Colorimetric Assay Conversion to Highly Sensitive Electrochemical Assay for Bimodal Detection of Arsenate Based on Cobalt Oxyhydroxide Nanozyme via Arsenate Absorption.

This study reports a novel and convenient bimodal method for label-free and signal-off detection of arsenate in environmental samples. Cobalt oxyhydroxide (CoOOH) nanoflakes with facile preparation and intrinsic peroxidase-like activity as nanozyme can efficiently catalyze the conversion of chromogenic substrate such as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with the presence of H2O2 into green-colored oxidation products. CoOOH nanoflakes can specifically bind with arsenate via electrostatic attraction and As-O bond interaction, which gives rise to inhibition of the peroxidase-like activity of CoOOH. Thus, through arsenate specific inhibition of CoOOH nanozyme toward ABTS catalysis, a simple colorimetric method was developed for arsenate detection with a detection limit of 3.72 ppb. Based on the system of CoOOH nanozyme and ABTS substrate, this colorimetric method can be converted into an electrochemical sensor for arsenate assay by the utilization of CoOOH nanoflake-modified electrode. The electrochemical measurement can be realized by chronoamperometry, which showed more sensitive and a lower limit of detection as low as 56.1 ppt. The applicability of this bimodal method was demonstrated by measuring arsenate and total arsenic in different real samples such as natural waters and soil extracted solutions, and the results are of satisfactory accuracy as confirmed by inductively coupled plasma mass spectrometry analysis. The bimodal strategy offers obvious advantages including a label-free step, convenient operation, on-site assay, low cost, and high sensitivity, which is promising for reliable detection of arsenate and total arsenic in environmental samples.

Fluorometric determination of the activity of the biomarker terminal deoxynucleotidyl transferase via the enhancement of the fluorescence of silver nanoclusters by in-situ grown DNA tails.

The activity of terminal deoxynucleotidyl transferase (TdTase) is a biomarker for routine diagnosis of acute leukemia. A method has been developed for the determination of TdTase activity. It is based on the use of silver nanoclusters (AgNCs) whose yellow fluorescence is enhanced by an in-situ grown DNA tail of TdTase-polymerized and guanine-rich DNA at the 3' end of a hairpin DNA. The fluorescence, best measured at excitation/emission peaks of 530/585 nm, increases linearly in the 1 to 35 mU mL-1 TdTase activity range. The detection limit is 0.8 mU mL-1. The method is cost-efficient, selective and convenient. It integrates enhancement of the fluorescence of AgNCs and target recognition into a single process. Graphical abstract Schematic presentation of a method for determination of TdTase activity. It is based on AgNCs fluorescence enhanced by in-situ grown TdTase-polymerized G-rich DNA tail. The method integrates AgNCs fluorescence enhancement and the target recognition into a single process.

Colorimetric and electrochemical arsenate assays by exploiting the peroxidase-like activity of FeOOH nanorods.

The authors describe an electrochemical and an optical method for the determination of As(V) by using iron oxyhydroxide (FeOOH) nanorods that display peroxidase-mimicking activity. The nanorods catalyze the oxidation of substrate ABTS by H2O2 to form a green product with an absorption maximum at 418 nm. If, however, As(V) is electrostatically adsorbed on the nanorods, the oxidation is gradually inhibited. A colorimetric assay was worked out based on these findings. Response is linear in the 0 to 8 ppb and 8 to 200 ppb As(V) concentration range, and the detection limit is 0.1 ppb. Even higher sensitivity is achieved in an electrochemical method which is based on the excellent electrical conductivity of FeOOH nanorods. Electrochemical analysis of As(V) was achieved by first adsorbing As(V) on the nanorods. This inhibits the ABTS reduction current signal, best measured at a potential of 150 mV (vs. Ag/AgCl). The linear range extends from 0.04 to 200 ppb, and the detection limit is as low as 12 ppt. Graphical abstract Schematic representation of FeOOH nanorod-based colorimetric and electrochemical assays for arsenate (As(V)). As(V) adsorbed on FeOOH nanorods inhibits the peroxidase-mimicking activity of nanorods, and a colorimetric and electrochemical dual-signal assay was constructed to achieve sensitive determination of As(V).

