Co-phase errors sensing method for Golay3 telescope system via a transfer network.

Optical sparse-aperture systems face severe challenges, including detecting and correcting co-phase errors. In this study, a search framework based on fine tuning a pre-trained network is proposed to analyze the co-phase errors of a Golay3 telescope system. Based on this, an error compensation control system is established. First, a hash-like binary code is created by fine-tuning the pre-trained model. Secondly, a pre-trained network is used to extract the deep features of the image, and an index database is built between the image features and the corresponding co-phase error values. Finally, the Top 1-ranked features and corresponding co-phase error values are returned through the hash-like binary code hierarchical deep search database to provide driving data for the error correction system. Numerical simulations and experimental results verify the method's validity. The experimental results show that the correction system works well when the dynamic piston is [-5,5]λ, and the tilt error range is [-15,15]µr a d. Compared with existing detection methods, this method does not require additional optical components, has a high correction accuracy, and requires a short training time. Furthermore, it can be used to detect piston and tilt errors simultaneously.

Semicarbazide-based fluorescent probe for detection of Cu2+ and formaldehyde in different channels.

Two fluorescent sensors with the receptor semicarbazide respectively at 7- (CAA) and 3-position (CAB) of coumarin were designed and synthesized. CAA exhibits fluorescence turn-on response to Cu2+ by triggering the intramolecular charge transfer (ICT) process via Cu2+-catalyzed hydrolysis, and can detect formaldehyde (FA) at different channel by inhibiting the photo-induced electron transfer (PET). However, CAB displays quite different responses: the photophysical properties hardly changed in the presence of FA; while a three-stage fluorescence response of fast quenching, steady increasing and slowly decreasing was found upon addition of Cu2+. The high selectivity enabled CAA a good candidate for quantification of Cu2+ and formaldehyde as well as bioimaging Cu2+ in living cells. Good linear relationships between the fluorescence intensity and analyte concentration were observed in the range of 0.1-30 µM for Cu2+ and 1.0-50 µM for FA, and their detection limits (LOD) were calculated to be 0.43 µM and 1.92 µM (3δ/k), respectively.

Fluorescent "AND" logic gates for simultaneous detection of thiols and protons: photophysical properties, mechanism and bioimaging of living cells.

Five fluorescent probes TP1-5 were demonstrated as two-input "AND" molecular logic gates for the detection of thiols and protons. The molecules were designed based on "thiol receptor-spacer1-fluorophore-spacer2-proton receptor" mode. The logic gates were constructed by employing maleimide, naphthalimide and morpholine (TP1-3)/N-methyl piperazine (TP4-5) as the thiol receptor, fluorophore and proton receptor, respectively. All probes show significant fluorescence enhancements upon addition of both protons and thiols. However, much weaker spectral responses were observed with the addition of only one single analyte. The fluorescence outputs, based on photoinduced electron transfer (PET) and (twisted) intramolecular charge transfer (TICT/ICT), were modulated by the proton receptor and linker. The length of spacer1 affects the responses toward thiols, whereas spacer2 influences the sensing performance toward protons. The difference between the pKa values of morpholine (∼5.80) and N-methyl piperazine (∼7.10) enables us to detect thiols in divergent pH circumstances. TP1-3 exhibit an excellent "AND" logic function for simultaneous detection of protons and thiols as well as bioimaging thiols in weakly acidic living cells. However, TP4 and TP5 are not good candidates for executing "AND" logic operation possibly due to the stronger electron donating properties and steric effect of N-methyl piperazine.

Application of torque sensitivity in the alignment of a Cassegrain system.

In order to improve the alignment accuracy of a Cassegrain system, to the best of our knowledge, a novel computer-aided alignment method based on torque sensitivity is proposed. Different from the traditional position sensitivity curve guiding scheme, the accurate position of the secondary mirror is not necessary while the torque sensitivity curve is generated. By establishing the relationship between the torque of the secondary mirror setting screw and the Zernike coefficients of the system, a practical quantitative alignment scheme for the Cassegrain system can be realized. For a two-mirror Cassegrain optical-mechanical system, an alignment scheme based on torque sensitivity is designed. The results show that the wavefront aberrations of three Cassegrain systems reach 0.0479λ,0.0537λ, and 0.0698λ respectively. It proves that the torque sensitivity curves can well guide the real alignment process.

