Multifacets of Fullerene-Metal Clusters: From Fundamental to Application

ConspectusBuckminsterfullerene, C60, was discovered through a prominent mass peak containing 60 atoms produced from laser vaporization of graphite, driven by Kroto's interest in understanding the formation mechanisms of carbon-containing molecules in space. Inspired by the geodesic dome-shaped architecture designed by Richard Buckminster Fuller, after whom the particle was named, C60 was found to have a football-shaped structure comprising 20 hexagons and 12 pentagons. It sparked worldwide interest in understanding this new carbon allotrope, resulting in the awarding of the Noble Prize in Chemistry to Smalley, Kroto, and Curl in 1996.Intrinsically, C60 is an exceptional species because of its high stability and electron-accepting ability and its structural tunability by decorating or substituting either on its exterior surface or interior hollow cavity. For example, metal-decorated fullerene complexes have found important applications ranging from superconductivity, nanoscale electronic devices, and organic photovoltaic cells to catalysis and biomedicine. Compared to the large body of studies on atoms and molecules encapsulated by C60, studies on the exteriorly modified fullerenes, i.e., exohedral fullerenes, are scarcer. Surprisingly, to date, uncertainty exists about a fundamental question: what is the preferable exterior binding site of different kinds of single atoms on the C60 surface?In recent years, we have developed an experimental protocol to synthesize the desired fullerene-metal clusters and to record their infrared spectra via messenger-tagged infrared multiple photon dissociation spectroscopy. With complementary quantum chemical calculations and molecular dynamics simulations, we determined that the most probable binding site of a metal, specifically a vanadium cation, on C60 is above a pentagonal center in an η5 fashion. We explored the bonding nature between C60 and V+ and revealed that the high thermal stability of this cluster originates from large orbital and electrostatic interactions. Through comparing the measured infrared spectra of [C60-Metal]+ with the observational Spitzer data of several fullerene-rich planetary nebulae, we proposed that the complexes formed by fullerene and cosmically abundant metals, for example, iron, are promising carriers of astronomical unidentified spectroscopic features. This opens the door for a real consideration of Kroto's 30-year-old hypothesis that complexes involving cosmically abundant elements and C60 exhibit strong charge-transfer bands, similar to those of certain unidentified astrophysical spectroscopic features. We compiled a VibFullerene database and extracted a set of vibrational frequencies and intensities for fullerene derivatives to facilitate their potential detection by the James Webb Space Telescope. In addition, we showed that upon infrared irradiation C60V+ can efficiently catalyze water splitting to generate H2. This finding is attributed to the novel geometric-electronic effects of C60, acting as "hydrogen shuttle" and "electron sponge", which illustrates the important role of carbon-based supports in single-atom catalysts. Our work not only unveils the basic structures and bonding nature of fullerene-metal clusters but also elucidates their potential importance in astrophysics, astrochemistry, and catalysis, showing the multifaceted character of this class of clusters. More exciting and interesting aspects of the fullerene-metal clusters, such as ultrafast charge-transfer dynamics between fullerene and metal and their relevance to designing hybrid fullerene-metal junctions for electronic devices, are awaiting exploration.

[Comparison of intraoperative neurophysiological monitoring between patients with arthrogryposis multiplex congenita and adolescent idiopathic scoliosis]

Objective: To compare the intraoperative neurophysiological monitoring (IONM) results between patients with arthrogryposis multiplex congenita (AMC) and adolescent idiopathic scoliosis (AIS) and to analyze the influence of congenital spinal deformity on IONM in AMC patients, thus to evaluate the efficiency of IONM in AMC patients. Methods: A cross-sectional study. The clinical data of 19 AMC patients underwent correction surgery from July 2013 to January 2022 in Nanjing Drum Tower Hospital were retrospectively reviewed. There were 13 males and 6 females with a mean age of (15.2±5.6) years, and the average Cobb angle of main curve was 60.8°±27.7°. And 57 female AIS patients of similar age and curve type with the AMC patients during the same period were selected as the control group, with an average age of (14.6±4.4) years and a mean Cobb angle of 55.2°±14.2°. The latency and amplitude of samatosensory evoked potentials (SSEPs) and transcranial electric motor evoked potentials (TCeMEPs) were compared between the two groups. The difference in IONM data between AMC patients with and without congenital spinal deformity was also evaluated. Results: The success rates of SSEPs and TCeMEPs were 100% and 14/19 for AMC patients, 100% and 100% for AIS patients. The SSEPs-P40 latency, SSEPs-N50 latency, SSEPs-amplitude, TCeMEPs-latency, TCeMEPs-amplitude showed no significant difference between AMC patients and AIS patients (P>0.05 for all). The side-difference of TCeMEPs-amplitude showed an increasing trend in AMC patients when compared with that in AIS patients, but there was no statistical difference between the two groups [(147.0±185.6) μV vs (68.1±311.4) μV, P=0.198]. The SSEPs-amplitude value was (1.4±1.1) μV on concave side in AMC patients with congenital spinal deformity, and it was (2.6±1.2) μV on concave side in AMC patients without congenital spinal deformity (P=0.041). The SSEPs-amplitude value was (1.4±0.8) μV on convex side in AMC patients with congenital spinal deformity, and it was (2.6±1.3) μV on convex side in AMC patients without congenital spinal deformity (P=0.028). Conclusions: The values of SSEPs-P40 latency, SSEPs-N50 latency, SSEPs-amplitude, TCeMEPs-latency and TCeMEPs-amplitude are similar in AMC and AIS patients. The SSEPs-amplitude of AMC patients with congenital spinal deformity is lower than that of AMC patients without congenital spinal deformity.

Thermal Methane Conversion to Formaldehyde Mediated by NiAlO3+ in the Gas Phase

Understanding the active sites and reaction mechanisms of Ni-based catalysts, such as Ni/Al₂O₃, toward methane is a prerequisite for improving their rational design. Here, the gas-phase reactivity of NiAlO₃⁺ cations toward CH₄ is studied using mass spectrometry combined with density functional theory. Similar to our previous study on NiAl₂O₄⁺, we find evidence for the formation of both the methyl radical (CH₃^•) and formaldehyde (CH₂O). The first step for methane activation is hydrogen atom abstraction by the terminal oxygen radical Ni(O)₂AlO^• from methane forming a [Ni(O)₂AlOH⁺, ^•CH₃] complex and leaving the Ni-oxidation state unchanged. The second C-H bond is subsequently activated by the association of a bridged Ni-O^2--Al. The oxidation state of the Ni atom is reduced from +3 to +1 during the formation of formaldehyde. Compared to Al₂O₃⁺/CH₄ and YAlO₃⁺/CH₄ systems, the Ni-atom substitution increases the overall reaction rate by roughly an order of magnitude and yields a CH₃^•/CH₂O branching ratio of 0.62/0.38. The present study provides molecular-level insights into the highly efficient gas-phase reaction mechanism contributing to an improved understanding of methane conversion by Ni/Al₂O₃ catalysts.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

