Antioxidant efficacy of amino acids in methyl linoleate at different relative humidities

Antioxidant efficacy of the amino acids methionine, tryptophan, aspartic acid, serine, alanine and arginine in methyl linoleate were compared to a methyl linoleate control at 2,50 or 79% relative humidity (RH) at 37°C. Antioxidant efficacy varied with RH and the individual amino acids. Arginine had the highest antioxidant efficacy at all RH values compared to the control. The efficacy of alanine was equal to that of arginine at RHs of 50 and 79% but was lower at 2% RH. The presence of aliphatic, alkaline amino, hydroxyl or thiol groups in the side chain of the amino acids increased the antioxidant efficacy at high RHs.     

Acid-base reactions on model MgO surfaces

Three MgO surfaces of different structures have been employed as models for study of the acid-base properties of MgO. Surface spectroscopies including XPS, UPS, and ISS were used to determine the nature and the absolute coverage of surface intermediates, and the nature of bonding sites upon adsorption of Brønsted acid molecules on these surfaces. Different behavior patterns of the Brønsted acid molecules with varying strengths on the three model surfaces provide insights into the site requirements for dissociation of Brønsted acids on MgO. The base-catalyzed Cannizzaro reaction of formaldehyde was observed on these model surfaces under UHV conditions.     

Rapid evaluation of olive oil quality by NIR reflectance spectroscopy

NIR spectroscopy calibrations have been developed for a range of quality parameters in olive oil, including FFA, PV, polyphenol content, induction time, chlorophyll, and the major FA. A set of 216 olive oil samples from throughout the Australian olive-growing areas were used to provide a representative range of quality. The variation in the oils tested virtually covered the range of the chemical standard limits described by the International Olive Oil Council. A FOSS NIRSystems^® 6500 spectrophotometer with a liquid cell holder was used. Multiple correlation coefficients squared (R ²) for minor components stearic acid (0.86), and linolenic acid (0.85) were relatively low because the concentration range is very narrow compared with the reproducibility of the reference method. However, the major FA, oleic (0.99) and linoleic (1.00), FFA (0.97), and chlorophyll (0.98) provided high levels of accuracy. All of the parameters measured were sufficiently accurate for routine screening of olive oil.     

中试规模制备L-茶氨酸及其衍生物

报道了中试规模制备L-茶氨酸和L-谷氨酰胺的一种方法。以廉价的L-谷氨酸为原料,采用邻苯二甲酰基作为保护基,保护L-谷氨酸的α-氨基,醋酐回流10 m in使其分子内脱水生成N-邻苯二甲酰-L-谷氨酸酐,在常温、常压条件下,分别与2 mol/L氨水和2 mol/L乙胺水溶液反应生成中间产物N-邻苯二甲酰-L-谷氨酰胺、N-邻苯二甲酰-L-茶氨酸,中间产物在室温条件下与0.5 mol/L水合肼反应48 h脱除保护基,分别以57%、61%的收率得到L-谷氨酰胺和L-茶氨酸。     

Synthesis and properties of aminopropyl nucleic acids

Oligonucleotides that contain up to three aminopropyl nucleoside analogues have been synthesized. Dimers of aminopropyl adenine and thymidine were prepared and used as building blocks by applying phosphoramidite chemistry. Both R and S isomers of the aminopropyl nucleosides were used. This incorporation led to a reduction of thermal stability of double-stranded DNA. Furthermore, the (R)-adenine analogue, which yielded (S)-APNA, can be considered as a candidate for universal base pairing.     

Separation and identification of phenolic acids and related compounds by gas chromatography and fourier transform infrared spectroscopy

Phenolic acids and related compounds were separated by gas chromatography using three separate columns. One of these columns was coupled to a Fourier transform infrared spectrometer. The trimethylsilyl derivatives could be separated and identified by comparing the relative retention times of the three different columns. However, where there was overlap, the accompanying infrared data clearly distinguished between the questionable derivatives, thus enabling characterization of all derivatives.The use of trade, firm, or corporation names in this article is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable.     

Zeolite‐catalyzed isomerization of oleic acid to branched‐chain isomers

Branched‐chain (bc) saturated fatty acids (SFA) have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids (UFA) and have better low‐temperature properties than linear SFA. Previous studies in converting UFA to bc‐FA using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting UFA to bc‐FA in higher yields and conversions. In this work, we examined the scope and potential of the zeolite‐catalyzed synthesis of bc‐FA starting from readily available monounsaturated linear FA. Our results show that common UFA such as oleic acid can be converted to bc‐isomers using modified Ferrierite zeolite catalysts with high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the FA chain were determined from the GC‐MS spectra of the picolinyl esters of the bc‐FA.     

Synthesis of Biodiesel from Soybean Oil using Heterogeneous KF/ZnO Catalyst

Biodiesel was produced by transesterification of soybean oil with methanol using ZnO loaded with KF as a solid base catalyst. It was found that the catalyst with 15 wt.% KF loading and calcined at 873 K showed the optimum activity. XRD, IR and Hammett indicator method were employed for the catalyst characterization. The results showed the activity of the catalysts was correlated with their basicity. The influence of various reaction variables on the conversion was also discussed.     

乙二醇单丁醚为溶剂制备共轭亚油酸的研究

以乙二醇单丁醚作为溶剂,KOH作催化剂,碱催化异构化法用豆油制备共轭亚油酸。通过正交设计,紫外光谱分析考察了4种因素对亚油酸转化率的影响,并得出制备高亚油酸油脂合适的工艺条件:反应温度135℃,反应时间3 h,强碱催化剂与原料质量比为0.4∶1,原料与溶剂质量比为2∶3。在此条件下,亚油酸的平均转化率达到96.8%。结果表明,该溶剂能使反应在均相体系中较为温和的温度条件下较短的时间内完成。     

The mechanism and kinetics of the electrochemical cleavage of azo bond of 2-hydroxy-5-sulfophenyl-azo-benzoic acids

The electrochemical reduction of 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(3-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(2-sulfophenyl)azo]benzoic acid and 2-hydroxy-5-azo-benzoic acid has been carried out in aqueous solutions at glassy carbon electrode using cyclic voltammetry and chronoamperometry. The position of sulfo substituent relative to azo bridge as well as pH of the solution have significant impact on the electrochemical behavior of these compounds. It has been proposed that these compounds are reduced predominantly as hydrazone tautomers resulting in corresponding hydrazo compounds. The overall electrochemical reduction follows DISP2 mechanism, ultimately leading to the 5-amino salicylic acid and sulfanilic acid. The rate determining step is the homogenous redox reaction between intermediate hydrazo compound and 5-amino salicylic acid quinoneimine. The mechanism is proposed in which activated complex of 5-amino salicylic acid quinoneimine and intermediate hydrazo compound is formed with the simultaneous loss of one proton.