Phase behavior and micellar properties of carboxylic acid end group modified pluronic surfactants

The micellar behavior of three different carboxylic acid end standing (CAE) surfactants has been characterized using conductometry, differential scanning calorimetry, isothermal titration calorimetry, and dynamic light scattering. The CAE surfactants are modified high molecular weight Pluronic (PEO-PPO-PEO triblock copolymer) surfactants. The influence of pH and salt additives on the critical micellization temperature (CMT) and the cloud point of the CAE surfactants have been studied. Both the CMT and the cloud points of the CAE surfactants increase as a function of pH and decrease as a function of ionic strength. For the CAE surfactants, the CMT varies by about 5 degrees C, and the cloud point shows a variation in the order of 20-30 degrees C, as compared to the unmodified Pluronics. From the different experimental techniques, it follows that at low pH values (pH<3.5), the CAE surfactants show the same micellar behavior as the unmodified Pluronic, while at high pH values (pH>6), the micellar properties of the CAE surfactants are considerably different from those observed for the corresponding Pluronic. It has been demonstrated that the CAE micelles are capable of removing simultaneously divalent ions and phenanthrane. The CAE surfactants are the first known anionic surfactants that show cloud point behavior with the addition of low concentrations of simple salts, such as, for example, NaCl.     

Large-scale carbohydrate analysis by capillary array electrophoresis: part 2. Data normalization and quantification

Automated 96-capillary array electrophoresis (CAE) methodology described in the first part of the present work offered large-scale high-performance profiling of oligo- and monosaccharides to fulfill the needs of bioindustrial laboratories. Sensitivity at low nanomolar concentration, good resolving power and reliability achieved in the experiments is invaluable for monitoring reaction products from enzymatic polysaccharide digestion with numerous applications in agricultural, chemical and food industries. In addition to optimization of mono- and oligosaccharide separations in CAE system and necessary operational protocol modifications, capillary-to-capillary and run-to-run variation in migration time and signal intensity necessitated development of data normalization tools. Internal fluorescent standards have been incorporated into the analysis aiding migration time normalization and CAE trace alignment. Data processing, visualization, and programming tools have been developed along with quantification approaches.     

Investigation on the machine calibration effect on the optimization through design of experiments (DOE) in injection molding parts

Achieving production quality is a key issue faced in injection molding. Before mass production, ensuring good production quality is one of the crucial factors in injection molding. To achieve good quality, CAE technology is beneficial to assist us either to make the process window approach or to integrate with optimization strategies to improve the quality. However, there are still some questions or challenges existed. For example, for general injection molding, the difference between CAE simulation prediction and real experimental observation is very often encountered. But its mechanism of this difference is not fully understood yet. When design of experiments (DOE) procedure is performed using CAE simulation, the optimal parameters obtained from CAE prediction are expected to be forwarded into the real molding trial. However, there is no guarantee to get results with good accuracy based on those optimal parameters. In this study, we have proposed a feasible methodology to uncover the difference and its internal mechanism between CAE simulation prediction and real experimental observation. It also includes the method to reduce that difference by calibrating the machine performance. Specifically, a standard procedure to calibrate the real performance of the injection machine using CAE technology has been constructed. Moreover, to realize the integration of CAE and DOE optimization strategy, the quality difference between the virtual CAE-DOE and the physical DOE optimization has been investigated before doing the machine calibration. The result showed that the difference between the virtual CAE-DOE and the physical DOE is almost same as that of the original injection molding design. However, after the machine calibration, the quality difference between the virtual CAE-DOE and the physical DOE optimization is reduced by 67%. It is noted that the machine calibration effect is quite significant in injection molding process development.     