[Surface-Enhanced Raman Scattering Study on Photocatalysis of PATP When Adsorbed on Ag/TiO2 Nanotubes].

Surface-enhanced Raman scattering (SERS) is spectroscopic technique with ultra-sensitivity and high selectivity and has attracted great attention because of the potential applications in various fields. P-aminothiophenol (PATP) is often used as SERS probe molecule because it is easy to adsorb on SERS substrates and produce high-quality SERS signals. TiO2 is extensively used as photocatalyst although its photocatalytic efficiency is still needed to be improved. Noble metal-modified TiO2 is one of current important techniques for maximizing the efficiency of photocatalytic efficiency. In this article, a kind of bifunctional SERS substrates, Ag/TiO2 nanotubes, with photocatalysis property were prepared, the TiO2 NTs were prepared by anodic oxidation and noble metal Ag nanoparticles were deposited on the surface of TiO2 NTs by photoreduction method. The photocatalysis of PATP on Ag/TiO2 NTs and on Ag mirror substrates were studied. The SERS signals of PATP were decreased with the ultraviolet irradiation time, however, on Ag mirror substrates, SERS intensity of PATP was slightly changed, which indicated the photocatalysis reaction of PATP on Ag/TiO2 NTs substrates. The kinetics analysis results indicate that the kinetics of the photocatalysis follows the first order of the dynamical reaction.

Postpolypectomy syndrome without abdominal pain led to sepsis/septic shock and gastrointestinal bleeding: A case report.

BACKGROUND: Postpolypectomy syndrome (PPS) is a rare postoperative complication of colonic polypectomy. It presents with abdominal pain and fever accompanied by coagulopathy and elevated inflammatory markers. Its prognosis is usually good, and it only requires outpatient treatment or observation in a general ward. However, it can be life-threatening. CASE SUMMARY: The patient was a 58-year-old man who underwent two colonic polypectomies, each resulting in life-threatening sepsis, septic shock, and coagulopathy. Each of the notable manifestations was a rapid drop in blood pressure, an increase in heart rate, loss of consciousness, and heavy sweating, accompanied by shortness of breath and decreased oxygen in the finger pulse. Based on the criteria of organ dysfunction due to infection, we diagnosed him with sepsis. The patient also experienced severe gastrointestinal bleeding after the second operation. Curiously, he did not complain of any abdominal pain throughout the course of the illness. He had significantly elevated concentrations of inflammatory markers and coagulopathy. Except for the absence of abdominal pain, his fever, significant coagulopathy, and elevated inflammatory marker concentrations were all consistent with PPS. Abdominal computed tomography and superior mesenteric artery computed tomography angiography showed no free air or vascular damage. Thus, the diagnosis of colon perforation was not considered. The final blood culture results indicated Moraxella osloensis. The patient was transferred to the intensive care unit and quickly improved after fluid resuscitation, antibiotic treatment, oxygen therapy, and blood transfusion. CONCLUSION: PPS may induce dysregulation of the systemic inflammatory response, which can lead to sepsis or septic shock, even in the absence of abdominal pain.

Electronic synergy between ligands of luminol and isophthalic acid for fluorescence ratiometric detection of Hg2.