[The related factors of postoperative recurrence in trigeminalneuralgia patients undergoing fully neuroendoscopic microvascular decompression]

Objective: To evaluate the related factors of postoperative recurrence intrigeminal neuralgia (TN) patients treated with fully neuroendoscopic microvascular decompression (MVD). Methods: The clinical baseline data and preoperative MRI imaging data of 112 patients with TN treated by neuroendoscopic MVD from December 2008 to December 2020 in the Department of Neurosurgery, Beijing Shijitan Hospital Affiliated to Capital Medical University were retrospectively analyzed, including: area ratio of cerebellopontine area (CPA)(healthy side/affected side), trigeminal nerve(TGN)length ratio(healthy side/affected side), TGN angle ratio(healthy side/affected side), and criminal vessel type. Multivariate Cox proportional hazards model was used to analyze the factors affecting postoperative recurrence. Results: Among the 112 patients in this group, there were 49 males and 63 females. The age ranged from 20 to 82 (59±9) years, and the course of disease was 0.05 to 30.00 (5.60±5.15) years. Pain was located on the left side in 43 cases (38.39%) and on the right side in 69 cases (61.61%), respectively. All patients were followed up for more than 1 year, with an average follow-up time of 21.5 months, and 11 cases recurred. Multivariate Cox regression analysis revealed that disease duration≥3 years(HR=9.34, 95%CI:1.12-39.07), CPA area ratio(healthy side/affected side)>1 (HR=27.47, 95%CI:1.69-44.20), criminal vessel type with vein(HR=35.39, 95%CI:1.26-18.60) and criminal vessel type with arteriovenous (HR=46.07, 95%CI: 2.74-27.75) were the main factors influencing recurrence of MVD surgery (all P<0.05). Conclusion: The disease duration≥3 years, CPA area ratio(healthy side/affected side)>1, and criminal vessel type with vein/arteriovenous are the relevant factors that affect the recurrence rate after the fully neuroendoscopic MVD treatment for trigeminal neuralgia.

Gas-Phase Mechanism of O.- /Ni2+ -Mediated Methane Conversion to Formaldehyde

The gas-phase reaction of NiAl₂ O₄ ⁺ with CH₄ is studied by mass spectrometry in combination with vibrational action spectroscopy and density functional theory (DFT). Two product ions, NiAl₂ O₄ H⁺ and NiAl₂ O₃ H₂ ⁺ , are identified in the mass spectra. The DFT calculations predict that the global minimum-energy isomer of NiAl₂ O₄ ⁺ contains Ni in the +II oxidation state and features a terminal Al-O^.- oxygen radical site. They show that methane can react along two competing pathways leading to formation of either a methyl radical (CH₃ ⋅) or formaldehyde (CH₂ O). Both reactions are initiated by hydrogen atom transfer from methane to the terminal O^.- site, followed by either CH₃ ⋅ loss or CH₃ ⋅ migration to an O^2- site next to the Ni²⁺ center. The CH₃ ⋅ attaches as CH₃ ⁺ to O^2- and its unpaired electron is transferred to the Ni-center reducing it to Ni⁺ . The proposed mechanism is experimentally confirmed by vibrational spectroscopy of the reactant and two different product ions.

Structural Characterization of Nickel-Doped Aluminum Oxide Cations by Cryogenic Ion Trap Vibrational Spectroscopy

Isolated nickel-doped aluminum oxide cations (NiO_m)(Al₂O₃)_n(AlO)⁺ with m = 1-2 and n = 1-3 are investigated by infrared photodissociation (IRPD) spectroscopy in combination with density functional theory and the single-component artificial force-induced reaction method. IRPD spectra of the corresponding He-tagged cations are reported in the 400-1200 cm^-1 spectral range and assigned based on a comparison to calculated harmonic IR spectra of low-energy isomers. Simulated spectra of the lowest energy structures generally match the experimental spectra, but multiple isomers may contribute to the spectra of the m = 2 series. The identified structures of the oxides (m = 1) correspond to inserting a Ni-O moiety into an Al-O bond of the corresponding (Al₂O₃)_1-3(AlO)⁺ cluster, yielding either a doubly or triply coordinated Ni²⁺ center. The m = 2 clusters prefer similar structures in which the additional O atom either is incorporated into a peroxide unit, leaving the oxidation state of the Ni²⁺ atom unchanged, or forms a biradical comprising a terminal oxygen radical anion Al-O^•- and a Ni³⁺ species. These clusters represent model systems for under-coordinated Ni sites in alumina-supported Ni catalysts and should prove helpful in disentangling the mechanism of selective oxidative dehydrogenation of alkanes by Ni-doped catalysts.

[Methylation detection of phosphatase and tensin homolog deleted on chromosome ten gene promoter in hepatocellular carcinoma samples by next-generation sequencing]

Objective: The purpose of this study is to use the next-generation sequencing (NGS) technology platform to detect the methylation rate of phosphatase and tensin homolog deleted on chromosome ten (PTEN) promoter region in hepatocellular carcinoma (HCC) tissue samples, and to analyze the clinical significance of its correlation with the prognosis of patients receiving sorafenib treatment. Methods: The 52 pairs of tumor tissue and para-cancerous tissue samples from HCC patients treated with sorafenib alone, which were collected and preserved in the Liver Tumor Diagnosis and Research Center of the former 302 Hospital of the People's Liberation Army by the National Natural Science Foundation of China Youth Project with the project batch number 81702986 in 2018, were extracted total DNA from the samples. Then the DNA samples were treated with bisulfite and specific primers were designed to amplify the PTEN promoter region. Finally, the amplified products were analyzed by second-generation sequencing. In the analysis of clinical significance of PTEN methylation, log-rank statistical analysis was used to calculate whether there was a statistical difference in survival between the patient groups. Results: The methylation rate of PTEN promoter region in tumor tissues (29.17%±9.58%) was significantly higher than that in paracancer tissues (4.17%±2.86%)(t=19.970,P<0.05). At the same time, in HCC tissues, the methylation rate of the PTEN promoter region is negatively correlated with its expression (F=47.270,P<0.000 1;Y=-1 800×X+38.03), and the PTEN methylation rate is negatively correlated with the prognosis of patients receiving the molecularly targeted drug Sorafenib (χ²=4.313,P<0.05). Conclusion: This study successfully established a new method for detecting methylation in the promoter region of PTEN, and the methylation rate of PTEN can be used as one of the targets of HCC diagnosis and targeted therapy.

[A challenge for colorectal surgeons: pathogenesis, progression and management of the secondary tumors of the ovary]

A common clinical problem encountered by colorectal surgeons is the secondary tumors of the ovary (STO), particularly in young female patients. Most STO are from the digestive tract, and the known possible metastatic mechanisms include lymphatic, hematogenous, and intraperitoneal spreading. The molecular and histopathological characteristics of STO from different sites are diverse. It is particularly important to correctly identify the origin and feature of STO, which should be clarified by combining medical history, histopathology, immunohistochemistry, molecular biology, imaging and other means. The prognosis of patients with STO is poor in general. Comprehensive therapies based on surgical resection can benefit some patients. There is no specific treatment for STO at present, but not giving up easily on these patients is the right choice that every surgeon should understand.

