The hydrogen bond between tryptophan and the host molecule induced fluorescence enhancement.

Tryptophan is one of important amino acids in the human body, therefore its detection is particularly important. The 3,5-bis(4-pyridyl)-4-amino-1,2,4-triazole (BPAT) organic molecule was designed to be used as fluorescence detectors to detect tryptophan molecules for the interaction between the host and the guest. BPAT shows good sensitivity and selectivity towards tryptophan compared with other amino acid molecules. The limit of detection obtained from formula 3δ/KSV is considered to be 5.43 × 10-7  mol/L. We speculated that this change is mainly caused by the hydrogen bond between tryptophan and the host molecule BPAT. This conjecture was verified by the controlled experiments with other host molecules.

Management of venous perforation during central venous catheterization in hemodialysis patients: Three case reports.

RATIONALE: In recent years, central venous catheterization (CVC) has become widely used for hemodialysis patients. Based on 3 cases, we discussed the detection and management of venous perforation at an early stage. PATIENTS CONCERNS: Patients 1 (male, 77 years), 2 (male, 82 years), and 3 (male, 30 years) were diagnosed with uremia and underwent hemodialysis. DIAGNOSES: Computed tomography suggested pneumomediastinum in patient 1 and pneumothorax in patient 2 after a replacement of the temporary hemodialysis catheter. In patient 3, X-ray suggested that the tip of the catheter was approximately at the plane of the fifth thoracic vertebrate after the temporary catheter was placed. INTERVENTIONS: In patients 1 and 2, the catheters were maintained where they were for about 2 weeks until a false lumen formed outside the catheter. In patient 3, the catheter was withdrawn at once when vein perforation was observed. OUTCOME: In patients 1 and 2, the catheters were adjusted successfully under digital subtraction angiography (DSA) guidance 2 weeks later. In patient 3, hemothorax developed, and a total of approximately 1000 mL of bloody fluid was drained. LESSONS: When venous perforation occurs during CVC, it is safer and more reliable to adjust or withdraw the catheter under DSA guidance after a false lumen forms outside the catheter.

Effect of surface-bound sulfide on oxygen reduction reaction on Pt: Breaking the scaling relationship and mechanistic insights.

A combined in situ electrochemical attenuated total reflection-surface enhanced IR absorption spectroscopy, microkinetic simulation, and density functional theory calculation study shows that not only can the adsorbed sulfide disproportionally affect the surface binding of OOH* (EOOH* ) vs OH* (EOH* ), i.e., breaking the original scaling relationship of pure metals (Ir, Pd, Pt, Au), to enhance oxygen reduction reaction (ORR) activity but can also be used as a reaction pathway alternating species to help deepen our mechanistic understanding of ORR.

Pathological significance of urinary complement activation in diabetic nephropathy: A full view from the development of the disease.

AIMS/INTRODUCTION: The aim of the present study was to obtain a full view of the changes of urinary complement activation products in the development of diabetic nephropathy and explore their possible significance in the disease process. MATERIALS AND METHODS: A total of 62 patients at different stages of diabetic nephropathy, 20 diabetes patients without nephropathy and 20 healthy persons were enrolled. Urinary complement activation products, including C3a, C5a and C5b-9, were measured, and their associations with the progression of the disease were analyzed. RESULTS: The urinary complement activation products increased markedly since the proteinuria stage, and were parallel with the progression of diabetic nephropathy. More severe renal tubular damage was observed in patients with higher levels of urinary complement activation products. The urinary complement activation products levels correlated closely with renal tubulointerstitial injury score and relative tubular interstitial volume. Multivariate regression analysis showed that elevated urinary complement activation products were independent risk factors for tubular injury in diabetic nephropathy patients. CONCLUSIONS: Urinary complement activation might have a role in renal tubular interstitial injury in patients with diabetic nephropathy, especially in patients at a later stage of the disease.

Lectin-induced renal local complement activation is involved in tubular interstitial injury in diabetic nephropathy.

