Ultrafast Response and High Selectivity of Diethylamine Gas Sensors at Room Temperature Using MOF-Derived 1D CuO Nano-Ellipsoids

Environmental and health monitoring requires low-cost, high-performance diethylamine (DEA) sensors. Materials based on metal-organic frameworks (MOFs) can detect hazardous gases due to their large specific surface area, many metal sites, unsaturated sites, functional connectivity, and easy calcination to remove the scaffold. However, developing facile materials with high sensitivity and selectivity in harsh environments for accurate DEA detection at a low detection limit (LOD) at room temperature (RT) is challenging. In this study, p-type semiconducting porous CuOx sensing materials were synthesized using a simple solvothermal process and annealed in an argon atmosphere at three different temperatures (x = 400, 600, and 800 °C). Significant variations in particle size, specific area, crystallite size, and shape were noticed when the annealing temperature was elevated. Cu-MIL-53 annealed at 400 °C (CuO-400) has a typical nanoellipsoid (NEs) shape with a length of 61.5 nm and a diameter of 33.2 nm. Surprisingly, CuO-400 NEs showed an excellent response to DEA with an ultra-LOD (Rg/Ra = 7.3 @ 100 ppb, 55% relative humidity), excellent selectivity and sensitivity (Rg/Ra = 236 @ 15 ppm), exceptional long-term stability and repeatability, and a fast response/recovery period at RT, outperforming most previously reported materials. CuO-400 NEs have outstanding gas-sensing characteristics due to their high porosity, 1D nanostructure, unsaturated Cu sites (Cu+ and Cu2+), large specific surface area, and numerous oxygen vacancies. This study presents a generic approach to produce future CuO derived from Cu-MOFs-sensitive materials, revealing new insights into the design of effective sensors for environmental monitoring at RT.

Advances in miniaturized nanosensing platforms for analysis of pathogenic bacteria and viruses

Pathogenic bacteria and viruses are the main causes of infectious diseases all over the world. Early diagnosis of such infectious diseases is a critical step in management of their spread and treatment of the infection in its early stages. Therefore, the innovation of smart sensing platforms for point-of-care diagnosis of life-threatening infectious diseases such as COVID-19 is a prerequisite to isolate the patients and provide them with suitable treatment strategies. The developed diagnostic sensors should be highly sensitive, specific, ultrafast, portable, cheap, label-free, and selective. In recent years, different nanosensors have been developed for the detection of bacterial and viral pathogens. We focus here on label-free miniaturized nanosensing platforms that were efficiently applied for pathogenic detection in biological matrices. Such devices include nanopore sensors and nanostructure-integrated lab-on-a-chip sensors that are characterized by portability, simplicity, cost-effectiveness, and ultrafast analysis because they avoid the time-consuming sample preparation steps. Furthermore, nanopore-based sensors could afford single-molecule counting of viruses in biological specimens, yielding high-sensitivity and high-accuracy detection. Moreover, non-invasive nanosensors that are capable of detecting volatile organic compounds emitted from the diseased organ to the skin, urine, or exhaled breath were also reviewed. The merits and applications of all these nanosensors for analysis of pathogenic bacteria and viruses in biological matrices will be discussed in detail, emphasizing the importance of artificial intelligence in advancing specific nanosensors.

Much Stronger Chemiluminescence of 9-Mesityl-10-methylacridinium Ion than Lucigenin at Neutral Conditions for Co2+ Detection

