Fringing Field Effect of Orbitrap and Its Compensation Method

Since it was introduced, the Orbitrap has been proved to be a powerful ion analyzer whose resolution is affected by the fringing field in the electrode structure. Orbitrap is an ultra-high precision instrument. The gap between two outer half electrodes and the design of ion perforation on one side of the outer electrode will produce fringing field effect, resulting in the distortion of the ideal electrostatic field. The distorted field formed in the internal space of Orbitrap will have a serious impact on the resolution. Thermo Fisher Scientific is the only company that has a patent on Orbitrap mass spectrometers and related technologies, however, it has not provided relevant materials to explain the problem in detail and specific solutions, and few researchers have conducted in-depth research. Therefore, it is necessary to study the influence of the distortion field caused by the ion perforation and the outer electrode gap on the resolution, and propose a solution to the fringing field effect. In this work, ion optical simulation software (SIMION) was used to establish ideal, distorted and corrected models, in order to measure the limiting resolution of the orbital trap by measuring the axial vibration period dispersion corresponding to different initial axial amplitudes and different orbital radius. By comparing the experimental and theoretical results of the ideal model, the reliability of the selection of simulation parameters and the calculation method of ion motion were verified. In the distortion model experiment, the ion axial motion period dispersion caused by the fringing field effect arising from the outer electrode gap and ion perforation and its influence on the resolution was investigated. In the correction model experiment, it was proved that the distortion field can be corrected by adjusting the voltage of the two compensating electrodes, so as to overcome the fringing field effect caused by the ion perforation and the outer electrode gap. In addition, it was also found that the axial flight period error caused by radial dispersion in the corrected model is smaller than that in the ideal model, and the difference between the two is small in the axial dispersion. The comprehensive result of the corrected model is better than that of the ideal model. Therefore, the error caused by scratches on the surface of the electrodes can be corrected by adjusting the voltage of the compensating electrodes. The final simulation results showed that the limiting mass resolution for m/z 100 ion can reach to 2 500 000

Research progress and development trend in polymer based on myrcene

Myrcene, as a kind of conjugated diene from plants, its unique side chain and double bond structure on side chain provided a new way for the synthesis of new materials. This article introduced the research progress of homopolymerization and co-polymerization of myrcene with other monomers, as well as the application of myrcene in preparation of new materials, and prospected its development trend with 25 references

Identification of interacting proteins of retinoid-related orphan nuclear receptor gamma in HepG2 cells

The retinoid-related orphan nuclear receptor gamma (RORγ)plays critical roles in regulation of development, immunity andmetabolism. As transcription factor usually forms a proteincomplex to function, thus capturing and dissecting of theRORγ protein complex will be helpful for exploring themechanisms underlying those functions. After construction ofthe recombinant tandem affinity purification (TAP) plasmid,pMSCVpuro RORγ-CTAP(SG), the nuclear localization ofRORγ-CTAP(SG) fusion protein was verified. Followingisolation of RORγ protein complex by TAP strategy, sevencandidate interacting proteins were identified. Finally, the heatshock protein 90 (HSP90) and receptor-interacting protein 140(RIP140) were confirmed to interplay with RORγ byco-immunoprecipitation. Interference of HSP90 or/and RIP140genes resulted in dramatically decreased expression ofCYP2C8 gene, the RORγ target gene. Data from this studydemonstrate that HSP90 and RIP140 proteins interact withRORγ protein in a complex format and function asco-activators in the RORγ-mediated regulatory processes ofHepG2 cells

Cross-immunizing potential of tumor MAGE-A epitopes recognized by HLA-A*02:01-restricted cytotoxic T lymphocytes

Almost all melanoma cells express at least one member of theMAGE-A antigen family, making the cytotoxic T cells (CTLs)epitopes with cross-immunizing potential in this family attractivecandidates for the broad spectrum of anti-melanomaimmunotherapy. In this study, four highly homologous peptides(P264: FLWGPRALA, P264I9: FLWGPRALI, P264V9:FLWGPRALV, and P264H8: FLWGPRAHA) from the MAGE-Aantigens were selected by homologous alignment. All fourpeptides showed high binding affinity and stability toHLA-A*02:01 molecules, and could prime CTL immune responsesin human PBMCs and in HLA-A*02:01/Kb transgenicmice. CTLs elicited by the four epitope peptides couldcross-lyse tumor cells expressing the mutual target antigens,except MAGE-A11 which was not tested. However, CTLs inducedby P264V9 and P264I9 showed the strongest target celllysis capabilities, suggesting both peptides may represent thecommon CTL epitopes shared by the eight MAGE-A antigens,which could induce more potent and broad-spectrum antitumorresponses in immunotherapy