QuEChERS-液相色谱-串联质谱法测定牛蛙肉中酰胺醇类抗生素及其代谢物

采用QuEChERS技术提取氯霉素、甲砜霉素、氟苯尼考及其代谢物氟苯尼考胺,建立液相色谱-串联质谱法（liquid chromatography-tandem mass spectrometry,LC-MS/MS）同时测定牛蛙肉中酰胺醇类抗生素及其代谢物的检测方法。结果表明：在0.1～50.0 ng/mL范围内,酰胺醇类抗生素及其代谢物质量浓度与其质谱响应值呈良好的线性关系,相关系数均大于0.999 1;检出限为0.007 5～0.003 0 μg/kg,定量限为0.025～0.100 μg/kg;加标回收率为94.3%～97.9%,相对标准偏差为0.8%～3.7%。     

Fatty acid composition, extraction, fractionation, and stabilization of bullfrog (Rana catesbeiana) oil

The oil extracted from the fat-storage organ (fat body) of the bullfrog (Rana catesbeiana) was characterized for its fatty acid composition. The main fatty acids were palmitic (18.1%), stearic (4.1%), myristic (2.7%), oleic (31.7%), and linoleic (12.9%) acids. Long-chain polyunsaturated fatty acids were also present in significant amounts, i.e., eicosapentaenoic (1.5%) and docosahexaenoic (4.7%), and were probably derived from the fish meal content of the diet. A partially fractionated oil was extracted from the homogenized and frozen fat body with an oleic acid content of 43.2%. The natural alkaloid boldine, added at 0.5 mg/g oil level, improved the oxidative stability by a factor ranging from 1.7 to 2.4, as assessed by the Oil Stability Index method between 90 and 110°C. The stabilization effect of boldine was higher than that of naringenin, morin, and quercitin and for the synthetic antioxidant butylated hydroxytoluene at the same concentration level.     

Correction of autofocusing errors due to specimen tilt for automated electron tomography

Transmission electron microscopy images acquired under tilted‐beam conditions experience an image shift as a function of defocus settings – a fact that is exploited as a method for defocus determination in most of the automated tomography data collection systems. Although the method was shown to be highly accurate for a large variety of specimens, we point out that in its original design it can strictly only be applied to images of untilted samples. The application to tilted samples and thus in automated electron tomography is impaired mainly due to a defocus change across the images, resulting in reduced accuracy. In this communication we present a method that can be used to improve the accuracy of the basic autofocusing procedures currently used in systems for automated electron tomography.     

橘霉素免疫牛蛙肌肉蛋白柱的制备及其吸附橘霉素作用分析

用橘霉素人工抗原-佐剂免疫牛蛙,研究牛蛙肌肉蛋白质对橘霉素结合能力的大小。将能与橘霉素结合的蛋白质用海藻酸钠制粒。取6.4?mg橘霉素人工抗原免疫牛蛙肌肉蛋白质,使用海藻酸钠质量浓度4?g/100?mL、氯化钙质量浓度5?g/100?mL、戊二醛交联体积分数0.2%、交联时间2?h,制备海藻酸钙包埋蛋白质凝胶微球。取海藻酸钙凝胶微球2?g装填成固相小柱,以2?mL红曲米橘霉素提取液过柱,以20?mL超纯水洗脱杂质,与市售免疫亲和柱色谱图比较,均没有杂质干扰峰。以橘霉素标准液作为上样液,以70%乙腈-三氟乙酸作为橘霉素洗脱液,洗脱剂量为5?mL,回收率为86.7%,柱容量为0.101?μg/g。采用自制的牛蛙免疫蛋白柱和市售免疫亲和柱测得红曲米中橘霉素含量分别为0.037?μg/g和0.043?μg/g。     

浅谈牛蛙皮的制革工艺

以美国大牛蛙皮为原料,通过对其组织构造的研究,提出了一套牛蛙皮制革的工艺路线,并对牛蛙皮的涂饰进行了初步的探讨。     

Analyzing acoustic interactions in natural bullfrog (Rana catesbeiana) choruses.

Analysis of acoustic interactions between animals in active choruses is complex because of the large numbers of individuals present, their high calling rates, and the considerable numbers of vocalizations that either overlap or show close temporal alternation. The authors describe a methodology for recording chorus activity in bullfrogs (Rana catesbeiana) using multiple, closely spaced acoustic sensors that provide simultaneous estimates of sound direction and sound characteristics. This method provides estimates of location of individual callers, even under conditions of call overlap. This is a useful technique for understanding the complexity of the acoustic scene faced by animals vocalizing in groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)