高效液相色谱法测定饲料中辛硫磷残留量

提出了高效液相色谱法测定饲料中辛硫磷残留量的方法。样品经乙酸乙酯提取,氨基固相萃取小柱净化,所得净化液以反相C18色谱柱为分离柱,以乙腈-水(65+35)混合溶液为流动相,在检测波长280nm处进行测定。辛硫磷的质量浓度与其峰面积在0.10～0.50mg·L-1范围内呈线性关系,方法的检出限(3S/N)为0.10mg·kg-1。加标回收率在80.0%～88.2%之间,测定值的相对标准偏差(n=5)在1.6%～6.5%之间。     

The effect of feed composition on the behavior of chemically selective displacement systems

In this paper we examine whether adding a more retained protein to the feed will mitigate displacer–protein interactions in the column, thus affecting the displacement modality that occurs (chemically selective vs. traditional displacement chromatography). STD-NMR experiments were carried out to probe displacer–protein interactions for the chemically selective displacer chloroquine diphosphate and the results indicated that this displacer only had measurable interactions with the protein α-chymotrypsinogen A. For a two component feed mixture containing ribonuclease A and α-chymotrypsinogen A, the separation resulted in the displacement of ribonuclease A, with the more hydrophobic α-chymotrypsinogen A remaining on the column. On the other hand, when the experiment was repeated with cytochrome c added to the feed, all three feed proteins were displaced. Column simulations indicated that the combination of sample self-displacement occurring during the introduction of the feed, along with the dynamics of the initial displacement process at the column inlet was responsible for this behavior. These results indicate that for this class of hydrophobic-based selective displacers, in order for the protein to be selectively retained, the protein should be the most strongly retained feed component.     

Evaluation of matrix solid‐phase dispersion extraction for 11 β‐agonists in swine feed by liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive liquid chromatography with tandem mass spectrometry method was developed for the determination of 11 β‐agonists (clenbuterol, salbutamol, ractopamine, terbutaline, fenoterol, cimaterol, isoxsuprine, mabuterol, mapenterol, clenproperol, and tulobuterol) in swine feed. This rapid, simple, and effective extraction method was based on matrix solid‐phase dispersion. The limit of quantification of clenbuterol, cimaterol, mabuterol, salbutamol, terbutaline, mapenterol, clenproperol, and tulobuterol was 1 μg/kg and that of ractopamine, fenoterol, and isoxsuprine was 2 μg/kg. The recoveries of β‐agonists spiked in swine feeds at a concentration range of 1–8 μg/kg were >83.1% with relative standard deviations <9.3%. This rapid and reliable method can be used to efficiently separate, characterize, and quantify the residues of 11 β‐agonists in swine feeds with advantages of simple pretreatment and environmental friendliness.     

Does application of cement kiln exhausts affect root nodule biochemistry and soil N2-fixing microbes?

The research work carried out on cement exhausts centers mostly around vegetation and crop productivity (1-3) with little or no work on root nodulation. Soil plus foliar application of exhaust dusts did not affect soil/nodule rhizobial population, nodule initiation, and possible N₂-fixing capacity inCajanus cajan, Vigna radiata, Vigna mungo,Vigna catjung, andGlycine max. The nodular biochemistry was investigated in detail. The heme protein leghemoglobin was higher compared to the control. The levels of intermediary N compounds like total ureides of the nodules, which may serve as indirect evidence of symbiotic N₂ fixation, were higher in the treated plants. There were also increments in free proline, free amino acids, soluble proteins, soluble starch, soluble sugars, total nitrogen, and phenols in the treated plants. The levels of total nitrates, soluble sucrose, and soluble SH compounds of the nodule of the control and treated plants did not show a significant difference. The activities of ascorbate peroxidase, catalase, glutathione reductase, and Superoxide dismutase were significantly higher, possibly indicating their role in alleviation of H₂O₂ and O ₂ ^- damage by the exhausts. Enzymes like nitrate reductase, nitrite reductase, and glutamine synthetase, and also the activities of acid and alkaline phosphatases were not affected. The presence of beneficial soil microbes likeAzotobacter, Azospirillum, and mycorrhizae was not affected at all.     

