Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex

The controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular MnIII-corrole complex, which is modified on the three meso-positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO2. Electrochemical reduction of MnIII leads to an electroactive MnII species, which binds CO2 and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO2 to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h−1, when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the MnIII-corrole center. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

The amyloid fibril-forming properties of the amphibian antimicrobial peptide uperin 3.5

The amphibian skin is a vast resource for bioactive peptides, which form the basis of the animals' innate immune system. Key components of the secretions of the cutaneous glands are antimicrobial peptides (AMPs), which exert their cytotoxic effects often as a result of membrane disruption. It is becoming increasingly evident that there is a link between the mechanism of action of AMPs and amyloidogenic peptides and proteins. In this work, we demonstrate that the broad-spectrum amphibian AMP uperin 3.5, which has a random-coil structure in solution but adopts an α-helical structure in membrane-like environments, forms amyloid fibrils rapidly in solution at neutral pH. These fibrils are cytotoxic to model neuronal cells in a similar fashion to those formed by the proteins implicated in neurodegenerative diseases. The addition of small quantities of 2,2,2-trifluoroethanol accelerates fibril formation by uperin 3.5, and is correlated with a structural stabilisation induced by this co-solvent. Uperin 3.5 fibril formation and the associated cellular toxicity are inhibited by the polyphenol (-)-epigallocatechin-3-gallate (EGCG). Furthermore, EGCG rapidly dissociates fully formed uperin 3.5 fibrils. Ion mobility-mass spectrometry reveals that uperin 3.5 adopts various oligomeric states in solution. Combined, these observations imply that the mechanism of membrane permeability by uperin 3.5 is related to its fibril-forming properties.Antonio N. Calabrese, Yanqin Liu, Tianfang Wang, Ian F. Musgrave, Tara L. Pukala, Rico F. Tabor, Lisandra L. Martin, John A. Carver, John H. Bowi

Elucidating the origins of high preferential crystal orientation in quasi‐2D perovskite solar cells

Incorporating large organic cations to form 2D and mixed 2D/3D structures significantly increases the stability of perovskite solar cells. However, due to their low electron mobility, aligning the organic sheets to ensure unimpeded charge transport is critical to rival the high performances of pure 3D systems. While additives such as methylammonium chloride (MACl) can enable this preferential orientation, so far, no complete description exists explaining how they influence the nucleation process to grow highly aligned crystals. Here, by investigating the initial stages of the crystallization, as well as partially and fully formed perovskites grown using MACl, the origins underlying this favorable alignment are inferred. This mechanism is studied by employing 3-fluorobenzylammonium in quasi-2D perovskite solar cells. Upon assisting the crystallization with MACl, films with a degree of preferential orientation of 94%, capable of withstanding moisture levels of 97% relative humidity for 10 h without significant changes in the crystal structure are achieved. Finally, by combining macroscopic, microscopic, and spectroscopic studies, the nucleation process leading to highly oriented perovskite films is elucidated. Understanding this mechanism will aid in the rational design of future additives to achieve more defect tolerant and stable perovskite optoelectronics

Substrate specificity of a peptidyl-aminoacyl-l/d-isomerase from frog skin

In the skin of fire-bellied toads (Bombina species), an aminoacyl-l/d-isomerase activity is present which catalyses the post-translational isomerization of the l- to the d-form of the second residue of its substrate peptides. Previously, this new type of enzyme was studied in some detail and genes potentially coding for similar polypeptides were found to exist in several vertebrate species including man. Here, we present our studies to the substrate specificity of this isomerase using fluorescence-labeled variants of the natural substrate bombinin H with different amino acids at positions 1, 2 or 3. Surprisingly, this enzyme has a rather low selectivity for residues at position 2 where the change of chirality at the alpha-carbon takes place. In contrast, a hydrophobic amino acid at position 1 and a small one at position 3 of the substrate are essential. Interestingly, some peptides containing a Phe at position 3 also were substrates. Furthermore, we investigated the role of the amino-terminus for substrate recognition. In view of the rather broad specificity of the frog isomerase, we made a databank search for potential substrates of such an enzyme. Indeed, numerous peptides of amphibia and mammals were found which fulfill the requirements determined in this study. Expression of isomerases with similar characteristics in other species can therefore be expected to catalyze the formation of peptides containing d-amino acids

Preserving Charge and Oxidation State of Au(III) Ions in an Agent-Functionalized Nanocrystal Model System

Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of, the active center is indispensable. We. present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support With potential Impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery. Employing scanning tunneling microscopy and -spectroscopy in combination with photoemission spectroscopy,we clarify at the single-molecule level the underlying mechanisms of this exceptional adsorption mode. It is based on the balance between a high-energy oxidation state and an electrostatic screening-response of the surface (image charge). Modeling with first principles methods reveals submolecular details of the metal-ligand bonding interaction and completes the study by providing an Illustrative electrostatic.. model relevant for ionic metalorganic agent molecules, in general

"Polimorfi e poligami e un po’ anche polipi."

Cultural studies are underlining ambiguity and fluidity concepts to grasp how gender narratives have been changing since the upheaval of 1968. Scholars have acknowledged that traditional masculinity has been challenged and remolded as a result of second-wave feminism. However, representations of masculinity have yet to be examined in one of the key moments of postwar Italian culture: the sociopolitical turmoil of the late 1970s. Bologna was the center of the Italian Movement of 1977. Its subcultural scene flourished thanks to the confluence of young creatives at the DAMS University of Bologna, where Umberto Eco taught. The symbolic productions of this scene provide brilliant portrayals of the reshaping of gender becoming ambiguous and fluid. This article examines the literary representations of masculinity in exemplary works by the three most notable authors tied to subcultural Bologna: Andrea Pazienza, Enrico Palandri, and Pier Vittorio Tondelli. My argument is that their narrative constructions of masculinity reveal three remarkably different reactions to second-wave feminism and to the challenging and remolding of gender in the late 1970s. These reactions are a tendency towards resentful and sarcastic rejection of pro-feminist discomfort, an aestheticizing acceptance of melancholic and ambiguous masculinities, and a postmodern turn towards the conception of gender fluidity. Furthermore, displacement, ambiguity and fluidity can be observed in the mixed language and experimental syntax. In doing so, this paper sheds new light on the transition toward postmodern and backlash gender narratives in the subsequent decade

How do places of origin influence access to mobility in the global age? An analysis of the influence of vulnerability and structural constraints on Senegalese translocal livelihood strategies

Literature has often underlined the relevance of mobility for modern lifestyles. However, it has frequently overlooked that mobility has long been the rule in Senegal. There, mobility has allowed households to cope with environmental and economic vulnerability. Over the last decades, households have extended their traditional mobility through internal and international migration. This paper investigates how place-related vulnerability and structural constraints influence the way Senegalese households construct translocal spaces and livelihood strategies in the global age. For this purpose, a multi-sited ethnographic study has been conducted at four villages in Senegal and at two immigration destinations in Italy and Spain. The empirical results show that vulnerability and structural constraints in the home place do not prevent households from adopting strategies based on mobility, but rather influence the composition of translocal spaces, the ability to move between places, and the construction of translocal livelihood strategies