SYNTHESIS AND BIOLOGICAL EVALUATION OF NEW NEURAMINIDASE INHIBITORS DERIVED FROM SIALIC ACID AS POTENTIAL ANTIVIRAL AGENTS

The development of new, potent and selective bacterial, viral and human sialidase (neuraminidase) inhibitors is an important issue to be pursued in order to achieve both useful therapeutical and biochemical tools. In fact, these hydrolytic enzymes can represent a good target since they play key roles in some physio-pathological processes by regulating the levels of sialic acid (such as the N-acetyl neuraminic acid; Neu5Ac) presents in glycoconjugates. In addition, in the design of inhibitors against a specific member of this class of enzymes is critical to take into account that these proteins share some common features such as the tridimensional structure of their catalytic domain, but, on the other hand, they show a very low sequence identity. Indeed, the only conserved residues are some active site amino acids essential for the catalytic mechanism. This thesis work was focused on the synthesis of hemagglutinin-neuraminidase (HN) inhibitors against the Newcastle virus (NDV), a member of the Paramyxoviridae family and strictly related to human parainfluenza viruses (hPIVs). NDV is a single-stranded RNA virus which could affect most species of both domestic and wild birds, causing significant and substantial economic losses in the poultry industry. To date, vaccination is the preferential instrument to border the infection, but when this procedure is not applicable, an efficient antiviral therapy could be the only useful way to control NDV outbreaks. At this purpose, the HN glycoproteins of paramyxoviruses represent an excellent target to be hit because they have some key roles in viral lifecycle: a) allowing viral attachment to the target cell; b) promoting the fusion process and, finally c) ensuring the release of the neo-synthesized virions. Over the past years, while some 2,3-unsaturated Neu5Ac derivatives (DANA derivatives) have been marketed as inhibitors against influenza virus neuraminidases (belonging to Orthomyxoviridae family), no compounds reach the clinical phase for paramyxoviruses treatment. In particular, few molecules have been developed for NDV-HN, and the N-trifluoroacetyl derivative of DANA (FANA) was still the best inhibitor until my thesis work. So, the necessity to find new, potent and possibly selective inhibitors against paramyxoviruses-HNs remain a key issue. At this purpose, the successful strategy, resulted fundamental to develop new NDV-HN inhibitors, was based on a multidisciplinary approach that combined the use of a) the chemical synthetic procedures, b) the computational docking studies and c) some biochemical activity assays. More in detail, the attention was directed to the study of two classes of inhibitors: \uf0a7 Some C5 or C4/C5 modified 2,3-unsaturated DANA derivatives, as reversible inhibitors. \uf0a7 Some scarcely investigated C2 modified 3,4-unsaturated Neu5Ac analogues, as irreversible ones. We finally reached satisfying results, regarding both classes of inhibitors: a) The understanding of the influence of the C5 N-perfluorinated substituents on the inhibitory activity of some 2,3-unsaturated DANA analogues, as potent and reversible NDV-HN inhibitors. b) The discovery of a new C5 N-perfluorinated inhibitor against NDV-HN as potent as FANA (the best NDV-HN inhibitor previously published) but more selective for NDV-HN towards human NEU3. c) The significant achievements of five new, potent and selective C4 and C5 modified 2,3-unsaturated DANA derivatives. All these compounds, combining the C4 azido or C4 p-toluensolfonamido group with the C5 N-perfluorinated chains, showed IC50 values in the nanomolar range; thus, they are up to 15-fold more potent than FANA. d) The set-up of more efficient synthetic procedures to achieve the 3,4-unsaturated Neu5Ac derivatives in high yields and \u3b2-anomeric stereoselectivity. e) The set-up of a smart and rapid method to unequivocally attribute the C2 configuration of the 3,4-unsaturated Neu5Ac inhibitors, via a 1,7-lactonization reaction. f) The mechanism elucidation of an unreported and unexpected chemical scrambling between the C4 and the C5 position of Neu5Ac derivatives (through a previously uncharacterized reaction intermediate). In addition, the rigid and induced fit docking simulation results permitted me to speculate on the interactions of the synthesized inhibitors with some active site amino acids, such as Lys236, a well know key residue involved in NDV-NH catalytic site activation mechanism and in fusion promotion activity. The comprehension of ligand/receptor interactions could lead to the development of molecules able to block, not only the neuraminidase activity of NDV-HN or other paramyxoviruses-HN, but also other viral functions mediated by these enzymes. Some of the obtained results allowed the publication of two scientific articles: \uf0a7 Rota, P., La Rocca, P., Piccoli, M., Montefiori, M., Cirillo, F., Olsen, L., Orioli, M., Allevi, P., and Anastasia, L. (2018) Potent Inhibitors against Newcastle Disease Virus Hemagglutinin-Neuraminidase, ChemMedChem 13, 236-240. \uf0a7 Rota, P., Papini, N., La Rocca, P., Montefiori, M., Cirillo, F., Piccoli, M., Scurati, R., Olsen, L., Allevi, P., and Anastasia, L. (2017) Synthesis and chemical characterization of several perfluorinated sialic acid glycals and evaluation of their in vitro antiviral activity against Newcastle disease virus, MedChemComm 8, 1505-1513

