The antibody orientational labeled by StaphylococcusA protein improve the sensitivity of Gold Immunochromatography Assay

The antibody of Cry1Ab-51 was immobilized orientationly in a simple and effective way on Colloidal gold nanoparticles(CGNP) by The staphylococcal protein A(SPA) affinity with the FC fragement of mouse IgG.The lateral flow detection test strip assembled with the probe by orientational labeled method at the optimum operational conditons (new probe) is 10 times more sensitive than the test strip assembled with the probe labeled by Adsorption(conventionally probe). The affinity experiment have shown that the affinity of the new probe is much higher than the conventionally probe. The Immunochromatography gold strip(ICG strip) assembled by the new probe was highly specific to Cry1Ab with no cross-reaction with other transgenic proteins. And it was proved that the specificity of the new probe have no significant change. Furthermore, the ICG strips assembled by the new probe could be stored for 12 months under dry conditions without significant loss of sensitivity.The Orientational labeling the antibodies with Staphylococcus A protein on Colloidal gold proved to be suitable for improving the sensitivity of the ICG strips.

Hydrazine Hydrate and Dissolved Oxygen-Triggered Near-Infrared Chemiluminescence from CuInS2@ZnS Nanocrystals for Bioassays

The overwhelming majority of commercially available chemiluminescence (CL) assays are conducted in the eye-visible region. Herein, a near-infrared (NIR) aqueous CL strategy was proposed with CuInS₂@ZnS nanocrystals (CIS@ZnS NCs) as emitters. Hydrazine hydrate (N₂H₄·H₂O) could inject electrons into the conduction band of the CIS@ZnS NCs and simultaneously transformed to the intermediate radical N₂H₃^•. N₂H₃^• reduced dissolved oxygen (O₂) to O₂^-•, while the O₂^-• could inject holes into the valence band of the CIS@ZnS NCs. The recombination of electrons and holes at Cu⁺ defects in CIS@ZnS NCs eventually yielded efficient NIR CL at around 824.1 nm, which is the longest waveband for NCs CL to the best of our knowledge. The NIR CL could be conveniently performed in the neutral aqueous medium (pH 7.0) with a quantum yield of 0.0155 Einstein/mol and was successfully employed for constructing a signal-off CL biosensor with ascorbic acid as the analyte as well as a signal-on CL biosensor for determining ascorbate oxidase, which indicates that this NIR CL system has a promising potential for bioassays in diverse ways.

5-Aminopyridine-2-carboxylic acid as appropriate ligand for constructing coordination polymers with luminescence, slow magnetic relaxation and anti-cancer properties

Five new coordination polymers (CPs) constructed of aminopyridine-2-carboxylate (ampy) ligand have been synthesized and fully characterized. Three of them correspond to metal-organic chains built from the coordination of ampy to sodium and lanthanides with formulae [MNa(ampy)₄]_n (M = terbium (2), erbium (1) and ytterbium (3)) resembling a previously reported dysprosium material which shows anticancer activity. On another level, the reaction of Hampy with cobalt and copper ions ({[CoK(ampy)₃(H₂O)₃](H₂O)₃}_n (4) and [Cu(ampy)₂]_n (5)) lead to CPs with variable dimensionalities, which gives the opportunity of analyzing the structural properties of this new family. Lanthanide materials display solid state intense photoluminescent emissions in both the visible and near-infrared region and exhibit slow relaxation of magnetization with frequency dependence of the out-of-phase susceptibility. More interestingly, in our search for multifunctional materials, we have carried out antitumor measurements of these compounds. These multidisciplinary studies of metal complexes open up the possibility for further exploring the applications in the fields of metal-based drugs.

Radiocarbon Tracers in Toxicology and Medicine: Recent Advances in Technology and Science

This review summarizes recent developments in radiocarbon tracer technology and applications. Technologies covered include accelerator mass spectrometry (AMS), including conversion of samples to graphite, and rapid combustion to carbon dioxide to enable direct liquid sample analysis, coupling to HPLC for real-time AMS analysis, and combined molecular mass spectrometry and AMS for analyte identification and quantitation. Laser-based alternatives, such as cavity ring down spectrometry, are emerging to enable lower cost, higher throughput measurements of biological samples. Applications covered include radiocarbon dating, use of environmental atomic bomb pulse radiocarbon content for cell and protein age determination and turnover studies, and carbon source identification. Low dose toxicology applications reviewed include studies of naphthalene-DNA adduct formation, benzo[a]pyrene pharmacokinetics in humans, and triclocarban exposure and risk assessment. Cancer-related studies covered include the use of radiocarbon-labeled cells for better defining mechanisms of metastasis and the use of drug-DNA adducts as predictive biomarkers of response to chemotherapy.