A cam-based laser-induced fluorescence scanner for capillary array electrophoresis

Capillary array electrophoresis (CAE) is an important high throughput analytical technique. Laser-induced fluorescence (LIF) has been the dominant detection method for CAE owing to its low limit of detection (LOD) and wide linear dynamic range (LDR). Linear LIF scanners were first used in CAE because linear motions of an objective match well with a common planar array of capillaries. A problem with linear scanners is that the motor is required accelerating/decelerating so that all capillaries can be properly scanned, which makes motion control complicated and reduces the duty cycle. Rotary scanners were developed to overcome this problem. While rotary scanners have been successfully applied in CAE, the capillaries have to be arranged in a circular format, which can be inconvenient in some cases. In this report, we describe a cam-based LIF scanner as an alternative technique for CAE detection. In this system, a rotary motor is mechanically linked with a capillary holder via a cam. During operation, the motor carries the cam in a rotary motion that drives an array of capillaries on the holder to move back and forth across the objective for fluorescence detection. Using this design, the capillaries can be parallel-arranged in a plane while the motor acceleration/deceleration is avoided. To demonstrate the feasibility of this approach, we constructed a prototype instrument with a constant-velocity scanning distance of ∼10 mm, a scanning frequency of 3 Hz and a duty cycle of ∼70%. The scanner exhibited a LOD of 69 pM of fluorescein and a LDR of 3.5 orders of magnitude. Multiplexed capillary SDS-PAGE was performed on this scanner for protein separations.     

纤维素芳族酯热致液晶对PET结晶成核作用的研究

用自制的热致液晶性纤维素芳族酯(CAE)作聚对苯二甲酸乙二醇酯(PET)的成核剂,研究了PET/CAE体系(CAE含量≤1%)在110～200℃温度范围内的等温结晶动力学特性.结果表明,CAE能显著加快PET结晶速率(Z),Z随结晶温度和CAE含量变化均有极大值Z_max(T_C)和Z_max(W_CAE),Z_max(T_C)对应的温度T_max随CAE含量增加而降低,CAE促进PET结晶的作用机理与普通成核剂不同.     

Quick Profile Die Balancing of Automotive Rubber Seal Extrusion by CAE Technology

The extrusion process of a type of automotive rubber seal was considered by using Computer Aided Engineering (CAE) technology. Based on the die balancing requirement, CAE technology was utilized to speed up the die development and balancing process. The rubber material was EPDM and unacceptable extrusion deformation was found by using a parallel die. More balancing dies were then designed following the procedures proposed by the die balancing method and the effect of them was evaluated with respect to CAE analytical results. It was found that the addition of an opening section in the die would provide a more uniform velocity distribution at the die exit than the parallel die. The length of opening section was also found to affect the die balancing and so an optimum length of the opening section was determined by CAE analysis. Further optimization of the die was carried out by adjusting the local length of the opening section. Finally, a real die was cut based on the optimization results and used for production. Ideal profile products were obtained and very small and acceptable deviation from the die was observed, which validated the advantage and accuracy of CAE technology combined with die balancing requirement.     

Capillary array electrophoresis for the research of asymmetric transformation reaction of L-proline to D-proline

One asymmetric transformation reaction of L-proline (L-Pro) to D-proline was studied by a home-made capillary array electrophoresis (CAE) for the first time. The aldehyde catalysts and the organic acid solvents for the asymmetric transformation reaction were rapidly screened and the enantiomeric excess values of the asymmetric product of L-Pro were directly obtained from the electrophoretogram of CAE.     

Determination of stability constants of valinomycin complexes with ammonium and alkali metal ions by capillary affinity electrophoresis

Capillary affinity electrophoresis (CAE) has been employed to investigate quantitatively the interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with univalent cations, ammonium and alkali metal ions, K(+), Cs(+), Na(+), and Li(+), in methanol. The study involved measuring the change in effective electrophoretic mobility of valinomycin while the cation concentrations in the BGE were increased. The corresponding apparent stability (binding) constants of the valinomycin-univalent cation complexes were obtained from the dependence of valinomycin effective mobility on the cation concentration in BGE using a nonlinear regression analysis. The calculated apparent stability constants of the above-mentioned complexes show the substantially higher selectivity of valinomycin for K(+) and Cs(+) ions over Li(+), Na(+), and NH(4)(+) ions. CAE proved to be a suitable method for the investigation of both weak and strong interactions of valinomycin with small ions.     