Stimulus-responsive double-ligand luminol-Eu-IPA infinite coordination polymer nanoparticles (luminol-Eu-IPA CPNPs) were prepared as a ratiometric fluorescence probe for highly selective detecting Hg2+. The CPNPs were constituted of Eu3+ as the nuclear metal coordinated by isophthalic acid (IPA) together with luminol as an auxiliary ligand. The photoinduced electron transfer (PET) occurring from IPA to luminol prevented the antenna effect between IPA and Eu3+, leading to the quench fluorescence of Eu3+ under light excitation. As Hg2+ has a high affinity to N atom of luminol and the spin-orbit coupling effect, spectroscopically and magnetically silent properties, the fluorescence intensity of luminol was quenched. Meanwhile, the PET effect between luminol and IPA was interrupted under the presence of Hg2+. This process resulted in a significant decrease in the fluorescence intensity of luminol and a significant increase in the fluorescence intensity of Eu3+. Therefore, the fluorescence ratiometric detection of Hg2+ was performed by monitoring the ratio of the fluorescence at 617 nm of Eu3+ to that at 430 nm of luminol. The linear range was from 0.05 to 20 µM with a detection limit as low as 13.2 nM Hg2+ (S/N = 3). Due to the fluorescence of luminol be quenched and the effect of PET be disrupted simultaneously, the probe exhibiting excellent detection selectively can avoid false positive signals, which was demonstrated for monitoring mercury ions in real water samples. Precision in positioning ligands in CPNPs is an advantage to achieve high specificity in comparison to traditional organic dendrimers or precious metal nanomaterials.

Maximal azimuthal resolution needed in measurements of head-related transfer functions.

The head-related transfer function (HRTF) is a continuous function of sound source position. Measurement of the HRTF can only be undertaken at discrete positions in space, however. Determination of angular resolutions so as to reconstruct HRTFs at unmeasured positions has been an open problem. Azimuthal Fourier analysis was proposed to analyze the variation in the HRTF in each elevation plane. As a result, an azimuthal sampling theorem and a corresponding interpolation formula were derived. It was proved that the maximal azimuthal resolution of measurements is 360 degrees /(2Q+1), where Q represents the highest order in the truncation of the azimuthal Fourier expansion of the HRTF. The maximal azimuthal resolutions for the HRTF with and without arrival time correction were investigated. Results show that the arrival time correction can reduce the burden of measurements, since a larger azimuthal resolution is possible without introducing obvious interpolation error. A psychoacoustic experiment was also conducted to evaluate the proposed theorem.

Engulfment and Cell Motility Protein 1 Protects Against DSS-induced Colonic Injury in Mice via Rac1 Activation.

BACKGROUND AND AIMS: Mucosal healing is an emerging therapeutic goal that could result in clinical remission of inflammatory bowel disease [IBD]. We sought to determine the role of engulfment and cell motility protein 1 [ELMO1] in wound healing in vitro and in vivo and to investigate the underlying pathways. METHODS: RNA transcriptome sequencing was performed to detect the expression profiles of mRNA between inflamed tissues and corresponding non-inflamed tissues of IBD patients, followed by Gene Expression Omnibus [GEO] datasets and western blot analysis. The effects of ELMO1 overexpression or knockdown on cell migration and proliferation were determined. The dependence of these effects on Rac1 was assessed using a Rac1 inhibitor [NSC23766] and a Rac1 pull-down assay. We identified the underlying pathways involved by Gene Ontology [GO] analysis. A dextran sulphate sodium [DSS]-induced colitis model was established to evaluate the role of ELMO1 in colonic mucosal healing. RESULTS: ELMO1 was upregulated in inflamed tissues compared with corresponding non-inflamed tissues. ELMO1 overexpression increased cell migration in a Rac1-dependent manner. Depletion of ELMO1, or NSC23766 administration, abolished this effect. GO analysis revealed that ELMO1 overexpression preferentially affected pathways involved in cytoskeletal regulation and wound healing, which was demonstrated by enhanced F-actin staining and increased numbers of extending lamellipodia in cells overexpressing ELMO1. In DSS-induced colitis, systemic delivery of pSin-EF2-ELMO1-Pur attenuated colonic inflammation and promoted recovery from colonic injury. The protective effect of ELMO1 was dependent on Rac1 activation. CONCLUSIONS: ELMO1 protects against DSS-induced colonic injury in mice through its effect on epithelial migration via Rac1 activation.

Fluorescence-based Polymerase Amplification for the Sensitive Detection of DNA Methyltransferase Activity.

