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This work reported an efficient and accurate liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of seventeen mycotoxins in Puerariae lobatae radix, a frequently used traditional Chinese medicine (TCM). The effects of four different clean-up methods, including TC-M160, TC-T220, Mycosep 227, and QuEChERS method, on the recoveries of mycotoxins were investigated and compared. Finally, TC-M160 was chosen for better recovery and repeatability for mycotoxins analysis. The analytes were separated on an Agilent ZORBAX SB C18 column (4.6 mm x 250 mm, 5 μm particle size), and eluted with a mobile phase consisting of (A) water containing 0.1% formic acid and (B) acetonitrile containing 0.1% formic acid at a flow rate of 0.6 mL/min. The separated compounds were detected by a triple quadrupole mass spectrometer operating in positive electrospray ionization with multiple reaction monitoring (MRM) mode. The results of method validation accorded with the requirement of analytical method for mycotoxins in COMMISSION REGULATION (EC) No 401/2006. The developed method was successfully applied for determination of mycotoxins in seventeen batches of Puerariae lobatae radix collected from different provinces of China. Three batches of them were found with contamination of mycotoxins AFB1 at (0.751 ± 0.176) μg/kg, T-2 at (1.10 ± 0.01) μg/kg, and T-2 at (0.853 ± 0.044) μg/kg, respectively. The results demonstrated that the proposed method was suitable for monitoring mycotoxins residues in Puerariae lobatae radix. [ABSTRACT FROM AUTHOR]

The ring-opening polymerization of ethylene carbonate was examined using ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and 1-butyl-3-methylimidazolium chlorozincate ([bmim]Cl-(ZnCl2)x), as polymerization catalysts. It was shown that the polymerization was accompanied with decarboxylation and chain cleavage reaction. As the reaction time increased, the monomer conversion increased and the content of ethylene carbonate units in the resultant polymer decreased, while the polymer molecular weight increased at first, reached a maximum and then decreased. It was also found that not only the polymerizing activity of the [bmim]Cl-(ZnCl2)x but also its performance for suppressing the decarboxylation and chain cleavage increased with the molar fraction of ZnCl2. It was deduced that the catalytic performance of ionic liquids mainly depended on their inorganic anions and that the larger the amount of these anions in the reaction system, the better the catalytic performance. The polymerizing activity of ionic liquids was much higher than conventional catalysts often used for the polymerization of ethylene carbonate. [ABSTRACT FROM AUTHOR]

Three new Zn(ii) metal–organic coordination polymers, [Zn3(STDC)3(py)2] (1), [Zn3(STDC)3(4,4′-bpy)] (2), [Zn3(STDC)3(bpea)] · 3H2O (3), where H2STDC = trans-stilbene-4,4′-dicarboxylic acid, py = pyridine, 4,4′-bipy = 4,4′-bipyridine, bpea = 1,2-bis(4-pyridyl)ethane, were prepared by solvothermal reactions of Zn(ii) acetate with H2STDC in the presence of py or linear bis(pyridyl) molecules. Compound 1is a 2D triangle-tessellated layered network based on a pinwheel trinuclear zinc-carboxylate clusters as secondary building unit with py as the terminal ligand. Compounds 2and 3contain similar layers, which are linked into layer-pillared 3D frameworks by the ditopic bipy or bpea ligand in place of py. Comparing the structures of 2and 3, the increase in pillar length does not lead to increased multiplicity in interpenetration, due to the limitation of the intralayer space dimensions, but it induces expanded and unequal interlayer separations. [ABSTRACT FROM AUTHOR]

Protonolysis reactions of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3(Ln = Pr, Nd, Sm, Eu) with 3 equiv of 4,6-dimethylpyrimidine-2-thiol (dmpymtH) gave rise to the four Ln(III) pyrimidine-2-thionate complexes Li[Ln(dmpymt)4] (Ln = Pr (1), Nd (2), Sm (3), Eu (4)). Compounds 1−4were characterized by elemental analysis, IR and 1H NMR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analysis shows that the structures of 1−4are similar and each eight-coordinate Ln(III) ion is chelated by four dmpymt ligands. Complexes 1−4display excellent catalytic performance in the cyclodimerization of isocyanates to produce substituted ureas via elimination of CO, which represents the first example of lanthanide thiolates exhibiting a high catalytic activity and a high selectivity in the cyclodimerization of isocyanates. The effects of the solvents, temperatures, catalyst loadings, and rare-earth metals on the catalytic activities of the complexes were examined. [ABSTRACT FROM AUTHOR]

