The designed near-infrared (NIR) fluorescent probe (DDAP) could be effectively hydrolyzed by HA, accompanied with significant changes in both colour and fluorescence spectrum. The sensing mechanism was fully investigated by fluorescence spectroscopy, NMR and mass spectra. DDAP exhibited excellent selectivity and sensitivity toward HA over a variety of human plasma proteins, hydrolases, and abundant biomolecules found in human body. The probe has been successfully applied to measure native HA in diluted plasma samples and the secreted HA in the hepatocyte culture supernatant. DDAP has also been used for fluorescence imaging of HA reabsorption in living renal cells, and the results show that the probe exhibits good cell permeability, low cytotoxicity and high imaging resolution. Furthermore, DDAP has been successfully used for real-time tracking the uptaking and degradation of albumin in ex vivo mouse kidney models for the first time. All these results clearly demonstrated that DDAP-based assay held great promise for real-time sensing and tracking HA in complex biological systems, which would be very useful for basic researches and clinical diagnosis of HA-associated diseases.

Concepts: Fluorescence, Spectroscopy, Cell, Ultraviolet, Molecular biology, Fluorescence spectroscopy, Fluorescent lamp, Fluorometer