Co-N/C-900 metal-organic framework-derived nanozyme as a H2O2-free oxidase mimic for the colorimetric sensing of L-cysteine.

Nanozymes have attracted considerable attention as a new type of promising artificial enzyme in recent years. Here, an oxidase-like cobalt-nitrogen-carbon (Co-N/C-900) nanozyme with well-regulated metal atom spatial distribution has been derived from Co-Zn bimetal zeolitic imidazolate framework precursors and used to develop a facile colorimetric sensing method for L-cysteine. With the aid of Co-N/C-900, the colorless 3,3',5,5'-tetramethylbenzidine (TMB) was oxidized to blue oxidized TMB in the absence of H2O2. However, the oxidation was inhibited after the addition of L-cysteine, and the blue color faded to colorless. Thus, Co-N/C-900 exhibited quite good oxidase-like activity with high catalytic efficiency. Therefore, a facile and efficient colorimetric method to sensitively determine L-cysteine with a low detection limit of 33 nM (S/N = 3) has been developed. Furthermore, favorable selectivity and anti-interference ability towards the determination of L-cysteine based on this approach have also been achieved. It is believed that this colorimetric method for the detection of L-cysteine based on Co-N/C-900 will show potential applications in bioscience and bioengineering.

Characterization of a high-resolution 2D transmission ion chamber for independent validation of proton pencil beam scanning of conventional and FLASH dose delivery.

INTRODUCTION: Ultra-high dose rate (FLASH) radiotherapy has become a popular research topic with the potential to reduce normal tissue toxicities without losing the benefit of tumor control. The development of FLASH proton pencil beam scanning (PBS) delivery requires accurate dosimetry despite high beam currents with correspondingly high ionization densities in the monitoring chamber. In this study, we characterized a newly designed high-resolution position sensing transmission ionization chamber with a purpose-built multichannel electrometer for both conventional and FLASH dose rate proton radiotherapy. METHODS: The dosimetry and positioning accuracies of the ion chamber were fully characterized with a clinical scanning beam. On the FLASH proton beamline, the cyclotron output current reached up to 350 nA with a maximum energy of 226.2 MeV, with 210 ± 3 nA nozzle pencil beam current. The ion recombination effect was characterized under various bias voltages up to 1000 V and different beam intensities. The charge collected by the transmission ion chamber was compared with the measurements from a Faraday cup. RESULTS: Cross-calibrated with an Advanced Markus chamber (PTW, Freiburg, Germany) in a uniform PBS proton beam field at clinical beam setting, the ion chamber calibration was 38.0 and 36.7 GyE·mm2 /nC at 100 and 226.2 MeV, respectively. The ion recombination effect increased with larger cyclotron current at lower bias voltage while remaining ≤0.5 ± 0.5% with ≥200 V of bias voltage. Above 200 V, the normalized ion chamber readings demonstrated good linearity with the mass stopping power in air for both clinical and FLASH beam intensities. The spot positioning accuracy was measured to be 0.10 ± 0.08 mm in two orthogonal directions. CONCLUSION: We characterized a transmission ion chamber system under both conventional and FLASH beam current densities and demonstrated its suitability for use as a proton pencil beam dose and spot position delivery monitor under FLASH dose rate conditions.

Zeolitic imidazole framework derived N-doped porous carbon/metal cobalt nanoparticles hybrid for oxygen electrocatalysis and rechargeable Zn-air batteries.

Bifunctional electrocatalysts with high catalytic property for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for high-performance zinc-air batteries (ZnABs). In this study, an efficient bifunctional electrocatalyst with hollow structure (C-N/Co (1/2)) has been successfully prepared through carbonization of ZIF-8@ZIF-67 and evaporation of Zn ions at high temperature. With Co nanoparticles encapsulated by an N-doped porous carbon matrix, the catalyst exhibits excellent stability in aqueous alkaline solution over an extended period and good tolerance to the methanol crossover effect. The integration of an N-doped graphitic carbon outer shell and Co nanoparticles enables high ORR and OER activity, as evidenced by ZnAB using the catalyst C-N/Co (1/2) in an air cathode.

Current delivery limitations of proton PBS for FLASH.

PURPOSE: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS. METHODS: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA. The impact of the effective field dose rate from cyclotron current, spot spacing, slew time and field size were studied. RESULTS: When scanning magnet slew time and energy switching time are not considered, single energy effective field FLASH dose rate (≥40 Gy/s) can only be achieved with less than 4 × 4 cm2 fields when the cyclotron output current is above 500 nA. Slew time and energy switching time remain the limiting factors for achieving high effective dose rate of the field. The dose rate-time structures were obtained. The amount of the total dose delivered at the FLASH dose rate in single energy layer and volumetric field was also studied. CONCLUSION: It is demonstrated that while it is difficult to achieve FLASH dose rate for a large field or in a volume, local FLASH delivery to certain percentage of the total dose is possible. With further understanding of the FLASH radiobiological mechanism, this study could provide guidance to adapt current clinical multi-field proton PBS delivery practice for FLASH proton radiotherapy.

