Analysis of the Electrochemical Oxidation of Multiwalled Carbon Nanotube Tower Electrodes in Sodium Hydroxide

Towers of aligned multiwalled carbon nanotubes (MWCNTs) were electrochemically oxidized in aqueous 1 M NaOH. An oxidation current that decayed with time was monitored using amperometry at a fixed potential. Cyclic voltammetry showed that the background current and electrode capacitance increased after oxidation without significantly affecting the faradaic current from the reduction of ferricyanide. Oxidation in NaOH caused morphological changes and increased hydrophilicity of the MWCNT tower electrodes. XPS spectra indicated increased oxygen on the surface after oxidation, while Raman spectra indicated that a large amount of amorphous carbon was present before and after oxidation.     

The glycan patterns at the individual glycosylation sites in orosomucoid from allergic reaction patients

Summary Little is known about the alterations that have occurred at the individual glycosylation sites in allergy patients or how these glycosylation patterns may change after anti-allergy treatments. Using reverse-phase HPLC, we have quantitated the glycoforms present at the individual glycosylation sites on orosomucoid isolated from the sera of allergic reaction patients and an allergic reaction patient treated with the antihistamine Terfenadine. The glycan structures isolated from the five glycosylation sites for the individual taking Terfenadine were all within normal ranges. It is suggested that if the changes in glycosylation in OMD in the allergic state are functionally driven, then it should be possible to correlate biological activities with quantitative changes at the individual glycosylation sites, and hence further define the role of OMD in allergy and inflammation.     

Microdrop analysis of a bead-based immunoassay

The progress to electrochemical detection of a microbead-based immunoassay in small volumes has led to a reduced assay time and lower detection limits. Three electrochemical techniques are described for an immunoassay with detection in a microdrop. The techniques are amperometric detection with a rotating disk electrode (RDE), a microelectrode, and an interdigitated array (IDA) electrode. An enzyme-labeled sandwich immunoassay with mouse IgG as the model analyte is used to demonstrate the three techniques. The microbead assay is carried out in a test tube using a magnet to control bead collection. Once the immunocomplex is formed on the microbead, the beads are transferred to a microdrop where the enzyme, either alkaline phosphatase or β-galactosidase, generates 4-aminophenol (PAP). PAP is oxidized at the electrode with an applied potential of +290 mV vs. Ag/AgCl. For all three techniques, the upper limit of the dynamic range was 1000 ng/ml mouse IgG, and the detection limits were: 50 ng/ml for the RDE, 40 ng/ml for the microelectrode, and 26 ng/ml for the IDA electrode.     

Looking at long molecules in solution: what happens when they are subjected to Couette flow?

Knowing the structure of a molecule is one of the keys to deducing its function in a biological system. However, many biomacromolecules are not amenable to structural characterisation by the powerful techniques often used namely NMR and X-ray diffraction because they are too large, or too flexible or simply refuse to crystallize. Long molecules such as DNA and fibrous proteins are two such classes of molecule. In this article the extent to which flow linear dichroism (LD) can be used to characterise the structure and function of such molecules is reviewed. Consideration is given to the issues of fluid dynamics and light scattering by such large molecules. A range of applications of LD are reviewed including (i) fibrous proteins with particular attention being given to actin; (ii) a far from comprehensive discussion of the use of LD for DNA and DNA-ligand systems; (iii) LD for the kinetics of restriction digestion of circular supercoiled DNA; and (iv) carbon nanotubes to illustrate that LD can be used on any long molecules with accessible absorption transitions.     

荧光寿命的快速傅里叶变换拟合方法

介绍了一种利用快速傅里叶变换算法对稀土掺杂物质的荧光寿命进行数据拟合的方法。稀土掺杂物质可用来制备多种光学传感器,用于温度、pH值等多种参量测量领域。本方法利用快速傅里叶变换(FFT)结果作为基础,从非零项的相位角的正切值得出被测的荧光寿命,具有速度快、误差小、不受本底干扰等一系列优点。以掺铒光纤为例,通过数字仿真将本方法与其它几种传统的拟合方法进行了比较。快速傅里叶变换方法的测量偏差不到Prony方法的50％,为对数似合(log-fit)方法测量偏差的1／6。另外,快速傅里叶变换方法由于不受本底噪声影响,可以不必在信号处理时去掉本底噪声,因而可以明显缩短测量时间。     

Linear dichroism for the detection of single base pair mutations

Flow linear dichroism is shown to be able to detect single base mismatches in a polymerase chain reaction (PCR) amplimers from exon 10 of the human beta-glucocerebrosidase gene (associated with Gaucher disease) over a kilobase long with no post PCR manipulation.     

Effect of ion implantation on quantum well infrared photodetectors

Ion implantation is a postgrowth processing technique which, when combined with annealing, can be used to tune the absorption wavelength of quantum well devices. We have implanted and annealed, three different quantum well infrared photodetector structures, and measured the absorption spectra of the samples by Fourier transform spectroscopy. The peak absorption wavelength shift of each structure has been calculated as a function of diffusion length by simulating the diffusion processes. We found different diffusion rates for the structures and attribute this to different numbers of as-grown defects. Our results indicate that agglomeration of single defects into defect clusters limits the ability of ion implantation to tune the wavelength of a structure with a higher number of as-grown defects. Thus, a structure with the lowest number of as-grown defects is most useful for fabricating a multi-color quantum well photodetector by ion implantation, because in this case ion implantation can enhance the diffusion rate considerably leading to large red- shift in peak absorption wavelength.