9-Mesityl-10-methylacridinium ion (Acr+-Mes) is a donor-acceptor molecule with a much longer lifetime and a higher energy electron transfer excited state than natural photosynthetic reaction centers. Unlike lucigenin with a coplanar geometry, Acr+-Mes has an orthogonal geometry. There is no π conjugation between Acr+ and Mes. Due to its special electron donor-acceptor structure, it does not rely on strong alkalinity to generate an electron transfer state like lucigenin, which makes it possible to achieve chemiluminescence (CL) under weakly alkaline or neutral conditions. In this study, we report Acr+-Mes CL for the first time. Acr+-Mes generates about 400 times stronger CL intensity than lucigenin under neutral conditions (pH = 7) using KHSO5 as the coreactant. Moreover, Co2+ can enhance Acr+-Mes/KHSO5 CL remarkably. Acr+-Mes/KHSO5 CL enables Co2+ detection with a linear range of 0.5-500 nM and a limit of detection of 28 pM (S/N = 3). This method was tested for the detection of Co2+ in lake water, and the standard recovery rate of 96.8-107% was achieved. This study provides a new way to develop efficient CL systems in neutral solutions.

Recent advances in microchip electrophoresis for analysis of pathogenic bacteria and viruses

Life-threatening diseases, such as hepatitis B, pneumonia, tuberculosis, and COVID-19, are widespread due to pathogenic bacteria and viruses. Therefore, the development of highly sensitive, rapid, portable, cost-effective, and selective methods for the analysis of such microorganisms is a great challenge. Microchip electrophoresis (ME) has been widely used in recent years for the analysis of bacterial and viral pathogens in biological and environmental samples owing to its portability, simplicity, cost-effectiveness, and rapid analysis. However, microbial enrichment and purification are critical steps for accurate and sensitive analysis of pathogenic bacteria and viruses in complex matrices. Therefore, we first discussed the advances in the sample preparation technologies associated with the accurate analysis of such microorganisms, especially the on-chip microfluidic-based sample preparations such as dielectrophoresis and microfluidic membrane filtration. Thereafter, we focused on the recent advances in the lab-on-a-chip electrophoretic analysis of pathogenic bacteria and viruses in different complex matrices. As the microbial analysis is mainly based on the analysis of nucleic acid of the microorganism, the integration of nucleic acid-based amplification techniques such as polymerase chain reaction (PCR), quantitative PCR, and multiplex PCR with ME will result in an accurate and sensitive analysis of microbial pathogens. Such analyses are very important for the point-of-care diagnosis of various infectious diseases.

Electrochemical Detection of Dopamine using a Phenyl Carboxylic Acid-Functionalized Electrode Made by Electrochemical Reduction of a Diazonium Salt

A glassy carbon electrode (GCE) has been modified by an in situ electrochemical reduction of an aryldiazonium salt generated from the reaction of 4-aminobenzoic acid and sodium nitrite in acidic ethanolic solution. The as-prepared phenyl carboxylic acid-modified glassy carbon electrode has been, for the first time, used for the electrochemical determination of dopamine. Under optimal experimental parameters, outstanding electrocatalytic activity, high sensitivity at a LOD of 5.6×10^-9  m, and broad linearity of 0.1 to 1000 μm were obtained. The crafted electrochemical platform demonstrated excellent stability, specificity, and anti-interference capability towards the sensing of dopamine.

Dithiothreitol-Lucigenin Chemiluminescent System for Ultrasensitive Dithiothreitol and Superoxide Dismutase Detection

1,4-Dithiothreitol (DTT), a highly water-soluble and well-known reducing agent for preservation and regeneration of sulfhydryl groups in biomedical applications, has been developed as an efficient and stable coreactant of lucigenin for the first time. DTT efficiently reacts with lucigenin to generate intense chemiluminescence (CL), eliminating the need for external catalysts to facilitate the lucigenin CL. The DTT-lucigenin CL is approximately 15-fold more intense when compared with the lucigenin-H₂O₂ classical system. Superoxide dismutase (SOD) remarkably quenches the DTT-lucigenin CL. Based on this phenomenon, a newly developed CL approach for the determination of SOD was proposed with a linear range of 0.01-1.5 μg/mL and a limit of detection of 2.2 ng/mL. Various factors affecting the CL emission of the DTT-lucigenin probe were studied and optimized. Plausible mechanistic pathways for the CL coreaction of lucigenin with DTT were proposed and fully discussed. Our proposed method not only has the merit of being selective toward the target analytes but also eliminates the need for the complex synthesis of luminescent probes and facilitates the sensitive detection of SOD in human serum and cosmetics SOD raw material with satisfactory recoveries.