Protonolysis reactions of [Zn(dmpzm)Et2] (1) with acetic or formic acid in different molar ratios gave rise to four mononuclear zinc complexes [ZnEt(dmpzm)(L)] (2: L = OAc; 3: L = HCOO) and [Zn(dmpzm)(L)2] (4: L = OAc; 5: L = HCOO), one nonanuclear zinc complex [Zn(μ4-O)2(ZnEt)6- (μ3-OAc)4(μ'3-OAc)2{Zn(dmpzm)Et}2] (6), and one tetranuclear zinc complex [Zn4(μ4-O)(dmpzm)3Et3] (7). Compounds 1-7 were characterized by elemental analysis, IR spectra, 1H NMR spectra, and the crystal structures of 1, 3, 4, 6, and 7 were determined by single-crystal X-ray crystallography. In the structures of 1, 3, and 4, the central Zn atom is tetrahedrally coordinated by two N atoms of one dmpzm and two C atoms of two Et groups (1), or one C atom of one Et group and one O atom of formate ligand (3), or two O atoms of two acetates (4). In the structure of 6, a heptanuclear [Zn(μ4-O)2(ZnEt)6(μ3-OAc)4] core is connected with two [Zn(dmpzm)Et]+ fragments via a pair of μ'3-OAc ligands. Compound 7 consists of a Zn4(μ4-O) tetrahedron in which three Zn atoms are further saturated by two N atoms from dmpzm ligands and an ethyl group while one Zn center is coordinated by three C atoms from the methylene group of the three dmpzm ligands. [ABSTRACT FROM AUTHOR]

Protonolysis reactions of [Zn(dmpzm)Et2] (1) with acetic or formic acid in different molar ratios gave rise to four mononuclear zinc complexes [ZnEt(dmpzm)(L)] (2: L = OAc; 3: L = HCOO) and [Zn(dmpzm)(L)2] (4: L = OAc; 5: L = HCOO), one nonanuclear zinc complex [Zn(μ4-O)2(ZnEt)6- (μ3-OAc)4(μ'3-OAc)2{Zn(dmpzm)Et}2] (6), and one tetranuclear zinc complex [Zn4(μ4-O)(dmpzm)3Et3] (7). Compounds 1-7 were characterized by elemental analysis, IR spectra, 1H NMR spectra, and the crystal structures of 1, 3, 4, 6, and 7 were determined by single-crystal X-ray crystallography. In the structures of 1, 3, and 4, the central Zn atom is tetrahedrally coordinated by two N atoms of one dmpzm and two C atoms of two Et groups (1), or one C atom of one Et group and one O atom of formate ligand (3), or two O atoms of two acetates (4). In the structure of 6, a heptanuclear [Zn(μ4-O)2(ZnEt)6(μ3-OAc)4] core is connected with two [Zn(dmpzm)Et]+ fragments via a pair of μ'3-OAc ligands. Compound 7 consists of a Zn4(μ4-O) tetrahedron in which three Zn atoms are further saturated by two N atoms from dmpzm ligands and an ethyl group while one Zn center is coordinated by three C atoms from the methylene group of the three dmpzm ligands. [ABSTRACT FROM AUTHOR]

Protonolysis reactions of [Zn(dmpzm)Et2] (1) with acetic or formic acid in different molar ratios gave rise to four mononuclear zinc complexes [ZnEt(dmpzm)(L)] (2: L = OAc; 3: L = HCOO) and [Zn(dmpzm)(L)2] (4: L = OAc; 5: L = HCOO), one nonanuclear zinc complex [Zn(μ4-O)2(ZnEt)6(μ3-OAc)4(μ′3-OAc)2{Zn(dmpzm)Et}2] (6), and one tetranuclear zinc complex [Zn4(μ4-O)(dmpzm)3Et3] (7). Compounds 1–7were characterized by elemental analysis, IR spectra, 1H NMR spectra, and the crystal structures of 1, 3, 4, 6, and 7were determined by single-crystal X-ray crystallography. In the structures of 1, 3, and 4, the central Zn atom is tetrahedrally coordinated by two N atoms of one dmpzm and two C atoms of two Et groups (1), or one C atom of one Et group and one O atom of formate ligand (3), or two O atoms of two acetates (4). In the structure of 6, a heptanuclear [Zn(μ4-O)2(ZnEt)6(μ3-OAc)4] core is connected with two [Zn(dmpzm)Et]+fragments viaa pair of μ′3-OAc ligands. Compound 7consists of a Zn4(μ4-O) tetrahedron in which three Zn atoms are further saturated by two N atoms from dmpzm ligands and an ethyl group while one Zn center is coordinated by three C atoms from the methylene group of the three dmpzm ligands. [ABSTRACT FROM AUTHOR]

