光催化降解丙酮的原位红外研究

对催化剂.Pt/V2O5/MgF2在反应温度为120～150℃之间进行了光催化降解丙酮的研究,研究在可见光下进行,发现反应温度对光催化反应有明显的影响.在排除热反应的情况下,温度升高能加速丙酮的光催化反应.丙酮的光催化反应是从它的甲基上开始的,可能先生成了CH3COCH2O-吸附物,它进一步被氧化成丙酮醛、丙酮酸以及碳二醛、乙酸和碳一吸附物种,最终氧化成CO2和水.在没有光和较低的反应温度下,有CO生成,但是在可见光的照射下CO被迅速转化成CO2.研究表明,V2O5/MgF2与Pt/V2O5/MgF2为可见光条件下具备活性的光催化剂.     

Photochemistry of a naphthalene-thymine dyad in the presence of acetone

Irradiation of dyad 1 in aqueous acetone leads to the introduction of an acetonyl substituent at the naphthalene 5-position, to give photoproduct 2. The proposed reaction mechanism involves electron transfer from the naphthalene excited singlet state to the ketone. Neither thymine dimers, nor acetone photoadducts involving the thymine ring were detected. These photoproducts would arise from the thymine triplet excited state, which in dyad 1 must be efficiently depopulated via a fast intramolecular energy transfer to the naphthalene chromophore, due to the lower energy of its excited triplet state.     

Optimization of protein extraction and solubilization for mature grape berry clusters

Protein extraction from grape berries has been challenging, particularly in mature berries, which can have sugar concentrations as high as 26%. Grape skins and seeds contain large amounts of polyphenols, which can also interfere with efficient protein extraction. In plants, two extraction protocols, TCA/acetone-based and phenol-based methods, have been mainly used to extract proteins from different organs or tissues on many species. However, few results have been reported for grape berry clusters. We wanted to determine which of these protocols was optimal for berry clusters in order to achieve both efficient protein extraction and high spot resolution on 2-D gels. Four protocols, derived from either TCA/acetone or phenol procedures, were tested on mature Cabernet Sauvignon whole berry clusters. The phenol-based protocols were superior to the TCA/acetone methods, showing larger protein yields and greater spot resolution on 2-D gels. One method was clearly superior to the rest, a phenol-based extraction method combined with resuspension in the presence of both urea and thiourea as chaotropes. A total of 81 spots were excised and identified following MALDI-TOF/TOF MS analyses. Their identification helped further characterize the specificity of each extraction procedure.     

An implementable approach to obtain reproducible reduced ion mobility

Ion mobility spectrometry is increasingly in demand for medical applications and its potential for implementation in food quality and safety or process control suggest rising use of instruments in this field as well. All those samples are commonly extremely complex and mostly humid mixtures. Therefore, pre-separation techniques have to be applied. As ion mobility spectrometers with gas-chromatographic pre-separation acquire a huge amount of data, effective data processing and automated evaluation by comparison of detected peak pattern with data bases have to be utilised. This requires accurate on-line calibration of the instruments to guarantee reproducible results, in particular with respect to identification of an analyte by determination of its ion mobility and retention time. To reduce environmental and instrumental influence, the reduced ion mobility is used. It is derived from the drift time normalised to electric field, length of the drift region and to temperature and pressure of the drift gas (traditional method). All data required for this normalisation are afflicted with a particular error and thus leading to a deviation of the calculated ion mobility value. Furthermore, this traditional method enables a calculation of the reduced ion mobility only after the measurement. To avoid those errors and to enable on-line calibration of ion mobility, an instrument specific factor is implemented generally representing all relevant variables. This factor can be determined from an initial measurement of few spectra and can thereafter be applied on the following measurement. The application of this approach obtained reproducible reduced ion mobility values for positive and negative ions over a broad drift time range and for common variation of ambient conditions as well for varying instrument conditions such as electric fields respectively drift times and in different drift gases. Moreover, the reduced ion mobility is available already during the measurements with a significantly higher reliability and accuracy which was increased to a factor of 5 compared to the traditional ion mobility determination and enables an on-line identification of analytes for the first time.