Chemiluminescence of lucigenin-tetracycline and its application for sensitive determination of procyanidin

Tetracycline was reported to trigger intense lucigenin chemiluminescence (CL). Based on its significant quenching to lucigenin-tetracycline CL, procyanidin was detected. The mechanism of the lucigenin-tetracycline CL and its quenching by procyanidin were proposed. Under the optimum conditions, the calibration curve is linear in the range of 10–1000 nM for procyanidin with a detection limit of 4.4 nM. The RSD for nine replicate determinations of procyanidin was less than 1.7%. Moreover, this method was satisfactorily applied to the determination of procyanidin in human urine samples and health food capsule of grape seed.

Dimeric G-Quadruplex: An Efficient Probe for Ultrasensitive Fluorescence Detection of Mustard Compounds

Some mustard compounds (mustards) are highly toxic chemical warfare agents. Some are explored as new anticancer drugs. Therefore, the fast, selective, and sensitive detection of mustards is extremely important for public security and cancer therapy. Mustards mostly target the N7 position on the guanine bases of DNA. The guanine-rich G-quadruplex DNA (G4) has been widely studied in the sensing area, and it was found that dimeric G4 (D-G4) could dramatically light up the fluorescence intensity of thioflavin T (ThT). Based on this, we used for the first time the D-G4 DNA as a selective probe for ultrasensitive fluorescence detection of nitrogen mustard (NM). When NM occupies the N7 on guanine, it can block the formation of the D-G4 structure due to the steric hindrance, and hence, it inhibits the combination of D-G4 with ThT, leading to a sharp decrease of fluorescence intensity. The proposed reaction mechanism is proved using ultraviolet-visible (UV-Vis) spectra, circular dichroism (CD) spectra, and polyacrylamide gel electrophoresis. Herein, the concentration of D-G4/ThT used is as low as 50 nM due to its highly fluorescent performance, enabling both high sensitivity and low cost. NM can be detected with a wide linear range from 10 to 2000 nM. The detection limit of NM reaches a surprisingly low concentration of 6 nM, which is 2 or 3 orders of magnitude lower than that of previously developed fluorescence methods for mustards and simulants.

Detection of ascorbic acid based on its quenching effect on luminol-artemisinin chemiluminescence

We find that luminol can react with artemisinin (ART) to produce chemiluminescence (CL) in the absence of a catalyst and ascorbic acid (AA) can quench luminol-ART CL. Based on its efficient inhibition effect on luminol-ART CL, a new AA detection method is established. The calibration curve for the determination of AA is in the linear range of 5 × 10^-7 M to 1 × 10^-4 M with a detection limit of 50 nM, which is more sensitive than many other reported methods. This CL approach was utilized to detect AA in vitamin C tablets by applying the standard addition method, and the recoveries of 104.0%, 96.8% and 103.4% were obtained, respectively, at concentrations of 1 μM, 5 μM and 10 μM with a RSD value of less than 3.6%. This developed method for AA assay is distinguished by its fastness, reproducibility, easy operation and good selectivity.

Development of luminol-fluorescamine-PVP chemiluminescence system and its application to sensitive tyrosinase determination

Fluorescamine is a popular fluorescent probe. We report for the first time that luminol chemiluminescence (CL) can be enhanced by fluorescamine in the presence of PVP. The CL intensity of luminol-fluorescamine-PVP is about 26 times stronger than that of luminol. Both the removal of oxygen and the addition of superoxide dismutase (SOD) decrease CL intensity, thiourea and NaN₃ have little effect on CL intensities, indicating that O₂^•- is critical for CL. Interestingly, o-quinone generated from phenol by tyrosinase obviously inhibited the CL intensity. Inspired by such quenching effect on the luminol-fluorescamine-PVP CL system, a sensitive CL sensing for the determination of tyrosinase activity was developed. The method can detect tyrosinase in the range of 0.07-1.5 μg mL^-1 (0.19-4.02 U mL^-1) with the detection limit of 0.035 μg mL^-1 (0.094 U mL^-1). Moreover, this method exhibits satisfied recoveries for the spiked human serum samples.