Catalytic Co-Conversion of CH4 and CO2 Mediated by Rhodium-Titanium Oxide Anions RhTiO2. Angew Chem Int Ed Engl 2021;60:13788-13792. [PMID: 33890352 PMCID: PMC8251526 DOI: 10.1002/anie.202103808]

Catalytic co‐conversion of methane with carbon dioxide to produce syngas (2 H₂+2 CO) involves complicated elementary steps and almost all the elementary reactions are performed at the same high temperature conditions in practical thermocatalysis. Here, we demonstrate by mass spectrometric experiments that RhTiO₂⁻ promotes the co‐conversion of CH₄ and CO₂ to free 2 H₂+CO and an adsorbed CO (CO_ads) at room temperature; the only elementary step that requires the input of external energy is desorption of CO_ads from the RhTiO₂CO⁻ to reform RhTiO₂⁻. This study not only identifies a promising active species for dry (CO₂) reforming of methane to syngas, but also emphasizes the importance of temperature control over elementary steps in practical catalysis, which may significantly alleviate the carbon deposition originating from the pyrolysis of methane.

Effects of partial substitution of NaCl on myofibrillar protein properties from pearl mussel Hyriopsis cumingii muscle: Structural characteristics and aggregation behaviors

The effects of NaCl and its partial substitutes (KCl, MgCl₂ and CaCl₂) on solubility, structural characteristics and aggregation behaviors of myofibrillar protein (MP) from pearl mussel muscle were investigated and compared. MP at 0.6 M NaCl was beneficial to protein unfolding and showed excellent potential functional properties. When NaCl was substituted in low level, MPs also showed good solubility and ordered microstructure as well as NaCl, especially MgCl₂ and CaCl₂, due to the unfolding of α-helical structures and subsequently exposed tyrosine residues and hydrophobic groups. However, the obviously increased disulfide bonds and hydrophobic interactions in high substitution level indicated the excessive non-sodium salts had negative effects on molecular rearrangement, leading to irregular and overly tight of microstructure. Thus, NaCl partially substituted by KCl, MgCl₂ and CaCl₂ in low substitution level is promising to improve functional properties of MP in low-sodium meat products.

The sequential activation of H2 and N2 mediated by the gas-phase Sc3N+ clusters: Formation of amido unit

The activation and hydrogenation of nitrogen are central in industry and in nature. Through a combination of mass spectrometry and quantum chemical calculations, this work reports an interesting result that scandium nitride cations Sc₃N⁺ can activate sequentially H₂ and N₂, and an amido unit (NH₂) is formed based on density functional theory calculations, which is one of the inevitable intermediates in the N₂ reduction reactions. If the activation step is reversed, i.e., sequential activation of first N₂ and then H₂, the reactivity decreases dramatically. An association mechanism, prevalent in some homogeneous catalysis and enzymatic mechanisms, is adopted in these gas-phase H₂ and N₂ activation reactions mediated by Sc₃N⁺ cations. The mechanistic insights are important to understand the mechanism of the conversion of H₂ and N₂ to NH₃ synthesis under ambient conditions.

Direct Identification of Acetaldehyde Formation and Characterization of the Active Site in the [VPO4 ].+ /C2 H4 Couple by Gas-Phase Vibrational Spectroscopy

The gas‐phase reaction of the heteronuclear oxide cluster [VPO₄]^.+ with C₂H₄ is studied under multiple collision conditions at 150 K using cryogenic ion‐trap vibrational spectroscopy combined with electronic structure calculations. The exclusive formation of acetaldehyde is directly identified spectroscopically and discussed in the context of the underlying reaction mechanism. In line with computational predictions it is the terminal P=O and not the V=O unit that provides the oxygen atom in the barrier‐free thermal C₂H₄→CH₃CHO conversion. Interestingly, in the course of the reaction, the emerging CH₃CHO product undergoes a rather complex intramolecular migration, coordinating eventually to the vanadium center prior to its liberation. Moreover, the spectroscopic structural characterization of neutral C₂H₄O deserves special mentioning as in most, if not all, ion/molecule reactions, the neutral product is usually only indirectly identified.

[Clinical significance of ascitic interleukin-7 expression levels in cirrhotic patients complicated with spontaneous bacterial peritonitis]

Objective: To observe ascitic interleukin-7 expression level in cirrhotic patients complicated with spontaneous bacterial peritonitis, and to detect the effect of recombinant human IL-7 on CD4(+) and CD8(+)T lymphocyte function. Methods: A total of 84 patients with liver cirrhosis who were hospitalized from August 2017 to April 2018 were selected. Among them, 51 cases were complicated with cirrhosis and untainted ascites, and 33 cases were cirrhosis complicated with spontaneous bacterial peritonitis. Peripheral blood and ascites were collected routinely. The levels of IL-7 in peripheral blood and ascites were measured by enzyme-linked immunosorbent assay. CD4(+)T cells and CD8(+)T cells were purified from ascites, and were stimulated with recombinant IL-7. Cellular proliferation, key transcription factors for mRNA, and cytokines production by CD4(+)T cells in response to IL-7 stimulation was measured. mRNA expression corresponding to perforin, granzyme B, and granulysin as well as cytokines production by CD8(+)T cells was also measured in response to IL-7 stimulation. Cytolytic and non-cytolytic activity of CD8(+)T cells in response to IL-7 stimulation was also investigated in both direct and indirect contact co-culture system. Measurement data of the normal distribution were compared between the two groups by Student's t-test and the data before and after stimulation were compared by paired t-test. Measurements that did not conform to normal distribution were compared between the two groups using Mann-Whitney U test, and data before and after stimulation were compared using Wilcoxon paired test. Results: There was no significant statistical difference in serum IL-7 levels between the two groups [(5 001 ± 1 458) pg/ml vs. (4 768 ± 1 128) pg/ml, P = 0.41]. The level of ascitic IL-7 in cirrhotic patients complicated with SBP was significantly lower than cirrhosis patients with untainted ascites [(966.4 + 155.8) pg/ml vs. (792.1 + 126.4) pg/ml, P < 0.01]. Recombinant IL-7 stimulation promoted the proliferation of CD4(+) and CD8(+)T cells from ascites in patients with liver cirrhosis complicated by SBP. T-bet mRNA relative expression and IFN-γ secretion in CD4(+)T cells was also elevated in response to IL-7 stimulation in vitro. Moreover, IL-7 stimulation also increased the mRNA expressions of perforin, granzyme B, and granulysin as well as productions of IFN-γ and TNF-α by CD8(+)T cells. Recombinant IL-7 stimulation elevated cytolytic and non-cytolytic activity of CD8(+)T cells from ascites in patients with liver cirrohosis complicated by SBP, which manifested as increased target cell death and IFN-γ production in both direct and indirect contact co-culture system. Conclusion: Ascitic IL-7 promotes T lymphocyte function in patients with liver cirrhosis complicated with SBP.

