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In order to explore the enantioselectivity of new uranyl receptors to chiral organophosphorus pesticides (COPs), we designed a novel ligand: 2‐(2‐hydroxy‐3‐methoxyphenyl)‐9‐(2‐hydroxyphenyl)thiopyrano[3,2‐h]thiochromene‐4,7‐dione (HTTDN) and constructed a new receptor of Uranyl‐HTTDN by complexation of HTTDN with uranyl. The complexation and enantioselectivity of Uranyl‐HTTDN to COPs of R/S‐methamidophos (R/S‐MAPs) and R/S‐acephates (R/S‐APs) were studied using density functional theory (DFT) method in this paper. The results showed that in vacuum and toluene, Uranyl‐HTTDN could effectively recognize R/S‐MAPs by complexation with oxygen of phosphoryl of methamidophos, with enatioselectivity coefficients of 91.80% and 86.74%, respectively. In vacuum, water, and acetone, Uranyl‐HTTDN could also effectively identify R/S‐APs by the oxygen of phosphoryl coordinating with U, and enatioselectivity coefficients toward R/S‐APs were 99.41%, 91.09%, and 93.84%, respectively. These results could provide valuable information and theoretical reference for the further experiments of COPs separation. [ABSTRACT FROM AUTHOR]

A six‐membered ring lactam derivative was introduced in a parallel manner into uranyl–salophens with R/S configuration (R‐/S‐AUSRLs), which were used as receptors to coordinate with guests of cis−/trans‐methylcyclohexylamines (cis−/trans‐MCHAs). Using density functional theory calculations at the B3LYP/6‐311G** level and RECP, an insight into the coordination complexes of the R‐/S‐AUSRLs with cis−/trans‐MCHAs was obtained. The results showed that the U atoms of receptors could coordinate with the N atoms of four kinds of cis−/trans‐1,2 or − 1,4 guests, but the two kinds of cis−/trans‐1,3 guests could not be converged by the same method in the process of structural optimization due to steric hindrance, and thus the cis−/trans‐1,3 guests could not be coordinated with the R‐/S‐AUSRLs. The mode of coordination of the R‐/S‐AUSRLs with the guests displayed a significant difference. And the change of R‐AUSRL coordination ability to the cis−/trans‐MCHAs was very large, but that of S‐AUSRL was small. Overall, the stability of the R‐series coordination complexes was higher than that of the corresponding S‐series coordination complexes, and the R‐AUSRL receptor had better coordination selectivity and higher molecular recognition to the cis−/trans‐MCHA guests than the S‐AUSRL receptor. However, the coordination ability of S‐AUSRL with the cis−/trans‐MCHAs was stronger than that of R‐AUSRL. It was expected that these results could provide insightful information and theoretical guidance for understanding the molecular recognition of R‐/S‐AUSRLs for cis−/trans‐type cyclohexylamine derivatives. [ABSTRACT FROM AUTHOR]

Bovine liver cytochrome b (cyt b), with heme bound noncovalently, has been converted into a cyt c-like protein (cyt b N57C) by constructing a thioether linkage between the heme and the engineered cysteine residue. With no X-ray or NMR structure available, we herein performed a molecular modeling study of cyt b N57C. On the other hand, using amino acid sequence information for a newly discovered member of the cyt b family, domestic silkworm cyt b (DS cyt b), we predicted the protein structure by homology modeling in combination with MD simulation. The modeling structure shows that both Cys57 in cyt b N57C, and Cys56, a naturally occurring cysteine in DS cyt b, have suitable orientations to form a thioether bond with the heme 4-vinyl group, as the heme is in orientation A. In addition to providing structural information that was not previously obtained experimentally, these modeling studies provide insight into the formation of cyt c-like thioether linkages in cytochromes, and suggest that c-type cyt b maturation involves a b-type intermediate. [ABSTRACT FROM AUTHOR]

The biological toxicity of uranyl ion (UO) lies in interacting with proteins and disrupting their native functions. The structural and functional consequences of UO interacting with cytochrome b (cyt b), a small membrane heme protein, and its heme axial ligand His39Ser variant, cyt b H39S, were investigated both experimentally and theoretically. In experiments, although cyt b was only slightly affected, UO binding to cyt b H39S with a K of 2.5 μM resulted in obvious alteration of the heme active site, and led to a decrease in peroxidase activity. Theoretically, molecular simulation proposed a uranyl ion binding site for cyt b at surface residues of Glu37 and Glu43, revealing both coordination and hydrogen bonding interactions. The information gained in this study provides insights into the mechanism of uranyl toxicity toward membrane protein at an atomic level. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Apocytochrome b 5 (apocyt b 5) with heme removal from the heme-binding core 1, and its mutants with amino acid replaced in the hydrophobic core 2, namely apocyt b 5 Y7P, P81A and H15R/S20E, have been subjected to molecular dynamics (MD) simulation at high temperature (500K) for elucidating their folding behaviors. The early events upon thermal induced unfolding were found to be in good agreement with available experimental results, and the lowest stability of Y7P was predicted among the four apoproteins. The influences of these key residues on protein folding behavior were compared directly at an atomic level. At the same time, the influences of non-native interactions of hydrogen bonds and salt-bridges on protein stabilities were analyzed in detail. The insights from current MD simulations are valuable for understanding the apoprotein folding and the holoprotein formation in terms of heme proteins. [Copyright &y& Elsevier]