Recent advances in nanomaterial-based capillary electrophoresis

This review gives a summary of applications of different nanomateials, such as gold nanoparticles (AuNPs), carbon-based nanoparticles, magnetic nanoparticles (MNPs), and nano-sized metal organic frameworks (MOFs), in electrophoretic separations. This review also emphasizes the recent works in which nanoparticles (NPs) are used as pseudostationary phase (PSP) or immobilized on the capillary surface for enhancement of separation in CE, CEC, and microchips electrophoresis.

Electrochemiluminescence of 3,4,9,10-perylenetetracarboxylic acid/oxamic hydrazide and its application in the detection of tannic acid

The electrochemiluminescence of 3,4,9,10-perylenetetracarboxylic acid/oxamic hydrazide is reported and used for tannic acid detection for the first time.

Hierarchical concave layered triangular PtCu alloy nanostructures: rational integration of dendritic nanostructures for efficient formic acid electrooxidation

The rational construction of multi-dimensional layered noble metal nanostructures is a great challenge since noble metals are not layer-structured materials. Herein, we report a one-pot hydrothermal synthetic method for PtCu hierarchical concave layered triangular (HCLT) nanostructures using dl-carnitine, KI, poly(vinylpyrrolidone), CuCl2, and H2PtCl6. The PtCu HCLT nanostructure is comprised of multilayered triangular dendrites. Its layer number is tunable by changing dl-carnitine concentrations, and the concavity/convexity of the PtCu triangle nanostructures is tunable by changing the H2PtCl6/CuCl2 ratio or KI concentrations. Hierarchical trigonal bipyramid nanoframes are also obtained under certain conditions. Because of its advantageous nanostructure and bimetallic synergetic effect, the obtained PtCu HCLT nanostructure exhibits enhanced electrocatalytic activity and prolonged stability to formic acid oxidation compared to commercial Pt black, Pd/C and some other nanostructures.

A single-electrode electrochemical system for multiplex electrochemiluminescence analysis based on a resistance induced potential difference

A single-electrode electrochemical system uses only one electrode for multiplex experiments, and is a highly cheap platform for high throughput analysis.

Developing low-cost and simple electrochemical systems is becoming increasingly important but still challenged for multiplex experiments. Here we report a single-electrode electrochemical system (SEES) using only one electrode not only for a single experiment but also for multiplex experiments based on a resistance induced potential difference. SEESs for a single experiment and multiplex experiments are fabricated by attaching a self-adhesive label with a hole and multiple holes onto an ITO electrode, respectively. This enables multiplex electrochemiluminescence analysis with high sensitivity at a very low safe voltage using a smartphone as a detector. For the multiplex analysis, the SEES using a single electrode is much simpler, cheaper and more user-friendly than conventional electrochemical systems and bipolar electrochemical systems using electrode arrays. Moreover, SEESs are free from the electrochemiluminescent background problem from driving electrodes in bipolar electrochemical systems. Since numerous electrodes and cover materials can be used to fabricate SEESs readily and electrochemistry is being extensively used, SEESs are very promising for broad applications, such as drug screening and high throughput analysis.