Activation-induced cytidine deaminase (AID) is a single-stranded (ss) DNA-specific cytidine deaminase that initiates 19 heavy chain (IgH) class switch recombination (CSR) and Ig somatic hypermutation (SHM) by deaminating cytidines within, respectively, IgH switch (5) regions and lg variable region (V) exons. AID that is phosphorylated on serine residue 38 interacts with replication protein A (RPA), a ssDNA binding protein, to promote deamination of transcribed double-stranded DNA in vitro, which, along with other evidence, suggests that AID may similarly gain access to transcribed S regions and V exons in vivo. However, the physiological role of AID phosphorylation at serine residue 38 (S38). and even the requirement for the S38 residue, with respect to CSR or SHM has been debated. To address this issue, we used gene targeting to generate an endogenous mouse AID locus that produces AID in which S38 is substituted with alanine (AIDS38A), a mutant form of AID that retains similar catalytic activity on ssDNA as WT AID (AIDWT). B cells homozygous for the AIDS38A mutation show substantially impaired CSR and SHM, correlating with inabilty of AIDS38A to interact with endogenous RPA. Moreover, mice haploinsufficient for AIDS38A have even more severely impaired CSR when compared with mice haploinsufficient for AIDWT, with CSR levels reduced to nearly background levels. These results unequivocally demonstrate that integrity of the AID S38 phosphorylation site is required for normal CSR and SHM in mice and strongly support a role for AID phosphorylation at S38 and RPA interaction in regulating CSR and SHM. [ABSTRACT FROM AUTHOR]

Contraction of smooth muscle depends on the balance of myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP) activities. Because MLCK activation depends on the activation of calmodulin, which requires a high Ca2+ concentration, phosphatase inhibition has been invoked to explain contraction at low cytosolic Ca2+ levels. The link between activation of the Ca2+-independent protein kinase Cε (PKCε) and MLC phosphorylation observed in the esophagus (ESO) (Sohn UD, Cao W, Tang DC, Stull JT, Haeberle JR, Wang CLA, Harnett KM, Behar J, and Biancani P. Am J Physiol Gastrointest Liver Physiol 281: G467-G478, 2001), however, has not been elucidated. We used phosphatase and kinase inhibitors and antibodies to signaling enzymes in combination with intact and saponin-permeabilized isolated smooth muscle cells from ESO and lower esophageal sphincter (LES) to examine PKCεdependent, Ca2+-independent signaling in ESO. The phosphatase inhibitors okadaic acid and microcystin-LR, as well as an antibody to the catalytic subunit of type 1 protein serine/threonine phosphatase, elicited similar contractions in ESO and LES. MLCK inhibitors (ML-7, ML-9, and SM-I) and antibodies to MLCK inhibited contraction induced by phosphatase inhibition in LES but not in ESO. The PKC inhibitor chelerythrine and antibodies to PKCE, but not antibodies to PKCβII, inhibited contraction of ESO but not of LES. In ESO, okadaic acid triggered translocation of PKCε from cytosolic to particulate fraction and increased activity of integrin-linked kinase (ILK). Antibodies to the mitogen-activated protein (MAP) kinases ERK1/ERK2 and to ILK, and the MAP kinase kinase (MEK) inhibitor PD-98059, inhibited okadaic acid-induced ILK activity and contraction of ESO. We conclude that phosphatase inhibition potentiates the effects of MLCK in LES but not in ESO. Contraction of ESO is mediated by activation of PKCε, MEK, ERK1/2, and ILK. [ABSTRACT FROM AUTHOR]

Manganese-based layered coordination polymer ([Mn-(tfbdc)(4,4'-bpy)(H20)2], Mn--LCP) with microporous structure was synthesized by reaction of 2,3,5,6-tetrafluoroterephthalatic acid(H2tfbdc) and 4,4'-bipyridine(4,4'-bpy) with manganese(ll) acetate tetrahydrate in water solution. Mn--LCP was characterized by elemental analysis, IR spectra, thermogravimetric analysis, X-ray single-crystal structure analysis, and powder X-ray diffraction. Magnetic susceptibility data from 300 to 1.8K show that there is a weak antiferromagnetic exchange between Mn(n) ions in Mn--LCP. As anode material, the Mn--LCP electrode exhibits an irreversible high capacity in the first discharge process and a reversible lithium storage capacity of up to about 390 mA h/g from the fourth cycle. It might provide a new method for finding new electrode materials in lithium-ion batteries [ABSTRACT FROM AUTHOR]