Comparison between numerical models for the simulation of moving contact lines

The aim of this study is to discus different numerically models for the simulation of moving contact lines in the context of a Volume of Fluid–Continuum Surface Force (VoF–CSF) method. We focus on the particular situation of spreading drops. We first present the numerical methods used for the simulation of moving contact line i.e. static contact angle versus dynamic contact angle, no slip condition versus slip condition. A grid and time convergence is performed for the different models. We show that the integration of the Continuum Surface Force using the finite volume method results in a grid dependence at the onset of the spreading. The static and dynamic models are compared to experiments. It is shown that the dynamic models based on the Cox’s relation for the dynamic contact angle are able to reproduce experiments while static models overestimate the spreading time and are not able to reproduce the Tanner regime. The difference between static and dynamic models is shown to increase with the Ohnesorge number

Inertial coalescence of droplets on a partially wetting substrate

We consider the growth rate of the height of the connecting bridge in rapid surface-tension-driven coalescence of two identical droplets attached on a partially wetting substrate. For a wide range of contact angle values, the height of the bridge grows with time following a power law with a universal exponent of 2/3, up to a threshold time, beyond which a 1/2 exponent results, that is known for coalescence of freely-suspended droplets. In a narrow range of contact angle values close to 90°, this threshold time rapidly vanishes and a 1/2 exponent results for a 90° contact angle. The argument is confirmed by three-dimensional numerical simulations based on a diffuse interface method with adaptive mesh refinement and a volume-of-fluid method

Numerical simulation of spreading drops

We consider a liquid drop that spreads on a wettable surface. Different time evolutions have been observed for the base radius r depending of the relative role played by inertia, viscosity, surface tension and the wetting condition. Numerical simulations were performed to discuss the relative effect of these parameters on the spreading described by the evolution of the base radius r(t) and the spreading time tS. Different power law evolutions r(t) ∝ tⁿ have been observed when varying the parameters. At the early stage of the spreading, the power law t½ (n = 1/2) is observed as long as capillarity is balanced by inertia at the contact line. When increasing the viscosity contribution, the exponent n is found to increase despite the increase of the spreading time. The effect of the surface wettability is observed for liquids more viscous than water. For a small contact angle, the power law t½ is then followed by the famous Tanner law t1/10 once the drop shape has reached a spherical cap

Spectroscopic and metal binding properties of a de novo metalloprotein binding a tetrazinc cluster

De novo design provides an attractive approach, which allows one to test and refine the principles guiding metalloproteins in defining the geometry and reactivity of their metal ion cofactors. Although impressive progress has been made in designing proteins that bind transition metal ions including iron–sulfur clusters, the design of tetranuclear clusters with oxygen‐rich environments remains in its infancy. In previous work, we described the design of homotetrameric four‐helix bundles that bind tetra‐Zn2+ clusters. The crystal structures of the helical proteins were in good agreement with the overall design, and the metal‐binding and conformational properties of the helical bundles in solution were consistent with the crystal structures. However, the corresponding apo‐proteins were not fully folded in solution. In this work, we design three peptides, based on the crystal structure of the original bundles. One of the peptides forms tetramers in aqueous solution in the absence of metal ions as assessed by CD and NMR. It also binds Zn2+ in the intended stoichiometry. These studies strongly suggest that the desired structure has been achieved in the apo state, providing evidence that the peptide is able to actively impart the designed geometry to the metal cluster

Lack of effect of apolipoprotein C3 polymorphisms on indices of liver steatosis, lipid profile and insulin resistance in obese Southern Europeans.

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.BACKGROUND: Apolipoprotein C3 (APOC3) is a component of triglyceride-rich lipoproteins, and APOC3 rs2854116 and rs2854117 polymorphisms have been associated with non-alcoholic fatty liver disease, hypertriglyceridaemia, and insulin-resistance. OBJECTIVE: To determine if the APOC3 variants alter the susceptibility of obese subjects to develop liver damage, hypertrigliceridaemia, and insulin-resistance. METHODS: The study was carried out on 585 unrelated obese Italians (median body mass index BMI = 41 kg/m2) who were genotyped for the rs2854116 and rs2854117 variants. All participants underwent oral glucose tolerance tests (OGTT), with measurement of glucose, insulin, lipid parameters. Indices of insulin-resistance (HOMA and ISI) were calculated. Alanine transaminase (ALT) and aspartate transaminase (AST) were used as markers of liver injury. RESULTS: The study subjects were divided into two groups: those homozygous for the wild-type alleles at both SNPs (-482C and -455T alleles) and those who were carriers of at least one variant allele or both (-482T, -455C or both). Also each SNP was analysed independently. No significant differences were found in ALT and AST levels and in the lipid profile between the two groups. Insulin concentrations, glucose tolerance and insulin sensitivity were similar in the two groups. CONCLUSION: We did not identify any significant association between APOC3 polymorphisms and fatty liver disease, lipids, and insulin-resistance in obese subjects, thus not confirming the suggested role of these APOC3 gene sequence variants

Effet de l'hysteresis de l'angle de contact sur la coalescence de deux gouttes sur une paroi