Overcoming multidrug resistance using folate receptor-targeted and pH-responsive polymeric nanogels containing covalently entrapped doxorubicin

Multidrug resistance (MDR) contributes to failure of chemotherapy. We here show that biodegradable polymeric nanogels are able to overcome MDR via folic acid targeting. The nanogels are based on hydroxyethyl methacrylamide-oligoglycolates-derivatized poly(hydroxyethyl methacrylamide-co-N-(2-azidoethyl)methacrylamide) (p(HEMAm-co-AzEMAm)-Gly-HEMAm), covalently loaded with the chemotherapeutic drug doxorubicin (DOX) and subsequently decorated with a folic acid-PEG conjugate via copper-free click chemistry. pH-Responsive drug release is achieved via the acid-labile hydrazone bond between DOX and the methacrylamide polymeric network. Cellular uptake and cytotoxicity analyses in folate receptor-positive B16F10 melanoma versus folate receptor-negative A549 lung carcinoma cells confirmed specific uptake of the targeted nanogels. Confocal microscopy demonstrated efficient internalization, lysosomal trafficking, drug release and nuclear localization of DOX. We also show that DOX resistance in 4T1 breast cancer cells results in upregulation of the folate receptor, and that folic acid targeted nanogels can be employed to bypass drug efflux pumps, resulting in highly efficient killing of resistant cancer cells. In conclusion, folic acid functionalized nanogels with pH-controlled drug release seem to hold significant potential for treating multidrug resistant malignancies.

PEG stabilized DNA – poly(ferrocenylsilane) polyplexes for gene delivery

Polycationic poly(ferrocenylsilane)s (PFS) with tunable amounts of PEG side chains were used for the condensation of DNA into polyplexes of 110 nm in 5.0 mM HEPES.

A miniature origami biofuel cell based on a consumed cathode

A miniature origami BFC has been fabricated from a MnO₂–graphite flake consumed solid-state cathode.

G-quadruplex enhanced fluorescence of DNA-silver nanoclusters and their application in bioimaging

Guanine proximity based fluorescence enhanced DNA-templated silver nanoclusters (AgNCs) have been reported and applied for bioanalysis. Herein, we studied the G-quadruplex enhanced fluorescence of DNA-AgNCs and gained several significant conclusions, which will be helpful for the design of future probes. Our results demonstrate that a G-quadruplex can also effectively stimulate the fluorescence potential of AgNCs. The major contribution of the G-quadruplex is to provide guanine bases, and its special structure has no measurable impact. The DNA-templated AgNCs were further analysed by native polyacrylamide gel electrophoresis and the guanine proximity enhancement mechanism could be visually verified by this method. Moreover, the fluorescence emission of C3A (CCCA)4 stabilized AgNCs was found to be easily and effectively enhanced by G-quadruplexes, such as T30695, AS1411 and TBA, especially AS1411. Benefiting from the high brightness of AS1411 enhanced DNA-AgNCs and the specific binding affinity of AS1411 for nucleolin, the AS1411 enhanced AgNCs can stain cancer cells for bioimaging.

A universal method for the preparation of functional ITO electrodes with ultrahigh stability

A universal method for electrodeposition of various materials onto an indium tin oxide (ITO) coated substrate with high mechanical stability, which solves one of the most important problems concerning the modified ITO electrodes in practical applications, is presented.

Visible-light-enhanced electrocatalysis and bioelectrocatalysis coupled in a miniature glucose/air biofuel cell

A glucose/air biofuel cell (BFC) that can convert both chemical and light energy into electricity is described. Polyterthiophene (pTTh), a photoresponsive conducting polymer, serves as cathode and catalyzes the reduction of oxygen. Taking advantage of the good environmental stability and exceptional optical properties of pTTh, the assembled BFC exhibits excellent stability and a fast photoresponse with an open-circuit voltage (V(oc)) of 0.50 V and a maximum power output density (P(max)) of 23.65 μW cm(-2) upon illumination by visible light of 10 mW cm(-2) , which is an enhancement of ca. 22 times as compared to P(max) in the dark. Additionally, we propose a possible mechanism for this enhancement. Fabricating a BFC in this manner provides an energy conversion model that offers high efficiency at low cost, paving an avenue for practical solar energy conversion on a large scale.

