The Effect of Geometrical Isomerism of 3,5-Dicaffeoylquinic Acid on Its Binding Affinity to HIV-Integrase Enzyme: A Molecular Docking Study

A potent plant-derived HIV-1 inhibitor, 3,5-dicaffeoylquinic acid (diCQA), has been shown to undergo isomerisation upon UV exposure where the naturally occurring 3trans,5trans-diCQA isomer gives rise to the 3cis,5trans-diCQA, 3trans,5cis-diCQA, and 3cis,5cis-diCQA isomers. In this study, inhibition of HIV-1 INT by UV-induced isomers was investigated using molecular docking methods. Here, density functional theory (DFT) models were used for geometry optimization of the 3,5-diCQA isomers. The YASARA and Autodock VINA software packages were then used to determine the binding interactions between the HIV-1 INT catalytic domain and the 3,5-diCQA isomers and the Discovery Studio suite was used to visualise the interactions between the isomers and the protein. The geometrical isomers of 3,5-diCQA were all found to bind to the catalytic core domain of the INT enzyme. Moreover, the cis geometrical isomers were found to interact with the metal cofactor of HIV-1INT, a phenomenon which has been linked to antiviral potency. Furthermore, the 3trans,5cis-diCQA isomer was also found to interact with both LYS156 and LYS159 which are important residues for viral DNA integration. The differences in binding modes of these naturally coexisting isomers may allow wider synergistic activity which may be beneficial in comparison to the activities of each individual isomer

Brazilian cave heritage under siege

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Xenopus laevis as UberXL for nematodes

The effect of invasive species on local parasite dynamics is often overlooked. The African Clawed Frog Xenopuslaevis (Daudin, 1802) (Anura: Pipidae) is a global invader, with established populations on four continents and is a domestic exotic in southern Africa. Despite a century of parasitological surveys, the current study reports seven previously unrecorded nematode species parasitising X. laevis across South Africa. These are adult Capillaria sp. and Falcaustra sp. from the intestine, third stage larvae of Contracaecum sp. encysted in the body cavity, third stage larvae of Paraquimperia sp. and Tanqua sp. from the intestine and two different species of second stage nematode larvae from the lungs and kidneys, respectively. Morphological descriptions,  photomicrographs and molecular data of the 18S and 28S rRNA and COI genes are provided to aid future investigations. We propose that these nematodes could well be using X. laevis as a definitive, paratenic and intermediate host, probably involving native fish, piscivorous birds, semi-aquatic reptiles and invertebrates in their life cycles. All recovered nematodes are recorded for the first time herein in association with X. laevis, except for the genus Contracaecum, members of which have previously been recorded from invasive X. laevis from California and Chile. The current study illustrates that X. laevis is an important parasite reservoir in its native range, with implications for its role in the invasive range. The fact that none of these nematodes could be identified to species level underscores the importance of providing morphological descriptions and molecular data when reporting on parasitological surveys, especially those of known invasive species. Keywords: African clawed frog, Capillaria, Contracaecum, Falcaustra, Paraquimperia; parasite reservoir, Tanqu

The Hormetic Effect Observed for Benzalkonium Chloride and Didecyldimethylammonium Chloride in <i>Serratia</i> sp. HRI

Hormesis, or the hormetic effect, is a dose- or concentration-dependent response characterised by growth stimulation at low concentrations and inhibition at high concentrations. The impact of sub-lethal levels of disinfectants on the growth of Serratia species is critical to understanding the increasing number of outbreaks caused by this pathogen in healthcare settings. Serratia sp. HRI and Serratia marcescens ATCC 13880 were cultivated in sub-lethal levels of benzalkonium chloride (BAC), Didecyldimethylammonium chloride (DDAC), and VirukillTM. The maximum specific growth rates, doubling times, and cell counts were compared. The results revealed significant increases in maximum specific growth rates and shorter doubling times for Serratia sp. HRI when cultivated in sub-lethal levels of BAC and DDAC. The significant stimulatory effect of sub-lethal levels of these disinfectants for Serratia sp. HRI represents the first time hormesis has been observed in a Gram-negative bacterium for any disinfectant. Furthermore, this study is the first to observe the hormetic effect after treatment with DDAC and the second study to date analysing the impact of sub-lethal levels of disinfectants on the growth of bacterial species

Biodiversity - Confronting amphibian declines and extinctions

Stopping further global losses of amphibian populations and species requires an unprecedented conservation response