The potential of antimicrobial peptides (AMPs) as an alternative to conventional therapies is well recognized. Insights into the biological and biophysical properties of AMPs are thus key to understanding their mode of action. In this study, the mechanisms adopted by two AMPs in disrupting the gram-negative Escherichia coli bacterial envelope were explored. BP100 is a short cecropin A-melittin hybrid peptide known to inhibit the growth of phytopathogenic gram-negative bacteria. pepR, on the other hand, is a novel AMP derived from the dengue virus capsid protein. Both BP100 and pepR were found to inhibit the growth of E. coli at micromolar concentrations. Zeta potential measurements of E. coli incubated with increasing peptide concentrations allowed for the establishment of a correlation between the minimal inhibitory concentration (MIC) of each AMP and membrane surface charge neutralization. While a neutralization-mediated killing mechanism adopted by either AMP is not necessarily implied, the hypothesis that surface neutralization occurs close to MIC values was confirmed. Atomic force microscopy (AFM) was then employed to visualize the structural effect of the interaction of each AMP with the E. coli cell envelope. At their MICs, BP100 and pepR progressively destroyed the bacterial envelope, with extensive damage already occurring 2 h after peptide addition to the bacteria. A similar effect was observed for each AMP in the concentration-dependent studies. At peptide concentrations below MIC values, only minor disruptions of the bacterial surface occurred.

This is an Author's Original Manuscript of an article published in Assessment and Evaluation in Higher Education, 2014, vol. 39, núm. 5, p. 592-610, available online at: http://dx.doi.org/10.1080/02602938.2013.860077Peer assessment provides students with multiple benefits during their learning process. The aim of our study is to examine students' perception of peer assessment. Questionnaires were administered before and after the peer-assessment process to 416 students studying 11 different subjects in four different fields taught at the University of Girona. Results suggest that students have a positive predisposition towards this methodology, both before and after its implementation. Students perceive it as a both motivating and recommended methodology that facilitates the acquisition of learning at different levels. As for its limitations, students highlight the responsibility that comes with it and a certain amount of distrust in fellow students' abilities to peer-asses

Short peptides of 11 residues were synthesized and tested against the economically important plant pathogenic bacteriaErwinia amylovora,Pseudomonas syringae, andXanthomonas vesicatoriaand compared to the previously described peptide Pep3 (WKLFKKILKVL-NH₂). The antimicrobial activity of Pep3 and 22 analogues was evaluated in terms of the MIC and the 50% effective dose (ED₅₀) for growth. Peptide cytotoxicity against human red blood cells and peptide stability toward protease degradation were also determined. Pep3 and several analogues inhibited growth of the three pathogens and had a bactericidal effect at low micromolar concentrations (ED₅₀of 1.3 to 7.3 μM). One of the analogues consisting of a replacement of both Trp and Val with Lys and Phe, respectively, resulted in a peptide with improved bactericidal activity and minimized cytotoxicity and susceptibility to protease degradation compared to Pep3. The best analogues can be considered as potential lead compounds for the development of new antimicrobial agents for use in plant protection either as components of pesticides or expressed in transgenic plants.