How machine learning can assist the interpretation of ab initio molecular dynamics simulations and conceptual understanding of chemistry

Molecular dynamics simulations are often key to the understanding of the mechanism, rate and yield of chemical reactions. One current challenge is the in-depth analysis of the large amount of data produced by the simulations, in order to produce valuable insight and general trends. In the present study, we propose to employ recent machine learning analysis tools to extract relevant information from simulation data without a priori knowledge on chemical reactions. This is demonstrated by training machine learning models to predict directly a specific outcome quantity of ab initio molecular dynamics simulations - the timescale of the decomposition of 1,2-dioxetane. The machine learning models accurately reproduce the dissociation time of the compound. Keeping the aim of gaining physical insight, it is demonstrated that, in order to make accurate predictions, the models evidence empirical rules that are, today, part of the common chemical knowledge. This opens the way for conceptual breakthroughs in chemistry where machine analysis would provide a source of inspiration to humans.

Chemi- and Bioluminescence of Cyclic Peroxides

Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behind chemiexcitation in both chemi- and bioluminescence. First, the uncatalyzed thermal dissociation of 1,2-dioxetane is presented and analyzed to explain, for example, the preference for triplet excited product states and increased yield with larger nonreactive substituents. The catalyzed fragmentation reaction and related details are then exemplified with substituted 1,2-dioxetanone species. In particular, the preference for singlet excited product states in that case is explained. The review also examines the diversity of specific solutions both in Nature and in artificial systems and the difficulties in identifying the emitting species and unraveling the color modulation process. The related subject of excited-state chemistry without light absorption is finally discussed. The content of this review should be an inspiration to human design of new molecular systems expressing unique light-emitting properties. An appendix describing the state-of-the-art experimental and theoretical methods used to study the phenomena serves as a complement.

Spin-Crossover Iron(II) Coordination Polymer with Fluorescent Properties: Correlation between Emission Properties and Spin State

A spin-crossover coordination polymer [Fe(L1)(bipy)]_n (where L = a N₂O₂^2- coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4'-bipyridine) was synthesized and exhibits a 48 K wide thermal hysteresis above room temperature (T_1/2↑ = 371 K and T_1/2↓ = 323 K) that is stable for several cycles. The spin transition was characterized using magnetic measurements, Mössbauer spectroscopy, and DSC measurements. T-dependent X-ray powder diffraction reveals a structural phase transition coupled with the spin transition phenomenon. The dimeric excerpt {(μ-bipy)[FeL1(MeOH)]₂}·2MeOH of the coordination polymer chain crystallizes in the triclinic space group P1̅ and reveals that the packing of the molecules in the crystal is dominated by hydrogen bonds. Investigation of the emission properties of the complexes with regard to temperature shows that the spin crossover can be tracked by monitoring the emission spectra, since the emission color changes from greenish to a yellow color upon the low spin-to-high spin transition.

Coupling the folding of a β-hairpin with chelation-enhanced luminescence of Tb(III) and Eu(III) ions for specific sensing of a viral RNA

Rational modification of a natural RNA-binding peptide with a lanthanide EDTA chelator, and a phenanthroline ligand yields a highly selective luminescent sensor. The sensing mechanism relies on the RNA-triggered folding of the peptide into a β-hairpin, which promotes the coordination of the phenanthroline sensitizer, and the efficient sensitization of complexed lanthanide ions.

Lanthanide-based luminescence biolabelling

Multiplexing, time-resolution, FRET…lanthanide-based biolabels reveal exceptional spectroscopic properties for bioanalytical applications.

Pr(III) luminescence enhancement by chelation in solution and in sol-gel glass

Due to the weak emission of lanthanide ions in solution, it is common practice to form complexes of the lanthanide ions with organic ligands that strongly absorbs light and transfers the energy to the lanthanide ion center via the antenna effect. The organic ligands 2-6-pyridinedicarboxylate (L1) and the polytonic diazine (N-N) ligand L2 (C22H16N12O2) were used to synthesize two Pr(III) complexes, namely: Pr-L1 (Na3[Pr(C7H3NO4)3]) and Pr-L2. The prepared complexes were further encapsulated in an optically transparent sol-gel glass. The synthesized ligands and complexes were characterized by FTIR and (1)H NMR. Room temperature luminescence of Pr-L1 and Pr-L2 complexes in solution and in sol-gel glass were investigated using a spectrofluorometer. Excitation at the maximum absorption wavelength of the ligands (280nm) resulted in the typical visible luminescence (centered at around 600nm) resulting from the (1)D2→(3)H4 transition of the Pr(III) ion, which contributes to the efficient energy transfer from the absorbing ligand L1 to the chelated Pr(III) ion (an antenna effect) while the Pr(III) luminescence is not efficiently sensitized by ligand L2. The obtained emission spectra indicated that the excitation energy level for the central Pr(III) is in a slightly lower location than ligand L1 excitation triplet (T1) level and can accept the energy transfer from T1 efficiently.

