ABSTRACT
Nonmagnetic graphene-based van der Waals heterotrilayers exhibit peculiar electronic features such as energetically and/or spatially resolved Dirac rings/cones. Here, using first-principles calculations we study the effect of magnetic proximity effect and mirror symmetry of antiferromagnetic CrAs2 monolayer sandwiched between graphene on the Dirac cones. We clearly identify the common vertical shift of the Dirac bands in the spin up channel. While in the spin down channel, we surprisingly observe the remarkable transverse splitting Dirac cones. The underling mechanism can be attributed to the static electric field caused by the charge transfer between the interlayers, and the polarized field arising from the weakly magnetized graphene. Both fields collectively give rise to an inequivalent space inversion broken between graphene and CrAs2 layers. Such unique Dirac states are absent in its nonmagnetic or ferromagnetic counterpart, ferromagnetic heterotrilayer with the glide symmetry, and graphene/CrAs2 heterobilayer. Our findings would provide a new insight into the correlation between Dirac cones and magnetic monolayer sandwiched between graphene.
ABSTRACT
AIM: To express the major capsid protein of human papillomavirus type 16 L1(HPV 16 L1) in E.coli and identify its immune activity. METHODS: The L1 gene of HPV 16 was cloned into the expression vector pThioHisC. The recombinant expression vector was transformed into E.coli, and the HisC-L1 protein was expressed under IPTG induction. The fusion protein was characterized by SDS-PAGE and Western blot. RESULTS: The HPV16-L1 gene in plasmid pThioHisC was expressed in E.coli as a fusion protein with M(r) about 70,800. The fusion protein reacted specifically with antibodies against HPV16-L1. CONCLUSION: The HPV-16 L1 gene was expressed successfully in E.coli, which provides necessary basis for preparing HPV-16 L1 vaccine in human.