[Hepatitis B core antigen promotes invasion of hepatocellular carcinoma cell line HepG2.2.15 via Toll-like receptor 4]

Objective: To investigate the effect of hepatitis B core antigen (HBcAg) in promoting the invasion of hepatitis B virus (HBV)-related hepatocellular carcinoma cell line HepG2.2.15 and the role of Toll-like receptor 4 (TLR4) in the mechanism. Methods: TLR4 mRNA and protein expression in HepG2 cells and HepG2.2.15 cells was measured by reverse transcription real-time PCR and Western blot analysis, respectively. HepG2.2.15 cells were transfected with TLR4 specific small interfering RNA (siRNA) to silence TLR4 expression, and stimulated by recombinant HBcAg in culture. The invasion of cells was measured by Transwell invasion assay. The expression of TLR4 signaling pathway-related proteins in the cultured cells and proinflammatory cytokines in the supernatant was also determined. The student's t-test, one-way ANOVA, and SNK-q test were used for statistical analysis. Results: TLR4 mRNA and protein expression in HepG2.2.15 cells was significantly higher than that in HepG2 cells. TLR4 siRNA transfection remarkably down-regulated TLR4 expression in HepG2.2.15 cells. Inhibiting TLR4 expression and/or HBcAg stimulation did not affect the proliferation of HepG2.2.15 cells. However, HBcAg stimulation significantly increased the invasion ability of HepG2.2.15 cells and the secretion of proinflammatory cytokines [including interferon (IFN)-γ, interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α]. Inhibiting TLR4 expression significantly reduced HBcAg-induced cellular invasion. Meanwhile, HBcAg stimulation elevated the expression of MyD88 and TRIF in HepG2.2.15 cells. TLR4 silencing inhibited HBcAg-induced increase in the expression of MyD88, while it showed no significant impact on TRIF expression. Conclusion: HBcAg can promote the invasion of HepG2.2.15 cells. The TLR4/MyD88 signaling pathway may be involved in this process by inducing the expression of proinflammatory cytokines.

The HNO- radical anion: A proposed intermediate in diazeniumdiolate synthesis using nitric oxide and alkoxides

The strategy of synthesizing diazeniumdiolates (X-N(O)=NO^-) through the coexistence of nitric oxide and alkoxides (RO^-) was introduced by Wilhelm Traube 120 years ago. Today, despite the wide use of diazeniumdiolate derivatives to release nitric oxide in the treatment of cancer, the first step of the reaction mechanism for diazeniumdiolate synthesis remains a mystery and is thought to be complex. We have studied the gas-phase reactions of nitric oxide with alkoxides at room temperature. An electron-coupled hydrogen transfer is observed, and the radical anion HNO^- is the only ionic product in these reactions. HNO^- can further react with nitric oxide to form N₂O and HO^-.

[Relationships between serum cystatin C, chemerin levels and subclinical atherosclerosis in type 2 diabetes mellitus patients]

Objective: To investigate the relationships between serum cystatin C (Cys C), chemerin levels and subclinical atherosclerosis in type 2 diabetes mellitus (T2DM) patients. Methods: A cross-sectional study was carried out between January 2016 and January 2018, and T2DM patients with carotid intima-media thickness (IMT) less than 1.1 mm were selected as subjects (100 males and 80 females, aged 40-60 years). The brachial-ankle pulse wave velocity (baPWV) ≥ 1 700 cm/s was set as the observation group (subclinical atherosclerosis) and baPWV<1 700 cm/s as the control group (non-subclinical atherosclerosis). Physical and blood examination were performed in both groups. Serum Cys C and chemerin levels were measured and their relationship with subclinical atherosclerosis was analyzed. Results: There was a statistically significant correlation between serum creatinine (r=0.167, P=0.011) and baPWV in the observation group, but not in the control group (r=0.105, P=0.070). Multiple linear regression analysis showed that age, duration of diabetes, serum creatinine, estimated glomerular filtration rate (eGFR), Cys C and chemerin were independently associated with baPWV, while high sensitive C reactive protein (hsCRP) and glycosylated hemoglobin (HbA1c) were not associated with baPWV. The elevation of serum Cys C (β'=0.393, P=0.003) and chemokine (β'=0.340, P=0.007) were correlative factors for atherosclerosis. Conclusion: The level of serum Cys C and chemerin is possibly related to the occurrence and development of subclinical atherosclerosis in T2DM patients.

Selective Conversion of Methane by Rh1-Doped Aluminum Oxide Cluster Anions RhAl2O4-: A Comparison with the Reactivity of PtAl2O4. J Phys Chem A 2018;122:3950-3955. [PMID: 29578712 DOI: 10.1021/acs.jpca.8b02483]

Studying the elementary reactions of single-noble-metal-atom-doped species can give theoretical guidance for the design of related single-atom catalysis. Using a combination of mass spectrometry and density functional theory calculations, the reaction of RhAl₂O₄^- with the most stable alkane molecule CH₄ under thermal conditions has been studied. The methane tends to be converted into syngas (free H₂ and adsorbed CO) with activation of four C-H bonds. In sharp contrast, formaldehyde was generated in the previously reported reaction of PtAl₂O₄^- with CH₄. Density functional theory calculations show that the difference in reactivity between RhAl₂O₄^- and PtAl₂O₄^- is found to be due to a higher energy barrier of the third C-H bond activation for the Pt analogue. This work provides the first comparative study on the reactivity of single noble-metal atoms (Rh, Pt) on the same cluster support (Al₂O₄^-) and can be helpful for rational design of single-atom catalysts for selective methane conversion.

Reactivity of amino acid anions with nitrogen and oxygen atoms

Gas-phase reaction of deprotonated tyrosine with a ground state O atom generates five ionic products.

A Lady with Confusion and Seizure after Ingestion of Lidocaine for Dyspepsia

We report a 29-year-old lady who developed confusion, agitation and seizure after the ingestion of a self-mixture of 3 grams of lidocaine with antacid for treatment of dyspepsia. She developed two episodes of seizure requiring diazepam, propofol and intubation. There was no significant cardiac toxicity and she was discharged on day 3. This is the first reported adult case of seizure in the literature after intentional ingestion of lidocaine for treatment of dyspepsia. The use of local anaesthetic in gastrointestinal cocktail for dyspepsia and its safety are highlighted. Advances in the management of local anaesthetic overdose are also discussed.

Acute Urinary Retention: How Useful is an Ambulatory Care Protocol?

Introduction

Acute urinary retention (AUR) is a common urological presentation to emergency departments (ED). An ambulatory care protocol had been developed allowing trial without catheterization (TWOC) instead of admission to hospital after catheterization in the ED. This study aimed to evaluate the efficacy of the ambulatory care protocol for patients with AUR. The secondary aim was to identify any independent predictor(s) for successful weaning of urinary catheter in a short duration.

