Physico-chemical characterization of model bio-membranes and their interaction with potential therapeutic peptides

In the present Ph.D. thesis an extensive structural and functional study on model bio-membranes is presented. The first part of my research has been focused to understand how the lipid composition of the bio-membranes affects their biophysical properties and modulates their interactions with peptides. One of the biological processes involving lipid composition is the interaction between antimicrobial peptides (AMPs) and biological membranes. In fact, the selective interaction of AMPs with prokaryotic cells arises from the difference in the chemical composition between prokaryotic and eukaryotic membranes. Different mechanisms of membrane destruction have been proposed, depending on physico-chemical properties of AMPs and of the target bio-membranes. Among the large number of AMPs present in nature, Myxinidin, from hagfish (Myxine glutinosa L.), is a promising antimicrobial candidate due to its antibacterial activity against different pathogenic Gram negative and Gram positive bacteria. This thesis reports a comparative study of the interaction between Myxinidin and its mutant WMR with two model bio-membranes at different composition and complexity. In particular, in order to understand the role of lipid composition in the peptide-membrane interaction, two different models of bio-membranes have been studied mimicking P. aeruginosa and E. coli cell cytoplasmic membranes. The final goal was to elucidate the effect of amino acid residues substitutions of the peptides and the role of lipid composition on the antibacterial activity of Myxinidin and WMR against these two model bio-membranes.The collected data have allowed to recognize the AMPs specificity for a particular lipid composition and to propose a mechanism of membrane destabilization. In order to study the role of lipid composition in biological processes, another important model bacterial bio-membrane has been studied. In particular the work has been focused on a particular model of bio-membrane representative of Bradyrhizobium BTAi1 Gram negative bacterium, containing an unusual lipopolysaccharide (LPS) in which the lipid A is covalently linked to a hopanoid moiety The aim of this study was to understand the effect of this unique lipid A in modulating the stability and rigidity of the outer membrane of Bradyrhizobium BTAi1 strain. To obtain a wide physico-chemical characterization of the analyzed systems, a combined experimental strategy has been adopted, including spectroscopic and calorimetric techniques such as Circular Dichroism (CD) to study the secondary structure of peptides and its changes in lipid environment; Fluorescence to estimate the microenvironment of the peptides in the vesicles; Dynamic Light Scattering (DLS) to estimate the size and distribution of the liposomes in the absence and in the presence of peptides; (NMR) to obtain information about the conformation of the peptides in membrane environment; Electron Paramagnetic Resonance (EPR) to investigate the dynamics of the lipid hydrophobic tails in the bilayer; Differential Scanning Calorimetry (DSC) to understand the thermotropic behavior of liposomes and the effect of peptides on their phase transition; Isothermal Titration Calorimetry (ITC) to study the energetic of the interaction process between peptides and liposomes

“Good Vibrations”: A workshop on oscillations and normal modes

We describe some theatrical strategies adopted in a two hour workshop in order to show some meaningful experiments and the underlying useful ideas to describe a secondary school path on oscillations, that develops from harmonic motion to normal modes of oscillations, and makes extensive use of video analysis, data logging, slow motions and applet simulations. Theatre is an extremely useful tool to stimulate motivation starting from positive emotions. That is the reason why the theatrical approach to the presentation of physical themes has been explored by the group “Lo spettacolo della Fisica” (http://spettacolo.fisica.unimi.it) of the Physics Department of University of Milano for the last ten years (Carpineti et al., JCOM, 10 (2011) 1; Nuovo Cimento B, 121 (2006) 901) and has been inserted also in the European FP7 Project TEMI (Teaching Enquiry with Mysteries Incorporated, see http://teachingmysteries.eu/en) which involves 13 different partners coming from 11 European countries, among which the Italian (Milan) group. According to the TEMI guidelines, this workshop has a written script based on emotionally engaging activities of presenting mysteries to be solved while participants have been involved in nice experiments following the developed path

Hydrogeological and hydrogeochemical monitoring in the Cumae archaeological site (Phlegraean Fields, southern Italy)

Phlegraean Fields, hydrogeological model, hydrochemical facie

Smarcad1 mediates microbiota-induced inflammation in mouse and coordinates gene expression in the intestinal epithelium

Background How intestinal epithelial cells interact with the microbiota and how this is regulated at the gene expression level are critical questions. Smarcad1 is a conserved chromatin remodeling factor with a poorly understood tissue function. As this factor is highly expressed in the stem and proliferative zones of the intestinal epithelium, we explore its role in this tissue. Results Specific deletion of Smarcad1 in the mouse intestinal epithelium leads to colitis resistance and substantial changes in gene expression, including a striking increase of expression of several genes linked to innate immunity. Absence of Smarcad1 leads to changes in chromatin accessibility and significant changes in histone H3K9me3 over many sites, including genes that are differentially regulated upon Smarcad1 deletion. We identify candidate members of the gut microbiome that elicit a Smarcad1-dependent colitis response, including members of the poorly understood TM7 phylum. Conclusions Our study sheds light onto the role of the chromatin remodeling machinery in intestinal epithelial cells in the colitis response and shows how a highly conserved chromatin remodeling factor has a distinct role in anti-microbial defense. This work highlights the importance of the intestinal epithelium in the colitis response and the potential of microbial species as pharmacological and probiotic targets in the context of inflammatory diseases

WATZON: the Italian network of ecohydrology and critical zone observatories

The Italian initiative WATZON (WATer mixing in the critical ZONe) is a network of instrumented sites, bringing together six pre-existing long-term research observatories monitoring different compartments of the Critical Zone - the Earth's permeable near-surface layer from the tops of the trees to the bottom of the groundwater. These observatories cover different climatic and physiographic characteristics over the country, providing information over a climate and eco-hydrologic transect connecting the Mediterranean to the Alps. With specific initial scientific questions, monitoring strategies, databases, and modeling activities, the WATZON observatories and sites is well representative of the heterogeneity of the critical zone and of the scientific communities studying it. Despite this diversity, all WATZON sites share a common eco-hydrologic monitoring and modelling program with three main objectives: 1) assessing the description of water mixing process across the critical zone by using integrated high-resolution isotopic, geophysical and hydrometeorological measurements from point to catchment scale, under different physiographic conditions and climate forcing; 2) testing water exchange mechanisms between subsurface reservoirs and vegetation, and assessing ecohydrological dynamics in different environments by coupling the high-resolution data set from different critical zone study sites of the initiative with advanced ecohydrological models at multiple spatial scales; 3) developing a process-based conceptual framework of ecohydrological processes in the critical zone to translate scientific knowledge into evidence to support policy and management decisions concerning water and land use in forested and agricultural ecosystems. This work provides an overview of the WATZON network, its objectives, scientific questions, and data management, with a specific focus on existing initiatives for linking data and models based on WATZON data