[Natural Water Chemistry Change in the Surface Water of Chengdu and Impact Factors].

To investigate the impact of megacities on the chemistry of surface waters, monthly sampling and monitoring were conducted in the Chengdu section of the Minjiang and Tuojiang River basin, corresponding to the upper reaches of the Yangtze River since the spring of 2019, including the influent and effluent water samples from 57 sewage treatment plants in Chengdu. All the samples were analyzed for major ions and other water chemistry parameters, and compared with the historical data of the Minjiang and Tuojiang River. The results showed that the Chengdu surface water still presented a natural chemistry with medium-low total dissolved solids(TDS), and calcium bicarbonate chemistry type, which is the natural consequence of the weathering of carbonate rocks in the basin effected by the weathering of silicates and evaporites. The natural water chemistry of the surface waters in Chengdu presented monthly variation, i.e.,the concentration of major ions and TDS was higher in the dry season compared to the wet season, reflecting the variations of point source. Spatially, the concentration of major ions and TDS downstream of the city was higher than those in the upper reaches, and the concentration in the tributary was higher than that in the mainstream, which may reflect urban influence. Further analyses, such as simulation calculations, indicated that urban activities were the major driving factor for the chemistry change in the surface waters in Chengdu, which is evidenced by the significant contribution of the sewage discharge to the elevated Cl- and Na+ and the ratio of hardness/alkalinity>1 from anthropogenic acid gas emissions. A comparison with the water chemistry of the Minjiang and Tuojiang River in the 1960s indicated that, the current Cl-/Na+ ratio has significantly increased, which has been evidenced by a salinization trend. As a megacity nearest to the source of the Yangtze River, the impact of Chengdu on the natural water chemistry of the Yangtze River system and its environmental effects deserves more attention.

[Distribution and Bioavability of Phosphorus in Surface Sediments in Megalopolis: A Case Study of Chengdu].

A total of 33 surface sediments were collected from rivers in Chengdu. The content of phosphorus species was measured with the chemical continuous extraction method (SMT) and in situ monitoring techniques (DGT). Multivariate statistical analysis was used to analyze the spatial distribution of phosphorus species in sediments. The release flux of DGT-P in sediments and their pore water was calculated in this study. It is helpful to understand the influence of sediment endogenous pollution and human activities on the environment. The results show that the phosphorus species have a spatial variability. The average content of TP in the surface sediments is 1132.41 mg·kg-1, which is higher than the background value of 365.00 mg·kg-1 in Chengdu. The Ca-P is the most dominant species, accounting for 70.58% of the TP on average. The study area is divided into three groups based on spatial clustering. Groups 1 and 3 show large differences of phosphorus morphological structures, while Group 2 is small. The contents of phosphorus in the surface sediment of Groups 1 and 3 are generally higher than those of Group 2. The DGT-P concentration has a good correlation with the soluble DTP concentration, bioavailable Fe/Al-P, and OP concentration, respectively. The DGT technology can be used as a fast, in situ, reliable method for measurements of the bioavailable content of sediments. The higher release fluxes of bioavailable phosphorus are N8, W11, and N2, which are 20.05, 17.13, and 14.79 mg·(m2·d)-1 respectively. The available phosphorus release capacity is closely related to human activities.

[Spectroscopy study on the selectively distinguishing cefalexin with the molecular imprinted polymer].

Molecular imprinted polymers of cefalexin (CFL) were prepared by non-covalent molecular imprinting technique in the present paper. Using CFL as template molecule, acrylamide (AM) or methacrylic acid (MAA) as functional monomer, ethylene dimethacrylate (EGDMA) as cross-linker, AIBN as initiator and methanol as porogen agent, different molecularly imprinted polymers (MIPs) of CFL were synthesized by bulk or suspension polymerization as synthetic method. The intermolecular action between AM and CFL was investigated by UV and IR spectrophotometric analysis, and the results indicated that polymerizing functional monomer AM could bond effectively with template molecule CFL. By using UV spectrophotometric analysis method, it was found that the MIP prepared with AM-EGDMA by bulk polymerization showed the highest binding capacity for CFL. Test of selective adsorption made clear that the MIP represented more excellent identification property to CFL than to cefadroxol and ampicillin. The MIPs were used as solid-phase extraction sorbent for extraction and enrichment of CFL in actual samples. And the recoveries for CFL extraction were found to be 99.3%-99.7% (n=3), demonstrating the feasibility of the prepared MIPs for CFL extraction.

Probing stereoselective inhibition of the acyl binding site of cholesterol esterase with four diastereomers of 2'-N-alpha-methylbenzylcarbamyl-1, 1'-bi-2-naphthol.

BACKGROUND: Recently there has been increased interest in pancreatic cholesterol esterase due to correlation between enzymatic activity in vivo and absorption of dietary cholesterol. Cholesterol esterase plays a role in digestive lipid absorption in the upper intestinal tract, though its role in cholesterol absorption in particular is controversial. Serine lipases, acetylcholinesterase, butyrylcholinesterase, and cholesterol esterase belong to a large family of proteins called the alpha/beta-hydrolase fold, and they share the same catalytic machinery as serine proteases in that they have an active site serine residue which, with a histidine and an aspartic or glutamic acid, forms a catalytic triad. The aim of this work is to study the stereoselectivity of the acyl chain binding site of the enzyme for four diastereomers of an inhibitor. RESULTS: Four diastereomers of 2'-N-alpha-methylbenzylcarbamyl-1, 1'-bi-2-naphthol (1) are synthesized from the condensation of R-(+)- or S-(-)-1, 1'-bi-2-naphthanol with R-(+)- or S-(-)-alpha-methylbenzyl isocyanate in the presence of a catalytic amount of pyridine in CH2Cl2. The [alpha]25D values for (1R, alphaR)-1, (1R, alphaS)-1, (1S, alphaR)-1, and (1S, alphaS)-1 are +40, +21, -21, and -41 degrees, respectively. All four diastereomers of inhibitors are characterized as pseudo substrate inhibitors of pancreatic cholesterol esterase. Values of the inhibition constant (Ki), the carbamylation constant (k2), and the bimolecular rate constant (ki) for these four diastereomeric inhibitors are investigated. The inhibitory potencies for these four diastereomers are in the descending order of (1R, alphaR)-1, (1R, alphaS)-1, (1S, alphaR)-1, and (1S, alphaS)-1. The k2 values for these four diastereomers are about the same. The enzyme stereoselectivity for the 1, 1'-bi-2-naphthyl moiety of the inhibitors (R > S, ca. 10 times) is the same as that for 2'-N-butylcarbamyl-1, 1'-bi-2-naphthol (2). The enzyme stereoselectivity for the alpha-methylbenzylcarbamyl moiety of the inhibitors is also R > S (2-3 times) due to the constraints in the acyl binding site. CONCLUSION: We are the first to report that the acyl chain binding site of cholesterol esterase shows stereoselectivity for the four diastereomers of 1.