Synthesis of Asp-based lactam cyclic peptides using an amide-bonded diaminodiacid to prevent aspartimide formation.

Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a ß-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cyclo[Lys9,Asp13] KIIIA7-14 and 1Y.

Comparison of inhibitory effects and mechanisms of lactonic sophorolipid on different pathogenic bacteria.

Crude sophorolipids (SLs) have been proven to perform varying degrees of inhibitory effects on different pathogenic bacteria. However, systematic comparative studies of pure lactonic sophorolipid (LSL) among different types of bacteria are few. In this study, the antibacterial effects and mechanisms of LSL on pathogenic bacteria of Staphylococcus aureus, Lactobacillus sp., Pseudomonas aeruginosa, and Escherichia coli were investigated. Bacteriostatic circle, antibacterial rate, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of LSL on different pathogenic bacteria were measured. Then, the antibacterial mechanisms of LSL on S. aureus and P. aeruginosa were explored using ultrastructural observation, cell membrane permeability analysis, intracellular ATP content determination, and extracellular UV absorption detection. With the minimum MIC and MBC values of 0.05 and 0.20 mg/ml, LSL exhibited the best inhibitory effect against S. aureus, followed by P. aeruginosa. LSL showed no significant inhibitory effect on E. coli and Lactobacillus sp. For both S. aureus and P. aeruginosa, LSL achieved bacteriostatic and bactericidal effects by destroying the cell wall, increasing the permeability of the cell membrane and leading to the flow out of intracellular contents. However, the action mode and action intensity of LSL on the cell wall and membrane of these two bacteria were significantly different. LSL had a greater influence on the cell membrane of S. aureus by "leaking," while it exhibited a stronger effect on the cell wall of P. aeruginosa by "blasting." These results contributed to a better understanding of the relationship between LSL and different bacterial cell structures, further suggesting the conclusion that LSL might be used for the targeted treatment of special pathogenic bacteria.

Chemoselective tandem SN2'/SN2''/inter- or intramolecular Diels-Alder reaction of γ-vinyl MBH carbonates with phenols and o-hydroxychalcones.

An unprecedented consecutive SN2'/SN2'' addition of phenol to γ-vinyl MBH carbonate forms a reactive diene intermediate, followed by a dimerization/elimination process to give functionalized exocyclohexenes with excellent chemoselectivity. When using o-hydroxychalcones as pronucleophiles, an SN2'/SN2''/intramolecular Diels-Alder reaction sequence occurs, selectively producing a series of pharmaceutically intriguing tricyclic chromane derivatives with good diastereoselectivity. The good nucleophilicity and fair nucleofugicity exhibited by phenoxy anion play a pivotal role in the SN2'' addition step.

P(NMe2)3 mediated cyclopropanation of α-methylene-ß-lactams for rapid syntheses of spirocyclopropyl ß-lactams.

An expedient cyclopropanation of α-methylene-ß-lactams with α-ketoesters mediated by P(NMe2)3 has been developed. This reaction enables rapid access to a series of functionalized spirocyclopropyl ß-lactams in good yields from bench-stable starting materials under mild conditions. The experimental results indicated that the C3-substituent of the α-methylene-ß-lactam not only significantly impacted the reaction efficiency and stereochemistry but also played a pivotal role in determining the chemoselectivity of the reaction.

Mutant breeding of Starmerella bombicola by atmospheric and room-temperature plasma (ARTP) for improved production of specific or total sophorolipids.

To enhance specific or total sophorolipids (SLs) production by Starmerella bombicola for specific application, mutant library consisting of 106 mutants from 7 batches was constructed via atmospheric and room-temperature plasma (ARTP). When compared to the wild strain, 11, 36 and 12 mutants performed increases over 30% in lactonic, acidic or total SLs production. Genetic stability investigation showed that 8, 7, and 4 mutants could maintain the improved SLs production capacity. Mutants of A6-9 and A2-8 were selected out for enhanced specific SLs and total SLs production in fed-batch cultivation in flask. Without optimization, A6-9 obtained the highest reported lactonic SLs production of 51.95 g/l and A2-8 performed comparable acidic and total SLs production of 68.75 g/l and 100.33 g/l with all the reported stains. The structural composition of the obtained SLs was analyzed by HPLC and LC/MS, and the results confirmed the enhancement of SLs and certain SL components. These mutants would be important in industrial applications because the production and purification costs of SLs could be greatly reduced. Besides, the acquisition of these mutants also provided materials for the investigation of regulation mechanism of SLs biosynthesis for further genetic engineering of S. bombicola. Furthermore, critical micelle concentration (CMC), minimum surface tension (STmin) and hydrophilic-lipophilic balance (HLB) of the SLs obtained from the wild and mutant strains were also examined and compared. These results demonstrated the feasibility of obtaining SLs with different properties from different strains and the high efficiency of mutation breeding of S. bombicola by ARTP.

