Evaluation of Sample Preparation Methods for Non-Target Screening of Organic Micropollutants in Urban Waters Using High-Resolution Mass Spectrometry

Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers.

Molecular weight characterization of single globular proteins using optical nanotweezers

We trap a set of molecular weight standard globular proteins using a double nanohole optical trap.

Preparation of DNA Ladder Based on Multiplex PCR Technique

DNA molecular weight standard control, also called DNA marker (ladder), has been widely used in the experiments of molecular biology. In the paper, we report a method by which DNA marker was prepared based on multiple PCR technique. 100–1000 bp DNA fragments were amplified using the primers designed according to the 6631 ~ 7630 position of lambda DNA. Target DNA fragments were amplified using Touchdown PCR combined with hot start PCR, respectively, followed extracted by phenol/chloroform, precipitated with ethanol and mixed thoroughly. The results showed that the 100–1000 bp DNA fragments were successfully obtained in one PCR reaction, the bands of prepared DNA marker were clear, the size was right and could be used as control in the molecular biology experiment. This method could save time and be more inexpensive, rapid, simple when compared with the current DNA Ladder prepared means.

Glucose isomerase from Streptomyces rubiginosus – potential molecular weight standard for small-angle X-ray scattering

Stability of solutions of glucose isomerase from Streptomyces rubiginosus on long-term storage and on exposure to synchrotron radiation has been studied by the small-angle X-ray scattering (SAXS) method. The values of the radii of gyration and forward scattering do not change significantly on storage and on exposure to synchrotron radiation. The mean value of the radius of gyration characterizing glucose isomerase is R G = 3.27 ± 0.02 nm. For comparison, a SAXS study of monodispersive and aggregated bovine serum albumin (BSA) has been carried out. The results show that glucose isomerase could be a more stable molecular weight standard for SAXS than BSA.