Activity Determinants in Linear Spider Venom Peptide Fragments Against MRSA

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  Activity Determinants in Linear Spider Venom Peptide Fragments Against MRSA Abstract Objective: Using neural networks, we previously identified linear fragments of spider venom peptides active against methicillin-resistant Staphylococcus aureus (MRSA). Among them, peptide IX (IWLSLMKFAGKHL-NH 2 ) with a C -terminal amide displayed high antibacterial potency, whereas its non-amidated analogue, peptide X, was inactive. Peptide IX incorporates into zwitterionic multilamellar liposomes of dioleoylphosphatidylcholine (DOPC) without disrupting them, and also into anionic liposomes of dioleoylphosphatidylglycerol (DOPG) mimicking the MRSA cell membrane, leading to bilayer disruption. This study aims to elucidate the reasons for peptide X inactivation.  Methods: According to ¹H NMR spectroscopy, peptide X in water is governed by the ionization of the His12 residue. ³¹P NMR data show that peptide X interacts with DOPC and DOPG membranes. Monte Carlo simulations revealed conformati...

Insights into the distribution and ecology of the funnelweb spider Macrothele calpeiana in Portugal

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Insights into the distribution and ecology of the funnelweb spider Macrothele calpeiana in Portugal

Abstract

Biodiversity surveys are critical to prevent decline and extinction of ill-/unknown species through timely conservation action. This is particularly relevant when the species are neither iconic nor flagships, therefore lessening the potential for accessing conservation means, such as in the case of the mygalomorph spider Macrothele calpeiana. The species is endemic to southern Iberia but its distribution and ecology is barely documented in Portugal. Therefore, we made a comprehensive survey throughout its estimated range in the south of the country. The species is spread unevenly and patchily throughout low mountainous terrain in south/southwest Portugal, preferably along shale/ greywacke/clay roadside banks. It seems rare in the surrounding limestone area to the south and absent from the peneplain to the north. The webs were found in groups averaging 10.0±15.2 webs/site and predominantly orientated to the northern quadrants (68.1%), possibly to compensate for higher summer temperatures. Yet, this trend showed a reverse tendency in the north of the range, suggesting a possible temperature moderating effect of the nearby Atlantic ocean. The surrounding vegetation is largely dominated by cork oak forest, tall strawberry tree/ heather thicket, or open cork/holm oak woodland. Other vegetation types are low scrub, pine or eucalypt stands in smaller proportions. M. calpeiana seems constrained by specific microhabitat and microclimatic conditions, suggesting that it may be at risk from climate change and habitat disturbance.

Luís Palma, Ana Filipa Palmeirim "Insights into the distribution and ecology of the funnelweb spider Macrothele calpeiana in Portugal," Arachnology, 20(5), 659-669, (8 July 2026)