A dramatic platform for oxygen reduction reaction based on silver nanoclusters

We report a high-yield strategy for the synthesis of very small silver nanoclusters (2 to 5 silver atoms) formed from conventional silver salts and scaffolds as high-performance catalysts for oxygen reduction reaction (ORR). The work demonstrates that Ag NCs are excellent catalysts for ORR and show great potential in alkaline fuel cells.

High-performance BiOBr ultraviolet photodetector fabricated by a green and facile interfacial self-assembly strategy

We have fabricated a BiOBr film for the first time through water-air interfacial self-assembly, which is a green, easily processable and environmentally friendly strategy. Moreover, an ultraviolet photodetector based on the BiOBr film exhibited excellent stability and a fast response time.

Development and characterization of novel microsatellite markers in the rock bream fish Oplegnathus fasciatus

The rock bream fish Oplegnathus fasciatus is one of the most popular aquaculture species in China. In the present study, 15 novel polymorphic microsatellite loci were isolated and characterized from a wild population of O. fasciatus from the Zhoushan coast of China. The number of alleles per polymorphic locus ranged from 4 to 9 in a sample of 30 individuals. Observed and expected heterozygosities per locus varied from 0.267 to 0.767 and from 0.395 to 0.859, respectively. Eleven of the 15 microsatellite loci conformed to Hardy-Weinberg equilibrium. No significant linkage disequilibrium between pairs of loci was detected. The present microsatellite markers could provide a useful tool for the genetic analyses of O. fasciatus.

Isolation and characterization of novel microsatellite loci in Nibea albiflora

Eleven novel microsatellite loci were isolated from a (CA)10-enriched genomic DNA library of Nibea albiflora. The characteristics of these microsatellites were determined in a sample of 48 N. albiflora individuals. The number of alleles at the 11 microsatellite loci ranged from 5 to 25, with an average of 13.5 per locus. The observed and expected heterozygosities varied from 0.583 to 0.917 and from 0.568 to 0.964, respectively. Eight of the 11 microsatellite loci conformed to the Hardy-Weinberg equilibrium. No significant linkage disequilibrium was found among all 11 loci. These polymorphic microsatellites will be useful for population genetic analyses of N. albiflora.

Multifunctional AS1411-functionalized fluorescent gold nanoparticles for targeted cancer cell imaging and efficient photodynamic therapy

Herein, one multifunctional AS1411-functionalized fluorescent gold nanoparticles (named NAANPs) is synthesized and successfully applied for both targeted cancer cell imaging and efficient photodynamic therapy (PDT). The NAANPs are obtained by functionalizing the gold nanoparticles with AS1411 aptamer and then bound with one porphyrin derivative N-methylmesoporphyrin IX (NMM). Using HeLa cells over expressing nucleolin as representative cancer cells, the formed NAANPs can target to the cell surface via the specific AS1411-nucleolin interaction, which can discriminate the cancer cells from normal ones (e.g. HEK293) unambiguously. That the fluorescence intensity of NMM increased significantly upon binding to AS1411 G-quadruplex makes the NAANPs appropriate fluorescence reagent for cell imaging. Meanwhile, NMM can also be used as a photosensitizer, thus irradiation of the NAANPs by the white light from a common electric torch can lead to efficient production of cytotoxic reactive oxygen species for establishing a new type of PDT to cancer cells. Gold nanoparticles play the roles of both carrier and enhancer of the functional groups onto the cells. In addition, they not only possess inherently certain cytotoxicity to the cancer cells, but also boost the cellular uptake of the fluorescent groups. As a result, the efficiency of both the targeted cell imaging and PDT could be ensured.

A visible multi-digit DNA keypad lock based on split G-quadruplex DNAzyme and silver microspheres

A novel visible multi-digit DNA keypad lock system was fabricated based on split G-quadruplex DNAzyme and silver microspheres. The final result of the keypad lock can be easily recognized by the naked eye and the number of inputs for the keypad lock can be flexibly adjusted. This molecular platform showed excellent scalability and flexibility.