Degradation and Transformation of Lignin by a Fungus Aspergillus Flavus Strain F-1.

BACKGROUND: Lignin is the largest natural aromatic polymer in nature and is also a unique aromatic-based biopolymer, accounting for nearly 30% of the earth's organic carbon. Generally, lignin is regarded as waste and is mainly used as a low- value fuel that is burned to generate heat and energy to solve the problem of biomass waste; for this obstacle of lignin, highly efficient biodegradation plays a critical role in developing an environmentally friendly technique for lignin biotransformation. OBJECTIVES: This study intends to isolate and purify several microbial strains from nature. It also explores how their lignin degradation is able to enhance the biodegradation and recycling of biomass and the reclamation of lignin in wastewater from pulp and paper mills. MATERIALS AND METHODS: Lignin-degrading microbial strains were isolated from soil using medium containing sodium lignosulphonate as the sole carbon source. They were then screened by aniline blue and guaiacol plate, and then the best strain was chosen and identified. The conventional one-factor method was used to optimize various parameters that affect lignin's degradation ability. RESULTS: The strain possessing the highest lignin biodegradation ability was identified and denominated as Aspergillus Flavus F-1. After optimization, the maximum degradation rate of lignin, 44.6% within 3 days, was obtained at pH 7.0, 30 ℃, 2.5 g·L-1 ammonium sulfate, 2 g·L-1 lignin and 0.5 g·L-1 glucose. The results show the LiP and Lac secreted from Aspergillus Flavus F-1 played the main role in the degradation of lignin. CONCLUSION: One microbial strain, Aspergillus Flavus F-1, was successfully isolated with a lignin-degrading ability that can cut the lignin into fragments. This provides a promising candidate for the transformation and utilization of crop waste biomass for various industrial purposes.

The complete chloroplast genome sequence of Red Asparagus Lettuce (Lactuca sativa var. asparagine L. red) (Asteraceae), endemic to China.

Red Asparagus Lettuce (Lactuca sativa var. asparagina L. red) is an endemic vegetable species to China. The complete chloroplast (cp) genome of it is 152,744 bp in size and comprises a pair of inverted repeat regions of 25,033 bp each, a large single-copy (LSC) region of 84,103 bp and a small single-copy (SSC) region of 18,575 bp. A total of 131 genes were annotated in the cp genome, including 86 protein-coding genes, 8 ribosomal RNA genes, and 37 transfer RNA genes. The overall GC content of the Red Asparagus Lettuce cp genome was 37.55%. Phylogenetic analysis indicated that Red Asparagus Lettuce was more phylogenetically related to L. sativa.

Revealing differences in metabolic flux distributions between a mutant strain and its parent strain Gluconacetobacter xylinus CGMCC 2955.

A better understanding of metabolic fluxes is important for manipulating microbial metabolism toward desired end products, or away from undesirable by-products. A mutant strain, Gluconacetobacter xylinus AX2-16, was obtained by combined chemical mutation of the parent strain (G. xylinus CGMCC 2955) using DEC (diethyl sulfate) and LiCl. The highest bacterial cellulose production for this mutant was obtained at about 11.75 g/L, which was an increase of 62% compared with that by the parent strain. In contrast, gluconic acid (the main byproduct) concentration was only 5.71 g/L for mutant strain, which was 55.7% lower than that of parent strain. Metabolic flux analysis indicated that 40.1% of the carbon source was transformed to bacterial cellulose in mutant strain, compared with 24.2% for parent strain. Only 32.7% and 4.0% of the carbon source were converted into gluconic acid and acetic acid in mutant strain, compared with 58.5% and 9.5% of that in parent strain. In addition, a higher flux of tricarboxylic acid (TCA) cycle was obtained in mutant strain (57.0%) compared with parent strain (17.0%). It was also indicated from the flux analysis that more ATP was produced in mutant strain from pentose phosphate pathway (PPP) and TCA cycle. The enzymatic activity of succinate dehydrogenase (SDH), which is one of the key enzymes in TCA cycle, was 1.65-fold higher in mutant strain than that in parent strain at the end of culture. It was further validated by the measurement of ATPase that 3.53-6.41 fold higher enzymatic activity was obtained from mutant strain compared with parent strain.

One-step fermentation of pretreated rice straw producing microbial oil by a novel strain of Mortierella elongata PFY.