BACKGROUND: Complement has been suggested to be involved in diabetic nephropathy (DN), but the exact significance and underlying mechanisms remain unclear. Data about renal local complement activation in DN patients is scarce. The purpose of the study was to clarify the significance and mechanism of renal local complement activation in DN. METHODS: Sixty-two biopsy-proven DN patients were recruited. Renal expression of C1Q, factor B, C5b-9, MBL and MBL-associated serine protease 1 (MASP1) were detected and associated with the kidney damage. RESULTS: C5b-9, MBL and MASP1 was found to increase with the progression of DN. Especially, the level of C5b-9, MBL and MASP1 in tubular interstitium was closely associated with the damage degree of tubular interstitium. In addition, MBL and MASP1 co-localized and their levels in tubular interstitium correlated with the levels of C5b-9 in tubules and tubular interstitium. CONCLUSION: Increased renal local complement activation was present in DN patients and might contribute to the kidney damage, especially tubular interstitial damage. MBL pathway might play an important role in renal tubular interstitial complement activation. Methods against complement activation or MBL pathway might be effective in reducing renal tubular interstitial damage in DN patients.

Irrelevance of Carbon Monoxide Poisoning in the Methanol Oxidation Reaction on a PtRu Electrocatalyst.

Based on detailed in situ attenuated total-reflection-surface-enhanced IR reflection absorption spectroscopy (ATR-SEIRAS) studies of the methanol oxidation reaction (MOR) on Ru/Pt thin film and commercial Johnson-Matthey PtRu/C, a revised MOR enhancement mechanism is proposed in which CO on Pt sites is irrelevant but instead Pt-Ru boundary sites catalyze the oxygen insertion reaction that leads to the formation of formate and enhances the direct reaction pathway.

D-penicillamine assisted hydrothermal synthesis of Bi2S3 nanoflowers and their electrochemical application.

Single crystalline flower-like Bi2S3 nanostructures were successfully synthesized via a simple, facile and green hydrothermal method, with the assistance of D-penicillamine. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and found their morphologies mainly depend on the ratios of Bi(3+) to D-penicillamine, as well as the reaction temperature and time. And the possible growth mechanism has been discussed in some detail. In addition, the as-prepared Bi2S3 nanoflowers show good hydrogen storage ability. This strategy can be potentially expanded to prepare other metal chalcogenides materials.

Capping polymer-enhanced electrocatalytic activity on Pt nanoparticles: a combined electrochemical and in situ IR spectroelectrochemical study.

Unexpected yet highly remarkable and intriguing observations of the polymer-enhanced electro-catalytic activity of the Pt nanoparticles for electro-oxidations of both methanol and formic acid were reported. In situ FTIR investigation suggests strongly that the observed activity enhancements are highly likely due to the PVP-induced additional reaction pathways. These observations may open up a new paradigm of research in which the protecting/stabilizing organic ligands can now be incorporated as an advantageous part and/or a finer catalytic activity tuner of a nanocatalytic system.

A non-intermetallic PtPb/C catalyst of hollow structure with high activity and stability for electrooxidation of formic acid.

A non-intermetallic PtPb/C catalyst of hollow structure is synthesized through a simple reduction method, and exhibits an activity as high as 3.6 times that of commercial Pd black and a much higher stability for electrooxidation of formic acid.

Nonenzymatic amperometric sensing of glucose by using palladium nanoparticles supported on functional carbon nanotubes.