Methods

This was a prospective cohort study. A total of 143 male patients presenting with an episode of AUR underwent urinary catheterization once. Those who were unable to pass urine afterwards were catheterized again and discharged home with a urinary catheter in-situ (Day 0). On Day 3, ability of spontaneous urination was assessed. If failed, spontaneous urination was assessed again on Day 6.

Results

Successful TWOC was recorded in 50.3% of the 143 patients after first catheterization. The cumulative successful rates for first (Day 3) and second (Day 6) follow-ups were 76.9% and 79.0%, respectively. Among the associated predictors, only the urine retention volume on first catheterization was found to be independently associated with successful TWOC, using binary logistic regression (p=0.001).

Conclusion

The ambulatory care protocol was successful in weaning off urinary catheter for 50.3% of patients with AUR after first catheterization and a further 26.6% on Day 3, making a cumulative success rate of 76.9%. Those who failed TWOC on Day 3 would get little benefit on further trials. The first catheterization volume was independently associated with the chance of successful TWOC.

Reactions of Sulfur- and Oxygen-Containing Anions with Hydrogen Atoms: A Comparative Study

Reactions of hydrogen atoms with small sulfur-containing anions, SCN^-, CH₃COS^-, C₆H₅COS^-, ^-SCH₂COOH, C₆H₅S^-, 2-HOOCC₆H₄S^-, and related oxygen-containing anions, OCN^-, CH₃COO^-, C₆H₅COO^-, HOCH₂COO^-, C₆H₅O^-, 2-HOOCC₆H₄O^-, have been studied both experimentally and computationally. The experimental results show that associative electron detachment (AED) is the only channel for the reactions. The rate constants for reactions between sulfur-containing anions and H atoms are generally higher than for the related oxygen-containing anions with the exception of the reaction of SCN^-. The generally higher reactivity of the sulfur anions contrasts with previous results where AED reactivity was found to correlate with reaction exothermicity. Density functional theory calculations indicate that the reaction enthalpies, the characteristics of the reaction potential energy surfaces, and other structural and electronic factors can influence the reaction rate constants. This study indicates that organic sulfur anions can be more reactive than related oxygen anions in the interstellar medium where hydrogen atoms are abundant.

Thermal Methane Conversion to Syngas Mediated by Rh1-Doped Aluminum Oxide Cluster Cations RhAl3O4<sup/>

Laser ablation generated RhAl₃O₄⁺ heteronuclear metal oxide cluster cations have been mass-selected using a quadrupole mass filter and reacted with CH₄ or CD₄ in a linear ion trap reactor under thermal collision conditions. The reactions have been characterized by state-of-the-art mass spectrometry and quantum chemistry calculations. The RhAl₃O₄⁺ cluster can activate four C-H bonds of a methane molecule and convert methane to syngas, an important intermediate product in methane conversion to value-added chemicals. The Rh atom is the active site for activation of the C-H bonds of methane. The high electron-withdrawing capability of Rh atom is the driving force to promote the conversion of methane to syngas. The polarity of Rh oxidation state is changed from positive to negative after the reaction. This study has provided the first example of methane conversion to syngas by heteronuclear metal oxide clusters under thermal collision conditions. Furthermore, the molecular level origin has been revealed for the condensed-phase experimental observation that trace amounts of Rh can promote the participation of lattice oxygen of chemically very inert support (Al₂O₃) to oxidize methane to carbon monoxide.

Visual working memory deterioration preceding relapse in psychosis

BACKGROUND

Relapse is distressingly common after the first episode of psychosis, yet it is poorly understood and difficult to predict. Investigating changes in cognitive function preceding relapse may provide new insights into the underlying mechanism of relapse in psychosis. We hypothesized that relapse in fully remitted first-episode psychosis patients was preceded by working memory deterioration.

METHOD

Visual memory and verbal working memory were monitored prospectively in a 1-year randomized controlled trial of remitted first-episode psychosis patients assigned to medication continuation (quetiapine 400 mg/day) or discontinuation (placebo). Relapse (recurrence of positive symptoms of psychosis), visual (Visual Patterns Test) and verbal (Letter-Number span test) working memory and stressful life events were assessed monthly.

RESULTS

Remitted first-episode patients (n = 102) participated in the study. Relapsers (n = 53) and non-relapsers (n = 49) had similar baseline demographic and clinical profiles. Logistic regression analyses indicated relapse was associated with visual working memory deterioration 2 months before relapse [odds ratio (OR) 3.07, 95% confidence interval (CI) 1.19-7.92, P = 0.02], more stressful life events 1 month before relapse (OR 2.11, 95% CI 1.20-3.72, P = 0.01) and medication discontinuation (OR 5.52, 95% CI 2.08-14.62, P = 0.001).

CONCLUSIONS

Visual working memory deterioration beginning 2 months before relapse in remitted first-episode psychosis patients (not baseline predictor) may reflect early brain dysfunction that heralds a psychotic relapse. The deterioration was found to be unrelated to a worsening of psychotic symptoms preceding relapse. Testable predictors offer insight into the brain processes underlying relapse in psychosis.

The Nutritive Values in Different Varieties of Corn Planted in One Location Fed to Growing Pigs over Three Consecutive Years

This experiment was conducted to determine the effect of variety and planting year on the nutritive values of corn fed to growing pigs. Four corn varieties examined in this experiment were planted in the same village located in Longhua County, Heibei Province, China, in 2012, 2013, and 2014, respectively. During each year, corn was hand-harvested in early October and sun dried to about 14% moisture content. Three batches of twenty-four barrows (33.27±4.30, 31.88±2.93, 34.21±3.81 kg body wight [BW] in 2012, 2013, and 2014, respectively) were used and allotted to a complete block design with 4 diets and 6 replicate pigs per diet. Pigs were individually placed in metabolic crates. The four experimental diets were formulated by mixing each variety of corn and vitamins and minerals, respectively. A five-day collection period followed a seven-day diet acclimation period. The results indicated that variety of corn significantly influenced the available energy content (digestible energy [DE] on dry matter basis, p<0.05; metabolizable energy (ME) on dry matter basis, p<0.05, respectively), and the apparent total tract digestibility (ATTD) of organic matter (p<0.01), dry matter (p<0.05), gross energy (p<0.05), neutral detergent fiber (p<0.01), acid detergent fiber and ether extract (p<0.05). The planting year also significantly influenced the available energy contents (DE on dry matter basis, p<0.05; ME on dry matter basis, p<0.01, respectively) and the ATTD of neutral detergent fiber (p<0.01), acid detergent fiber (p<0.01), crude protein (p<0.01), and ether extract (p<0.01). No interaction was observed between the variety and planting year in DE and ME contents in corn. In conclusion, the variety and planting year significantly influenced the available energy and nutrient digestibility of corn fed to growing pigs.

