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Fluorescein derived Schiff base as fluorimetric zinc (II) sensor via ‘turn on’ response and its application in live cell imaging
摘要： A novel Schiff base L composed of fluorescein hydrazine and a phenol functionalized moiety has been designed and prepared via cost-effective condensation reaction, which is utilized for selective sensing of Zn2+ over other environmental and biological relevant metal ions in aqueous alcoholic solution under physiological pH range. The binding of Zn2+ to the receptor L is found to causes ~23 fold fluorescence enhancement of L. The 1:1 binding mode of the metal complex is established by combined UV–Vis, fluorescence, and HRMS (high-resolution mass spectroscopy) spectroscopic methods. The binding constant (Ka) for complexation and the limit of detection (LOD) of Zn2+ is calculated to be 2.86×104 M-1 and 1.59 μM, respectively. Further photophysical investigations including steady-state, time-resolved fluorescence analysis and spectral investigations including NMR (nuclear magnetic resonance), IR (infrared spectroscopy) suggest introduction of CHEF (chelation enhance fluorescence) with the suppression of C=N isomerization and PET (photo-induced electron transfer) mechanism for the strong fluorescent response towards Zn2+. Finally, the sensor L is successfully employed to monitor a real-time detection of Zn2+ by means of TLC (thin layer chromatography) based paper strip. The L is used in the cell imaging study using African green monkey kidney cells (Vero cells) for the determination of exogenous Zn2+ by Immunofluorescence Assay (IFA) process.
关键词： Schiff base,molecular logic gate,cell imaging,Zn sensor,PL and TCSPC,UV-Vis
更新于2025-09-23 15:23:52
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Binding of Clitoria ternatea L. flower extract with α-amylase simultaneously monitored at two wavelengths using a photon streaming time-resolved fluorescence approach
摘要： The binding of an extract from the flowers of Clitoria ternatea L. to the digestive enzyme α-amylase was investigated. This extract is a mixture of flavonoids, including anthocyanins, and has been previously shown to inhibit the activity this enzyme. This has implications for modulating starch digestion. Since the extract contains a mixture of flavonoids, including anthocyanins, in order to investigate the kinetics, we made use of time-resolved fluorescence to simultaneously monitor two different emission bands emanating from the extract. This measurement was enabled by the use of a “photon streaming” approach and changes in fluorescence lifetime and intensity were used to follow the interaction. A longer wavelength band (655 nm) was ascribed to anthocyanins in the mixture and these were observed to bind at a rate an order of magnitude slower than other flavonoids present in the extract, monitored at a shorter wavelength (485 nm). Changes in the fluorescence emission of the extract upon binding were further assessed by the use of decay associated spectra.
关键词： TCSPC,Butterfly pea,Anthocyanins,Enzyme inhibition,Flavonoids
更新于2025-09-23 15:21:21
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Distance-Resolving Raman Radar Based on a Time-Correlated CMOS Single-Photon Avalanche Diode Line Sensor
摘要： Remote Raman spectroscopy is widely used to detect minerals, explosives and air pollution, for example. One of its main problems, however, is background radiation that is caused by ambient light and sample fluorescence. We present here, to the best of our knowledge, the first time a distance-resolving Raman radar device that is based on an adjustable, time-correlated complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode line sensor which can measure the location of the target sample simultaneously with the normal stand-off spectrometer operation and suppress the background radiation dramatically by means of sub-nanosecond time gating. A distance resolution of 3.75 cm could be verified simultaneously during normal spectrometer operation and Raman spectra of titanium dioxide were distinguished by this system at distances of 250 cm and 100 cm with illumination intensities of the background of 250 lux and 7600 lux, respectively. In addition, the major Raman peaks of olive oil, which has a fluorescence-to-Raman signal ratio of 33 and a fluorescence lifetime of 2.5 ns, were distinguished at a distance of 30 cm with a 250 lux background illumination intensity. We believe that this kind of time-correlated CMOS single-photon avalanche diode sensor could pave the way for new compact distance-resolving Raman radars for application where distance information within a range of several metres is needed at the same time as a Raman spectrum.
关键词： time-correlated single photon counting (TCSPC),remote Raman spectroscopy,CMOS single-photon avalanche diode (SPAD),time interval measurement,distance-resolving Raman radar,stand-off Raman spectrometer
更新于2025-09-23 15:21:21
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0.16 μm–BCD Silicon Photomultipliers with Sharp Timing Response and Reduced Correlated Noise
摘要： Silicon photomultipliers (SiPMs) have improved significantly over the last years and now are widely employed in many different applications. However, the custom fabrication technologies exploited for commercial SiPMs do not allow the integration of any additional electronics, e.g., on-chip readout and analog (or digital) processing circuitry. In this paper, we present the design and characterization of two microelectronics-compatible SiPMs fabricated in a 0.16 μm–BCD (Bipolar-CMOS-DMOS) technology, with 0.67 mm × 0.67 mm total area, 10 × 10 square pixels and 53% fill-factor (FF). The photon detection efficiency (PDE) surpasses 33% (FF included), with a dark-count rate (DCR) of 330 kcps. Although DCR density is worse than that of state-of-the-art SiPMs, the proposed fabrication technology enables the development of cost-effective systems-on-chip (SoC) based on SiPM detectors. Furthermore, correlated noise components, i.e., afterpulsing and optical crosstalk, and photon timing response are comparable to those of best-in-class commercial SiPMs.
关键词： Silicon photomultiplier (SiPM),photon counting,photon number resolution,optical crosstalk,time-correlated single-photon counting (TCSPC),afterpulsing
更新于2025-09-23 15:21:01
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Chemical cross-linking of a variety of green fluorescent proteins as F?rster resonance energy transfer donors for Yukon orange fluorescent protein: A project-based undergraduate laboratory experience
摘要： F?rster resonance energy transfer (FRET) is the basis for many techniques used in biomedical research. Due to its wide use in molecular sensing, FRET is commonly introduced in many biology, chemistry, and physics courses. While FRET is of great importance in the biophysical sciences, the complexity and dif?culty of constructing FRET experiments has resulted in limited usage in undergraduate laboratory settings. Here, we present a practical undergraduate laboratory experiment for teaching FRET using a diverse set of green-emitting ?uorescent proteins (FPs) as donors for a cross-linked Yukon orange FP. This laboratory experiment enables students to make the connection of basic lab procedures to real world applications and can be applied to molecular biology, biochemistry, physical chemistry, and biophysical laboratory courses.
关键词： Upper-division undergraduate,orange ?uorescent protein,?uorescence lifetimes,proteins,green ?uorescent protein,biochemistry,TCSPC,?uorescence spectroscopy
更新于2025-09-10 09:29:36