| Conotoxins and cobra neurotoxins are now two of the important polypeptide neurotoxins with much attention paid. Because of their particular characters, the study on these neurotoxins is not only a significant topic related to neurobiology and channel proteins' research, but also one project with great prospect in the medicine development as an analgesic drug and anti-tumor drug.SO3 is a new O-superfamily ω-conotoxin with analgesic activity obtained by gene cloning of analgesic conotoxin and peptide chemosynthesis. In present dissertation, studies on the analgesic mechanism of SO3 by using cellular biotechniques were carried out. It was observed that SO3 had little effect on the proliferation of PC-12 cells, but it could greatly inhibit the differentiation of PC-12 induced by NGF. SO3 also proved to have a protective action against brain hypoxic injury by hippocampal hypoxic experiments. The mechanism may be that SO3 can block the N-type calcium channel in pre-synaptical membrane. Thirdly, computer docking was performed to prove a theoretic possibility of combination of SO3 to N-type calcium channel protein.In the second part of work, a basic peptide with mass weight of 7597 Da was isolated and purified from the Naja naja atra venom . The results of protein sequencing and MALDI-TOF mass spectrometry showed that this peptide was a weak neurotoxin. Neurotoxicity and cytotoxicity assay were performed. It was found that, despite of low neurotoxicity, when applied to several non-neural cell lines, this weak neurotoxin exhibits synergic effects with cardiotoxins, which is firstly reported.
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