Efficient construction of recombinant adenovirus expression vector of the Qinchuan cattle LYRM1 gene

In this study, we cloned the coding DNA sequence (CDS) region of Qinchuan cattle LYR motif-containing 1 (LYRM1) and constructed a recombinant adenovirus expression vector to examine the function of LYRM1 on the cellular level. Total RNA was extracted from the adipose tissue of Qinchuan cattle, cDNA was obtained by reverse transcription, and polymerase chain reaction was used to amplify the CDS region of the LYRM1 gene. The CDS-containing fragment was inserted into the shuttle vector pAdTrack-CMV to construct pAdTrack-CMV-LYRM1 vector. After linearization of pAdTrack-CMV-LYRM1 and the negative control vector pAdTrack-CMV by restriction endonuclease PmeI, the vectors were transformed into Escherichia coli BJ5183 containing pAdEasy-1 to obtain the recombinant adenovirus vector pAd-LYRM1 and pAd-CMV through homologous recombination. pAd-LYRM1 and pAd-CMV were then digested by PacI and transfected into the 293A cell line. The recombinant adenovirus Ad-LYRM1 and Ad-CMV was obtained at a concentration of 7 x 108 and 1.3 x 109 green fluorescent units/mL, respectively. Preadipocytes derived from Qinchuan cattle were separately infected with Ad-LYRM1 and Ad- CMV. Quantitative real-time polymerase chain reaction demonstrated that the expression of LYRM1 was increased by approximate 28,000-folds after the infection with recombinant adenovirus for 48 h. In conclusion, we successfully cloned the CDS region of the Qinchuan cattle LYRM1 gene, constructed the recombinant adenovirus expression vector, and obtained the adenovirus with high titer, providing valuable materials for studying the function of LYRM1 at the cellular level.

Osteoblast proliferation is enhanced upon the insulin receptor substrate 1 overexpression via PI3K signaling leading to down-regulation of NFκB and BAX pathway

The insulin receptor substrate 1 (IRS1) promotes bone formation via osteoblast proliferation mediated by PI3K/Akt signaling. A reduction in NFκB activity in osteoblasts results in an increase in bone formation. The NFκB signaling pathway leads to increased expression of BAX, which contributes to osteoblast apoptosis. The purpose of this study was to investigate the expression of recombinant plasmid enhanced green fluorescent protein-N1 (pEGFP-N1) that transferred IRS1 gene into osteoblasts in vitro and evaluate the effects of IRS1 overexpression on NFκBp65 and on BAX. Osteoblasts were transfected with pEGFP-N1 or pEGFP-N1 encoding wild-type IRS1 (pEGFP-N1-IRS1). Cell cycle analysis was performed using flow cytometry. The expression levels of NFκBp65 and BAX were measured by Western blotting. Our results revealed that overexpression of IRS1 stimulated osteoblast proliferation, as evidenced by an increase in the number of cells in the S phase compared to controls. IRS1 overexpression in osteoblasts activated the PI3K/Akt pathway, and inhibited expression of NFκBp65 and BAX. When osteoblasts transfected with pEGFP-N1-IRS1 were exposed to a PI3K inhibitor (LY294002), the effects of IRS1 overexpression were reversed. On the basis of our study, it seems that osteoblasts proliferated upon IRS1 overexpression due to inhibition of the NFκB pathway and downregulation of BAX through PI3K/Akt signaling.

Effects of bovine SMO gene polymorphisms on the body measurement and meat quality traits of Qinchuan cattle

Beef cattle breeding programs focus on improving important economic traits, including growth rates, and meat quantity and quality. Molecular marker-assisted selection based on genetic variation represents a potential method for breeding genetically improved livestock with better economic traits. Smoothened (SMO) protein is a signal transducer that contributes to the regulation of both osteogenesis and adipogenesis through the hedgehog pathway. In this study, we detected polymorphisms in the bovine SMO gene of Qinchuan cattle, and we analyzed their associations with body measurement traits (BMTs) and meat quality traits (MQTs). Using DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism, 3 novel single nucleotide polymorphisms were identified in the SMO gene of 562 cattle: 1 G > C mutation on exon 9 (G21234C) and 2 C > T mutations on exon 11 (C22424T and C22481T). Association analysis showed that polymorphisms on both the G21234C and C22424T loci significantly affected certain BMTs and MQTs (P < 0.05 or P < 0.01), whereas those on the C22481T locus did not (P > 0.05). Therefore, the SMO gene could be used as a candidate gene to alter BMTs and MQTs in Qinchuan cattle or for marker-assisted selection to breed cattle with superior BMTs and MQTs.

Polymorphisms in the delta-like 2 homolog gene and their association with growth and meat-quality traits in Qinchuan cattle

The delta-like 2 homolog (DLK2) modulates adipogenesis, hematopoiesis, osteogenesis, and other cell-differentiation processes. In the present study, we detected potential polymorphisms in the DLK2 gene in 604 individuals of Qinchuan cattle by using PCR-RFLP and DNA-sequencing methods. Herein, we identified five novel single-nucleotide polymorphisms (SNPs) (g.888G>A, g.910A>G, g.995G>A, g.4321A>G, g.4850A>G) and analyzed their association with measured traits. Four of the five analyzed polymorphisms were associated with at least one of the following traits: body weight (BW), chest depth (CD), chest circumference (CC), back fat thickness (BT), and rib-eye area (REA). To the best of our knowledge, our research is the first to report the association of DLK2 gene polymorphisms with growth and meat quality traits in Qinchuan cattle. In summary, the results of our study suggest that the DLK2 gene can be used as a candidate gene in beef cattle breeding.

New polymorphisms in the novel LYRM1 gene are associated with body measurement and meat quality traits in Qinchuan cattle

Body measurement and meat quality traits play important roles in the evaluation of productivity in cattle; they are influenced by genetic and environmental factors. Recent studies have shown that LYRM1 is a novel gene related to obesity and may influence fat deposition. We screened for new polymorphisms in the bovine LYRM1 gene and analyzed their association with body measurement and meat quality traits in cattle. DNA samples were obtained from 572 Qinchuan cattle aged from 18 to 24 months. DNA sequencing was used to find the LYRM1 single nucleotide polymorphisms (SNPs). Sequence analysis of LYRM1 revealed four novel SNPs in exon 3: G50A in coding region, C126A, A127T, and T128A in a 3'-untranslated region. G50A, A127T and T128A showed two genotypes: AG and GG, AA and AT, AT and TT, respectively; while C126A showed three genotypes: AA, AC and CC. Analysis showed that these four polymorphisms were significantly associated with body measurement and meat quality traits in the Qinchuan cattle population. We suggest that the LYRM1 gene can be used for marker-assisted selection to improve body measurement and meat quality traits in the Qinchuan cattle population.