Synthesis of 4,4′‐bis (4‐oxyphenoxy)benzophenone diglycidyl ether and the thermal stability for blends with 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexanecarboxylate

We synthesized novel aromatic epoxy, 4,4′‐bis(4‐oxyphenoxy)benzophenone diglycidyl ether (DGEEK), by a three step reaction sequence and then it was blended with 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexanecarboxylate (CAE). The DGEEK structure was confirmed by FT‐IR and ¹H‐NMR measurement. Also, we investigated thermal properties of DGEEK/CAE blend epoxy by differential scanning calorimeter (DSC) and thermogravimetry analyzer (TGA). The glass transition temperature increased but initial decomposition temperature of cured epoxy decreased through the increasing amounts of ether–ether–ketone group of the epoxy network structure. By increasing the DGEEK mole fraction in the DGEEK/CAE blend epoxy matrix, the curing peak temperature decreased and the curing activation energy for DGEEK/CAE blend epoxy systems showed a considerable decrease. Copyright © 2001 John Wiley & Sons, Ltd.     

Home-made capillary array electrophoresis for high-throughput amino acid analysis

A capillary array electrophoresis (CAE) with confocal rotary scanner for high-throughput carboxytetramethylrhodamine succinimidyl ester (TAMRA)-labeled amino acid (AA) analysis is presented. Performance of the CAE setup was evaluated with AA samples. Up to 128 capillaries could be detected in parallel. For the first time, the device was applied to separate the enantiomers of isoleucine, cysteine, and glutamic acid with cyclodextrin-modified electrolytes by capillary zone electrophoresis. Baseline separation of seven AAs is also demonstrated using micellar electrokinetic chromatography method.     

CAD-CAE及3D打印在《塑料制品设计》课程教学中的应用探索

在工科学生培养过程中引入先进的CIDO工程教育模式,对培养学生的实践能力和创新能力具有重要的作用和意义。本文在分析《塑料制品设计》课程教学特点的基础上,将工程实践中广泛应用的CAE/CAE技术引入课程教学,并进行了有益的探索,不仅对提高该课程教学效果有重要意义,同时可以促使学生学习和应用CAD/CAE软件。在此基础上,将制造业领域迅速发展的3D打印技术应用到课程教学,有助于学生了解先进技术,激发学生的学习兴趣并提高学生的创新能力。     

气辅注塑CAE模拟技术的理论基础及分析实例

阐述了CAE模拟技术在气体辅助注射成型模具设计过程中的重要意义；介绍了气体辅助注射成型充填流动分析及保压分析中塑料熔体所遵循的数学模型和粘度参数模型，并介绍了在粘性流体力学基础上对数学模型进行了合理的简化和假设的方法；运用CAE软件C—MOLD对汽车保险杠模具结构设计及成型工艺条件进行了气辅注射成型模拟分析，优化了气体充填成型工艺和充填效果，改善了制品表面质量和力学性能，提高了首试成功率。     

A novel collagenase-assisted extraction of active pharmaceutical ingredients from gelatin products for quantitative analysis by high performance liquid chromatography

High performance liquid chromatography (HPLC) is frequently used for quantifying drugs in gelatin capsules. Gelatin has a strong UV absorption that often overlaps with drug absorbances. Therefore, the gelatin capsules must be removed manually before analysis. This study describes a novel extraction method named collagenase-assisted extraction (CAE), which uses collagenase to degrade gelatin into fragments with reduced hydrophobicity, allowing gelatin-related peaks to elute immediately, eliminating interference with the drug peak and enabling use of whole gelatin capsules during drug quantification. Use of CAE eliminates powder loss when opening a gelatin capsule, allows extraction of drugs from the capsule, reduces analytical time, and extends HPLC column life.     

