Chao Qi

Properties of xyloglucan hydrogel as the biomedical sustained-release carriers

This study introduces an easy method of preparing xyloglucan hydrogel from xyloglucan, which is purified from tamarind seed gum. Xyloglucan hydrogel was prepared in 2xa0wt% solution by treating with β-galactosidase. Physical and chemical properties (molecular mass, size and viscosity) of xyloglucan hydrogel and xyloglucan solution were tested for a comparison. Experiments of drug release in vitro and in vivo were operated to investigate the potentialities of xyloglucan hydrogel as the biomedical sustained-release carriers for drug delivery system.

Preparation of a Novel Organoselenium Compound and Its Anticancer Effects on Cervical Cancer Cell Line HeLa

This study aims at developing new organoselenium compounds with good anticancer ability and low biotoxicity. Sucrose selenious ester (sucrose-Se) was synthesized by the reaction between sucrose and selenium oxychloride. MTT assay showed that sucrose-Se effectively inhibited the proliferation of cervical cancer cell line HeLa in a dose-dependent manner without cytostatic influence on human normal liver cell line HL-7702. Morphological observation and agarose gel electrophoresis demonstrated that sucrose-Se induced apoptosis to HeLa cells. In addition, sucrose-Se was able to inhibit proliferation of bladder carcinoma cell line 5637, human malignant melanoma cell line A375, and gastric carcinoma cell line MGC-803. Median lethal dose of sucrose-Se and sodium selenite was 290.0 and 13.1xa0ppm, respectively, in the acute toxicity test on mice. In conclusion, sucrose-Se has potential in cancer chemoprevention due its apoptosis induction capacity and low biotoxicity.

Intracellular Delivery of Mitomycin C with Targeted Polysaccharide Conjugates Against Multidrug Resistance

Intracellular targeted conjugates of xyloglucan and mitomycin C (MMC) were synthesized with a lysosomally degradable peptide spacer and galactosamine, a terminal moiety that can be used to target polymeric conjugates to hepatoma. The content of the MMC was about 3.5% (mol) in this conjugate. In an in vitro cytotoxicity experiment, the targeted prodrugs have higher cytotoxicity than free MMC against the drug resistant HepG2 cells. In a human tumor xenograft nude mouse model, the targeted prodrugs generated higher therapeutic effect than non-targeted prodrugs or free MMC. Together, these results suggest that targeted prodrugs, which have improved transfer efficiency and hepatocyte specificity, may be useful for the reversion of drug resistant HepG2 cells.

Determination of glutathione in apoptotic SMMC-7221 cells induced by xylitol selenite using capillary electrophoresis

ObjectiveTo determine the glutathione (GSH) content in a human hepatoma cell line (SMMC-7221) treated with xylitol/selenite, providing a part of an investigation of its anti-cancer mechanisms.ResultsThe nuclei of SMMC-7221 cells were stained with Hoechst 33258 in an apoptosis assay, and their morphology subsequently changed from circular to crescent shape. The calibration curve (r2xa0=xa00.992) was established, and GSH content markedly decreased after treated with 0.5 and 1xa0mg xylitol/selenite l−1 for 12, 36 and 60xa0h (12xa0h: from 95.57xa0±xa019.57 to 29.09xa0±xa07.74 and 24.27xa0±xa011.15; 36xa0h: from 70.73xa0±xa011.35 to 19.54xa0±xa06.39 and 9.35xa0±xa06.69; 60xa0h: from 72.63xa0±xa016.94 to 7.432xa0±xa03.84 and 0). The depletion rate of GSH was more related to the concentration of xylitol/selenite than the treatment time (from 69.95xa0±xa01.87 to 100xa0% vs. 0.22xa0±xa00.2 to 100xa0%).ConclusionsXylitol/selenite is a promising anti-cancer drug to induce apoptosis in SMMC-7221 cells. It may regulate the apoptosis through the co-action of multiple mechanisms related to GSH depletion.

Crystal structure of the mismatch-specific thymine glycosylase domain of human methyl-CpG-binding protein MBD4.

Methyl-CpG (mCpG) binding domain protein 4 (MBD4) is a member of mammalian DNA glycosylase superfamily. It contains an amino-proximal methyl-CpG binding domain (MBD) and a C-terminal mismatch-specific glycosylase domain, which is an important molecule believed to be involved in maintaining of genome stability. Herein, we determined the crystal structure of C-terminal glycosylase domain of human MBD4. And the structural alignments of other helix-hairpin-helix (HhH) DNA glycosylases show that the human MBD4 glycosylase domain has the similar active site and the catalytic mechanisms as others. But the different residues in the N-terminal of domain result in the change of charge distribution on the surface of the protein, which suggest the different roles that may relate some diseases.

Preparation of two organoselenium compounds and their induction of apoptosis to SMMC-7221 cells.

Two organoselenium compounds: xylitol selenious ester (xylitol-Se) and sucrose selenious ester (sucrose-Se) were synthesized, and their molecular structures were characterized in this study. In MTT assay, xylitol-Se and sucrose-Se showed cytostatic effects on human hepatocellular carcinoma cells SMMC-7221 in a dose-dependent manner, whereas they had no negative influences on the proliferation of human normal hepatic cells HL-7702 in the concentration range from 0.15 to 1.2xa0ppm Se. Morphological observation, agarose gel electrophoresis, and caspase-3 assay indicated that xylitol-Se and sucrose-Se induced mitochondrial apoptosis to SMMC-7221 cells, which is supported by the depletion of mitochondrial membrane potential and suppression of caspase-3 activity, indicating their ability of inducing apoptosis to cancer cells and great potentials as anticancer drugs.