Indomethacin-induced spectral responses of naphthalimide-based dyes to serum albumin: effects of substituent and spacer.

Four indomethacin-naphthalimide binaries with different proton receptors at 4-position of naphthalimide were designed and synthesized. N,N-Dimethylethylenediamine and N-methyl piperazine were served as proton receptors as well as solubility regulators. Indomethacin, an inhibitor for cyclooxygenase-2 overexpressed on cancer cells, was connected at the imine N through different spacers. The attachment of indomethacin significantly quenched the fluorescence of all compounds with obvious red-shift in the absorption maxima due to the strong photo-induced electron transfer process of the folded-state. Human serum albumin (HSA) triggered about 15-fold fluorescence enhancements of DMN-IMC-5 with 30 nm blue-shift. However, it caused much smaller fluorescence increments of other compounds, suggesting that indomethacin, the linker and proton receptor play critical roles in HSA identification. Fluorescence bioimaging results show that indomethacin enables the naphthalimide-based compounds to fluorescent imaging living cells. Molecular docking reveals that the introduction of indomethacin improved the binding affinity of the dyes to HSA.

Selective bioimaging of cancer cells and detection of HSA with indomethacin-based fluorescent probes.

Two fluorescent probes were designed by connecting indomethacin to coumarin through different linkers. The introduction of indomethacin quenched the fluorescence of coumarin-based probes with apparent red-shifts in the absorption and emission maxima, probably due to the photoinduced electron transfer (PET) from the indomethacin to the fluorophore and the formation of folding conformation. The addition of human serum albumin (HSA) triggered about 40-fold fluorescence enhancements of ADC-IMC-2 and ADC-IMC-6 with 85 nm blue-shifts. The probe with longer spacer ADC-IMC-6 exhibited ratiometric fluorescent response toward HSA, and that with shorter linker showed "off-on" fluorescence response to HSA. However, insignificant spectral changes of the reference compounds (ADC-6 and ADC-2) initiated by HSA implied that indomethacin played critical role in the identification of HSA. The competitive assays and molecular docking results reveal that the indomethacin in ADC-IMC-6 could tightly combine at drug site I of HSA. Fluorescence bio-imaging experiments show that both probes could distinguish cancer cells from normal cells.

Photophysics of perylene monoimide-labelled organocatalysts.

We designed and synthesized cinchona alkaloid derivates PMI-BnCPD, 1 and PMI-dHQD, 2, in which a fluorescent perylene monoimide unit is linked to the quinuclidine fragment. The latter acts as an electron donor, quenching the perylene imide fluorescence in polar solvents. In the organocatalytic application of these compounds, the electron donor is deactivated by binding to an electrophile, e.g. H+. We show that this restores the fluorescence, allowing the compounds to signal the electrophile binding step that occurs in many catalytic reactions. In order to demonstrate that charge transfer is indeed the fluorescence quenching mechanism, we detected the charge separated state by means of transient absorption spectroscopy. Incidentally, the excited state absorption bands of the locally excited and charge transfer states are very similar. The activity of the fluorophore labeled organocatalyst 1 in a fluorogenic Michael addition reaction is demonstrated.

A mitochondria-targeted near infrared ratiometric fluorescent probe for the detection of sulfite in aqueous and in living cells.

A near infrared fluorescent probe YSP for sulfite was synthesized, in which a julolidine fused with a pyran-2-one was employed as the fluorophore and the vinyl activated by an indole salt as the receptor. The introduction of julolidine and indole salt strengthens the electron push-pull effect of the probe and allows it to absorb (597 nm) and emit (681 nm) in red wavelength region. The addition of sulfite to the C˭C bond led to prominent blue-shifts in both absorption (171 nm) and emission (165 nm) spectra, which made it possible for colorimetric and ratiometric fluorescent detection of sulfite. NMR titration results illustrated that the determination of sulfite is a two-step process: nucleophilic addition of sulfite to the unsaturated carbon of C˭N in indole ring followed by intramolecular rearrangement through a four-membered ring to form adduct-B with shorter absorption wavelength. In addition, the cationic feature of YSP enables the probe to be specifically localized in mitochondria, and it could ratiometric bioimaging sulfite in living HepG-2 and L929 cells.

