Mendes, B. | bioRxiv Science

bioRxiv2025

D-amino acid substitution and cyclisation enhance the stability and antimicrobial activity of arginine-rich peptides

Cationic peptides rich in arginine are potent antimicrobials but face challenges due to enzymatic degradation and potential host toxicity. We screened eight linear arginine-rich peptides for antimicrobial and haemolytic activity, identifying R4F4 as the most active. However, its efficacy decreased in the presence of human serum and trypsin. To enhance stability, we developed three R4F4 derivatives--D-R4F4, cyclic R4F4, and R4F4-C16--plus one R4-based peptide (R4-C16). Cyclisation and D-amino acid substitution significantly improved protease resistance and antimicrobial activity. Using fluorescence imaging, microscopy, and RNA sequencing, we revealed a complex mechanism involving membrane disruption, oxidative stress modulation, and transcriptomic changes in bacterial metabolic pathways. The R4F4-based peptides also displayed strong antibiofilm activity and good cytocompatibility. Our findings highlight the benefits of peptide optimisation--particularly D-amino acid incorporation and cyclisation--in improving stability and function. This work informs future design of antimicrobial peptides and deepens understanding of their multifaceted biological effects.

microbiology↗

bioRxiv2018

In-season internal and external training load quantification of an elite European soccer team

Elite soccer teams that participate in European competitions often have a difficult schedule, involving weeks in which they play up to three matches, which leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over the subsequent hours and days. Inadequate time recovery between matches can expose players to the risk of training and competing whilst not fully recovered. Controlling the level of effort and fatigue of players to reach higher performances during the matches is therefore critical. Therefore, the aim of the current study was to provide the first report of seasonal internal and external training load (TL) that included Hooper Index (HI) scores in elite soccer players during an in-season period. Sixteen elite soccer players were sampled, using global position system, session rating of perceived exertion (s-RPE) and HI scores during the daily training sessions throughout the 2015-2016 in-season period. Data were analysed across ten mesocycles (M: 1 to 10) and collected according to the number of days prior to a match. Total daily distance covered was higher at the start (M1 and M3) compared to the final mesocycle (M10) of the season. M1 (5589m) reached a greater distance than M5 (4473m) (ES = 9.33 [12.70, 5.95]) and M10 (4545m) (ES = 9.84 [13.39, 6.29]). M3 (5691m) reached a greater distance than M5 (ES = 9.07 [12.36, 5.78]), M7 (ES = 6.13 [8.48, 3.79]) and M10 (ES = 9.37 [12.76, 5.98]). High-speed running distance was greater in M1 (227m), than M5 (92m) (ES = 27.95 [37.68, 18.22]) and M10 (138m) (ES = 8.46 [11.55, 5.37]). Interestingly, the s-RPE response was higher in M1 (331au) in comparison to the last mesocycle (M10, 239au). HI showed minor variations across mesocycles and in days prior to the match. Every day prior to a match, all internal and external TL variables expressed significant lower values to other days prior to a match (p<0.01). In general, there were no differences between player positions.\n\nConclusionsOur results reveal that despite the existence of some significant differences between mesocycles, there were minor changes across the in-season period for the internal and external TL variables used. Furthermore, it was observed that MD-1 presented a reduction of external TL (regardless of mesocycle) while internal TL variables did not have the same record during in-season match-day-minus.

physiology↗