La coalescence sur une paroi est abordée numériquement avec pour objectif l'étude de l'influence de  l'hysteresis de l'angle de contact. L'approche numérique utilisée est la méthode VOF  du code JADIM de l'IMFT. Nous présentons des résultats du mouillage 2D et 3D. Les simulations utilisant un modèle d'angle dynamique et prenant en compte l'hysteresis de l'angle de contact sont comparées à des simulations utilisant un angle statique constant

Handcrafted Metal Enzymes as Convenient Reporters in Biosensors

Leveraging their inherent metal cores, metalloproteins assume pivotal roles in orchestrating intricate natural transformations. This fundamental importance extends to invaluable applications in in vitro diagnostics and biosensing, encompassing immunoassays and electrochemical sensors 1. Bolstered by recent strides in computational protein design, our endeavors have yielded bespoke enzymes, marking significant milestones in the field 2. Through diverse strategies, we have crafted compact yet potent models housing multiple metal sites. This exposition shines a spotlight on chosen designs, elucidating their potential within the domain of sensing technology. We first show that by asymmetrization of the heme environment and precise positioning of the residues at the distal site, with Fe-Mimochrome 6*a (FeMC6*a), we reached unprecedented selectivity in hydrogen peroxide activation leading to a peroxide sensor 3, a catalytic nanoconjugate 4, a signal enhancer in lateral-flow immunoassays 5, and efficient dye degradation for bleaching applications 6. Finally, we describe our efforts in bioelectronics by coupling a photosensitizing zinc porphyrin with a 3kDa iron-sulphur designed protein, leading to the first fully artificial light-harvested electron cascade 7. In perspective, our designed metalloproteins will be equipped for the next-generation of biosensors. Financial support by the Campania Region (Programma Operativo FESR Campania 2014 - 2020, Asse 1), and MUR (Next Generation EU – Piano Nazionale di Ripresa e Resilienza, PNRR-Mission 4 Component 2 Investment 1.4 “Agritech National Research Center” – Spoke 2, and PRIN project SEA-WAVE 2020BKK3W9) is gratefully acknowledged. 1. Hussein, H. A.; Hassan, R. Y. A.; Chino, M.; Febbraio, F. Point-of-Care Diagnostics of COVID-19: From Current Work to Future Perspectives. Sensors 2020, 20 (15), 4289. 2. Leone, L.; Chino, M.; Nastri, F.; Maglio, O.; Pavone, V.; Lombardi, A. Mimochrome, a Metalloporphyrin-Based Catalytic Swiss Knife. Biotechnology and Applied Biochemistry 2020, 67 (4), 495–515. 3. Zambrano, G.; Nastri, F.; Pavone, V.; Lombardi, A.; Chino, M. Use of an Artificial Miniaturized Enzyme in Hydrogen Peroxide Detection by Chemiluminescence. Sensors 2020, 20 (13), 3793. 4. Zambrano, G.; Chino, M.; Renzi, E.; Di Girolamo, R.; Maglio, O.; Pavone, V.; Lombardi, A.; Nastri, F. Clickable Artificial Heme-Peroxidases for the Development of Functional Nanomaterials. Biotechnology and Applied Biochemistry 2020, 67 (4), 549–562. 5. Renzi, E.; Piper, A.; Nastri, F.; Merkoçi, A.; Lombardi, A. An Artificial Miniaturized Peroxidase for Signal Amplification in Lateral Flow Immunoassays. Small 2023, 2207949. 10.1002/smll.202207949 6. Chino, M.; La Gatta, S.; Leone, L.; De Fenza, M.; Lombardi, A.; Pavone, V.; Maglio, O. Dye Decolorization by a Miniaturized Peroxidase Fe-MimochromeVI*a. International Journal of Molecular Sciences 2023, 24 (13), 11070. 7. Chino, M.; Di Costanzo, L. F.; Leone, L.; La Gatta, S.; Famulari, A.; Chiesa, M.; Lombardi, A.; Pavone, V. Designed Rubredoxin Miniature in a Fully Artificial Electron Chain Triggered by Visible Light. Nat Commun 2023, 14 (1), 2368