Spectroscopic Study of a Cinchona Alkaloid-Catalyzed Henry Reaction.

A spectroscopic study of an organocatalytic Henry reaction between nitroalkanes and aldehydes catalyzed by a quinidine-derived Cinchona alkaloid is described. The binding modes of the reaction substrates are investigated using electronic absorption and fluorescence spectroscopy and further corroborated by nuclear magnetic resonance measurements. Aldehydes are shown to associate with both the 6'-OH group and the basic quinuclidine nitrogen of the catalyst, whereas nitroalkanes do not exhibit a clear binding mode. Reaction progress kinetic analysis reveals that the reaction is first-order in both of the substrates and the catalyst. Second, the reaction proceeds approximately five times faster in the excess of the nitroalkanes than in the excess of the aldehydes, suggesting that binding of the aldehydes results in the inhibition of the catalyst. Aldehydes deactivate the basic quinuclidine site, thus suppressing the deprotonation of the nitroalkanes which is the proposed initial step in the reaction cycle.

A fluorescence turn-on probe for human (bovine) serum albumin based on the hydrolysis of a dioxaborine group promoted by proteins.

A fluorescence "off-on" probe CBF, constructed by incorporating a dioxaborine unit into a microenvironment-sensitive fluorophore, was developed for serum albumin (SA). Upon binding to SA, the dioxaborine group in CBF was hydrolyzed into ß-diketonate, which triggered dramatic fluorescence enhancement (over 1000-fold) along with a remarkable blue-shift (∼100 nm). The bioimaging results suggested that more SA were taken in by cancer cells.

Highly sensitive detection of cysteine over glutathione and homo-cysteine: New insight into the Michael addition of mercapto group to maleimide.

A fluorescence "off-on" probe CMP for thiols was designed with coumarin as the fluorophore and maleimide as the receptor. The fluorescence of the coumarin was quenched through photoinduced electron transfer (PET) from the fluorophore to maleimide group. The Michael addition of the mercapto group toward maleimide formed a thioether with relatively weak fluorescence. The intramolecular nucleophilic substitution of amino group in cysteine (Cys) to alkylthio produced a much stronger fluorescent amino adduct, which was supported by UPLC-MS and NMR titration. The above sensing mechanism ensured CMP a highly sensitive probe toward Cys over GSH and Hcy. The fluorescence intensity at 495nm was linear with Cys concentration over the range of 0-10µM with a detection limit of 14nM and a rapid response time of 20min. High selectivity and good competition of the probe toward thiols over other biologically relevant species enabled us to monitor mercapto-containing proteins as well as fluorescence imaging Cys in living cells.

A ratiometric fluorescence probe for selective detection of sulfite and its application in realistic samples.

A new fluorescent probe 7-(diethylamino)-3-((1e,3e)-5-oxo-5-phenylpenta-1,3-dien-1-yl)-2H-chromen-2-one (SPH), based on Michael addition mechanism, was designed and synthesized for selective detection of sulfite. The probe was constructed by incorporating an α,ß-unsaturated ketone conjugated with a CË­C bond into the coumarin fluorophore as a specifical reaction site for sulfite utilizing its nucleophilic property. The extra conjugated CË­C bond induced obvious red-shifts in both absorption and emission maxima, and remarkably promoted the nucleophilic addition rate. Once treated with sulfite, the solution's color changed from orange to yellow companied with a strong blue-green fluorescence. The ratio of fluorescence intensity at 488nm and 630nm (I488/I630) was linear with sulfite concentration over the range of 0-80µM with a detection limit of 0.23µM. High selectivity and good competition of the probe toward sulfite over other anions and thiols enable us to monitor sulfite levels in realistic samples as well as in living HeLa cells.

Highly Selective Fluorescent Turn-On Probe for Protein Thiols in Biotin Receptor-Positive Cancer Cells.

