Credible and Facile Fluorometric Detection of Soybean Trypsin Inhibitor Activity with a Water-Soluble Poly(diphenylacetylene) Derivative

Herein,a novel method for fl uorometric detection of soybean trypsin inhibitor(SBTI)activity based on a water-soluble poly(diphenylacetylene)derivative was reported.Fluorescence quenching of the polymer via p-nitroaniline,produced from the trypsin-catalyzed decomposition of N-benzoyl-DL-arginine-4-nitroanilide hydrochloride(L-BAPA),was well described using the Stern-Volmer equation.SBTI activity was quantitatively assessed based on changes in the fl uorescence intensity of the polymer.This strategy has several advantages,such as high sensitivity and ease of operation.Moreover,its applicability to other biochemical analyses is promising.

Fluorometric Determination of Terbium by Aromatic armed 1,4,7-triazacyclononane

Terbium and N,N′,N' tri(3,5 diamino benzenesulfonyl) 1,4,7 triazacyclononane (TDABS Tacn) form a stable chelate having a 1∶1 molar ratio in dilute aqueous solution. The fluorescence property of the chelate was studied under the experimental conditions (pH 8.4 in H 3BO 3 KCl NaOH buffer, λ EX =309 nm, λ EM =374 nm). The fluorescence intensity is a linear function of concentration in the range of 5.0×10 -6 to 4.2×10 -4 mol/L for terbium. The relative standard deviation is less than ±2.0%. When tolerable amount of other metal ions were added to the solution of terbium chelate, the fluorescence intensity can be determined without interference. These results suggest that aromatic armed polyazamacrocycle can be used for the terbium determination.

Iron-Mediated Oxidative DNA Damage Detected by Fluorometric Analysis of DNA Unwinding in Isolated Rat Liver Nuclei

Studies were performed to determine the extent of nuclear DNA degradation induced by iron, iron-ascorbate, or iron-bleomycin under aerobic conditions in a model system using isolated rat liver nuclei. The effects of five antioxidants (catalase, superoxide dismutase, dimethyl sulfoxide, glutathione and diallyl sulfide) on this oxidative nuclear damage were also investigated. At the 0.05 level for statistical significance, iron induced concentration-dependent DNA degradation, and this effect was enhanced by ascorbate and bleomycin. The antioxidants catalase, dimethyl sulfoxide, and diallyl sulfide significantly reduced the iron-ascorbate-induced DNA damage, whereas superoxide dismutase and dimethyl sulfoxide significantly reduced iron-bleomycin-induced damage. Glutathione significantly increased the iron-bleomycin-induced DNA damage. These results suggest that the reactive oxygen species generated by iron, iron-ascorbate, and iron-bleomycin are responsible for the DNA strand breaks in isolated rat liver nuclei.

Determination of Amantadine Residue in Honey by Solid-phase Extraction and High-performance Liquid Chromatography with Pre-column Derivatization and Fluorometric Detection

Amantadine （AMA） is an anti-viral drug used in apiculture to protect honeybee against the sacbrood virus （Morator aetatulae）. This study described a reliable high-performance liquid chromatographic （HPLC） method for analyzing AMA in honey using a solid-phase extraction （SPE） cartridge （Plexa PCX） for purification, 4-fluoro-7- nitro-2,1,3-benzoxadiazole （NBD-F） as a pre-column derivatization agent, and fluorometric detection （λex =470 nm, λem=530 nm）. The chromatographic separation was performed on an XDB C18 column （150×4.6 mm i.d.） using 0.1% trifluoroacetic acid/acetonitrile （35 ; 65, V/V） as the mobile phase at a flow rate of 1.0 mLomin 1 with a run time of 20 min. Under these optimal conditions, a linear relationship was observed in the range of 0.025--1.0μg·mL-1 with a good correlation coefficient （0.998） and low limit of detection （0.0080 μg·g-1）, the recoveries were all above 90%, and the intra-day and inter-day precision （RSD） ranged from 3.4%--5.1%.

Optically tunable fluorescent carbon nanoparticles and their application in fluorometric sensing of copper ions

A series of carb on nano particles(CNPs)with emissi on wavele ngth ranging from 483 to 525 nm were prepared by hydrothermal treatme nt of poly-3-thiopheneacetic acid(PTA)and NaOH.The emission wavelength and surface oxidation degree of CNPs were shown to be controllable by simply adjusti ng NaOH concentration.These CNPs prese nted obvious fluoresce nee spectral response toward copper ions(Cu^2+)through static quenching caused synergistically by electron transfer and inner filter effect.The O-and S-containing groups on the surface of CNPs were dem on strated to be resp on sible for their outsta nding sensing performa nee.Based on that,a CN Ps-based ratiometric fluoresce nt probe for Cu^2+with a high fluoresce nee quenching rate constant of 1.4×10^5 L/mol and a short resp onse time(10 s)was developed.Their practical applications in detecting Cu^2+in pond water and living cells were also dem on strated.

