Histidine-containing host-defence skin peptides of anurans bind Cu2+. An electrospray ionisation mass spectrometry and computational modelling study

Mg alloy surface immobilised with caerin peptides acquires enhanced antibacterial ability and putatively improved corrosion resistance

Magnesium (Mg) has mechanical properties similar to human bones and Mg alloy is considered ideal medical implant material. However, the high velocity of degradation inside the human inner environment severely hampers the usage of Mg alloys. In this study, caerin peptide 1.9 (F3) and a modified sequence of caerin 1.1 (F1) with anti-bacterial activity, were covalently immobilised on the surface of Mg alloys by plasma chemical click reaction. The in vitro antibacterial activity and corrosion resistance of these caerin peptide-immobilised Mg alloys were investigated in Dulbecco's Modified Eagle Medium (DMEM) solution. Un-immobilised Mg alloy sample, blank drug-sensitive tablet (BASD) and a commonly used antibiotics Tazocin were used for comparison. Results showed that peptide immobilised Mg samples showed observable improved corrosion resistance and prolonged antibacterial effect compared to non-immobilised Mg alloy and free caerin peptides. These results indicate that coating Mg alloy with caerin peptides obviously increases the alloy's antibacterial ability and putatively improves the corrosion resistance in vitro. The mechanism underlying the prolonged antibacterial effect for annealed Mg alloys immobilised with the peptides (especially F3) remains unclear, which worth further experimental and theoretical investigation.

Caerin 1 Antimicrobial Peptides That Inhibit HIV and Neisseria May Spare Protective Lactobacilli

Although acquired immunodeficiency syndrome (AIDS) caused by the human immunodeficiency virus (HIV) is a manageable disease for many, it is still a source of significant morbidity and economic hardship for many others. The predominant mode of transmission of HIV/AIDS is sexual intercourse, and measures to reduce transmission are needed. Previously, we showed that caerin 1 antimicrobial peptides (AMPs) originally derived from Australian amphibians inhibited in vitro transmission of HIV at relatively low concentrations and had low toxicity for T cells and an endocervical cell line. The use of AMPs as part of microbicidal formulations would expose the vaginal microbiome to these agents and cause potential harm to protective lactobacilli. Here, we tested the effects of caerin 1 peptides and their analogs on the viability of two species of common vaginal lactobacilli (Lactobacillus rhamnosus and Lactobacillus crispatus). Several candidate peptides had limited toxicity for the lactobacilli at a range of concentrations that would inhibit HIV. Three AMPs were also tested for their ability to inhibit growth of Neisseria lactamica, a close relative of the sexually transmissible Neisseria gonorrhoeae. Neisseria lactamica was significantly more sensitive to the AMPs than the lactobacilli. Thus, several candidate AMPs have the capacity to inhibit HIV and possible N. gonorrhoeae transmission at concentrations that are significantly less harmful to the resident lactobacilli.

The membrane-active amphibian peptide caerin 1.8 inhibits fibril formation of amyloid β1-42

The amphibian host-defense peptide caerin 1.8 [(1)GLFKVLGSV(10)AKHLLPHVVP(20)VIAEKL(NH2)] inhibits fibril formation of amyloid β 1-42 [(1)DAEFRHDSG(10)YEVHHQKLVF(20)FAEDVGSNKG(30)AIIGLMVGGV(40)VIA] [Aβ42] (the major precursor of the extracellular fibrillar deposits of Alzheimer's disease). Some truncated forms of caerin 1.8 also inhibit fibril formation of Aβ42. For example, caerin 1.8 (1-13) [(1)GLFKVLGSV(10)AKHL(NH2) and caerin 1.8 (22-25) [KVLGSV(10)AKHLLPHVVP(20)VIAEKL(NH2)] show 85% and 75% respectively of the inhibition activity of the parent caerin 1.8. The synthetic peptide KLVFFKKKKKK is a known inhibitor of Aβ42 fibril formation, and was used as a standard in this study. Caerin 1.8 is the more effective fibril inhibitor. IC50 values (± 15%) are caerin 1.8 (75 μM) and KLVFFKKKKKK (370 μM). MALDI mass spectrometry shows the presence of a small peak corresponding to a protonated 1:1 adduct [caerin 1.8/Aβ42]H(+). Molecular dynamics simulation suggests that both hydrogen bonding and hydrophobic interactions between Aβ42 and caerin 1.8 facilitate the formation of a 1:1 complex in water. Fibril formation from Aβ42 has been proposed to be based around the (16)KLVF(20)F region of Aβ42; this region in the 1:1 complex is partially blocked from attachment of a further molecule of Aβ42.