Serotypes, genotypes and antimicrobial resistance patterns of human diarrhoeagenic Escherichia coli isolates circulating in southeastern China

Diarrhoeagenic Escherichia coli (DEC) infection is a major health problem in developing countries. The prevalence and characteristics of DEC have not been thoroughly investigated in China. Consecutive faecal specimens from outpatients with acute diarrhoea in nine sentinel hospitals in southeastern China were collected from July 2009 to June 2011. Bacterial and viral pathogens were detected by culture and RT-PCR, respectively. DEC isolates were further classified into five pathotypes using multiplex PCR. The O/H serotypes, sequence types (STs) and antimicrobial susceptibility profiles of the DEC isolates were determined. A total of 2466 faecal specimens were collected, from which 347 (14.1%) DEC isolates were isolated. DEC was the dominant bacterial pathogen detected. The DEC isolates included 217 EAEC, 62 ETEC, 52 EPEC, 14 STEC, one EIEC and one EAEC/ETEC. O45 (6.6%) was the predominant serotype. Genotypic analysis revealed that the major genotype was ST complex 10 (87, 25.6%). Isolates belonging to the serogroups or genotypes of O6, O25, O159, ST48, ST218, ST94 and ST1491 were highly susceptible to the majority of antimicrobials. In contrast, isolates belonging to O45, O15, O1, O169, ST38, ST226, ST69, ST31, ST93, ST394 and ST648 were highly resistant to the majority of antimicrobials. DEC accounted for the majority of bacterial pathogens causing acute diarrhoea in southeastern China, and it is therefore necessary to test for all DEC, not only the EHEC O157:H7. Some serogroups or genotypes of DEC were highly resistant to the majority of antimicrobials. DEC surveillance should be emphasized.

Biological control of postharvest sour rot of citrus by two antagonistic yeasts

AIMS

To investigate antifungal effects of two antagonistic yeasts on postharvest sour rot caused by Geotrichum citri-aurantii in citrus and evaluate possible mechanisms.

METHODS AND RESULTS

Cell suspension of Cryptococcus laurentii at 10(8) to 10(9) cells per ml effectively reduced sour rot incidence from 55.6% among untreated control fruit to 29.9-20.7% after 5 days of incubation at 26 degrees C. Application of cell-free culture filtrate of C. laurentii was effective in reducing the sour rot, but the effectiveness was lower than that of the cell suspension (1 x 10(8) cells per ml). In addition, C. laurentii multiplied more rapidly than Rhodosporidium paludigenum at 26 degrees C. The fruit inoculated with the two yeasts demonstrated changes in peroxidase and superoxide dismutase activity. Cryptococcus laurentii, in particular, was capable of inducing a striking response in treated citrus fruits.

CONCLUSIONS

The antifungal ability of C. laurentii can be attributed to the competitions of nutrients and space, defensive responses and possible secretion of antibiotic compounds.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of such antagonists may constitute an important alternative to synthetic fungicides for controlling postharvest sour rot in citrus.

Solid-phase synthesis of tetrahydro-1,4-benzodiazepin-2-one derivatives

An efficient method for solid-phase construction of tetrahydro-1,4-benzodiazepin-2-one scaffold is described. Polymer-bound 4-(bromomethyl)-3-nitrobenzoic acid was reacted with alpha-amino acid methyl esters, followed by nitro group reduction and hydrolysis. Subsequent intramolecular cyclization and alkylation at N(4) afforded the structurally diverse products in high yields and excellent purities.

[Introduction of the chromogenic gene to the plant growth-promoting rhizobacteria of cucumber]

Using a bicomponent transposition system with the E. coli lacZY gene cloned between Tn7 termini, a sensitive, selectable marker based on expression of the E. coli lac operon genes encoding beta-galactosidase and lactose permease was transformed into the rifampicin resistant mutant of plant growth-promoting rhizobacteria of cucumber, Pseudomonas aeruginosa CN116 and Pseudomonas corrugata CN31, respectively. Transformants were conferred the ability to utilize lactose as a sole carbon source and the ability to cleave the chromogenis substrate X-Gal to show a specific blue color. Southern blotting analysis showed that lacZY gene was inserted into the genome DNA of target strains. Compared with the wild type strains, the cultural characters, morphological features, growth promoting and disease control effects of transformants were almost unchanged, except the new marked phenotype. This marker system enabled the detection of lac+ transformants at sensitivity of 10 CFU/g soil, which makes the further studies on PGPR more easily.