Imidazobenzimidazole fused aza-calix[4]arenes:Synthesis,structure,and Zn^(2+)-selective colorimetric-fluorometric sensor

Tetra(amino)azacalix[4]arene skeleton was functionalized at the bridging NH sites using various aromatic aldehydes via formation of imidazobenzimidazole fused heterocycles.X-ray single crystal analysis revealed distorted 1,3-alternate conformations for the resulting macrocycles.Anthracenyl and pyrenyl modified imidazobenzimidazole fused aza-calix[4]arenes existed as dimers in the solid state,associated mainly through-stacking interactions between the planar polycyclic fluorophores.The tetrapyrenyl modified product was further used as a Zn^(2+)-selective sensor,which showed naked-eye detected color change and enhanced excimer emission.The stoichiometry between the sensor and Zn2+was determined to be 1:1 and the association constant was 1.1×10^(5)L/mol.The sensing process was highly selective and showed strong anti-interference with presence of other cations.The UV-vis spectral changes in the sensing process were completely reversible by alternate addition of Zn^(2+) and F^(-),showing an efficient“on-off-on”result.

Fluorometric determination of trace selenium in β-CD/SDS aqueous solution

A proper mixture of β-cyclodextrin and sodium dodecylsulfate in aqueous solution was found to show a synergistic enhancement of the fluorescence intensity of 4,5-benzopiaselenol. The determination of trace selenium can be carried out directly in aqueous solution.

Rice Repetitive DNA Sequence RRD3:a Plant Promoter and Its Application to RNA Interference

Previously, a moderately repetitive DNA sequence （RRD3） was cloned from rice （Oryza sativa L.） by DNA renaturation kinetics. Sequence analysis revealed several conserved promoter motifs, including four TATA-boxes and a CAAT-box, and promoter activity was shown in Escherichia coli and mammalian expression systems. Here, we inserted the RRD3 fragment into the plant promoter-capture vector, pCAMBIA1391Z, and examined whether the RRD3 fragment has promoter activity in plants. Transgenic tobacco and rice calli both showed β-glucuronidase （GUS） activity, indicating that RRD3 can act as a promoter in both monocot and dicot plants. Based on the promoter characteristic of RRD3, we designed a plant universal binary vector, pCRiRRD3, which is suitable for performing researches on plant RNA interference. This vector has two multiple cloning sites to facilitate sense and antisense cloning of the target sequence, separated by an intron fragment of 200 bp. The efficiency of the vector for gene silencing was assayed by histochemical and quantitative fluorometric GUS assays in transgenic tobacco. These research results suggested that this plant RNAi vector pCRiRRD3 can effectively perform gene silencing researches on both monocot and dicot plants.

Effects of fulvic acid and humic acid on aluminum speciation in drinking water

This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water. Factors including the concentration of residual chlorine and pH value had been concerned. Aluminum species investigated in the experiments included inorganic mononuclear, organic mononuclear, mononuclear, polymer, soluble, and suspended forms. It was found that the effects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight. Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation; while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L （calculated as TOC）. Aluminum species, in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid, were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton, and varied little with reaction time. Within pH range 6.5-7.5, soluble aluminum increased notably in water with organic matter. As the concentration of residual chlorine increased, the effects of fulvic acid and humic acid became weak. The reactions between humic acid, fulvic acid with large molecular weight, and aluminum were considered to be a multi-dentate coordination process. With the consideration of aluminum bioavailability, reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5-7.5 were recommended during drinking water treatment.