Who are Prone to Develop Adverse Effects with Oral Tramadol? a Retrospective Cohort Study

Objective

Oral tramadol is a commonly prescribed analgesic in Hong Kong. Significant adverse effects are frequently observed in our locality. Our study aims to describe the rate of significant adverse effect that warrant discontinuation of oral tramadol and identify the risk factors for development of adverse effect.

Design

Retrospective cohort study.

Methods

Adult patients aged greater than 18 years old admitted to the emergency medicine ward of a large-scale local hospital in Hong Kong being prescribed with oral tramadol during in-hospital stay were recruited. Significant adverse effects during the hospital stay were observed as the outcome of interest.

Results

A total of 575 subjects were recruited. 29.9% experienced significant adverse effects likely related to tramadol. Age (p=0.006; odds ratio [OR] = 1.017, 95% confidence interval [CI] = 1.005-1.029) and sex (p=0.006; OR=1.696, 95% CI= 1.166-2.465) were statistically significant predictors of adverse effects after oral tramadol.

Conclusion

Our study suggests that female and increasing age patients are significant predictors for the development of adverse effect after taking oral tramadol. Possible adverse effects should be explained to the patients careful especially the higher risk groups. (Hong Kong j. emerg.med. 2014;21:3-9)

Novel SNPs in the exon region of bovine DKK4 gene and their association with body measurement traits in Qinchuan cattle

The aim of this study was to determine whether single nucleotide polymorphisms (SNPs) of bovine Dickkopf homolog 4 (DKK4) are associated with body measurement traits in Qinchuan cattle. By using PCR-SSCP technology and DNA sequencing, we discovered 5 DKK4 SNPs in Qingchuan cattle, including -65G>A and -77G>T in the 5'-untranslated region, 1532C>G and 1533T>C in exon 2, and 2088C>T in exon 3. The sequencing map showed that 1532C>G and 1533T>C were in close linkage disequilibrium and were treated as 1532C>G-1533T>C in this study. Allele frequencies were calculated and analyzed by the chi-square test, which showed that -65G>A and 1532C>G-1533T>C were in Hardy-Weinberg equilibrium (P > 0.05), whereas -77G>T and 2088C>T were not in all 633 tested Qinchuan cattle individuals (P < 0.01). Gene heterozygosity (HE), effective allele number (NE), and polymorphism information content (PIC) were 0.407, 1.686, and 0.324 at -65G>A; 0.472, 1.894, and 0.361 at -77G>T; 0.476, 1.908, and 0.363 at 1532C>G-1533T>C; and 0.218, 1.279, and 0.195 at 2088C>T. We also evaluated the potential association of these SNPs with body measurement traits in all 633 individuals; the results suggest that several SNPs in Qinchuan cattle DKK4 were significantly associated with body length, hip height, rump length, hip width, heart girth, and pin bone width (P < 0.05 and P < 0.01). These results suggest that bovine DKK4 could be used as candidate gene for Qinchuan cattle breeding.

Effect of Zn impurity in K0.8Fe(2-δ-x)Zn(x)Se2

A series of K(0.8)Fe(2-δ-x)Zn(x)Se(2) single-crystal samples with nominal compositions 0 ≤ x ≤ 0.05 were grown and their physical properties were measured in order to study the effect of Zn impurity. It is found that the Zn impurity (x ≤ 0.02) does not affect the superconducting transition temperature T(c) significantly. Meanwhile the hump in resistivity which corresponds to the transition from the insulating to metallic phase quickly shifts towards low temperatures. The results imply that there should be a phase separation in this system and Zn impurity causes the enhancement of the insulating phase. The negligible effect of Zn impurity on T(c) suggests an s-wave pairing in the superconducting phase. Meanwhile there is a possibility that the Zn impurity may selectively enter into the insulting phase.

Superconductivity induced by Ni doping in SmFe(1-x)Ni(x)AsO

Superconductivity with a T(c) of about 10 K is observed in the Ni-doped SmFe(1-x)Ni(x)AsO system. The measurements of resistivity and magnetic susceptibility show that the spin-density wave (SDW) order is quickly suppressed with increasing Ni content, and superconductivity emerges as x≥0.04. T(c)(mid) shows a maximum of 10.8 K at x = 0.06, and it drops to lower than 2 K as x>0.12. Meanwhile, the upper critical field (H(c2)(0)) is estimated to be about 40 T for the optimally-doped sample (x = 0.06). The normal state thermopower is negative for all the Ni-doped samples, indicating that an electron-type charge carrier dominates in the transport properties. Moreover, the magnitude of the room-temperature thermopower increases with increasing Ni content, and then shows a broad peak around x = 0.06. We found that there is an obvious correlation between the anomalously enhanced thermopower and superconductivity. A phase diagram is derived based on the transport measurements and a dome-like T(c)(x) curve is established.

Early diffusion weighted imaging and expression of heat shock protein 70 in newborn pigs with hypoxic ischaemic encephalopathy

OBJECTIVE

To establish a cerebral hypoxia ischaemic model in piglets and to explore the early diffusion weighted imaging (DWI) as well as the expression of heat shock protein 70 (HSP70) with hypoxic ischaemic encephalopathy (HIE).

METHODS

Twenty four 3 day old piglets were permanently ligated common carotid arteries bilaterally and ventilated with 3% oxygen for 30 minutes, and their brains were examined at three hours, six hours, and 24 hours after hypoxic ischaemia with T2 weighted images and diffusion weighted images. Apparent diffusion coefficient (ADC) values were measured and HSP70 expression was detected in the central and peripheral regions of lesions.

RESULTS

Abnormal signal intensity was detected on DWI and ADC maps in three hypoxic ischaemic groups. ADC values in the central lesions rapidly decreased, whereas ADC values in the peripheral regions reduced prominently at 24 hours after hypoxic ischaemia. There were significant differences (p<0.01) between ADC values of the central regions and the peripheral regions of lesions. The number of HSP70 positive cells was low at three hours, raised at the highest peak at six hours, and then rapidly decreased. There was statistical difference between HSP70 positive cells in the central regions and those in peripheral regions (p<0.01).

CONCLUSION

DWI may identify more early lesions, and improve conspicuity in the acute setting. ADC values can be used as an objective measure for hypoxic ischaemic injury. Tissue reversibility can be further reflected according to the information of ADC values and HSP70 immunohistochemical staining.