Synthesis and properties of oligonucleotides carrying isoquinoline imidazo[1,2-a]azine fluorescent units

Oligonucleotides carrying novel fluorescent compounds with a dipolar isoquinoline imidazo[1,2-a]azine core were prepared. Analysis of the melting curves demonstrates that DNA duplexes carrying these fluorescent labels at their ends have a slight increase in DNA duplex stability. The UV absorption and fluorescent properties of the oligonucleotide conjugates were analyzed. The fluorescent label is sensitive to duplex formation, as cooperative melting curves are also observed at 366 nm and fluorescence has a large increase upon denaturation. Cell uptake studies allow observation of these fluorescently labeled oligonucleotides internalized into HeLa cells.

Spectral resolution of molecular ensembles under ambient conditions using surface plasmon coupled fluorescence emission

We report the ability to spectrally resolve excited-state ensembles of pyranine (Py) utilizing nanometer-thick metal films as a low-cost analytical tool. Surface plasmon coupling allows to mitigate the effect of spectral broadening that is responsible for blurring the emission spectrum at room temperature, a situation common in conventional fluorescence spectroscopy. The approach is especially useful in the case when several excited-state species are present. Fluorescence emission from closely located protonated, deprotonated, and excimer species of Py couple into surface plasmons and are easily separated and observed with 11-14 fold intensity enhancements. Furthermore, the ultranarrowband photon-sorting of emission from microenvironments in a multispecies system is performed in this study using instruments that are readily available in most laboratories without employing any deconvolution procedure and/or additional dispersive optics.

Absorption and fluorescence emission spectroscopic characters of naphtho-homologated yy-DNA bases and effect of methanol solution and base pairing

A comprehensive theoretical study of electronic transitions of naphtho-homologated base analogs, namely, yy-T, yy-C, yy-A, and yy-G, was performed. The nature of the low-lying excited states is discussed, and the results are compared with those from experiment and also with those of y-bases. Geometrical characteristics of the lowest excited singlet pipi* and npi* states were explored using the CIS method, and the effects of methanol solution and paring with their complementary natural bases on the relevant absorption and emission spectra of these modified bases were examined. The calculated excitation and emission energies agree well with the measured data, where experimental results are available. In methanol solution, the fluorescence from yy-A and yy-G would be expected to occur around 539 and 562 nm, respectively, suggesting that yy-A is a green-colored fluorophore, whereas yy-G is a yellow-colored fluorophore. The methanol solution was found to red-shift both the absorption and emission maxima of yy-A, yy-T, and yy-C, but blue-shift those for yy-G. Generally, though base pairing has no significant effects on the absorption and fluorescence maxima of yy-A, yy-C, and yy-T, it blue-shifts those for yy-G.

Absorption and fluorescence emission spectroscopic characters of size-expanded yDNA bases and effect of deoxyribose and base pairing

We present an ab initio study of the optical absorption and emission spectra of size-expanded nucleic acid base analogues (yA, yT, yT-m, yG, yG-t2, and yC) obtained by benzo homologation (see Krueger, A. T.; Lu, H.; Lee, A. H. F.; Kool, E. T. Acc. Chem. Res. 2007, 40, 141 and references therein). Also examined were the effects of linking to deoxyribose and hydrogen bonding to their natural complementary bases (T, A, C, and G, respectively). The calculated excitation and emission energies are in good agreement with the measured data where experimental results are available. The geometries corresponding to the first excited singlet state of yA and yT are found to be quasi-planar, while those for yG and yC are nonplanar. In general, binding to deoxyribose will red shift the absorbance and fluorescence emission maxima of the y-bases. The ground-state geometries of the Watson-Crick analog base pairs (yAT, yTA, yGC, and yCG) are found to be planar, and the calculated interaction energies are very close to those of natural base pairs, indicating that the y-bases can pair with their natural complementary partners to generate stable base pairs. The base pairing has no significant effects on the fluorescence emission of yA, yC, and yT, but blue shifts the fluorescence emission of yG by 22 nm.

Elucidation of multiple-point interactions of pyranine fluoroprobe during the gelation

We have studied the multiple-point interactions of the pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt; 3sPyOH) fluoroprobe with polymer chains during the free-radical polymerization of acrylamide (AAm) by using the steady state fluorescence measurements. We observed a considerable blue shift from 515nm to 406nm in the emission spectra due to a C-O ether bond formation between the hydroxylic oxygen of 3sPyOH and a terminal C-atom of the growing AAm chain. Furthermore ionic (electrostatic) interactions occur between the three ionized sulfonic acid groups (SO(3)(-)) of 3sPyOH and protonated amide groups on the AAm chains. These electrostatic interactions also cause a gradual red shift in the maximum of the short-wavelength-peak, from 406nm to 430nm. The results showed that the pyranine can be used as a probe for real time monitoring of the polymerization process of AAm system since it monitors both the progression of the polymerization via chemical binding over OH group and the change in the local density of the polymerizing sample by means of the gradual red shift in the short-wavelength-peak via ionic interactions over SO(3)(-) groups.