Enzymatic Synthesis of Halogen Derivatives of Aromatic Amino Acids Labeled with Hydrogen Isotopes

The isotopomers of halogenated amino acids （2＇-F-L-phenylalanine, 3＇-F- and 3＇-Cl-L-tyrosine, as well as 5＇-F-, 5＇-Br-and 6＇-F-L-tryptophan） specifically labeled with deuterium at α- and 13-carbon atom of the side chain were synthesized by enzymatic catalyzed H/D exchange in fully deuteriated incubation medium. The extent and site of deuterium incorporation were confirmed by ^1H NMR （proton nuclear magnetic resonance） spectra.     

Do Aphid Colonies Amplify their Emission of Alarm Pheromone?

When aphids are attacked by natural enemies, they emit alarm pheromone to alert conspecifics. For most aphids tested, (E)-beta-farnesene (EBF) is the main, or only, constituent of the alarm pheromone. In response to alarm pheromone, alerted aphids drop off the plant, walk away, or attempt to elude predators. However, under natural conditions, EBF concentration might be low due to the low amounts emitted, to rapid air movement, or to oxidative degradation. To ensure that conspecifics are warned, aphids might conceivably amplify the alarm signal by emitting EBF in response to EBF emitted by other aphids. To examine whether such amplification occurs, we synthesized deuterated EBF (DEBF), which allowed us to differentiate between applied and aphid-derived chemical. Colonies of Acyrthosiphon pisum were treated with DEBF, and headspace volatiles were collected and analyzed for evidence of aphid-derived EBF. No aphid-derived EBF was detected, suggesting that amplification of the alarm signal does not occur. We discuss the disadvantages of alarm signal reinforcement.     

Microstructure change and deuterium permeation behavior of the yttrium oxide coating prepared by MOCVD

Deuterium permeation measurements and microstructure analysis on yttrium oxide coating deposited by metal organic chemical vapor deposition (MOCVD) were studied. The composition and microstructure of the coating can be adjusted by tuning sublimation temperature and deposition temperature. It is found that the coating sublimated at 150 °C and deposited at 600 °C possesses compact surface morphology with no pinholes or cracking was observed. Moreover, the oxygen/yttrium ratio corresponding well to the stoichiometric Y₂O₃ was observed by X-ray photoelectron spectroscopy (XPS) with no moving of Y3d binding energy doublet peaks and O1s binding energy peak at different depth throughout the coating. The permeation properties of coatings depended much on the microstructure. The coating sublimated at 150 °C and deposited at 600 °C exhibits the best permeability property with PRF values 412–244 at 873–973 K. However, a permeability drop, especially for the 800 °C deposited coating was observed. It was believed that the obvious increase of pinhole and crack density caused the increase of deuterium permeability. Furthermore, the existence of (Fe,Cr)₂O₃, forming a grid structure in the natural oxide layer of stainless steel, increases its hydrogen permeability.     

The application of SNIF‐NMR and IRMS combined with C,H and O isotopes for detecting the geographical origin of Chinese wines

The regional origin of Chinese wines was investigated using two important complementary techniques, site‐specific natural isotopic fractionation nuclear magnetic resonance (SNIF‐NMR) and isotope ratio mass spectrometry (IRMS). Twenty samples from five different grape varieties were collected from north Xinjiang in 2009, along with 100 wine samples from five different regions during 2010–2013. The (D/H)_I and (D/H)_II in wine ethanol ranged from 95.10 to 102.86 ppm and from 115.99 to 126.39 ppm using SNIF‐NMR, respectively. The ¹³C/¹²C of wine ethanol and ¹⁸O/¹⁶O of wine water were detected using IRMS. The δ¹³C value (?23.36‰) in coastal regions was higher than that in continental regions (?27.75‰). The temperature is the key for δ¹³C value. The δ¹⁸O ranged from ?1.94 to 4.57‰. The δ¹⁸O values were only positive in north Xinjiang which had the arid climate and strong sunshine. No difference was found for isotope ratios for wines made from five different grape varieties in north Xinjiang. All data evaluated by principal component analysis and linear discriminant analysis showed that the best method to distinguish the regional wine origin correctly is a combination of (D/H)_I, (D/H)_II, R, δ¹³C and δ¹⁸O. Therefore, natural multi‐elemental isotope ratios are effective in contributing to wine quality control in the Chinese market.