Fluorescent labeling of nisin Z and assessment of anti-listerial action

Biomolecule labeling by fluorescent markers has emerged as an innovative methodology for bio-analytical purposes in foodmicrobiology, medicine and pharmaceutics due to the great advantages of thismethod such as precision, wide detection limits, and in vivo recognition. Fluorescent nisin Z was synthesized by linking the carboxyl group and amino group of nisin Z and 5-aminoacetamido fluorescein (AAA-flu). This new structure was fully characterized by mass spectrometry with a molecular weight of 3717.3 Da. Intracellular K+ leakage and transmembrane electrical potential (Δψ)were used to evaluate the antibacterial action of the labeledmolecule against three listerial strains and demonstrated that nisin Z endured the labeling processwithout any activity loss. In vivo activity of labeled nisin was observed by confocal laser microscope which revealed its localization at the septum of listerial cell division sitewhere themembrane-bound cellwall precursor lipid II ismaximal. Fluorescent nisin Z showed its great potential as a tool to study antibacterial mechanism of action of nisin in biological system

Retinyl esters form lipid droplets independently of triacylglycerol and seipin

Lipid droplets store neutral lipids, primarily triacylglycerol and steryl esters. Seipin plays a role in lipid droplet biogenesis and is thought to determine the site of lipid droplet biogenesis and the size of newly formed lipid droplets. Here we show a seipin-independent pathway of lipid droplet biogenesis. In silico and in vitro experiments reveal that retinyl esters have the intrinsic propensity to sequester and nucleate in lipid bilayers. Production of retinyl esters in mammalian and yeast cells that do not normally produce retinyl esters causes the formation of lipid droplets, even in a yeast strain that produces only retinyl esters and no other neutral lipids. Seipin does not determine the size or biogenesis site of lipid droplets composed of only retinyl esters or steryl esters. These findings indicate that the role of seipin in lipid droplet biogenesis depends on the type of neutral lipid stored in forming droplets