Highly sensitive and selective detection of cytochrome P450 46A1 activity by a ultra-high-performance liquid chromatography-tandem mass spectrometry method

Cytochrome P450 46A1 (CYP46A1) is a key enzyme responsible for metabolizing cholesterol to 24-hydroxycholesterol in the brain, and thus might serve as a therapeutic target for several neurodegenerative disorders including Parkinson's disease, Alzheimer's disease and Huntington's disease. However, an applicable, sensitive and reliable method for the precise measurement of CYP46A1 activities in complex biological samples remains limited. In this study, a novel ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for highly sensitive and selective determination of 24-hydroxycholesterol was developed to characterize CYP46A1 activity. The mass spectrometric detection was performed using multiple reaction monitoring for 24-hydroxcholesterol at m/z 385.2 → 367.2. The limit of quantification for 24-hydroxycholesterol using this UPLC-MS/MS method was as low as 10 nM, which is lower than those reported previously. The method also showed favorable accuracy and precision. Meanwhile, the short- and long-term stability of this method was fully validated. In addition, the method was successfully applied to investigate the kinetic properties of 24-hydroxycholesterol formation by CYP46A1.

Electrochemical sensing of methyl parathion on magnetic molecularly imprinted polymer

The electrochemical detection of methyl parathion in fish was performed by preconcentrating the pesticide on magnetic molecularly imprinted polymer and further readout on magneto-actuated electrode by square wave voltammetry. The magnetic molecularly imprinted polymer was synthesized by a magnetic core-shell strategy, using methacrylic acid as a functional monomer, and selected by theoretical calculation using the density functional theory (DFT). The characterization of this material was performed by SEM, TEM and XRD. Moreover, the binding capacity and selectivity towards methyl parathion was studied and compared with the corresponding magnetic non-imprinted polymer. The magneto-actuated electrochemical sensor showed outstanding analytical performance for the detection of methyl parathion in fish, with a limit of detection of as low as 1.22 × 10^-6 mg L^-1 and recovery values ranging from 89.4% to 94.7%. The magnetic molecularly imprinted polymer successfully preconcentrated the analyte from the complex samples and paves the way to incorporate this material in other platforms for the detection of this pesticide in the field of environmental control and food safety.

Rapid screening and identification of active ingredients in licorice extract interacting with V3 loop region of HIV-1 gp120 using ACE and CE-MS

The binding of envelope protein gp120 to glycosphingolipids is very important during the human immunodeficiency virus entering into the host cell. This step occurs in the V3 loop region in particularly. The conserved core sequence of V3 loop in gp120 was named R15K. Anti-HIV drug targeting to R15K would avoid the drug-resistance caused by HIV-1 genetic diversity. Here, for the first time, affinity capillary electrophoresis (ACE) and capillary electrophoresis-mass spectrometry (CE-MS) were used for establishing a simple, rapid and effective method of screening the licorice extract for biological activity (anti-HIV), which avoided the complicated isolation and purification process. R15K, 3'-sialyllactose (the positive control), and d-galactose (the negative control) were used for the development and validation of ACE method. After the interaction between licorice extract and R15K was confirmed by ACE, the relative active ingredients were isolated by SPE and their structures were determined by CE-ESI-MS online. In this research, two mixtures from licorice extract were found to be active. Furthermore, glycyrrhizin and licorice saponin G2 were verified as the main ingredients that significantly interacted with R15K via CE-MS and LC-MS. The results of quantitative assays showed that the active mixture contained glycyrrhizin of 74.23% and licorice saponin G2 of 9.52%. Calculated by Scatchard analysis method, glycyrrhizin/R15K complex had the highest binding constant (1.69 ± 0.08) × 10(7)L/mol among 27 compounds isolated from licorice extract. The anti-HIV activity of glycyrrhizin was further confirmed by bioactive experiment of cellular level. This strategy might provide a high throughput screening and identifying platform for seeking HIV-1 inhibitors in natural products.