Sensitive detection of mercury and copper ions by fluorescent DNA/Ag nanoclusters in guanine-rich DNA hybridization

In this work, we designed a new fluorescent oligonucleotides-stabilized silver nanoclusters (DNA/AgNCs) probe for sensitive detection of mercury and copper ions. This probe contains two tailored DNA sequence. One is a signal probe contains a cytosine-rich sequence template for AgNCs synthesis and link sequence at both ends. The other is a guanine-rich sequence for signal enhancement and link sequence complementary to the link sequence of the signal probe. After hybridization, the fluorescence of hybridized double-strand DNA/AgNCs is 200-fold enhanced based on the fluorescence enhancement effect of DNA/AgNCs in proximity of guanine-rich DNA sequence. The double-strand DNA/AgNCs probe is brighter and stable than that of single-strand DNA/AgNCs, and more importantly, can be used as novel fluorescent probes for detecting mercury and copper ions. Mercury and copper ions in the range of 6.0-160.0 and 6-240 nM, can be linearly detected with the detection limits of 2.1 and 3.4 nM, respectively. Our results indicated that the analytical parameters of the method for mercury and copper ions detection are much better than which using a single-strand DNA/AgNCs.

Analysis of synonymous codon usage in FAD7 genes from different plant species

In this study, the codon bias of the FAD7 genes among 10 different plant species was analyzed to identify general patterns of codon usage in the FAD7 genes. Our results showed that U-ended or A-ended codons were preferentially used in FAD7 for dicots, whereas G-ended or C-ended codons were preferentially used in FAD7 for monocots. An ENC-plot showed that some other factors may influence the codon usage of FAD7, except mutation bias in plant species. A correlation analysis between the codon adaptation index and GC or GC3s contents demonstrated that the codon usage bias of the FAD7 gene in plant species could be influenced by the gene expression level. The cluster analysis of relative synonymous codon usage values and phylogenetic trees of protein sequences for FAD7 genes confirm that the codon preference of FAD7 is influenced by genetic relationships. Moreover, Arabidopsis thaliana and Nicotiana tabacum were predicted to be the most appropriate expression hosts for the FAD7 genes from dicots, and Zea mays may be suitable for the expression of the FAD7 genes from monocots. Our results provide useful insights into the evolutionary relationships of plant species.

Sequencing and transcriptional analysis of the biosynthesis gene cluster of abscisic acid-producing Botrytis cinerea

Botrytis cinerea is a model species with great importance as a pathogen of plants and has become used for biotechnological production of ABA. The ABA cluster of B. cinerea is composed of an open reading frame without significant similarities (bcaba3), followed by the genes (bcaba1 and bcaba2) encoding P450 monooxygenases and a gene probably coding for a short-chain dehydrogenase/reductase (bcaba4). In B. cinerea ATCC58025, targeted inactivation of the genes in the cluster suggested at least three genes responsible for the hydroxylation at carbon atom C-1' and C-4' or oxidation at C-4' of ABA. Our group has identified an ABA-overproducing strain, B. cinerea TB-3-H8. To differentiate TB-3-H8 from other B. cinerea strains with the functional ABA cluster, the DNA sequence of the 12.11-kb region containing the cluster of B. cinerea TB-3-H8 was determined. Full-length cDNAs were also isolated for bcaba1, bcaba2, bcaba3 and bcaba4 from B. cinerea TB-3-H8. Sequence comparison of the four genes and their flanking regions respectively derived from B. cinerea TB-3-H8, B05.10 and T4 revealed that major variations were located in intergenic sequences. In B. cinerea TB-3-H8, the expression profiles of the four function genes under ABA high-yield conditions were also analyzed by real-time PCR.

A new C₁₉-diterpenoid alkaloid from the roots of Aconitum duclouxii

A new C₁₉-diterpenoid alkaloid, ducloudine F (1), was obtained from the roots of Aconitum duclouxii, along with eight known alkaloids (2-9) isolated from this species for the first time. Their structures were established on the basis of extensive spectroscopic analyses. The antimicrobial activities of these compounds were investigated.

Three new diterpenoid alkaloids from the roots of Aconitum duclouxii

Three new C₁₉-diterpenoid alkaloids, ducloudines C (1), D (2), and E (3), were isolated from the roots of Aconitum duclouxii. Their structures were established on the basis of extensive spectroscopic analyses. Ducloudine C (1) is the first aconitine-type C₁₉-diterpenoid alkaloid with a C=O group at C-3 and a C=C bond between C-1 and C-2. All compounds were tested for their biological activities against one pathogenic fungi and two pathogenic bacteria.

Medelamine C, a new omega-hydroxy alkylamine derivative from endophytic Streptomyces sp. YIM 66142

A new alkylamine derivative and a common fatty acid were isolated from Streptomyces sp. YIM 66142. On the basis of spectral data, including HRMS, NMR and 2D NMR, their structures were determined as medelamine C (1) and isomyristic acid (2). The omega-hydroxyl group in structure 1 is rare in a natural alkylamine. The possible biosynthetic pathway in the genus Streptomyces from isomyristic acid (2) to medelamines is proposed. Compound 1 showed no obvious cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, SW480 cell lines. The omega-hydroxyl and the acetyl at NH in compound 1 decreased its cytotoxicity in comparison with that of medelamine.

