Micellisation of β-casein

We measured the dynamic (DLS) and static (SLS) light scattering behaviour of β-casein solutions in a 25 mM Na phosphate buffer at neutral pH as a function of temperature. At low temperatures (0 °C) β-casein is predominantly in a monomer state. With rising temperature micelles are formed with a (concentration-dependent) transition temperature in the range 15–30 °C. The transition is accompanied by a clear positive excess heat capacity. In DLS we observe two relaxation modes. The fast mode is attributed to the diffusive motion of the micelles and leads to a hydrodynamic radius of about 12 nm. The slow mode cannot be attributed to ‘physical’ particles. It is attributed to polydispersity or equivalently to long-range concentration fluctuations as proposed by Leclerc and Calmettes [15 and 16]. From SLS measurements we obtained the molecular mass and divided by the mass of a monomer (24 kDa) it gives the micellisation number, which seems to level off to about 30 at 40 °C. The measured micellisation number is predicted quite satisfactorily from a thermodynamic model for the calorimetric data as developed by Mikheeva et al. [26] and based on the shell model of Kegeles [24 and 25].     

Potential applications of microcalorimetry for the study of physical processes in pharmaceuticals

In calorimetry, the heat-flow to or from a sample is measured as a function of time (isothermal calorimetry) or temperature (scanning calorimetry). The technique is not dependent on the physical form of the sample and is usually non-destructive (exceptions include temperature-induced irreversible phase transitions and thermal decomposition). The inherent sensitivity of modern instruments allows measurements on the micro-Watt scale. Calorimetry is highly suited to the study of pharmaceutical systems because small sample masses are usually required and the technique is very sensitive to changes induced by, for instance, formulation or processing. It is the purpose of this review to show applications of both isothermal and scanning calorimetry in the field of physical and bio-physical pharmacy. Potential applications include studies of physical stability, excipient compatibility, chemical stability and the study of the potential interactions of and between macromolecules such as lipids, surfactants, and nucleic acids.     

Fe3O4@Au纳米星颗粒作为循环SERS基底用于农药残留物的检测

本文首先采用共沉淀的方法制备了Fe3O4纳米颗粒,随后经柠檬酸钠和对苯二酚还原氯金酸的方法在Fe3O4纳米颗粒的表面生成刺状Au纳米结构,进而获得Fe3O4@Au纳米星颗粒。该Fe3O4@Au纳米星颗粒作为SERS基底,用作农药残留物福美双和敌瘟磷的检测。由于高密度的Au纳米结构的尖端效应,该基底显示出高敏感的SERS活性。最后利用Fe3O4纳米颗粒的磁性,将其用于循环SERS测试,研究了其循环使用特性。     

Two immunoassay formats for fully automated CRP detection in human serum

Immunoassays are a proven approach towards fast, sensitive, cost-effective and easy-to-use analytical systems which are able to measure a variety of interesting analytes, especially in medical diagnostics. Herein, we report two assay formats, binding inhibition and sandwich assay format, for detection of C-reactive protein (CRP) in human serum. Both assays were characterised and compared with respect to their suitability and adaption into a complete sensor system. An automated, optical biosensor system, based on evanescent field technology, was used to carry out a full threefold calibration in each case. Owing to the resulting working ranges, 0.044–2.9 mg L⁻¹ and 0.13–22.9 mg L⁻¹, respectively, the assays qualify for use in detecting high-sensitivity CRP (C-reactive protein).     

一种基于室温工作的量子点光电探测器的微光读出和应用研究

针对量子点光电探测器线列进行微光检测研究,量子点探测器采用AlAs/GaAs/AlAs双势垒结构,GaAs宽阱中分别有一个InAs量子点(QDs)和In_0.15Ga_0.85As量子阱(QW),建立一个简单的器件模型进行分析。常温下,在632.8 nm He-Ne激光照射下,当光功率为 0.01 pW时,器件偏压-0.5 V,积分时间80.2 μs,电压响应率达到7.0×1011 V·W-1,具有非常高的灵敏度,这种光电探测器在300 K温度下可以探测光功率小于10-14 W极弱光。以这种量子点光电探测器为核心研制的高灵敏度光谱仪和分子超光谱系统结合对生物组织样本进行检测,研制了一种图谱相互验证,互为校正的生物组织光谱测量系统。     

High-sensitivity matrix-assisted laser desorption/ionization Fourier transform mass spectrometry analyses of small carbohydrates and amino acids using oxidized carbon nanotubes prepared by chemical vapor deposition as matrix

In matrix-assisted laser desorption/ionization (MALDI) Fourier transform mass spectrometry (FTMS) analyses of small oligosaccharides and amino acids, high sensitivities for oligosaccharides (10 fmol) were obtained by introducing oxidized carbon nanotubes (CNTs) with short and open-end structure as valuable matrix. The CNTs were deposited in porous anodic alumina (PAA) templates by chemical vapor deposition. Transmission electron microscopy (TEM) images show that those CNTs include low levels of amorphous carbon. Thus, the background interference signals generally caused by amorphous carbon powder in CNTs can be reduced effectively. Experiments also confirmed that the FTMS signal intensity of CNTs prepared in PAA template is much lower than that of commercial multi-wall carbon nanotubes (MCNTs). Moreover, the purified process for CNTs with mixed acid (H₂SO₄ and HNO₃) also contributed to the minimization of background. Intense signals corresponding to alkali cation adduct of neutral carbohydrates and amino acids have been acquired. In addition, reliable quantitative analyses for urine and corn root were also achieved successfully. The present work will open a new way to the application of oxidized CNTs as an effective matrix in MALDI MS research.     

高速转镜干涉成像光谱仪

介绍一种高速转镜干涉光谱仪原理,提出一种基于该原理的干涉成像光谱仪,该成像光谱仪有较大视场角,提高了扫描效率,特点是用带有倾角平面反射镜转动代替传统Michelson干涉成像光谱仪动镜的直线运动,解决了Michelson干涉成像光谱仪扫描效率低和不稳定的难题.