Caerulomycins and collismycins share a common paradigm for 2,2'-bipyridine biosynthesis via an unusual hybrid polyketide-peptide assembly Logic

Caerulomycins (CAEs) and collismycins (COLs), which mainly differ in sulfur decoration, are two groups of structurally similar natural products containing a 2,2'-bipyridine (2,2'-BP) core, derivatives of which have been widely used in chemistry. The biosynthetic pathways of CAEs and COLs remain elusive. In this work, cloning of the CAE biosynthetic gene cluster allowed us to mine a highly conserved gene cluster encoding COL biosynthesis in a Streptomyces strain that was previously unknown as a 2,2'-BP producer. In vitro and in vivo investigations into the biosynthesis revealed that CAEs and COLs share a common paradigm featuring an atypical hybrid polyketide synthase/nonribosomal peptide synthetase system that programs the 2,2'-BP formation. This likely involves an unusual intramolecular cyclization/rearrangement sequence, and a difference in processing of the sulfhydryl group derived from the same precursor cysteine drives the biosynthetic route toward CAEs or COLs.     

Integrated CMOS microchip system with capillary array electrophoresis

A complementary metal oxide semiconductor (CMOS)-capillary array electrophoresis (CAE) system has been used for DNA analysis. Because of its compactness and multiplex capability, the CAE-CMOS microchip is very suitable for the construction of a miniaturized high-throughput system for bioassays. Use of simultaneous laser-beam focusing on to the capillary array and a microscope objective contributed to the construction of the compact CMOS microchip-CAE system. To test the constructed system 100-base-pair (bp) DNA ladders and Hind III digest lambda DNA were separated in poly(vinylpyrrolidone) (PVP) sieving matrix. The miniaturized and integrated CMOS microchip system used in this work had great potential for combination with a variety of microfabricated devices for biomedical research.     

毛细管阵列电泳技术用于L-谷氨酸消旋化反应的条件优化

L-谷氨酸消旋化反应对于制备光学纯D-谷氨酸具有重要的意义。本文利用532 nm激光诱导荧光共聚焦检测式毛细管阵列电泳仪研究了L-谷氨酸基于席夫碱中间物的消旋化反应,采用羧基四甲基罗丹明琥珀酰亚胺酯(TAMRA)荧光探针标记消旋化产物后,以含有2 mmol/L环糊精(β-CD)的100 mmol/L Tris-硼酸缓冲液(pH 10)为分离电解质进行毛细管阵列电泳分析,在该条件下TAMRA标记的谷氨酸对映体可以得到基线拆分。详细考察了醛的种类及用量、羧酸溶剂的种类、反应体系的含水量对消旋化的影响,结果表明L-谷氨酸在含20%(体积分数)水的乙酸溶剂中,以水杨醛作为催化剂(水杨醛与L-谷氨酸的物质的量比为0.2)的优化条件下可以快速地被消旋化。     

DNA sequencing and genotyping in miniaturized electrophoresis systems

Advances in microchannel electrophoretic separation systems for DNA analyses have had important impacts on biological and biomedical sciences, as exemplified by the successes of the Human Genome Project (HGP). As we enter a new era in genomic science, further technological innovations promise to provide other far-reaching benefits, many of which will require continual increases in sequencing and genotyping efficiency and throughput, as well as major decreases in the cost per analysis. Since the high-resolution size- and/or conformation-based electrophoretic separation of DNA is the most critical step in many genetic analyses, continual advances in the development of materials and methods for microchannel electrophoretic separations will be needed to meet the massive demand for high-quality, low-cost genomic data. In particular, the development (and commercialization) of miniaturized genotyping platforms is needed to support and enable the future breakthroughs of biomedical science. In this review, we briefly discuss the major sequencing and genotyping techniques in which high-throughput and high-resolution electrophoretic separations of DNA play a significant role. We review recent advances in the development of technology for capillary electrophoresis (CE), including capillary array electrophoresis (CAE) systems. Most of these CE/CAE innovations are equally applicable to implementation on microfabricated electrophoresis chips. Major effort is devoted to discussing various key elements needed for the development of integrated and practical microfluidic sequencing and genotyping platforms, including chip substrate selection, microchannel design and fabrication, microchannel surface modification, sample preparation, analyte detection, DNA sieving matrices, and device integration. Finally, we identify some of the remaining challenges, and some of the possible routes to further advances in high-throughput DNA sequencing and genotyping technologies.     