DNA methyltransferase (MTase) is related to transcriptional repressor activity in biological functions. It is an essential for cancer diagnosis and therapeutics to detect DNA MTase activity sensitively. Here, a fluorescent system based on polymerase amplification has been developed to detect DNA adenine MTase (Dam) activity sensitively. The amplification is triggered by the probe DNA regions a, which are the primes of a polymerase-induced replicated reaction. They come from methylation and a digestion reaction of DNA S1-S1, including a 5'-GATC-3' sequence recognized by Dam MTase and methylation sensitive restriction endonuclease Dpn I. The intensities of fluorescence are dependent on the Dam MTase activity. The method shows fine sensitivity with a detection limit of 3.2 × 10-4 U mL-1 and specificity for Dam MTase. In human serum samples, the method has been successfully applied, and it has also been used to screen the inhibitors, which means that the developed method can be a powerful and potential tool for drug development and clinical diagnosis in the future.

[Isolation and analysis of a high expression promoter in rice].

The expression of plant gene is controlled by its promoter. The isolation and the function analysis of promoter are important for studying the genetic engineering and the regulation expression of plant genes. In this paper, we cloned a promoter, 0s252, which was predicted to be highly expressed in the stem of rice from the EST database. After the construction of the Os252::GUS expression vector, it was transformed into rice. The integration of transgenes into transgenic rice genome was confirmed through PCR analysis. X-Gluc staining showed that Os252 can promote GUS gene expression in leaf, stem and matured seed. GUS enzyme activities driven by Os252 promoter in leaf and seed are about 190% and 250% of that driven by the 35S promoter. Thus, the Os252 promoter can be applied for rice genetic engineering.

Plasma polypeptide hormone levels in rats with gastric ulcer after exposure to intense noise / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To observe changes of plasma polypeptide hormone levels in rats with gastric ulcer after exposure to intense noise, and to discuss their mechanism.</p><p><b>METHODS</b>80 Wistar rats were used in the study. Plasma levels of rat gastrin (GAS), motilin (MTL), osteocalcin (BGP), substance P (SP), neurotensin (NT) and somatostatin (SS) in rats were measured by radioimmunoassay.</p><p><b>RESULTS</b>(1) In non-noise-exposure but with gastric ulcer group, the plasma MTL [(160.70 +/- 40.34) pg/ml] and BGP [(27.63 +/- 13.13) pg/ml] levels on 10 d after gastric ulcer model operation were remarkably higher than those in control group [(89.21 +/- 49.94) pg/ml, (9.10 +/- 1.38) pg/ml respectively] (P < 0.05 and P < 0.01), while the GAS level was remarkably descended [(107.00 +/- 21.75) vs (158.48 +/- 20.92) pg/ml] (P < 0.01). (2) In noise-exposure but without gastric ulcer group, the plasma MTL [(312.80 +/- 207.42) pg/ml] and BGP [(17.76 +/- 12.33) pg/ml] levels on 10 d were also significantly increased as compared with the control group (P < 0.01 and P < 0.05 respectively), while the GAS levels didn't change. (3) In noise-exposure + gastric ulcer group, the areas of gastric ulcer on 10 d and 40 d after noise and operation [(15.33 +/- 7.26) and (15.11 +/- 12.45) mm(2) respectively] were significantly larger than those of the control [(8.22 +/- 6.66), (3.67 +/- 9.90) mm(2)] (P < 0.05). The plasma MTL levels on 10 d and 40 d [(244.44 +/- 68.11) and (191.20 +/- 60.50) pg/ml respectively] were higher than those in control group [(160.70 +/- 40.34) and (93.10 +/- 52.90) pg/ml respectively] (P < 0.01).</p><p><b>CONCLUSION</b>Intense noise exposure may make the rat gastric ulcer worsened and induce negative effect on healing of it. The gastrointestinal endocrine would be disturbed by combined effect of intense noise exposure with gastric ulcer in rats.</p>