Factors effecting aluminum speciation in drinking waterby laboratory research

Effects of aluminum on water distribution system and human health mainly attribute to its speciation in drinking water. Laboratory experiments were performed to investigate factors that may influence aluminum speciation in water supply system. The concentration of soluble aluminum and its transformation among other aluminum species were mainly controlled by kinetics processes of related reactions. Total aluminum concentration had a notable effect on the concentrations of mononuclear and soluble aluminum in the first 4 day; then its effect became weak. At pH above 7.50, both fluoride and orthophosphate had little effect on aluminum speciation; while, when the solution pH was below 7.50, the concentrations of mononuclear and soluble aluminum were proportional to the concentration of fluoride and inversely proportional to the concentration of orthophosphate. Both mononuclear and polynuclear silicic acids could complex with mononuclear aluminum by forming soluble aluminosilicates. In addition, the adding sequence of orthophosphate and aluminum into drinking water would also affect the distribution of aluminum species in the first 4 day. In order to minimize aluminum bioavailability in drinking water, it was suggested that orthophosphate should be added prior to coagulant process, and that the concentrations of fluoride and silicic acids should be controlled below 2.0 and 25 mg/L, respectively, prior to the treatment. The solution pH in coagulation and filtration processes should be controlled in the range of 6.50-7.50.

EFFECTS OF SEVERE HEMORRHAGE ON IN VIVO BRAIN AND SMALL INTESTINE MITOCHONDRIAL NADH AND MICROCIRCULATORY BLOOD FLOW

Severe body stress induced by hypoxemia and hypotension may lead to total body energy state deterioration.The perfusion of the most vital organs is maintained at the expense of“less vital”organs.In the present study,we used a multi-site multiparametric(MSMP)monitoring system for real-time evaluation of tissue blood flow(TBF)and mitochondrial NADH fluorescence of the brain and the small intestine following hemorrhage.In Group 1,uncontrolled hemorrhage,mean arterial pressure(MAP)was decreased to 40mmHg within 2 minutes and shed blood was re-infused after 30minutes.In Group 2,controlled hemorrhage,during the 30minutes of hemorrhage,MAP was kept at 40mmHg.During hemorrhage,in both groups,the intestinal TBF and NADH deteriorated,while the brain remained relatively well protected.In Group 1,all parameters partly recovered within the hemorrhage phase,while in Group 2,complete recovery occurred only after resuscitation.At the end of the experiment,both models showed a decrease in intestinal viability(TBF decreased,NADH increased),while the brain metabolic state in Group 2 declined slightly.Our unique multi-parametric monitoring device demonstrated that,under hemorrhage,the small intestine responded entirely differently from the brain.This may suggest the potential usefulness of the monitoring of less vital organs,as proxy organs,in critical conditions such as massive hemorrhage.The present study also highlights the importance of mitochondrial function monitoring in similar conditions in the clinical environment.

Optical Fiber Thermometer Based on the Fluorescence Life time

Anew opticalfiberfluorometricthermometerbased onthetemperature dependence ofthefluorescencelifetime of phosphoris described. The phase-locked detection (PLD) system is used to measure fluorescencelifetime. The characteristics ofthermometerare discussed and the experimentresults are given.

A selective detection of fluoride ions in DMSO by fluorescent and colorimetry competition assays based on 4-bromo-2,6-bis-(hydroxymethyl)phenol

A novel and very simple colorimetric and fluorometric method for selectively sensing F^- was proposed based on 4-bromo-2,6- bis（hydroxymethyl）phenol（BBHMP）,which is a simple and available phenolic receptor the absence of any special chromophoric function and with over wide range of anions（Cl^-,Br^-,I^-,AcO^-,HSO4^-,NO3^- and BzO^-） in DMSO media.The colorimetric method is described for naked-eye detection of F^- in the presence of the BBHMP.The BBHMP was found to show selective and sensitive fluorescence quenching response toward fluoride over than Cl^-,Br^-,I^-,AcO^-,HSO4^-,NO3^- and BzO^-.

A highly sensitive,dual-signal assay based on rhodamine B covered silver nanoparticles for carbamate pesticides

A highly sensitive sensor for determination of carbamate pesticides based rhodamine B（RB） modified silver nanoparticle（RB-AgNPs） was developed.Compared with the classical method,it combined colorimetric with fluorescence for detecting carbamate pesticides in complex solutions.Carbamate pesticides can inhibit the activity of acetylcholinesterase（AChE）,thus preventing the generation of thiocholine.On the other hand,thioncholine can transform the yellow RB-AgNPs solutions gray color and unquenches the fluorescence of RB simultaneously.Once the activity of AChE was inhibited by the pesticide,the color of the RB-AgNPs solution remains yellow and the fluorescence of RB molecules remains quenched.Under optimized experimental conditions,carbaryl was detected in a concentration range from 0.1 ng/L to 8.0ng/L with a detection limit of 0.023 ng/L（it was detected by fluorescence spectra）.This simple method is suitable for determination of carbamate pesticides in complex samples,such as tomato,apple and river water.