Reduced graphene oxide-supported cobalt oxide decorated N-doped graphitic carbon for efficient bifunctional oxygen electrocatalysis.

A high-performance composite bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been synthesized via in situ growth of a hybrid precursor of graphene oxide (GO) and cobalt-based zeolite imidazolium framework (ZIF-67) under hydrothermal condition, followed by calcination at elevated temperature. The as-prepared composite bifunctional catalyst is confirmed to possess a structure of N-GC/Co@CoO/rGO, with core-shell nanoparticles of Co@CoO encapsulated in nitrogen-doped graphitic carbon (N-GC) thin layers which are then overall supported by reduced graphene oxide (rGO) sheets. With N-GC furnishing high population of ORR active sites, CoO being active for OER which is further enhanced by a highly conductive metal core, rGO sheets enhancing the overall electronic conduction, as well as the multiple synergistic couplings in the composite materials, pronounced ORR and OER catalytic activities with superior stability have been achieved. The catalysts also showed excellent tolerance to the crossover effect to methanol, showing great potential in energy-related applications requiring efficient oxygen electrocatalysis.

Resonance assignments and secondary structure of a phytocystatin from Sesamum indicum.

A cDNA encoding a cysteine protease inhibitor, cystatin was cloned from sesame (Sesamum indicum L.) seed. This clone was constructed into an expression vector and expressed in E. coli and purified to homogeneous. The recombinant sesame cystatin (SiCYS) showed effectively inhibitory activity toward C1 cysteine proteases. In order to unravel its inhibitory action from structural point of view, multidimensional heteronuclear NMR techniques were used to characterize the structure of SiCYS. The full (1)H, (15)N, and (13)C resonances of SiCYS were assigned. The secondary structure of SiCYS was identified by using the assigned chemical shifts of (1)H(α), (13)C(α), (13)C(ß), and (13)CO through the consensus chemical shift index (CSI). The results of CSI analysis of SiCYS suggest eight ß-strands (residues 33-46, 51-61, 63-75, 80-87, 150-155, 157-169, 172-183, and 192-195) and two α-helices (residues 16-30, and 120-135).

[The Correlation between Blood Uric Acid and Goldstein Grading in Hepatolenticular Degeneration Patients with Different Chinese Medical Syndrome Types].

OBJECTIVE: To observe blood uric acid levels and Goldstein grading, as well as their correlation in Wilson's disease (WD) patients with different Chinese medical syndrome types. METHODS: Totally 906 WD patients in line with inclusive criteria were assigned to 6 groups, i.e., the heart spirit confused by phlegm group (HSCP, 26 cases), the phlegm-fire disturbing heart group (PFDH, 90 cases), the retention of damp-heat group (RDH, 113 cases), deficiency of qi and blood group (DQB, 168 cases), the deficiency of Gan-yin and Shen-yin group (DGYSY, 327 cases), the deficiency of Gan and Shen group (DGS, 182 cases) due to different Chinese medical syndrome types. Recruited were another 160 healthy subjects having similar ages and diet structures, who came for medical examinations, as the healthy control group. Venous blood was collected from the medial cubital vein of each-patient on an empty stomach in early mornings to detect blood uric acid levels. Results Blood uric acid levels were lower in each syndrome type group than in the healthy control group (146.08 +/- 67.24 micromol/L in the HSCP group; 157.08 +/- 69.77 micromol/L in the PFDH group; 162.58 +/- 97.72 micromol/L in the RDH group; 156.20 +/- 62.63 micromol/L in the DQB group; 161.83 +/- 111.23 micromol/L in the DGYSY group; 194.41 +/- 90.01 micromol/L in the DGS group; 242.39 +/- 87.55 micromol/L in the healthy control group, P < 0.01). Blood uric acid levels were higher in the DGYSY group than in the other 5 syndrome groups (P < 0.01). Correlation analyses between Goldstein grading and blood uric acid showed that, along with increased Goldstein grade (that was aggravating disease conditions), WD patients' blood uric acid levels decreased (P < 0.01). CONCLUSIONS: WD patient's blood uric acid levels decreased more. Blood uric acid levels and Goldstein grading were different in various Chinese medical syndrome types. Blood uric acid levels had certain value in assessing the severity of WD.