Sulfhydryl-containing proteins play critical roles in various physiological and biological processes, and the activities of those proteins have been reported to be susceptible to thiol oxidation. Therefore, the development of protein thiol target fluorescent probe is highly desirable. In the present work, a biotinylated coumarin fluorescence "off-on" probe SQ for selectively detecting protein thiols in biotin receptor-positive cancer cells was designed with a 2,4-dinitrobenzenesulfony as the thiol receptor. The probe exhibited dramatic fluorescence responses toward sulfhydryl-containing proteins (ovalbumin (OVA), bovine serum albumin (BSA)): up to 170-fold fluorescence enhancement with 70 nm blue-shift was observed with the addition of OVA. However, low molecular weight thiols (Cys, glutathione (GSH), Hcy) caused negligible fluorescence changes of SQ. In addition, biotin receptor-positive Hela cells displayed strong red and green fluorescence after incubation of SQ for 1 h; neither red nor green fluorescence signal could be visualized in biotin-negative normal lung Wi38 cells. These results imply that the probe has potential application in fluorescent imaging protein thiols on the surface of Hela cells.

Facile Preparation of Core-Shell Magnetic Metal-Organic Framework Nanoparticles for the Selective Capture of Phosphopeptides.

In regard to the phosphoproteome, highly specific and efficient capture of heteroideous kinds of phosphopeptides from intricate biological sample attaches great significance to comprehensive and in-depth phosphorylated proteomics research. However, until now, it has been a challenge. In this study, a new-fashioned porous immobilized metal ion affinity chromatography (IMAC) material was designed and fabricated to promote the selectivity and detection limit for phosphopeptides by covering a metal-organic frameworks (MOFs) shell onto Fe3O4 nanoparticles, taking advantage of layer-by-layer method (the synthesized nanoparticle denoted as Fe3O4@MIL-100 (Fe)). The thick layer renders the nanoparticles with perfect hydrophilic character, super large surface area, large immobilization of the Fe(3+) ions and the special porous structure. Specifically, the as-synthesized MOF-decorated magnetic nanoparticles own an ultra large surface area which is up to 168.66 m(2) g(-1) as well as two appropriate pore sizes of 1.93 and 3.91 nm with a narrow grain-size distribution and rapid separation under the magnetic circumstance. The unique features vested the synthesized nanoparticles an excellent ability for phosphopeptides enrichment with high selectivity for ß-casein (molar ratio of ß-casein/BSA, 1:500), large enrichment capacity (60 mg g(-1)), low detection limit (0.5 fmol), excellent phosphopeptides recovery (above 84.47%), fine size-exclusion of high molecular weight proteins, good reusability, and desirable batch-to-batch repeatability. Furthermore, encouraged by the experimental results, we successfully performed the as-prepared porous IMAC nanoparticle in the specific capture of phosphopeptides from the human serum (both the healthy and unhealthy) and nonfat milk, which proves itself to be a good candidate for the enrichment and detection of the low-abundant phosphopeptides from complicated biological samples.

Discrimination between streptavidin and avidin with fluorescent affinity-based probes.

Two biotinylated coumarin-based fluorescent probes SPS3 and RC3 were designed for differentiating between structurally similar proteins streptavidin (SA) and avidin (AV). A substituted phenyl group is introduced onto SPS3, which may quench the fluorescence through twist intramolecular charge transfer (TICT). The fluorescence of SPS3 is turned on, by restraining the TICT process, when the fluorophore is buried at the surface of SA. RC3 is constructed by incorporating a biotin molecule to a coumarin fluorophore through a 4-atom spacer. The fluorescence intensity of RC3 is enhanced significantly when its fluorophore enters into the less polar binding pocket of AV. SPS3 and RC3 could be applied in distinguishing between SA and AV as well as in fluorescence imaging of biotin receptor over-expressed Hela cells.

Multi-channel colorimetric and fluorescent probes for differentiating between cysteine and glutathione/homocysteine.

