Nisin is a cationic antimicrobial peptide produced by some lactic acid bacteria. However, expression of nisin resistance protein (NSR) could confer nisin resistance on some non-nisin-producing Lactococcus lactis. To deeply elucidate molecular mechanism underlying NSR-mediated nisin resistance, an NSR mutant with N-terminal 38 amino acid residues deleted (NSR?38) was overexpressed in Escherichia coli by fusion with GST. Purified NSR?38 was obtained through glutathione (GSH) affinity chromatography followed by cleavage of GST tag. Putative proteolytic activity of NSR?38 was determined in vitro against nisin. Antimicrobial activity analysis revealed that nisin lost its bactericidal activity after incubation with NSR?38. Further reversed-phase high performance liquid chromatography (RP-HPLC) analysis indicated that NSR?38 displayed proteolytic activity against nisin, thus inactivating the antimicrobial peptide. The current study paves the way for in-depth functional studies on NSR.

Objective To study a processing method for EEG signals mixed with EOG and ECG signals disturbance.Methods First,the EEG was denoised by the hard threshold method,the soft threshold method,the compromise threshold method and the ? law threshold method in the second generation wavelet,and then the denoised EEG which still contained EOG and ECG was separated by fast independent component analysis( FastICA) algorithm.Results The ? law threshold method of the second generation wavelet had better denoising effect and FastICA algorithm had more ideal separate performance.Conclusion It is an effective preprocessing method for EEG in denoising with the ? law threshold method of the second generation wavelet and then in separating disturbance of independent source with FastICA algorithm.