Copper-catalyzed arylation of biguanide derivatives via C-N cross-coupling reactions.

An efficient copper-catalyzed cross-coupling reaction of biguanide hydrochloride derivatives with both aryl iodides and bromides under mild conditions has been developed. The reaction occurred in good yields and tolerated aryl halides containing functionalities such as nitriles, sulfonamides, ethers, and halogens. Alkyl and cyclic substituted biguanidines were also well tolerated.

Primulinasilaniae sp. nov. (Gesneriaceae) from the limestone area of Guizhou Province, China.

Primulinasilaniae X.X.Bai & F.Wen, a new species of Primulina Hance (Gesneriaceae) from the limestone area of Wangmo County, Guizhou Province, is described and illustrated. The new species is similar to P.spiradiclioides Z.B.Xin & F.Wen, but can be easily distinguished from the latter by a combination of characteristics, especially in the lateral veins of its leaf and floral shape and tube. At present, three populations in one locality of this new taxon were found, totaling about 600 mature individuals. According to the IUCN Red List Categories and Criteria (Version 3.1), the species is provisionally assessed as Vulnerable [VU D1].

Determination of urinary adenosine using resonance light scattering of gold nanoparticles modified structure-switching aptamer.

A novel sensitive method has been developed for the detection of adenosine (AD) in human urine by using enhanced resonance light scattering (RLS). This method is based on the specific recognition and signal amplification of adenosine aptamer (Apt) coupled with gold nanoparticles (GNPs) via G-quartet-induced nanoparticle assembly, which was fabricated by triggering a structure switching of the 3' terminus G-rich sequence and aptamer duplex. RLS signal linearly correlated with the concentration of adenosine over the range of 6-115nM. The limit of detection (LOD) for adenosine is 1.8nM with relative standard deviations (RSD) of 2.90-4.80% (n=6). The present method has been successfully applied to determination of adenosine in real human urine, and the obtained results were in good agreement with those obtained by the HPLC method. Our investigation shows that the combination of the excellent selectivity of aptamer with the high sensitivity of the RLS technique could provide a promising potential for aptamer-based small molecule detection, and be beneficial in extending the application of RLS.

Rhodium(III)-Catalyzed Regioselective C(sp2)-H Functionalization of 7-Arylpyrazolo[1,5-a]pyrimidines with Dioxazolones as Amidating Agents.

Rh(III)-catalyzed C-H functionalization of 7-arylpyrazolo[1,5-a]pyrimidines was developed wherein the pyrazolo[1,5-a]pyrimidine moiety is reported for the first time to direct the C-H bond activation. Various 7-arylpyrazolo[1,5-a]pyrimidines underwent smooth C-H amidation with alkyl-, aryl-, and heteroaryl-substituted dioxazolones to afford the products in moderate to good yields. Mechanistic studies suggest that a six-membered rhodacycle intermediate involving N1 might play a key role in the regioselective catalytic cycle.

[Simulating the effects of climate change and fire disturbance on aboveground biomass of boreal forests in the Great Xing'an Mountains, Northeast China]. / æ°”å€™å˜åŒ–å’Œæž—ç«å¹²æ‰°å¯¹å¤§å ´å®‰å²­æž—åŒºåœ°ä¸Šç”Ÿç‰©é‡å½±å“çš„åŠ¨æ€æ¨¡æ‹Ÿ.

Predicting the effects of climate warming and fire disturbance on forest aboveground biomass is a central task of studies in terrestrial ecosystem carbon cycle. The alteration of temperature, precipitation, and disturbance regimes induced by climate warming will affect the carbon dynamics of forest ecosystem. Boreal forest is an important forest type in China, the responses of which to climate warming and fire disturbance are increasingly obvious. In this study, we used a forest landscape model LANDIS PRO to simulate the effects of climate change on aboveground biomass of boreal forests in the Great Xing'an Mountains, and compared direct effects of climate warming and the effects of climate warming-induced fires on forest aboveground biomass. The results showed that the aboveground biomass in this area increased under climate warming scenarios and fire disturbance scenarios with increased intensity. Under the current climate and fire regime scenario, the aboveground biomass in this area was (97.14±5.78) t·hm-2, and the value would increase up to (97.93±5.83) t·hm-2 under the B1F2 scenario. Under the A2F3 scenario, aboveground biomass at landscape scale was relatively higher at the simulated periods of year 100-150 and year 150-200, and the value were (100.02±3.76) t·hm-2 and (110.56±4.08) t·hm-2, respectively. Compared to the current fire regime scenario, the predicted biomass at landscape scale was increased by (0.56±1.45) t·hm-2 under the CF2 scenario (fire intensity increased by 30%) at some simulated periods, and the aboveground biomass was reduced by (7.39±1.79) t·hm-2 in CF3 scenario (fire intensity increased by 230%) at the entire simulation period. There were significantly different responses between coniferous and broadleaved species under future climate warming scenarios, in that the simulated biomass for both Larix gmelinii and Betula platyphylla showed decreasing trend with climate change, whereas the simulated biomass for Pinus sylvestris var. mongolica, Picea koraiensis and Populus davidiana showed increasing trend at different degrees during the entire simulation period. There was a time lag for the direct effect of climate warming on biomass for coniferous and broadleaved species. The response time of coniferous species to climate warming was 25-30 years, which was longer than that for broadleaf species. The forest landscape in the Great Xing'an Mountains was sensitive to the interactive effect of climate warming (high CO2 emissions) and high intensity fire disturbance. Future climate warming and high intensity forest fire disturbance would significantly change the composition and structure of forest ecosystem.