Catalytic mechanism of a family 3 beta-glucosidase and mutagenesis study on residue Asp-247

A family 3 beta-glucosidase (EC 3.2.1.21) from Flavobacterium meningosepticum has been cloned and overexpressed. The mechanistic action of the enzyme was probed by NMR spectroscopy and kinetic investigations, including substrate reactivity, secondary kinetic isotope effects and inhibition studies. The stereochemistry of enzymic hydrolysis was identified as occurring with the retention of an anomeric configuration, indicating a double-displacement reaction. Based on the k(cat) values with a series of aryl glucosides, a Bronsted plot with a concave-downward shape was constructed. This biphasic behaviour is consistent with a two-step mechanism involving the formation and breakdown of a glucosyl-enzyme intermediate. The large Bronsted constant (beta=-0.85) for the leaving-group-dependent portion (pK(a) of leaving phenols >7) indicates substantial bond cleavage at the transition state. Secondary deuterium kinetic isotope effects with 2,4-dinitrophenyl beta-D-glucopyanoside, o-nitrophenyl beta-D-glucopyanoside and p-cyanophenyl beta-D-glucopyanoside as substrates were 1.17+/-0.02, 1.19+/-0.02 and 1.04+/-0.02 respectively. These results support an S(N)1-like mechanism for the deglucosylation step and an S(N)2-like mechanism for the glucosylation step. Site-directed mutagenesis was also performed to study essential amino acid residues. The activities (k(cat)/K(m)) of the D247G and D247N mutants were 30000- and 200000-fold lower respectively than that of the wild-type enzyme, whereas the D247E mutant retained 20% of wild-type activity. These results indicate that Asp-247 is an essential amino acid. It is likely that this residue functions as a nucleophile in the reaction. This conclusion is supported by the kinetics of the irreversible inactivation of the wild-type enzyme by conduritol-B-epoxide, compared with the much slower inhibition of the D247E mutant and the lack of irreversible inhibition of the D247G mutant.

Rapid process for purification of an extracellular beta-xylosidase by aqueous two-phase extraction

A rapid process for purification of an extracellular beta-xylosidase with high purity was developed. The manipulation involved the precipitation of protein from culture medium and the extraction of enzyme from the resuspended crude protein solution by an aqueous-two phase separation. A linear random copolymer, PE62, with 20% ethylene oxide and 80% propylene oxide was employed in both stages of the purification. The enzyme was precipitated effectively by using 10% (w/v) PE62 and 5% (w/v) Na2HPO4. The aqueous two-phase extraction was performed with PE62 (10%)-NaH2PO4 (15%) as phase-forming reagent. SDS-PAGE analysis revealed that the purified enzyme is near homogeneity. The yield is about 100% with a purification factor of 8.8-fold. The whole process can be completed within an hour without any column chromatography.

Pulmonary haemorrhage in a patient with Kikuchi disease

Kikuchi disease is an immunologic disease and most commonly presents with cervical lymphadenopathy. It is usually self-limiting [1]. It is sometimes associated with systemic lupus erythematosus (SLE) [2], and can be associated with many complications including aseptic meningitis, neuropathy, brachial neuritis. It can also be associated with lymphoma, and may sometimes be misdiagnosed as such [3]. The following is the first reported case of Kikuchi disease associated with pulmonary haemorrhage. The patient died and no other cause of the pulmonary haemorrhage could be identified at post mortem.

An Aspergillus chitosanase with potential for large-scale preparation of chitosan oligosaccharides

A chitosan-degrading fungus, designated Aspergillus sp. Y2K, was isolated from soil. The micro-organism was used for producing chitosanase (EC 3.2.1.132) in a minimal medium containing chitosan as the sole carbon source. The induced chitosanase was purified to homogeneity from the culture filtrate by concentration and cationic SP-Sepharose chromatography. The purified enzyme is a monomer with an estimated molecular mass of 25 kDa by SDS/PAGE and of 22 kDa by gel-filtration chromatography. pI, optimum pH and optimum temperature values were 8.4, 6.5 and 65-70 degrees C, respectively. The chitosanase is stable in the pH range from 4 to 7.5 at 55 degrees C. Higher deacetylated chitosan is a better substrate. Chitin, xylan, 6-O-sulphated chitosan and O-carboxymethyl chitin were indigestible by the purified enzyme. By endo-splitting activity, the chitosanase hydrolysed chitosan to form chitosan oligomers with chitotriose, chitotetraose and chitopentaose as the major products. The enzyme hydrolyses chitohexaose to form chitotriose, while the chitopentaose and shorter oligomers remain intact. The N-terminal amino acid sequence of the enzyme was determined as YNLPNNLKQIYDDHK, which provides useful information for further gene cloning of this enzyme. A 275 g-scale hydrolysis of chitosan was performed. The product distribution was virtually identical to that of the small-scale reaction. Owing to the simple purification process and high stability of the enzyme, it is potentially valuable for industrial applications.

Effective induction, purification and characterization of Trichoderma koningii G-39 beta-xylosidase with high transferase activity

A beta-xylosidase was induced and purified from the culture filtrate of Trichoderma koningii G-39, grown in a medium containing 1% oat spelts xylan and 0.1% xylose. The presence of xylose unequivocally enhanced the induction of beta-xylosidase. The purified enzyme, which exhibited a significant alpha-arabinosidase activity, was obtained with high yield simply via ethanol precipitation and a single anion-exchange chromatography and was characterized as a monomeric glycoprotein with an estimated molecular mass of 104 kDa and a pI of 4.6. The K(m) values towards p-nitrophenyl beta-D-xylopyranoside and p-nitrophenyl alpha-L-arabinopyranoside are 0.04 and 7.5 mM, respectively. It is stable at pH 2.5-7.4, 37 degrees C. The pH and temperature optima are in the range of 3.5-4.0 and 55-60 degrees C, respectively. Contrary to most beta-xylosidases from other sources, Hg(2+) (up to 25 mM) has no effect on enzyme activity. Xylose was shown to inhibit the purified enzyme with a moderate K(i) value of 5 mM. The enzyme exhibited transxylosylation activity and was characterized as a 'retaining' enzyme, catalysing the hydrolysis of substrate with the retention of anomeric configuration.

Mechanistic study of beta-xylosidase from Trichoderma koningii G-39

The catalytic mechanism of the beta-xylosidase purified from the culture filtrate of Trichoderma koningii G-39 was investigated. By NMR spectroscopy, the stereochemistry of the enzyme catalyzing the hydrolysis of 2,4-dinitrophenyl and p-nitrophenyl-beta-D-xylosides was found unequivocally to involve retention of the anomeric configuration. Based on the k(cat) values of a series of arylxylosides with leaving group pK(a)s in the range of 4-10, an extended Bronsted plot was constructed with a slope (beta(lg)) near zero. Enzymatic hydrolysis of aryl-beta-D-xylosides in acetate buffer (pH 4.0) containing 3 or 5% methanol showed a constant product ratio (methylxyloside/xylose), indicating the presence of a common intermediate, probably the xylosyl-enzyme intermediate. In the presence of DTT, the k(cat) values of p-cyanophenyl-beta-D-xylopyranoside and p-nitrophenyl-beta-D-xylopyranoside increased greatly. A two-step mechanism involving the formation and breakdown of the xylosyl-enzyme intermediate was therefore proposed. The rate-limiting step is the breakdown of the intermediate. The secondary deuterium kinetic isotope effect (k(H)/k(D)) measured for 2,4-dinitrophenyl-beta-D-xyloside was 1.02+/-0.01, suggesting that the transition state for breakdown of the xylosyl-enzyme intermediate is S(N)2-like.