RESUMEN
The magnetic bistability of spin-crossover (SCO) materials is highly appealing for applications as molecular switches and information storage. However, switching of the spin state around room temperature remains challenging. In this work, we reported the successful manipulation of the spin states of two iron(II) complexes (1-Fe and 2-Fe) based on pyridylacylhydrazone ligands in manifold ways. Both complexes are stabilized in the low-spin (LS) state at room temperature because of the strong ligand-field strength imposed by the ligands. 2-Fe shows thermoinduced SCO above room temperature with a very large and reproducible hysteresis (>50 K), while 1-Fe remains in the LS state up to 400 K. Acidity-driven spin-state switching of the two complexes was achieved at room temperature as a result of the complex dissociation and release of iron(II) in its high-spin (HS) state. Recovery of the complex is feasible upon further alkalization treatment in the case of 1-Fe, allowing bidirectional modulation of the spin state of the metal center. Light-driven one-way switching from LS to HS is also achieved by virtue of E-to-Z isomerization at the CâN double bond, which results in dissociation of the complex because of the poor binding affinity in the Z configuration.
RESUMEN
The actA gene was amplified from Lm-4 strain of Listeria monocytogenes serotype 1/2a by PCR and inserted into T vector. Sequencing showed actA gene was 1833bp long and nucleotide homology was 100% compared with actA gene of Listeria monocytogenes EGD strain in GenBank. The cloned actA gene was then inserted into prokaryotic expression vector pGEX-6P-1 and pET respectively. The predicted fusion protein was detected by SDS-PAGE after IPTG induction of recombinant bacteria. The fusion protein expressed in both vectors showed approximate molecular weight of 120kDa and 97kDa. The expressed fusion protein His-ActA was purified and used as antigen to immunize BALB/c mice, hybridomas were generated with traditional hybridoma techniques. McAbs were screened by ELISA, four hybridoma cell lines secreting antibodies against ActA protein were established and the ELISA titer of these ascitic McAbs were around 1 :5 x 10(4) - 1: 1 x 10(5) . The subtype and specifity of McAbs were identified by kit and Western blot. The McAb 1A5 reacted with the expressed fusion protein GST-ActA and His-ActA in Western blot, consistent with that of mouse anti-Lm-4 polyclonal antibodies. The successful expression of ActA protein in E. coli and preparation of its monoclonal antibodies has provided useful tools for studies on the biological activity of ActA protein and its role in listerial pathogenesis.
