Interaction of antimicrobial peptide Plantaricin149a and four analogs with lipid bilayers and bacterial membranes

The amidated analog of Plantaricin149, an antimicrobial peptide from Lactobacillus plantarum NRIC 149, directly interacts with negatively charged liposomes and bacterial membranes, leading to their lysis. In this study, four Pln149-analogs were synthesized with different hydrophobic groups at their N-terminus with the goal of evaluating the effect of the modifications at this region in the peptide's antimicrobial properties. The interaction of these peptides with membrane models, surface activity, their hemolytic effect on red blood cells, and antibacterial activity against microorganisms were evaluated. The analogs presented similar action of Plantaricin149a; three of them with no hemolytic effect (< 5%) until 0.5 mM, in addition to the induction of a helical element when binding to negative liposomes. The N-terminus difference between the analogs and Plantaricin149a retained the antibacterial effect on S. aureus and P. aeruginosa for all peptides (MIC50 of 19 µM and 155 µM to Plantaricin149a, respectively) but resulted in a different mechanism of action against the microorganisms, that was bactericidal for Plantaricin149a and bacteriostatic for the analogs. This difference was confirmed by a reduction in leakage action for the analogs. The lytic activity of Plantaricin149a is suggested to be a result of the peptide-lipid interactions from the amphipathic helix and the hydrophobic residues at the N-terminus of the antimicrobial peptide.

Efeito da alteração ambiental sobre componentes psicológicos e parâmetros fisiológicos durante corrida em atletas / Effect of environment alteration in psychological components and physiological parameters during the treadmill running in athletes

Avaliou-se o efeito da alteração ambiental no afeto, percepção subjetiva do esforço e em parâmetros fisiológicos durante a corrida em atletas. Dezoito atletas de andebol atenderam a quatro sessões experimentais de corrida na esteira (linha de base, fragmentada, superestimada e indefinida) de 20 minutos. Foram avaliados: afeto, percepção subjetiva do esforço, frequência cardíaca e cortisol. Manipulou-se a informação sobre a duração da corrida. Verificou-se um aumento estatisticamente significativo para o afeto no decorrer da corrida das sessões "fragmentada" e "superestimada", assim como no nível de cortisol salivar aos 11 minutos da corrida. O controle do comportamento afetivo dos atletas parece amenizar desgastes fisiológicos frente a adversários desconhecidos e condições indefinidas de jogo.

It was evaluated the effect of environmental alteration in affect, perceived exertion and in physiological parameters during treadmill running in athletes. Eighteen handball players participated in four running experimental sessions (baseline, fragmented overrated and unknown) for 20 minutes. It was analyzed: affect, rating of perceived exertion, heart rate and cortisol. Information about the running duration was manipulated. It was observed a statistically significant increase in affect during the treadmill running for the "fragmented" and "overrated " sessions, as well as in salivary cortisol level at the 11th minute of running. The control of athletes' affective behavior seems to relieve physiological damage when facing unknown opponents and uncertain game conditions.