No abstract

No abstract

No abstract

N-Acylated homoserine lactones (AHLs) are produced by Gram-negative bacteria as communication signals and are frequently studied as mediators of the "quorum sensing" response of bacterial communities. Several reports have recently been published on the identification of AHLs from different species and attempts have been made to study their role in natural habitats, for example the surface of plant roots in the rhizosphere. In this article, different analytical methods, including bacterial biosensors and chromatographic techniques, are reviewed. A concept for assignment of the structures of AHLs is also presented. The retention behaviour of derivatives of AHLs containing beta-keto or hydroxyl groups and/or double bonds has been evaluated in relation to the separation behaviour of AHLs with saturated and unsubstituted alkanoyl chains. Samples have also been analysed by high resolution mass spectrometry (Fourier-transform ion-cyclotron-resonance mass spectrometry, FTICR-MS), nano liquid chromatography-electrospray ionization ion trap mass spectrometry (nano-LC-MS) and by the aid of a biosensor. The results obtained from ultra performance liquid chromatography (UPLC), FTICR-MS, nano-LC-MS, and bioassays have been compared to attempt structural characterisation of AHL without chemical synthesis of analytical standards. The method was used to identify the major AHL compound produced by the rhizosphere bacterium Acidovorax sp. N35 as N-(3-hydroxydecanoyl)homoserine lactone.

Organosulfates (OSs) derived from biogenic volatile organic compounds are important compounds signifying interactions between anthropogenic sulfur pollution and natural emission. In this work, we substantially expand the OS standard library through the chemical synthesis of 26 α-hydroxy OS standards from eight monoterpenes (i.e., α- and β-pinene, limonene, sabinene, Δ3-carene, terpinolene, and α- and γ-terpinene) and two sesquiterpenes (i.e., α-humulene and β-caryophyllene). The sulfation of unsymmetrically substituted 1,2-diol intermediates produced a regioisomeric mixture of two OSs. The major regioisomeric OSs were isolated and purified for full NMR characterization, while the minor regioisomers could only be determined by liquid chromatograph–mass spectrometer (MS). The tandem mass spectra of the molecular ion formed through electrospray ionization confirmed the formation of abundant bisulfate ion fragments (m/z 97) and certain minor ion fragments characteristic of the carbon backbone. A knowledge of the MS/MS spectra and chromatographic retention times for authentic standards allows us to identify α-hydroxy OSs derived from six monoterpenes and β-caryophyllene in ambient samples. Notably, among two possible regioisomers of α-hydroxy OSs, we only detected the isomers with the sulfate group at the less substituted carbon position derived from α-pinene, limonene, sabinene, Δ3-carene, and terpinolene in the ambient samples. This observation sheds light on the atmospheric OS formation mechanisms.

No abstract

The purpose of this research was to investigate the chemical profile, nutritional quality, antioxidant and hypolipidemic effects of Mexican chia seed oil (CSO) in vitro. Chemical characterization of CSO indicated the content of α-linolenic acid (63.64% of total fatty acids) to be the highest, followed by linoleic acid (19.84%), and saturated fatty acid (less than 11%). Trilinolenin content (53.44% of total triacylglycerols (TAGs)) was found to be the highest among seven TAGs in CSO. The antioxidant capacity of CSO, evaluated with ABTS•+ and DPPH• methods, showed mild antioxidant capacity when compared with Tocopherol and Catechin. In addition, CSO was found to lower triglyceride (TG) and low-density lipoprotein-cholesterol (LDL-C) levels by 25.8% and 72.9%respectively in a HepG2 lipid accumulation model. As CSO exhibits these chemical and biological characteristics, it is a potential resource of essential fatty acids for human use.

The characteristics of spatial and temporal distribution of tropospheric NO 2 column density concentration over China are presented, on the basis of measurements from the satellite instruments GOME and SCIAMACHY. From these observations, monthly averaged tropospheric NO 2 variations are determined for the period of 1997 to 2006. The trend and seasonal cycle are also investigated. The possible source of tropospheric NO 2 over megacity area is discussed in this paper. The results show a large growth of tropospheric NO 2 over eastern China, especially above the industrial areas with a fast economical growth, such as, Yangtze Rive Delta region and Pearl River Delta region because of the prominent anthropogenic activity. There is a rapid increase of tropospheric NO 2 over megacities in China. For instance, Shanghai had a linear significant increase in NO 2 columns of ~20% per year (reference year 1997) in the period of 1997-2006, which is the rapidest increase among all the selected cities. The seasonal pattern of the NO 2 concentration shows a difference between the east and west in China. In the eastern part of China, an expected winter maximum in seasonal cycle is found because of the prominent anthropogenic activity and meteorological conditions. In the western part this cycle shows a NO 2 maximum in summer time, which is attributed to natural emissions, especially soil emissions and lightning. A quickly increasing vehicle population may contribute to the increase of tropospheric NO 2 over megacities in China for the remarkable correlation for vehicle population with tropospheric NO 2.tropospheric NO 2 , satellite instruments, trend, seasonal cycle and sources Nitrogen oxides are emitted by all combustion processes and play a key part in the photochemically induced catalytic production of ozone, which results in summer smog and has increased levels of tropospheric ozone globally [1] . The photolysis of NO 2 leads to the photochemical formation of ozone (O 3 ) during daytime by a catalytic cycle involving organic peroxy radicals (RO 2 ), the hydroperoxy radical (HO 2 ), the hydroxyl radical (OH), volatile organic compounds (VOC) and carbon monoxide (CO). NO 2 can also react with O 3 to form the nitrate radical (NO 3 ), which is a strong oxidant and plays an important role in the nighttime chemistry. The main products of NO 2 in the troposphere are peroxyacetyl nitrate (PAN or CH 3 C(O)OONO 2 ) and nitric acid (HNO 3 ). The stability of PAN in the atmosphere is highly temperature-dependent, and NO 2 is released with increasing temperature. Nitric acid is produced by daytime reaction of NO 2 with the OH radical or by nighttime formation of N 2 O 5 followed by hydrolysis on aerosols [2,3] . Nitrogen dioxide (NO 2 ) as one of the most im-