阳离子-π作用的研究进展

摘要阳离子-π作用是一种存在于阳离子和芳香性体系之间的相互作用,与一些经典的作用（如氢键、静电和疏水相互作用）相比,被认为是一种新型分子间作用,普遍存在于生物体系中,对分子识别、蛋白质和核酸的结构与功能起着十分重要的作用．本文结合我们课题组的研究工作,对生物体内存在的典型的阳离子-π作用,以及有关阳离子-π作用的实验与理论计算研究进行综述．     

红薯酸奶的制备及其在贮藏期理化变化

以红薯浆、复原乳为原料,接入乳酸菌发酵后制得红薯酸奶;比较了3种添加不同比例红薯浆的红薯酸奶在4℃贮藏15d的总酸度、pH、活菌数、持水力(WHC)、酸乳胶体脱水收缩作用敏感性(STS)及感官的变化;结果表明:红薯酸奶在贮藏过程中,总酸度增加比较缓慢,添加量愈大,酸度增长愈平缓;说明添加50~60%的红薯浆能在一定程度上抑制酸奶的后酸化;乳酸菌活菌数在15d仍然保持在108CFU/mL以上;2#(50%红薯浆)红薯酸奶的品质稳定性及感官评价等在3种酸奶中最佳。     

Characteristics and New Measurement Method of NCSFs of Individual Color Mechanisms of Human Vision

We propose a new method for determining neural contrast sensitivity functions （NCSFs） of isolated color mechanisms based on the measurements of wave-front aberrations and isoluminant color contrast sensitivity functions （CSFs）. Compared with the traditional method, this technique avoids the coherent noise and speckle noise, which are brought by the interference of laser beams, and has great flexibility for the measurements of NCSF of different color mechanisms. Our experiments indicate that the mean NCSF and CSF of the red mechanism are higher than those of the green mechanism, respectively, while those of the blue mechanism are the lowest. However the relative heights of the peak of NCSF and CSF between red and green mechanisms vary in subjects. There are some individuals whose peak values of NCSF and/or CSF of green mechanism are higher than that of the red mechanism. The NCSFs and CSFs of isolated color mechanisms all exhibit the similar characteristics and variation tendency. With the statistical average, the NCSFs of the red, green and blue mechanisms are higher than the corresponding CSFs in the whole spatial frequency. Compared with the corresponding CSFs curves, the peaks of the NCSFs of isolated color mechanisms shift toward higher spatial frequencies, especially for that of blue mechanism which has a largest shift of 3.9 c/deg.     

FAAS测定利尿类中药材中的金属元素

探讨金属元素与篇蓄、猪苓等中医临床常用的利尿通淋类中药作用的物质基础之间的关系;采用王水对篇蓄、猪苓等利尿类中药进行消解,用火焰原子吸收光谱法(FAAS)测定药材中金属元素的含量.通过金属元素含量与利尿类中药利尿作用强弱的对比研究,探讨中药材的利尿功效与其所含元素含量的关联.7种利尿中药材中含所测定元素的总量依次为:盐车前子、泽泻、猪苓、地肤子、篇蓄、赤小豆、茯苓;利尿类中药的利尿作用可能与其所含的Na、Ca、Mg元素部分相关.     

分散固相萃取-气相色谱-质谱法测定含油脂食品中17种邻苯二甲酸酯

建立了含油脂食品中17种邻苯二甲酸酯的分散固相萃取-气相色谱-质谱法检测方法。奶茶样品经乙腈-甲基叔丁基醚(9∶1,V/V)提取后,提取液用MAS-PAEC分散固相萃取管进行净化。调味包样品经乙腈(正己烷饱和)-甲基叔丁基醚(19∶1,V/V)提取2次后,提取液用CNW分散固相萃取管进行净化。采用基质匹配标准外标法进行定量分析。结果表明,奶茶中17种邻苯二甲酸酯的加标回收率为82.2%～125.4%;相对标准偏差小于16.5%;方法检出限为100～200μg/L。调味包中17种邻苯二甲酸酯的加标回收率为70.9%～115.5%;相对标准偏差小于9.8%;方法检出限为400～800μg/L。本方法快速、精确、简易、廉价、稳定,可应用于含油脂食品中17种邻苯二甲酸酯的实际检测分析。     

IR and Raman Vibrational Assignments for Metal-free Phthalocyanine from Density Functional B3LYP／6-31G（d） Method

Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.     

STUDY ON INTERMITTENT SHEAR FLOW AND RELAXATION BEHAVIOR OF THERMOTROPIC LIQUID CRYSTALLINE POLYMER

Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation after cessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystalline polymer (TLCP). There are two kinds of intermittent shear flow: all start-up flows are in the same direction (intermittent flow forward: IFF) and start-up flows change their directions alternately (intermittent flow reversal: IFR). The results show that the stress of start-up flow of IFF and IFR in the test process is not superposed, indicating different changes of internal structure of thermotropic LCP (TLCP). Two main factors affect structure changes in the experimental time scale. One relates to long-term texture relaxation process, the other is an interchain reaction that becomes important after 30 min. The two factors raise the stress of IFF, but express complex effects for the stress of IFR. The latter factor becomes very important at long time annealing process. The relaxation behavior was also studied by the application of wide range relaxation spectrum calculated from the combined dynamic modulus, which gave three characteristic relaxation times (0.3, 10 and 600 s) ascribable to the relaxations of less-phase orientation, domain orientation, and domain deformation, respectively. The result also shows that the domain coalescence (texture relaxation), a long relaxation time, is a much slow process and lasts beyond 2400 s of the test time.