Solvothermal synthesis and structure of a new selenium-rich selenophosphate K(3)PSe(4).2Se(6)

The compound K(3)PSe(4).2Se(6) was synthesized at 110 degrees C via solventothermal techniques from binary starting materials and Se in acetonitrile. The compound crystallizes in the space group Fd macro 3 of the cubic system with eight formula units in a cell with a dimension of a = 16.415(2) A at T = 193 K. The structure contains an unusual intermixing of ionic and uncharged species. The selenophosphate tetrahedral trianions PSe(4)(3-) are surrounded by potassium cations; other potassium cations in the structure are coordinated to 12 selenium atoms from four Se(6) rings in a tetrahedral arrangement. There are no short contacts between adjacent selenium rings. Heating the same reaction mixture to 160 degrees C results in the formation of only needles of trigonal selenium.     

Oxalate-bridged dinuclear M2 units: dimers of dimers, cyclotetramers, and extended sheets (m = Mo, W, Tc, Ru, and Rh)

The electronic structures of D(4h)-M(2)(O(2)CH)(4) and the oxalate-bridged complexes D(2h)-[(HCO(2))(3)M(2)](2)(mu-O(2)CCO(2)) and D(4h)-[(HCO(2))(2)M(2)](4)(mu-O(2)CCO(2))(4) have been investigated by a symmetry analysis of their MM and oxalate-based frontier orbitals, as well as by electronic structure calculations on the model formate complexes (M = Mo and W {d(4)-d(4)}, Tc, Ru {d(6)-d(6)}, and Rh {d(7)-d(7)}). Significant changes in the ordering, interactions, and electronic occupation of the molecular orbitals (MOs) arise through both the progression from d(4) to d(7) metals and the change from second to third row transition metals. For M = Mo and W, the highest-occupied orbitals are delta based, while the lowest-unoccupied orbitals are oxalate pi based; for M = Tc, the highest-occupied orbitals are an energetically tight delta-based set of MOs, while the lowest-unoccupied orbitals are MM-based pi. For both Ru and Rh, the highest-occupied MOs are the MM pi* and delta*, respectively, while the lowest-unoccupied MOs, in both instances, are MM-based sigma. With the exception of M = Ru, all of the complexes are closed shell. From the progression M(2) --> [M(2)](2) --> [M(2)](4), we can envision the nature of bandlike structures for a 2-dimensional square grid of formula [M(2)(mu-O(2)CCO(2))](infinity). Only for Mo and W oxalates should good electronic communication between MM centers generate a band of significant width to lead to metallic conductivity upon oxidation.     

Alkyne coupling at a rhenium-monocarborane substrate: synthesis of Re,B-eta2:sigma-butadienyl complexes

Treatment of 7-NH(2)Bu(t)-nido-7-CB(10)H(12) in tetrahydrofuran (THF) with LiBu(n)(3 equiv) and then [ReBr(CO)(3)(THF)(2)] gives the rhenacarborane dianion [1-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)](2-), isolated as the bis-[N(PPh(3))(2)](+) salt (4). Iodine oxidation of this Re(I) intermediate gives the Re(III) complex [1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)] 6 in which the carborane functions formally as an 8-electron (6pi+ 2sigma) donor. Reaction of with ligands L in the presence of Me(3)NO gives substituted products [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-closo-2,1-ReCB(10)H(10)][L = PPh(3)(7a), CNXyl (7b; Xyl = C(6)H(3)Me(2)-2,6), or Bu(t)C triple bond CH (7c)]. Formation of complex 7c is unexpectedly accompanied by [1,2-mu-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)] 8a, in which an alkyne-derived dienyl group is bound to both the rhenium centre and to an adjacent boron vertex. Complex 8a is also obtained from 7c with Bu(t)C triple bond CH and Me(3)NO. The same reaction of 7c, using PhC triple bond CH or CNXyl instead of Bu(t)C triple bond CH, gives, respectively, [1,2-micro-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHPh}-closo-2,1-ReCB(10)H(9)] 8b and [1,2-micro-NHBu(t)-2-Bu(t)C triple bond CH-2-CO-2-CNXyl-closo-2,1-ReCB(10)H(10)] 9. Addition of donors L to results in displacement from rhenium of the pendant dienyl moiety, yielding [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-3-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)][L = PMe(3)(10a), CNBu(t)(10b)]. Single-crystal X-ray diffraction analyses have confirmed the novel structural features of compounds 6, 7c, 8b and 9.     

