Native agarose gel electrophoresis and electroelution: A fast and cost‐effective method to separate the small and large hepatitis B capsids

Hepatitis B core antigen (HBcAg) expressed in Escherichia coli is able to self‐assemble into large and small capsids comprising 240 (triangulation number T = 4) and 180 (triangulation number T = 3) subunits, respectively. Conventionally, sucrose density gradient ultracentrifugation and SEC have been used to separate these capsids. However, good separation of the large and small particles with these methods is never achieved. In the present study, we employed a simple, fast, and cost‐effective method to separate the T = 3 and T = 4 HBcAg capsids by using native agarose gel electrophoresis followed by an electroelution method (NAGE‐EE). This is a direct, fast, and economic method for isolating the large and small HBcAg particles homogenously based on the hydrodynamic radius of the spherical particles. Dynamic light scattering analysis demonstrated that the T = 3 and T = 4 HBcAg capsids prepared using the NAGE‐EE method are monodisperse with polydispersity values of ～15% and ～13%, respectively. ELISA proved that the antigenicity of the capsids was not affected in the purification process. Overall, NAGE‐EE produced T = 3 and T = 4 capsids with a purity above 90%, and the recovery was 34% and 50%, respectively (total recovery of HBcAg is ～84%), and the operation time is 15 and 4 times lesser than that of the sucrose density gradient ultracentrifugation and SEC, respectively.     

Microstructural and mechanical analysis of Cu and Au interconnect on various bond pads

Effects of High Temperature Storage (HTS) and bonding toward microstructure change of intermetallic compound (IMC) at the wire bonding interface of 3 types of bond pad (Al, AlSiCu and NiPdAu) were presented in this paper. Optical and electron microscope analyses revealed that the IMC growth rate of samples under 175 and 200 °C HTS increased in the order of Al > AlSiCu > NiPdAu. Besides, higher HTS and bonding temperatures also promoted higher IMC thickness. The compositional study showed that higher HTS and bonding temperature developed rapid interdiffusion in bonding interface. In the mechanical ball shear test, a decrease of the shear force of Al and AlSiCu bond pads after 500 h HTS was believed due to poorly developed IMC at bonding interface. On the other hand, shear force degradation at 1000 h was due to excessive growth of IMC that in turn causes the formation of defects. For NiPdAu bond pad, increasing trend of shear force with HTS duration at 175 °C implied a good reliability of the Cu wire bonding. The rapid microscopic inspection on Cu wired Al bond pad under HTS 175 °C showed the IMC development from the periphery to the center of the ball bond. However, after 500 h voids started to develop until the crack was observed at 1000 h.     

The mixed and multi model line balancing problem: a comparison

The balancing problem deals with the assignment of tasks to work stations. We can distinguish two approaches in the literature on the mixed model line balancing problem, that both transform this problem into a single model line balancing problem. These approaches use combined precedence diagrams and adjusted task processing times, respectively.An experiment was carried out to compare several heuristics based on the combined precedence diagram. A new optimisation method has been developed. The results indicate that the position of common tasks in the precedence diagram of the different models has a significant effect on both the CPU time and the unequal distribution of the total work content of single models among work stations. Moreover, good solutions with respect to the number of required stations go together with long CPU times. For several instances, we decreased the CPU times considerably without deteriorating the performance of the methods, by using a reversed combined precedence diagram.     

ON INDUCED PHOTOCHROMISM OF THE C-PHYCOCYANIN CHROMOPHORE: THE ZINC COMPLEX IN MICELLES*

Abstract— Absorption spectra of the chromophore of C-phycocyanin, in its free base form and as its zinc complex, were measured after denaturation with 8 M urea and with a cationic detergent. An acidic and an alkaline form of the zinc complex are distinguished. The acidic form shows photoreversible photochrom-ism, but only when it is embedded in detergent micelles. The photochromism is tentatively ascribed to a direct photoisomerization of the chromophore.     

PHOTOINHIBITION OF CHLOROPLAST REACTIONS

Abstract— An attemlpt was made to localize the site of photoinhibition of photosynthesis by measuring the decay of various chloroplast reactions after exposure to very strong light. A11 substrate reductions coupled to oxygen evolution as well as photophosphorylation mediated by PMS, proved equally sensitive to photoinhibition. Reactions involving only the long wave photosystem, such as TPN reduction with ascorbate as electron donor and photooxidation of cytochromec by detergent-treated chloroplasts were sensitive to a lower degree.
Photoinhibition irreversibly annihilated the 'variable' fraction of fluorescence emission —it decreased the steady state yield 2-3 fold and abolished the slow rise of the emission at the onset of illurnination.
It is concluded that the primary site of light inactivation is in, or close to, the trapping centers of the oxygen evolving step of photosynthesis. Pre-illumination leaves these traps in a state capable of draining light from sensitizing pigments but unable to perform useful photochemistry.     

Thermoanalytical studies of rubber oxidation catalyzed by metallic ions

The effects of several metallic ions on the oxidation of natural rubber were studied by differential scanning calorimetry (DSC). The activation energy of oxidation was evaluated from DSC curves. Cobalt, manganese, iron and copper ions decreased the activation energy of oxidation. Nickel, zinc and tin ions did not affect the activation energy. The effective ions are those which are able to undergo one-electron transfer redox reaction with hydroperoxide. Based on the activation energy values, the catalytic activities of metallic ions are: Co > Mn > Cu ? Fe > Ni ? Zn ? Sn.     

Determination of propamocarb in vegetables using polymer-based high-performance liquid chromatography coupled with electrospray mass spectrometry

A method for the determination of propamocarb in vegetables with liquid chromatography-electrospray ionisation mass spectrometry (LC-ESI-MS) was developed. The performance of a polymer-based analytical LC column for the separation was investigated. Residues of propamocarb were extracted from the matrix with methanol. Subsequently, the extract was directly injected into the LC-MS system, without any additional concentration or cleanup procedures. Separation of propamocarb from the matrix components was achieved on a polymethacrylate-based analytical column. Propamocarb was concurrently detected with electrospray ionisation mass spectrometry in the selected ion monitoring mode and two-stage full scan MS application. Quantitation was done with matrix-matched calibration standards of propamocarb. Unambiguous confirmation was achieved by comparison of the full scan product ion mass spectrum of the chromatographic peak in the sample with the spectrum of a standard solution of propamocarb at the same retention time. The analytical performance of the method was validated for five relevant matrices, spiking propamocarb at fortification levels from 0.05 to 15.0 mg kg(-1). This covers the range of maximum residue limits in agricultural commodities, stated in the Dutch national legislation. The mean recovery of propamocarb was better than 90% with a precision of less than 10% in both scanning applications. As could be concluded from the calibration curve and matrix background levels, observed in blank control samples, the estimated limit of detection was 25 microg kg(-1) for the two-stage full scan MS application. The method has been applied in a survey of 285 samples of lettuce, radish, leek, and cabbage for the presence of residues of propamocarb. In 50% of the samples analysed, a residue of propamocarb was detected.