A gold nanoparticles-modified aptamer beacon for urinary adenosine detection based on structure-switching/fluorescence-"turning on" mechanism.

A novel small molecule probe, aptamer beacon (AB), was introduced for adenosine (Ade) recognition and quantitative analysis. The Ade aptamer was engineered into an aptamer beacon by adding a gold nanoparticle-modified nucleotide sequence which is complementary to aptamer sequence (FDNA) at the 3'-end of FDNA. The fluorescence signal "turning on" was observed when AB was bound to Ade, which is attributed to a significant conformational change in AB from a FDNA/QDNA duplex to a FDNA-Ade complex. The Ade measurement was carried out in 20 mmol L(-1) Tris-HCl buffer solution of pH 7.4, ΔF signal linearly correlated with the concentration of Ade over the range of 2.0×10(-8) to 1.8×10(-6) mol L(-1). The limit of detection (LOD) for Ade is 6.0×10(-9) mol L(-1) with relative standard deviations (R.S.D) of 3.64-5.36%, and the recoveries were 98.6%, 100%, 102% (n=6), respectively. The present method has been successfully applied to determine Ade in human urine samples, and the obtained results were in good agreement with those obtained by the HPLC method. Our investigation shows that the unique properties of the AB could provide a promising potential for small molecules detection, and be benefit to extend the application of aptamer beacon technique.

A wireless magnetoelastic sensor for urinary 2-naphthol detection based on the precipitation of 2-naphthol with diazonium salts.

A wireless magnetoelastic sensor has been developed for the determination of 2-naphthol (2-NAP) in human urine. This method is based on the precipitation of 2-NAP with diazonium salts produced by the diazo-reaction of sulfamethoxazole (SMZ) with nitrite under a weak alkaline condition, resulting in a descending of the resonance frequency of a wireless magnetoelastic sensor. The frequence shift values (ΔF) of the sensor were directly proportional to the concentration in the range of 1.13 - 139 µmol L(-1) for 2-NAP with a correlation coefficient of 0.997 and a detection limit of 0.340 µmol L(-1). The relative standard deviations were 2.38, 2.40 and 2.44%, and the average recovery was 107% (n = 6). The proposed method has additional advantages of being less time-consuming, low cost and remote query, and can be applied for real-time and in situ monitoring of 2-NAP in human urine. It would be a benefit to extend the scope of applications of magnetoelastic sensing techniques.

Rapid simultaneous analysis of 1-hydroxypyrene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1- and 2-naphthol in urine by first derivative synchronous fluorescence spectrometry using Tween-20 as a sensitizer.

A novel method of first derivative synchronous fluorescence was developed for the rapid simultaneous analysis of trace 1-hydroxypyrene (1-OHP), 1-naphthol (1-NAP), 2-naphthol (2-NAP), 9-hydroxyphenanthrene (9-OHPe) and 2-hydroxyfluorene (2-OHFlu) in human urine. Only one single scan was needed for quantitative determination of five compounds simultaneously when Deltalambda=10 nm was chosen. In the optimal experimental conditions, there was a linear relationship between the fluorescence intensity and the concentration of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in the range of 1.75 x 10(-9) to 4.50 x 10(-6) mol L(-1), 3.64 x 10(-8) to 2.20 x 10(-4) mol L(-1), 8.18 x 10(-9) to 1.20 x 10(-4) mol L(-1), 3.26 x 10(-9) to 8.50 x 10(-5) mol L(-1) and 4.88 x 10(-9) to 5.50 x 10(-6) mol L(-1), respectively. The limits of detection (LOD) were found to be 5.25 x 10(-10) mol L(-1) for 1-OHP, 1.10 x 10(-8) mol L(-1) for 1-NAP, 2.46 x 10(-9) mol L(-1) for 2-NAP, 9.77 x 10(-10) mol L(-1) for 9-OHPe and 1.46 x 10(-9) mol L(-1) for 2-OHFlu. The proposed method is reliable, selective and sensitive, and has been used successfully in the determination of traces of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in human urine samples, whose results were in good agreement with those gained by the HPLC method.