A fungus strain producing microbial oils utilizing pretreated rice straw was isolated from soil. This strain was identified as Mortierella elongata PFY based on the morphology and internal transcribed spacer sequence. Using pretreated rice straw as substrate, the average yield of total lipids was 7.07% after 7 days fermentation. The GC-MS detection demonstrated that the lipids were composed of saturated fatty acids and polyunsaturated fatty acids. This work presents one new way to make the waste biomass (rice straw) valuable.

The co-transduction of Nurr1 and Brn4 genes induces the differentiation of neural stem cells into dopaminergic neurons.

Fetal brain tissue can be used in cell replacement therapy for PD (Parkinson's disease), but there is a poor donor supply of this tissue. NSCs (neural stem cells) may overcome this problem as they can be isolated and expanded in vitro. However, the usage of NSCs is limited because the differentiation of NSCs into specific dopaminergic neurons has proven difficult. In the present study, we investigated the effect of Nurr1 (nuclear receptor related factor 1), a transcription factor specific for the development and maintenance of the midbrain dopaminergic neurons on inducing the differentiation of NSCs into TH (tyrosine hydroxylase) immunoreactive dopaminergic neurons. Nonetheless, these cells exhibited an immature neuronal morphology with small cell bodies and short neurite processes, and they seldom expressed DAT (dopamine transporter), a late marker of mature dopaminergic neurons. However, forced co-expression of Nurr1 with Brn4, a member of the POU domain family of transcription factors, caused immature Nurr1-induced dopaminergic neurons to differentiate into morphologically and phenotypically more mature neurons. Thus the enriched generation of mature dopaminergic neurons by forced expression of Nurr1 with Brn4 may be of future importance in NSC-based cell replacement therapy for PD.

Structure and saccharification of rice straw pretreated with sulfur trioxide micro-thermal explosion collaborative dilutes alkali.

In this paper, a sulfur trioxide collaborative dilutes alkali method has been developed to pre-treat rice straw and it has been studied that the pre-treated rice straw structure affected the saccharification of the rice straw hydrolyzed by cellulose enzymatic hydrolysis. The results show that the reaction of the sulfur trioxide with rice straw resulted in the internal micro-thermal explosion, and the saccharification rate was 91% based on the pretreated rice straw with sulfur trioxide for 4h following 1% w/v NaOH treatment for 7h at 50°C.

Effects of Brn-4 on the neuronal differentiation of neural stem cells derived from rat midbrain.

NSCs (neural stem cells) provide a powerful research tool for the design and discovery of new approaches to cell replacement therapy during brain repair. However, the usefulness of this tool has been particularly obstructed by limited neuronal differentiation of NSCs. Brn-4, a member of the POU domain family of transcription factors, has been previously implicated in the development of neurons by expression analysis. Here, we directly investigated the effects of Brn-4 on the neuronal differentiation and development of NSCs derived from the E13 rat midbrain. We found that Brn-4 knockdown in NSCs resulted in a significant decrease of MAP-2-positive neurons with immature morphology. Overexpression of Brn-4 in NSCs markedly increased the production and maturation of newborn neurons. These results suggest that Brn-4 has a critical role in the neuronal differentiation of mesencephalic NSCs and the maturation of newborn neurons. Brn-4 may be utilized to manipulate NSCs for gene and cell therapy of several neurological diseases.

[Effect of blocking transforming growth factor beta signalling on culture-activated rat hepatic stellate cells].

OBJECTIVE: To study the effects of blocking transforming growth factor beta (TGF-beta) signalling on culture-activated rat hepatic stellate cells (HSCs). METHODS: After cultured in plastic dish for two days, HSCs were infected with adenovirus vector AdT beta-ExR or AdLacZ (control) at 10 multiplicity of infection (MOI) and incubated for four days. The expression of type I collagen, alpha-smooth muscle actin (alpha-SMA) and the proliferation of HSCs were analyzed by ELISA, western blot, immunocytochemistry and BrdU uptake respectively. RESULTS: The expression level of type I collagen in HSCs infected with AdT beta-ExR was 42.99% of that in HSCs infected with AdLacZ (q = 9.100, P < 0.001). The expression of alpha-SMA in HSCs infected with AdTbeta-ExR was also inhibited evidently. But the BrdU uptake in HSCs infected with AdLacZ was 49.24% of that in HSCs infected with AdTbeta-ExR (q = 7.835, P < 0.001). CONCLUSIONS: The blockade of TGF-beta signalling in cultured rat HSCs can inhibit their activation significantly, but promote their proliferation.