Antibacterial peptide can be easily degraded by protease and has the lethal effect on the host Escherichia coli. In order to solve these problems and further improve the expression ability of the Escherichia coli system, the antimicrobial peptide Spinosan-C of Paa spinosa was studied. First, the codon of Spinosan-C was optimized according to E. coli codon usage frequency. Then, the 8 multimeric Spinosan-C gene (8×Spinosan-C) was synthesized and cloned into prokaryotic expression vector pET-28a. The fusion antimicrobial peptide 8×Spinosan-C was further highly expressed in Escherichia coli strain Rosetta. The recombinant 8×Spinosan-C protein was then purified and cleaved specially by formic acid to generate the Spinosan-C monomer. Antibacterial test in vitro suggested that the cleaved Spinosan-C monomer had antibacterial bioactivity against the test bacteria. This study provides a technical reference for the largescale preparation of frog antimicrobial peptides.

Objective: To investigate the current status of professional identity among the undergraduates majoring in public affairs management and the related influence factors. Methods: A stratified cluster sampling method was used to conduct a questionnaire survey among the 115 undergraduates majoring in public affairs management in a medical university in Harbin, China, and the contents of the questionnaires included general status and professional identity. The t-test, one-way analysis of variance, and multiple linear regression analysis were used to analyze the influencing factors of professional identity. In-depth interviews were conducted for some students to explore the profound influencing factors for professional identity among the students majoring in public affairs management. Results: The overall level of professional identity was low among the undergraduates majoring in public affairs management in the medical university in Harbin, and the score of professional identity was 3.25±0.56. The scores of cognitive dimension, emotional dimension, behavioral dimension, and applicable dimension were 3.41±0.69, 3.21±0.78, 3.24±0.71, and 3.13±0.72, respectively. The multivariate analysis showed that grade, academic performance, major selection, and children number in family had significant influence on their professional identity. The students who were at grade four, who had high academic record (b=-0.276, P<0.01), who chose this major independently (b=-0.277, P<0.01), and who were the only child (b=-0.233, P<0.05) had a high score of professional identity. As for the undergraduates at different grades, the undergraduates at grades two and three had a significantly lower score of professional identity than those at grade four (b=-0.296 and -0.369, P<0.05), while there was no significant difference between the undergraduates at grades one and four (b=-0.008, P>0.05). Furthermore, the students with a high score of professional identity had higher possibility to pursue the job related to this major than those with a low score (3.39±0.53 vs. 2.92±0.49, t=4.414, P<0.01). Conclusion Universities should strengthen the publicity of the major of public affairs management, optimize the curriculum, and add job experience, so as to enhance professional identity among students with this major and provide talent for the field of public health management.