Sparsely cross-linked "nanogels" for microchannel DNA sequencing

We have developed sparsely cross-linked "nanogels", sub-colloidal polymer structures composed of covalently linked, linear polyacrylamide chains, as novel DNA sequencing matrices for capillary electrophoresis. The presence of covalent cross-links affords nanogel matrices with enhanced network stability relative to standard, linear polyacrylamide (LPA), improving the separation of large DNA fragments. Nanogels were synthesized via inverse emulsion (water-in-oil) copolymerization of acrylamide and N,N-methylenebisacrylamide (Bis). In order to retain the fluidity necessary in a replaceable polymer matrix for capillary array electrophoresis (CAE), a low percentage of the Bis cross-linker (< 10(-4) mol%) was used. Nanogels were characterized by multiangle laser light scattering and rheometry, and were tested for DNA sequencing by CAE with four-color laser-induced fluorescence (LIF) detection. The properties and performance of nanogel matrices were compared to those of a commercially available LPA network, which was matched for both weight-average molar mass (Mw) and extent of interchain entanglements (c/c*). Nanogels presented in this work have an average radius of gyration of 226 nm and a weight-average molar mass of 8.8 x 10(6) g/mol. At concentrations above the overlap threshold, nanogels form a clear, viscous solution, similar to the LPA matrix (Mw approximately 8.9 x 10(6) g/mol). The two matrices have similar flow and viscosity characteristics. However, because of the physical network stability provided by the internally cross-linked structure of the nanogels, a substantially longer read length ( approximately 63 bases, a 10.4% improvement) is obtained with the nanogel matrix at 98.5% accuracy of base-calling. The nanogel network provides higher-selectivity separation of ssDNA sequencing fragments longer than 375 bases. Moreover, nanogel matrices require 30% less polymer per unit volume than LPA. This is the first report of a sequencing matrix that provides better performance than LPA, in a side-by-side comparison of polymer matrices matched for Mw and extent of interchain entanglements.     

21世纪毛细管电泳技术及应用发展趋势

在21世纪，毛细管电泳技术面临着新的挑战和机遇，在其检测手段，仪器的小型化和集成化，以及分离模式上都存在着极大的发展空间，文中针对这三方面的发展趋势和毛细管电泳的应用进行了讨论。     

Application of capillary affinity electrophoresis and density functional theory to the investigation of valinomycin–lithium complex

Capillary affinity electrophoresis (CAE) and quantum mechanical density functional theory (DFT) have been applied to the investigation of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with lithium cation Li⁺. Firstly, from the dependence of effective electrophoretic mobility of Val on the Li⁺ ion concentration in the background electrolyte (BGE) (methanolic solution of 50 mM chloroacetic acid, 25 mM Tris, pH_MeOH 7.8, 0–40 mM LiCl), the apparent binding (stability) constant (K_b) of Val–Li⁺ complex in methanol was evaluated as log K_b = 1.50 ± 0.24. The employed CAE method include correction of the effective mobilities measured at ambient temperature, at different input power (Joule heating) and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25 °C and to the constant ionic strength 25 mM. Secondly, using DFT calculations, the most probable structures of the non-hydrated Val–Li⁺ and hydrated Val–Li⁺·3H₂O complex species were predicted.