Analysis of methoxypyrazines in wine using headspace solid phase microextraction with isotope dilution and comprehensive two-dimensional gas chromatography

This study reports an optimized headspace-solid phase microextraction (HS-SPME) method for the determination of methoxypyrazines in wine. Analysis was performed by using comprehensive two-dimensional gas chromatography with novel detection capabilities, including nitrogen phosphorus detection (GC x GC-NPD) and time-of-flight mass spectrometry (GC x GC-TOFMS). In the latter, stable isotope dilution was performed for the quantitation of 2-methoxy-3-(2-methylpropyl) pyrazine (IBMP), using labelled 2-(2H3)methoxy-3-(2-methylpropyl)pyrazine (d3-IBMP) as the internal standard, and resolution of the two analogues was facilitated using the deconvolution capabilities of the TOFMS. This research represents the first report of HS-SPME with isotope dilution and GC x GC-TOFMS (GC x GC-IDTOFMS). Analysis by GC x GC-NPD enabled detection limits of 0.5 ng/L for the quantitation of IBMP, which was superior to that obtained using GC x GC-IDTOFMS (1.95 ng/L). Nevertheless, both methods were adequately sensitive for real wine analysis, yielding highly comparable IBMP concentrations of 26.1 and 27.8 ng/L, respectively, from a Sauvignon blanc wine. The complexity of the real wine headspace was simplified as a result of selective detection using GC x GC-NPD and, in the case of GC x GC-IDTOFMS, the use of extracted ion chromatograms (EICs).     

Virtual Screening of Alkaloid and Terpenoid Inhibitors of SMT Expressed in Naegleria sp.

The pathogenic form of thermophilic Naegleria sp. i.e., Naegleria fowleri, also known as brain eating amoeba, causes primary amoebic encephalitis (PAM) with a >97% fatality rate. To date, there are no specific drugs identified to treat this disease specifically. The present antimicrobial combinatorial chemotherapy is hard on many patients, especially children. Interestingly, Naegleria fowleri has complex lipid biosynthesis pathways like other protists and also has a strong preference to utilize absorbed host lipids for generating energy. The ergosterol biosynthesis pathway provides a unique drug target opportunity, as some of the key enzymes involved in this pathway are absent in humans. Sterol 24-C Methyltransferase (SMT) is one such enzyme that is not found in humans. To select novel inhibitors for this enzyme, alkaloids and terpenoids inhibitors were screened and tested against two isozymes of SMT identified in N. gruberi (non-pathogenic) as well as its homolog found in yeast, i.e., ERG6. Five natural product derived inhibitors i.e., Cyclopamine, Chelerythrine, Berberine, Tanshinone 2A, and Catharanthine have been identified as potential drug candidates based on multiple criteria including binding affinity, ADME scores, absorption, and, most importantly, its ability to cross the blood brain barrier. This study provides multiple leads for future drug exploration against Naegleria fowleri.     

Enhancing the Photo and Thermal Stability of Nicotine through Crystal Engineering with Gentisic Acid

The use of crystal engineering to convert liquids into crystalline solids remains a powerful method for inhibiting undesired degradation pathways. When nicotine, a liquid sensitive to both light and air, is combined with the GRAS-listed compound, gentisic acid, the resulting crystalline solid, exhibits enhanced photo and thermal stability. Despite a modest ΔT_m of 42.7 °C, the melting point of 155.9 °C for the nicotinium gentisate salt is the highest reported for nicotine-containing crystalline solids. An analysis of the crystal packing and thermodynamic properties provides context for the observed properties.     

基于均值距离测度的医学图像配准

针对互信息测度在配准医学图像时易陷入局部极值、速度慢的缺点,提出了基于均值不等式的均值距离测度.首先根据均值不等式推导出5种均值距离测度：方根-算术均值距离(SAM)、方根-几何均值距离(SGM)、方根-调和均值距离(SHM)、算术-几何均值距离(AGM)、算术-调和均值距离(AHM).然后通过人体脑部CT/MR和MR-T1/PD图像的刚体配准实验,从函数曲线、配准精度、计算时间和收敛性能方面,对互信息与5种均值距离信息测度进行了比较与分析.实验结果表明,在不损失配准精度的前提下,AHM和SAM测度可以获得更快的配准速度,对噪声有很强的鲁棒性.     

Tuning Tetrazole Photochemistry for Protein Ligation and Molecular Imaging

Photochemistry provides a wide range of alternative reagents that hold potential for use in bimolecular functionalisation of proteins. Here, we report the synthesis and characterisation of metal ion binding chelates derivatised with disubstituted tetrazoles for the photoradiochemical labelling of monoclonal antibodies (mAbs). The photophysical properties of tetrazoles featuring extended aromatic systems and auxochromic substituents to tune excitation toward longer wavelengths (365 and 395 nm) were studied. Two photoactivatable chelates based on desferrioxamine B (DFO) and the aza-macrocycle NODAGA were functionalised with a tetrazole and developed for protein labelling with ⁸⁹Zr, ⁶⁴Cu and ⁶⁸Ga radionuclides. DFO-tetrazole ( 1 ) was assessed by direct conjugation to formulated trastuzumab and subsequent radiolabelling with ⁸⁹Zr. Radiochemical studies and cellular-based binding assays demonstrated that the radiotracer remained stable in vitro retained high immunoreactivity. Positron emission tomography (PET) imaging and biodistribution studies were used to measure the tumour specific uptake and pharmacokinetic profile in mice bearing SK-OV-3 xenografts. Experiments demonstrate that tetrazole-based photochemistry is a viable approach for the light-induced synthesis of PET radiotracers.     

Cryptanalysis and Improvement in Multi-Party Quantum Key Distribution Protocol with New Bell States Encoding Mode

International Journal of Theoretical Physics - Ma et al. [Int. J. Theor. Phys. (2021): 1328–1338] proposed a multi-party quantum key distribution (MQKD) protocol using Bell states, in which...