Use of inhibitors to evaluate coreceptor usage by simian and simian/human immunodeficiency viruses and human immunodeficiency virus type 2 in primary cells

We have used coreceptor-targeted inhibitors to investigate which coreceptors are used by human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency viruses (SIV), and human immunodeficiency virus type 2 (HIV-2) to enter peripheral blood mononuclear cells (PBMC). The inhibitors are TAK-779, which is specific for CCR5 and CCR2, aminooxypentane-RANTES, which blocks entry via CCR5 and CCR3, and AMD3100, which targets CXCR4. We found that for all the HIV-1 isolates and all but one of the HIV-2 isolates tested, the only relevant coreceptors were CCR5 and CXCR4. However, one HIV-2 isolate replicated in human PBMC even in the presence of TAK-779 and AMD3100, suggesting that it might use an undefined, alternative coreceptor that is expressed in the cells of some individuals. SIV(mac)239 and SIV(mac)251 (from macaques) were also able to use an alternative coreceptor to enter PBMC from some, but not all, human and macaque donors. The replication in human PBMC of SIV(rcm) (from a red-capped mangabey), a virus which uses CCR2 but not CCR5 for entry, was blocked by TAK-779, suggesting that CCR2 is indeed the paramount coreceptor for this virus in primary cells.

Ligand interactions with E-selectin. Identification of a new binding site for recognition of N-acyl aromatic glucosamine substituents of sialyl Lewis X

Several N-acylglucosamine derivatives of sialyl Lewis X (1-3) were prepared using a combined chemical enzymatic approach and evaluated as an inhibitor of E-selectin-mediated cellular adhesion. Compounds with aromatic functionality, 1 and 2, were found to be 3-10 times more potent than the N-acetyl derivative (14) in an ELISA E-selectin cell adhesion assay. Conformational analysis with NMR indicated that the sialyl Lewis x domain of 1 retained the conformation of the N-acetyl derivative (14) despite the presence of the N-naphthamido group. The dramatic order of magnitude increase in potency of these monovalent structures can be utilized to design more potent selectin-based cell adhesion inhibitors.

[Characteristics of traditional Chinese medicine syndromes in both spontaneous and variant angina. An analysis of 21 cases]

An analysis of TCM syndromes is reported in 21 cases with both spontaneous and variant angina as compared with 147 cases with effort angina. The results showed that 3 characteristic features were present, which were as follows: the Biao-Shi syndrome of cold condensation was more than that of the control group in ratio of 42.86% to 3.40%; the Ben-Xu syndrome of Yang deficiency was more and that of Qi deficiency less than those in the control group, and they were in ratio of 33.33% to 6.12% and 33.33% to 72.11% respectively. An absolute reduction of blood supply resulted from coronary spontaneous spasm in both spontaneous and variant angina causes severe chest pain during attacks as a cold condensation type. Hyperfunction of parasympathetic nerves often occurring in coronary heart disease with Yang deficiency is liable to vasoconstriction of the large coronary arteries leading to episodes of both spontaneous and variant angina. The presence of less Qi deficiency type may be related to the less impairment of cardiac function resulted from the short course in these cases and only relatively mild state of an illness, even no marked lesion in coronary arteries in a part of patients with both spontaneous and variant angina. No significant difference in TCM syndromes occurred between spontaneous and variant angina. Both Yang and Yin deficiency, as the Ben-Xu syndromes, were more present in angina of cold condensation type.(ABSTRACT TRUNCATED AT 250 WORDS)