Abstract: Heme transfer is commonly observed from one heme protein to the other such as from cytochrome b 5 (cyt b 5) to apo-myoglobin. In this study, instead of to another heme protein, we observed the heme transfer from wild-type (WT) cyt b 5, H39C cyt b 5 with heme axial ligand His39 mutated to Cys39, and DME cyt b 5 with heme replaced by protoporphyrin IX dimethyl ester, to a heme DNA aptamer, PS2.M, respectively, with a different rate constant. The heme transfer was further confirmed by the enhancement of peroxidase activity of the cyt b 5s–PS2.M system due to the formation of catalytic PS2.M–heme complex. This study provides valuable insights into both cyt b 5–heme and PS2.M–heme interactions and shows that heme transfer from heme protein to heme–aptamer can be used to evaluate the relative stability of heme proteins. In addition, this study sheds light on the maturation of heme proteins in vivo by interacting with DNA/RNA enzymes. [Copyright &y& Elsevier]

In this study, immune and molecular biological methods were used to identify the pathogen in a blood sample from a patient with dermatosis. Venous blood was collected and tested with Leish rK39 dipsticks. The lesion sample was collected and fixed in 75% ethanol, and DNA was extracted. The internal transcribed spacer 1 of rDNA and N-acetylglucosamine-1-phosphate transferase of Leishmania were amplified with PCR using primers LITSR-L5.8S and NAGTL1s-NAGTL4, respectively. The amplified products were sequenced and analyzed by BLAST. Weakly positive results were obtained for the gold-labeled Leish rK39 dipstick serological test. PCR resulted in products of 404 bp and 1 405 bp with primers LITSR-L5.8S and NAGTL1-NAGTL4, respectively. Both were 99.7% homologous to the corresponding sequence of Leishmania major. The accession number of the two sequences were KU975160 and KX150476. The case of dermatosis is diagnosed as imported cutaneous leishmaniasis and the pathogen is L. major.

A new spectrophotometric complexometric titration method coupled with chemometrics for the determination of mixtures of metal ions has been developed. In the method described here, the titrant is a mixture of EDTA and two indicators. In the process of titration, both the volumetric addition of titrant and the progress of titration reaction can be characterized simultaneously by chemometric calculation with the absorption spectra, and then the titration curves can be obtained. With the titration curves, a matrix equation can be established, and thus the concentration of each component in the mixture of metal ions can be calculated with principal component regression. The method only needs the information of absorption spectra to obtain the analytical results, and is free of volumetric measurements. So the method is simple, convenient and precise, and has been applied to the simultaneous determination of mixtures of calcium and magnesium using malachite green and Cu-PAN as indicators with satisfactory results.

The nitroxyl of nitrotyrosine can be substituted quantitatively by iodide when the nitroxyl is reduced to amino and then diazotized to diazonium. The iodide can be determined by catalytic spectrophotometric method with iodide-nitrous acid-arsenious acid system. Thus, a new catalytic spectrophotometric method combining the substitution of nitroxyl by iodide for the determination of nitrotyrosine has been established. The limit of detection is 0.002 mumol.L-1 and the linear range is 0.005-0.25 mumol.L-1. The method has been used for the determination of nitrotyrosine in the products of the reaction of tyrosine with peroxynitrite and the results are satisfactory.

The utilization of Meriones meridianus and Lagurus lagurus as alternative definitive hosts for Echinococcus multilocularis and E. granulosus was investingated. Tapeworm stage development of E. multilocularis was observed and their recovery rate was determined in the small intestine of M. meridianus and L. lagurus. These were compared with those in golden hamsters, which are known as alternative definitive hosts. The animals were treated with PTBA (prednisolone tertiary butylacetate) and PA (prednisolone acetate), after which M. meridianus showed the highest recovery rate, whereas L. lagurus had few or no worms. The recovery rate of worms from golden hamsters was between those of M. meridianus and L. lagurus. On day 20 post-infection, developing tapeworms with mature segments were collected from M. meridianus treated with PA. The worms were mostly from the proximal and medial small intestine. The three species of animals infected orally with E. granulosus were divided into two groups, PTBA-treated and non-treated control groups. PTBA promoted/enhanced the recovery rate of the worms until 5 days, but none or only a few worms were found in PTBA treated animals thereafter. The highest recovery rate was obtained from M. meridianus treated with PTBA on day 5 post-infection. Some worm developments were observed on days 5 and 10 post-infection. These results demonstrate that M. meridianus could be useful as an alternative definitive host of Echinococcus.