Designed copper metalloenzymes for the production of value-added chemicals

In the recent years, waste materials have attracted academic and industrial communities aiming to identify strategies to convert waste to value-added materials and chemicals.1 The reutilization of vegetable and industrial waste is therefore one of the main global challenges in mitigating environmental impact. The exploitation of such waste chemicals (e.g. lignin, chitin, cellulose, phenol-like species) for value-added products is considered of remarkable scientific and social impact. In particular, the oxidative degradation of recalcitrant polymeric substrates for the conversion into second-generation biofuels, as catalyzed by bacterial Lytic Polysaccharide MonoOxygenases (LPMOs), and the conversion of toxic phenol-like species into value-added products, as performed by Polyphenol Oxidases (PPOs), may represent the first step for the valorization of waste chemicals. Structural motif of the active site of LPMOs and PPOs, which both catalyzes the oxidation of exceedingly strong C-H bonds, are copper binding sites.2 Reproducing the catalytic features of these enzymes in de novo designed protein scaffolds3 can be important for structure-function relationship studies, but also for the development of efficient enzymes useful in waste treatment. To this end, we adopted helix-bundle scaffolds to accommodate these copper binding sites. These simple models represent a milestone in the development of synthetic metalloenzymes for the degradation and conversion of biomass into second generation fuels. Financial support by MUR (SEA-WAVE 2020BKK3W9) is gratefully acknowledged. 1. Fairley, P. Introduction: Next generation biofuels. Nature 474, S2–S5 (2011). 2. Solomon, E. I. et al. Copper Active Sites in Biology. Chem. Rev. 114, 3659–3853 (2014). 3. Nastri, F. et al. Engineering Metalloprotein Functions in Designed and Native Scaffolds. Trends Biochem. Sci. 44, 1022–1040 (2019)

Handcrafted Metal Enzymes Poised for Biotechnology Revolution

Thanks to their metal core, metalloproteins play a central role in some of the most difficult transformations in nature. For this reason, they are an invaluable tool in many industrial biotech applications, from denim aging to agricultural feed valorisation1. Over the last years, also supported by the recent advances in computational protein design, we have designed several custom-made enzymes, setting several milestones in the field2. By different approaches, we designed small, yet functional, models bearing multiple metal sites. In this contribution, some of them will be showcased, highlighting their potential in industrial biotechnology. We first show that by asymmetrization of the heme environment and precise positioning of the residues at the distal site, with Fe-Mimochrome 6*a (FeMC6*a), we reached unprecedented selectivity in hydrogen peroxide activation, leading to a peroxide sensor and to the smallest decolorization enzyme3. Then, we show how very small changes, like cobalt replacement in CoMC6*a, may induce a dramatic shift in catalytic activity, towards a high-pH insensitive artificial hydrogenase4. Finally, we describe our efforts to couple a photosensitizing zinc porphyrin with a 3kDa iron-sulphur designed protein, leading to the first fully artificial light-harvested electron cascade5. In perspective, our designed metalloproteins will be equipped for the biotechnology revolution. Financial support by the Campania Region (Programma Operativo FESR Campania 2014 - 2020, Asse 1) and MUR (SEA-WAVE 2020BKK3W9) is gratefully acknowledged. 1. Arbige,M.V.;Shetty,J.K.;Chotani,G.K.IndustrialEnzymology:TheNextChapter.Trendsin Biotechnology 2019, 37 (12), 1355–1366. 2. Leone,L.;Chino,M.;Nastri,F.;Maglio,O.;Pavone,V.;Lombardi,A.Mimochrome,aMetalloporphyrin- Based Catalytic Swiss Knife. Biotechnology and Applied Biochemistry 2020, 67 (4), 495–515. 3. Zambrano,G.;Nastri,F.;Pavone,V.;Lombardi,A.;Chino,M.UseofanArtificialMiniaturizedEnzymein Hydrogen Peroxide Detection by Chemiluminescence. Sensors 2020, 20 (13), 3793. 4. Le,J.M.;Alachouzos,G.;Chino,M.;Frontier,A.J.;Lombardi,A.;Bren,K.L.TuningMechanismthrough Buffer Dependence of Hydrogen Evolution Catalyzed by a Cobalt Mini-Enzyme. Biochemistry 2020, 59 (12), 1289–1297. 5. Chino,M.;Costanzo,L.D.;Leone,L.;Gatta,S.L.;Famulari,A.;Chiesa,M.;Lombardi,A.;Pavone,V. Designed Rubredoxin Miniature in a Fully Artificial Electron Chain Triggered by Visible Light., 2022. Preprint: dx.doi.org/10.21203/rs.3.rs-1473985/v

On the Interplay Between Roughness and Elastic Modulus at the Nanoscale: A Methodology Study with Bone as Model Material

: Atomic force microscopy (AFM)-based nanoindentation enables investigation of the mechanical response of biological materials at a subcellular scale. However, quantitative estimates of mechanical parameters such as the elastic modulus (E) remain unreliable because the influence of sample roughness on E measurements at the nanoscale is still poorly understood. This study re-examines the interpretation of roughness from a more rigorous perspective and validates an experimental methodology to extract roughness at each nanoindentation site-i.e., the local roughness γs-with which the corresponding E value can be accurately correlated. Cortical regions of a murine tibia cross-section, characterized by complex nanoscale morphology, were selected as a testbed. Eighty non-overlapping nanoindentations were performed using two different AFM tips, maintaining a maximum penetration depth of 10 nm for each measurement. Our results show a slight decreasing trend of E versus γs (Spearman's rank correlation coefficient ρ = -0.27187). A total of 90% of the E values are reliable when γs < 10 nm (coefficient of determination R2 > 0.90), although low γs values are associated with significant dispersion around E (γs = 0) = E0 = 1.18 GPa, with variations exceeding 50%. These findings are consistent with a qualitative tip-to-sample contact model that accounts for the pronounced roughness heterogeneity typical of bone topography at the nanoscale