Biphenyls from aerial parts of Ribes takare

Three new biphenyls, 4,7,8-trimethoxy-2,3-methylenedioxydibenzofuran (1), 7-hydroxy-4,8dimethoxy-2,3-methylenedioxydibenzofuran (2), and 3',5-dimethoxy-3,4-methylenedioxybiphenyl (3), along with eighteen known compounds (4-21) were isolated from the aerial part of Ribes takare D. Don. Their structures were elucidated on the basis of spectroscopic data. Compound 1 and compound 2 showed mild alpha-glucosidase inhibitory activity. (C) 2013 Guo-You Li and Dong-Mei Fang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved

Two New Polyketide Metabolites Isolated from Paraconiothyrium brasiliense

Two new polyketide metabolites, named ethyl 8-hydroxy-9-oxo-9H-xanthene-1-carboxylate (1) and 1,8-dihydroxy-2-(1-hydroxyethyl)anthracene-9,10-dione (2), along with six known compounds, were isolated from the fungus Paraconiothyrium brasiliense. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR experiments

Effect of microtopography on soil respiration in an alpine meadow of the Qinghai-Tibetan plateau

Soil respiration is an important component of terrestrial carbon cycling and is sensitive to environmental change. Most previous studies focus on the effect of soil temperature and moisture on soil respiration, whereas the impact of spatial heterogeneity (e.g., microtopography) is seldom studied. To test the impact of microtopography on soil respiration, we performed a field investigation to examine soil respiration, soil temperature, soil water content, soil total porosity, soil organic content, and plant biomass at a hummock site (composed of grass hummocks and inter-hummock areas) and an adjacent flat meadow of the Qinghai-Tibetan plateau. Similar seasonal dynamics of soil respiration in the grass hummocks, inter-hummock areas, and flat meadow were found in the alpine meadow of the Qinghai-Tibetan plateau. However, soil respiration of the grass hummocks was 79.3% and 413.9% higher than that of the flat meadow during the growing (April, June, August) and non-growing seasons (October, December, February), respectively. Although there was no difference in soil respiration between the inter-hummock areas and the flat meadow during the non-growing season, soil respiration was 42.5% higher at the inter-hummock areas than the flat meadow during growing season. Larger soil porosity, greater surface area, and more substrate supply, but not more root growth, likely contributed to the higher soil respiration of grass hummocks. Our findings suggest that the impact of spatial heterogeneity on soil respiration should be taken into consideration to facilitate the accurate estimation of soil carbon fluxes at ecosystem and regional scales

A general solution for opening double-stranded DNA for isothermal amplification

Nucleic acid amplification is the core technology of molecular biology and genetic engineering. Various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). However, most of these methods can only detect single stranded nucleic acid. Herein, we put forward a simple solution for opening double-stranded DNA for isothermal detection methods. The strategy employs recombination protein from E. coli (RecA) to form nucleoprotein complex with single-stranded DNA, which could scan double-stranded template for homologous sites. Then, the nucleoprotein can invade the double-stranded template to form heteroduplex in the presence of ATP, resulting in the strand exchange. The ATP regeneration system could be eliminated by using high concentration of ATP, and the 3'-OH terminal of the invasion strand can be recognized by other DNA modifying enzymes such as DNA polymerase or DNA ligase. Moreover, dATP was found to be a better cofactor for RecA, which make the system more compatible to DNA polymerase. The method described here is a general solution to open dsDNA, serving as a platform to develop more isothermal nucleic acids detection methods for real DNA samples based on it

New Orsellinic Acid Esters from Fungus Chaetomium globosporum

Seven new orsellinic acid esters, 1-7, and four known compounds were isolated from the solid, fermented rice culture of Chaetomium globosporum (cib-132). Their structures were elucidated by 1D- and 2D-NMR spectra, and the relative configuration of compound 1 was determined by X-ray crystallographic analysis

Selective tumor cell death induced by irradiated riboflavin through recognizing DNA G-T mismatch

Riboflavin (vitamin B2) has been thought to be a promising antitumoral agent in photodynamic therapy, though the further application of the method was limited by the unclear molecular mechanism. Our work reveals that riboflavin was able to recognize G-T mismatch specifically and induce singlestrand breaks in duplex DNA targets efficiently under irradiation. In the presence of riboflavin, the photo-irradiation could induce the death of tumor cells that are defective in mismatch repair system selectively, highlighting the G-T mismatch as potential drug target for tumor cells. Moreover, riboflavin is a promising leading compound for further drug design due to its inherent specific recognition of the G-T mismatch