Human brain distinctiveness based on EEG spectral coherence connectivity

The use of EEG biometrics, for the purpose of automatic people recognition, has received increasing attention in the recent years. Most of current analysis rely on the extraction of features characterizing the activity of single brain regions, like power-spectrum estimates, thus neglecting possible temporal dependencies between the generated EEG signals. However, important physiological information can be extracted from the way different brain regions are functionally coupled. In this study, we propose a novel approach that fuses spectral coherencebased connectivity between different brain regions as a possibly viable biometric feature. The proposed approach is tested on a large dataset of subjects (N=108) during eyes-closed (EC) and eyes-open (EO) resting state conditions. The obtained recognition performances show that using brain connectivity leads to higher distinctiveness with respect to power-spectrum measurements, in both the experimental conditions. Notably, a 100% recognition accuracy is obtained in EC and EO when integrating functional connectivity between regions in the frontal lobe, while a lower 97.41% is obtained in EC (96.26% in EO) when fusing power spectrum information from centro-parietal regions. Taken together, these results suggest that functional connectivity patterns represent effective features for improving EEG-based biometric systems.Comment: Key words: EEG, Resting state, Biometrics, Spectral coherence, Match score fusio

Evolution equation for a model of surface relaxation in complex networks

In this paper we derive analytically the evolution equation of the interface for a model of surface growth with relaxation to the minimum (SRM) in complex networks. We were inspired by the disagreement between the scaling results of the steady state of the fluctuations between the discrete SRM model and the Edward-Wilkinson process found in scale-free networks with degree distribution $P(k) \sim k^{-\lambda}$ for $\lambda <3$ [Pastore y Piontti {\it et al.}, Phys. Rev. E {\bf 76}, 046117 (2007)]. Even though for Euclidean lattices the evolution equation is linear, we find that in complex heterogeneous networks non-linear terms appear due to the heterogeneity and the lack of symmetry of the network; they produce a logarithmic divergency of the saturation roughness with the system size as found by Pastore y Piontti {\it et al.} for $\lambda <3$.Comment: 9 pages, 2 figure

Outbreak of COVID-19 infection in children: fear and serenity

OBJECTIVE: The recent outbreak of SARS-CoV-2 greatly involves the resources of the global healthcare system, as it affects newborns, adults, and elders. This infection runs in three major stages: a mild cold-like illness, a moderate respiratory syndrome and a severe acute interstitial pneumonia. SARS-CoV-2 infection seems to have a more benign evolution in children. As a matter of fact, low susceptibility and minor aggressivity have been highlighted in most cases. There are currently no effective antiviral drugs treatment for the affected children. No sufficient results have been reached by the use of interferon (IFN), lopinavir/ritonavir, orbidol, and oseltamivir in the treatment of the coronaviruses infection. The aim of this short review is to highlight the differences existing between COVID-19 cases in adults and children

Thermal management of a high speed permanent magnet machine for an aeroengine

The paper describes the mechanical and thermal design of a high speed, high power density synchronous permanent magnet machine for an aero engine starter generator system with a power rating of 150 kW and maximum speed of 32,000 rpm. As both mechanical and thermal aspects have a direct impact on machine overall performance and weight reduction, a critical design optimisation was carried out. Intensive cooling is guaranteed by direct liquid oil-cooling of stationary components; a stator sleeve is also introduced into the airgap to prevent excessive windage. Thermal investigations were carried out by the means of Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) analyses. Experimental validation also allowed the identification of most critical machine temperatures and the validation of the models developed. Finite Element Analysis(FEA) is used for the static structural analyses of the statorsleeve

Optical Nonreciprocity of Cold Atom Bragg Mirrors in Motion

Copyright © 2013 American Physical SocietyReciprocity is fundamental to light transport and is a concept that holds also in rather complex systems. Yet, reciprocity can be switched off even in linear, isotropic, and passive media by setting the material structure into motion. In highly dispersive multilayers this leads to a fairly large forward-backward asymmetry in the pulse transmission. Moreover, in multilevel systems, this transport phenomenon can be all-optically enhanced. For atomic multilayer structures made of three-level cold 87Rb atoms, for instance, forward-backward transmission contrast around 95% can be obtained already at atomic speeds in the meter per second range. The scheme we illustrate may open up avenues for optical isolation that were not previously accessible

Umbilical Cord Mesenchymal Stromal Cells for Cartilage Regeneration Applications

Chondropathies are increasing worldwide, but effective treatments are currently lacking. Mesenchymal stromal cell (MSCs) transplantation represents a promising approach to counteract the degenerative and inflammatory environment characterizing those pathologies, such as osteoarthritis (OA) and rheumatoid arthritis (RA). Umbilical cord-(UC-) MSCs gained increasing interest due to their multilineage differentiation potential, immunomodulatory, and anti-inflammatory properties as well as higher proliferation rates, abundant supply along with no risks for the donor compared to adult MSCs. In addition, UC-MSCs are physiologically adapted to survive in an ischemic and nutrient-poor environment as well as to produce an extracellular matrix (ECM) similar to that of the cartilage. All these characteristics make UC-MSCs a pivotal source for a stem cell-based treatment of chondropathies. In this review, the regenerative potential of UC-MSCs for the treatment of cartilage diseases will be discussed focusing on in vitro, in vivo, and clinical studies