Three fluorescent probes TP1­3 for thiols were rationally designed and synthesized to distinguish cysteine (Cys) from glutathione (GSH)/homocysteine (Hcy). TP1­3 are almost non-fluorescent and colorless 4-nitro-1,8-naphthalimide derivatives. Upon the substitution of nitro by Cys, TP1­3 were transformed into weakly fluorescent green-emitting 4-amino analogs via highly fluorescent blue-emitting thioether intermediates. The three-channel signaling capability allows discrimination between Cys and GSH/Hcy. The fluorescence intensity at 498 nm was linearly proportional to GSH concentration in the range of 0-20 µM, and the detection limit was 5 × 10(-8) mol L(-1). A good linear relationship between A446/A350 and Cys concentration was found in the range of 0-70 µM, and the detection limit was 2 × 10(-7) mol L(-1). Moreover, TP3 was used for living cell imaging as well as for detecting mercapto-containing proteins.

Colorimetric and fluorescent determination of sulfide and sulfite with kinetic discrimination.

Two fluorescent probes, m-PSP and p-PSP , for sulfite and/or sulfide were constructed by connecting a pyridinium ion to a coumarin fluorophore through an α,ß-unsaturated ketone. The presence of the pyridinium salt promoted the nucleophilic addition of sulfite and sulfide to the α,ß-unsaturated ketone, which could be visualized by dramatic changes in the solution's color and fluorescence intensity. Both probes exhibit good selectivity (the selectivity coefficients toward major interferences are less than 0.07) and high sensitivity for sulfite and sulfide over biothiols and other potential analytes. The detection limits of m-PSP for the analysis of sulfite and sulfide are calculated to 8.5 × 10(-7) M and 2.7 × 10(-7) M, respectively. Living cell imaging results indicate that both probes can be applied in biological systems.

Rational design of biotinylated probes: fluorescent turn-on detection of (strept)avidin and bioimaging in cancer cells.

Two fluorescent probes SPS1 and SPS2 were designed by connecting biotin to an environment-sensitive coumarin fluorophore. Streptavidin and avidin induced dramatical fluorescence changes in both probes. SPS2 has potential in fluorescent imaging of biotin receptor-enriched tumor cells.

A coumarin-based fluorescent probe for differential identification of sulfide and sulfite in CTAB micelle solution.

Sulfite and sulfide share several similarities in terms of chemical properties, such as nucleophilic and reducing reactivities. Therefore, they may disturb the detection of each other. In order to discriminate between these two kinds of sulfur-containing species, a new probe -N3 was developed, in which para-azidobenzenyl ketone was covalently incorporated to a coumarin fluorophore linked by a C=C double bond. Sulfite and sulfide can respectively react with the C=C double bond and the azido group to give different products, consequently, they can be differentially identified by UV-vis and fluorescence spectroscopy as well as by the naked eye. Selectivity and competition results reveal that -N3 is a good candidate for the detection of sulfide and sulfite. The bioimaging experiment demonstrates the potential of the -N3 probe for the differential imaging of sulfide and sulfite in living cells.

A novel, post-column micro-membrane reactor for fluorescent analysis of protein in capillary electrophoresis.

Based on the semipermeability of hollow fiber membranes, a post-column membrane reactor was developed for capillary electrophoresis (CE)-laser induced fluorescence (LIF) analysis of proteins by using a hollow fiber membrane to connect the separation and detection capillaries. The membrane length between the separation and detection capillaries was 1 mm. Driven by the chemical potential difference between the separation buffer inside the membrane and the fluorescence derivatization solution outside the membrane, the derivatization reagent can be easily drawn into hollow fiber membrane to react with proteins. Also, the separation buffer can be adjusted by the derivatization solution to match the conditions of derivatization without sample loss. The effect of the separation buffer on the derivatization reaction was investigated and the results showed that even a strong acidic solution and multiple additives can be adopted in the separation buffer without destroying the post-column derivatization of proteins. Under the optimized conditions, the highly sensitive detection of BSA was achieved with a detection limit of 3.3 nmol L(-1) and a linear calibration range from 0.007 to 0.1 mg mL(-1). The proposed CE-LIF system with a post-column membrane reactor was also successfully applied to the separation and detection of proteins in rat liver and loach muscle.