Medelamine C, A New ω-Hydroxy Alkylamine Derivative from Endophytic Streptomyces sp. YIM 66142

A new alkylamine derivative and a common fatty acid were isolated from Streptomyces sp. YIM 66142. On the basis of spectral data, including HRMS, NMR and 2D NMR, their structures were determined as medelamine C (1) and isomyristic acid (2). The ω-hydroxyl group in structure 1 is rare in a natural alkylamine. The possible biosynthetic pathway in the genus Streptomyces from isomyristic acid (2) to medelamines is proposed. Compound 1 showed no obvious cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, SW480 cell lines. The ω-hydroxyl and the acetyl at NH in compound 1 decreased its cytotoxicity in comparison with that of medelamine.

Synthesis and anticancer activity of glucosylated podophyllotoxin derivatives linked via 4β-triazole rings

A series of 4β-triazole-linked glucose podophyllotoxin conjugates have been designed and synthesized by employing a click chemistry approach. All the compounds were evaluated for their anticancer activity against a panel of five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, SW480) using MTT assays. Most of these triazole derivatives have good anticancer activity. Among them, compound 35 showed the highest potency against all five cancer cell lines tested, with IC₅₀ values ranging from 0.59 to 2.90 μM, which is significantly more active than the drug etoposide currently in clinical use. Structure-activity relationship analysis reveals that the acyl substitution on the glucose residue, the length of oligoethylene glycol linker, and the 4'-demethylation of podophyllotoxin scaffold can significantly affect the potency of the anticancer activity. Most notably, derivatives with a perbutyrylated glucose residue show much higher activity than their counterparts with either a free glucose or a peracetylated glucose residue.

Catalytic formation of silver nanoparticles by bovine serum albumin protected-silver nanoclusters and its application for colorimetric detection of ascorbic acid

We established a simple spectrophotometric and colorimetric method for detection of ascorbic acid based on the growth of silver nanoparticles in bovine serum albumin protected-silver nanoclusters (BSA-AgNCs) and Ag+ mixture. Due to the catalysis of BSA-AgNCs, ascorbic acid could reduce Ag+ to silver nanoparticles (NPs) at room temperature. The color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. The absorbance changes at 420 nm had a good relationship with ascorbic acid concentration. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 μM, with the corresponding limits of determination (3σ) of 0.16 μM.

Sesquiterpenes and an intermediate 1alpha, 6beta, 11-eudesmanetriol in the biosynthesis of geosmin from Streptomyces sp

One new sesquiterpene was isolated from the fermentation broth of Streptomyces sp. and the structure was elucidated by spectral analysis as caryolane-1, 6beta-diol (1). An intermediate 1alpha, 6beta, 11-eudesmanetriol (2) in the biosynthesis of geosmin was also found in this strain which proved sequence for the reactions, especially bicyclization preceding dealkylation.

Affinity chromatography of trypsin using chitosan as ligand support

Chitosan beads were prepared for use as affinity adsorbent carrier. The affinity ligand, chicken ovomucoid, was immobilized on the chitosan via a cross-linker, glutaraldehyde. The results showed that 60 mg chicken ovomucoid could be immobilized on l g chitosan, and the maximum binding capacity for trypsin was about 8.10(4) U/g dry adsorbent. The procedure for preparing the chitosan-based affinity adsorbents was much safer and simpler than when a Sepharose-based matrix was the support. Columns packed with the affinity adsorbents were employed for trypsin chromatography. The experimental results revealed that the affinity adsorbents possessed good mechanical strength and storage stability and could be also operated repeatedly. Chitosan was suitable for use as an affinity adsorbent support for laboratory-scale and large-scale purification.

A new kind of immobilized lipase in organic solvent and its structure model

In this paper, we used Ca-alginate gel beads coated with polyetheneimine and glutaraldehyde to adsorb Expansum penicillium lipase. The immobilized lipase catalyzed esterification of 1-dodecanol with dodecanoic acid in benzene. The results show that when the concentration of Ca-alginate, polyetheneimine (PEI) and glutaraldehyde is 1%, 6% and 1%, respectively, the activity of the immobilized lipase and the amount of adsorbed protein are the highest. The immobilized lipase is better than the SDS-immobilized lipase. The activity of the immobilized lipase connected by glutaraldehyde is higher than the activity of that without glutaraldehyde. The initial rate of the immobilized lipase and lyophilized lipase powder is 5.9 x 10(2) nmol/min.mgpr and 2.8 x 10(1) nmol/min.mgpr, respectively. After the immobilized lipase catalyzed the esterification reaction at 37 degrees C for about 12 hours, 93.3% of 1-dodecanol was converted to ester, but for lyophilized lipase powder, only 17.5% converted. Based on all above results, we have presumed and explained the structure of this kind of immobilized lipase.