A nonenzymatic electrochemical method was developed for glucose detection using an electrode modified with palladium nanoparticles (PdNPs)-functional carbon nanotubes (FCNTs). PdNPs were homogeneously modified on FCNTs through a facile spontaneous redox reaction and characterized by transmission electron microscopy. Based on the voltammetric and amperometric results, PdNPs efficiently catalyzed the oxidation of glucose at 0.40 V in the presence of 0.2M NaCl and showed excellent resistance towards poisoning from such interfering species as ascorbic acid, uric acid, and p-acetamidophenol. This anti-poisoning ability was investigated using analysis of the electrocatalytic products by in situ subtractively normalized interfacial Fourier transform infrared reflection spectroscopy, and the results indicated that no strongly adsorbed CO(ad) species could be found in the oxidation products, which was obviously different from the results obtained using Pt-based electrodes. In order to verify the sensor reliability, it was applied to the determination of glucose in urine samples. The results indicated that the proposed approach provided a highly sensitive, wide linear range, more facile method with good reproducibility for glucose determination, promising the development of Pd-based material in nonenzymatic glucose sensing.

[Studies on the reaction of norfloxacin with ovalbumin].

The interaction between norfloxacin (NRF) and ovalbumin (OVA) was studied by fluorescence and absorption spectroscopy. The binding constants and the binding sites were measured by fluorescence quenching method. It was found that the emission peak of OVA was positioned at 338 nm. When the norfloxacin was added into OVA solution gradually, the intensity of 338 nm emission peak of OVA decreased obviously and moved towards long wavelength. The experiment demonstrated that the higher the temperature, the lower the slopes of quenching curves of OVA in the presence of different amounts of NRF. It was confirmed that the combination of NRF with OVA is a single static quenching process. With the increase in the pH of the solution, the quenching efficiency decreased in the binding. From thermodynamic parameters, it can be judged that the binding power between OVA and NRF is electrostatic effect and H-bond formation. The UV-Vis absorption spectra of OVA in the presence of NRF show that the conformation of OVA changed.

Study on the binding of fluoride, bromide and iodide to ovalbumin by using ion-selective electrodes.

The interactions of F(-), Br(-) and I(-) with ovalbumin (OVA) were studied in acetate buffers of pH 5.68, at 288.15 K, 298.15 K and 308.15 K, using ion-selective electrodes. The data for the ion-protein systems were treated according to the Klotz equation, and the number of binding sites and the binding constants were determined. It is shown that the binding sites of F(-) on OVA molecule are more than those of Br(-) and I(-), and that the binding sites of F(-), Br(-) and I(-) on OVA molecule decreases with increasing temperature. At the same time, our studies indicate that the binding constants for the interactions of F(-), Br(-) and I(-) with OVA show a same trend: They decrease as temperature increases. These were reasonably interpreted with the structural and thermodynamic factors. The thermodynamic functions (DeltaG(), DeltaH(), DeltaS()) at different temperatures were calculated with thermodynamic equations, and the enthalpy change for the interactions were also determined by isothermal titration calorimetry (ITC) at 298.15 K, which indicate that the interactions of F(-), Br(-) and I(-) with OVA are mainly electrostatic interaction. Simultaneously, there are also partial desolvation of solutes and solvent reorganization effect.

Nanoparticle catalysts with high energy surfaces and enhanced activity synthesized by electrochemical method.

Electrochemical shape-controlled synthesis of metal nanocrystal (NC) catalysts bounded by high-index facets with high surface energy was achieved by developing a square-wave potential route. Tetrahexahedral Pt NCs with 24 {hk0} facets, concave hexoctahedral Pt NCs with 48 {hkl} facets, and multiple twinned Pt nanorods with {hk0} facets were produced. The method was employed also to synthesize successfully trapezohedral Pd NCs with 24 {hkk} facets, and concave hexoctahedral Pd NCs with 48 {hkl} facets. It has been tested that, thanks to the high-index facets with high density of atomic steps and dangling bonds, the tetrahexahedral Pt NCs exhibit much enhanced catalytic activity for equivalent Pt surface areas for electrooxidation of small organic fuels such as ethanol. These results demonstrate that the developed square-wave potential method has surmounted the limit of conventional chemical methods that could synthesize merely metal nanocrystals with low surface energy, and opened a new prospect avenue in shape-controlled synthesis of nanoparticle catalysts with high surface energy and enhanced activity.