Dynamic sieving capillary electrophoresis analysis of xylitol selenite-induced apoptosis in SMMC-7221 cells

DNA ladder fragments, regarded as a biochemical hallmark of apoptosis, have been separated quickly and successfully by capillary electrophoresis. Inter-nucleosomal DNA fragmentations induced by xylitol selenite were determined for the first time, while hydroxypropylmethylcellulose (HPMC) was served as the sieving matrix in dynamic sieving capillary electrophoresis. The calibration curve (r2xa0=xa00.991) was established and multiples of two different nucleosomes (140 and 180xa0bp) were formed in the presence of xylitol selenite. Selenium compounds inhibited carcinogenesis in animal models, SMMC-7221 cells and several other cells by increasing apoptosis. The described method was useful in elucidating the anticancer activities of xylitol selenite and other selenium compounds, which was more effective to detect small fragments than slab gel electrophoresis.

Identification and characterization of a chitin deacetylase from a metagenomic library of deep-sea sediments of the Arctic Ocean.

BACKGROUNDnThe chemical and biological compositions of deep-sea sediments are interesting because of the underexplored diversity when it comes to bioprospecting. The special geographical location and climates make Arctic Ocean a unique ocean area containing an abundance of microbial resources.nnnMETHODSnA metagenomic library was constructed based on the deep-sea sediments of Arctic Ocean. Part of insertion fragments of this library were sequenced. A chitin deacetylase gene, cdaYJ, was identified and characterized.nnnRESULTSnA metagenomic library with 2750 clones was obtained and ten clones were sequenced. Results revealed several interesting genes, including a chitin deacetylase coding sequence, cdaYJ. The CdaYJ is homologous to some known chitin deacetylases and contains conserved chitin deacetylase active sites. CdaYJ protein exhibits a long N-terminal and a relative short C-terminal. Phylogenetic analysis revealed that CdaYJ showed highest homology to CDAs from Alphaproteobacteria. The cdaYJ gene was subcloned into the pET-28a vector and the recombinant CdaYJ (rCdaYJ) was expressed in Escherichia coli BL21 (DE3). rCdaYJ showed a molecular weight of 43kDa, and exhibited deacetylation activity by using p-nitroacetanilide as substrate. The optimal pH and temperature of rCdaYJ were tested as pH7.4 and 28°C, respectively.nnnCONCLUSIONSnThe construction of metagenomic library of the Arctic deep-sea sediments provides us an opportunity to look into the microbial communities and exploiting valuable gene resources. A chitin deacetylase CdaYJ was identified from the library. It showed highest deacetylation activity under slight alkaline and low temperature conditions. CdaYJ might be a candidate chitin deacetylase that possesses industrial and pharmaceutical potentials.

Identification of Sare0718 As an Alanine-Activating Adenylation Domain in Marine Actinomycete Salinispora arenicola CNS-205

Background Amino acid adenylation domains (A domains) are critical enzymes that dictate the identity of the amino acid building blocks to be incorporated during nonribosomal peptide (NRP) biosynthesis. NRPs represent a large group of valuable natural products that are widely applied in medicine, agriculture, and biochemical research. Salinispora arenicola CNS-205 is a representative strain of the first discovered obligate marine actinomycete genus, whose genome harbors a large number of cryptic secondary metabolite gene clusters. Methodology/Principal Findings In order to investigate cryptic NRP-related metabolites in S. arenicola CNS-205, we cloned and identified the putative gene sare0718 annotated “amino acid adenylation domain”. Firstly, the general features and possible functions of sare0718 were predicted by bioinformatics analysis, which suggested that Sare0718 is a soluble protein with an AMP-binding domain contained in the sequence and its cognate substrate is L-Val. Then, a GST-tagged fusion protein was expressed and purified to further explore the exact adenylation activity of Sare0718 in vitro. By a newly mentioned nonradioactive malachite green colorimetric assay, we found that L-Ala but not L-Val is the actual activated amino acid substrate and the basic kinetic parameters of Sare0718 for it are Kmu200a=u200a0.1164±0.0159 (mM), Vmaxu200a=u200a3.1484±0.1278 (µM/min), kcatu200a=u200a12.5936±0.5112 (min−1). Conclusions/Significance By revealing the biochemical role of sare0718 gene, we identified an alanine-activating adenylation domain in marine actinomycete Salinispora arenicola CNS-205, which would provide useful information for next isolation and function elucidation of the whole cryptic nonribosomal peptide synthetase (NRPS)-related gene cluster covering Sare0718. And meanwhile, this work also enriched the biochemical data of A domain substrate specificity in newly discovered marine actinomycete NRPS system, which bioinformatics prediction will largely depend on.

Structure and Function of CW Domain Containing Proteins.

The CW domain is a zinc binding domain, composed of approximately 50- 60 amino acid residues with four conserved cysteine (C) and two to four conserved tryptophan (W) residues. The members of the superfamily of CW domain containing proteins, comprised of 12 different eukaryotic nuclear protein families, are extensively expressed in vertebrates, vertebrate-infecting parasites and higher plants, where they are often involved in chromatin remodeling, methylation recognition, epigenetic regulation and early embryonic development. Since the first CW domain structure was determined 5 years ago, structures of five CW domains have been solved so far. In this review, we will discuss these recent advances in understanding the identification, definition, structure, and functions of the CW domain containing proteins.