Effects of ergot alkaloids on liver function of piglets can be detected by the [13C]methacetin breath test irrespective of oral or intramuscular route of tracer administration

Ergot alkaloids (sum=total alkaloids, TA) originate from the phyto-pathogenic fungus Claviceps purpurea and might exert feed intake depressing and hepatotoxic effects on animals. The aim of the study was to evaluate TA effects on performance and liver function of piglets with the [¹³C]methacetin breath test and two routes of tracer administration (orally, p.o.; intramuscularly, i.m.). Two ergot batches were mixed into piglet diets resulting in 21 and 17 mg TA kg^?1 (Ergot-5 and -12, respectively) and compared with an ergot-free control diet. Feed intake was significantly depressed after feeding the ergot containing diets (p=<0.001). The time at maximum ¹³CO₂ exhalation (t _max) and the half-life (t _0.5) were not influenced by treatments and varied between 25 and 68 min after the p.o., and 28 and 62 min after the i.m. administration of [¹³C]methacetin, respectively. The cumulative ¹³C recovery (cPDR₃₀) was significantly lower due to feeding the diet Ergot-5 (6.6 %) compared with the Ergot-12 (8.8 %) and the control diet (9.7 %) irrespective of the route of tracer administration (p=0.044). As a discrimination of the diet effects through both tracer administration routes is possible, the i.m. application should be preferred in piglets as this causes less stress than the oral forced administration.     

A Review on the Use of Near-Infrared Spectroscopy for Analyzing Feed Protein Materials

Abstract: Due to the strong link between feed and food, the quality and safety of feed protein materials are of public concern. Firstly, this article summarizes the recent advances in near-infrared reflectance spectroscopy (NIRS) techniques applied to the chemical content and traceability analyses of feed protein materials. The results show the potential of NIRS as an efficient first-line screening tool for monitoring the quality and safety of feed protein materials. Finally, future prospects and the need to increase the feasibility of industrial applications and improve the limit of detection of NIRS techniques for feed protein materials are discussed.     

以实际问题解决吸引学生主动选修化学——校本课程“化学与考古”的案例分析

提升化学对学生的吸引力是促使学生选修化学、落实化学核心素养的前提。以校本选修课程“化学与考古”为例,从现代技术、物质性质、实验装备、反应原理、工艺、生物化学等多角度用化学知识解决考古与文保疑难,将抽象的化学知识落实到考古事例中探讨,主动创设情境帮助学生体验化学的魅力,为普高教学中化学知识的实用化提供新的视角。     

Latitudinal distribution of nitrogen isotopic composition in suspended particulate organic matter in tropical/subtropical seas

Natural nitrogen isotopic composition (δ¹⁵N) of suspended particulate organic matter (POM) and nitrogen fixation rates via ¹⁵N₂ assay were measured in surface waters along 120° E from 30° N to 30° S in the Asian marginal seas (the East/South China Seas and the Sulu/Celebes/Java Seas) and the northeastern Indian Ocean in November–December 2005 and March 2006. The POM δ¹⁵N values ranged from?1.8 to 12.2‰ with an average of 3.6‰ and showed a decreasing trend towards the equator in both hemispheres. In parallel, the measured N₂ fixation rates showed an increase from the subtropical to the tropical seas. This implies that a higher contribution of ¹⁵N-depleted POM was derived from enhanced N₂ fixation. Water temperature and the stability of water column were partly responsible for the observed variations in nitrogen fixation. The large-scale spatial variations in suspended POM δ¹⁵N and N₂ fixation rates suggest that the suspended POM δ¹⁵N may be a potential indicator of nitrogen fixation in surface waters in tropical/subtropical seas.     

Photobiochemical Production of Carbon Monoxide by Thermus thermophilus ba3‐Cytochrome c Oxidase

We report the photobiochemical production of carbon monoxide by a terminal ba₃‐cytochrome c oxidase from T. thermophilus HB8. FTIR and time‐resolved step‐scan FTIR spectroscopies were combined to probe this process and also monitor the concomitant binding of the produced gas to other intact ba₃ molecules forming the ba₃–CO complex. The activation of this mechanism by ba₃‐oxidase under visible excitation raises the question as to whether such a mechanism is physiologically relevant to the extreme environment in which it operates.     

高职食品生物化学新型实验教学体系和案例分析

构建包括基础型实验、综合型实验和设计型实验3个层次内容的食品生物化学新型实验教学体系,并依据典型案例分析,介绍如何妥善处理理论与实践、本课程与后续课程、课内与课外、教学与科研的关系。