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Ring-Closure Mechanisms Mediated by Laccase to Synthesize Phenothiazines, Phenoxazines, and Phenazines
2020, Hahn, Veronika, Mikolasch, Annett, Weitemeyer, Josephine, Petters, Sebastian, Davids, Timo, Lalk, Michael, Lackmann, Jan-Wilm, Schauer, Frieder
The green and environmentally friendly synthesis of highly valuable organic substances is one possibility for the utilization of laccases (EC 1.10.3.2). As reactants for the herein described syntheses, different o-substituted arylamines or arylthiols and 2,5-dihydroxybenzoic acid and its derivatives were used. In this way, the formation of phenothiazines, phenoxazines, and phenazines was achieved in aqueous solution mediated by the laccase of Pycnoporus cinnabarinus in the presence of oxygen. Two types of phenothiazines (3-hydroxy- and 3-oxo-phenothiazines) formed in one reaction assay were described for the first time. The cyclization reactions yielded C–N, C–S, or C–O bonds. The syntheses were investigated with regard to the substitution pattern of the reaction partners. Differences in C–S and C–N bond formations without cyclization are discussed.
Ni-In Synergy in CO2Hydrogenation to Methanol
2021, Zhu, Jiadong, Cannizzaro, Francesco, Liu, Liang, Zhang, Hao, Kosinov, Nikolay, Filot, Ivo A.W., Rabeah, Jabor, Brückner, Angelika, Hensen, Emiel J.M.
Indium oxide (In2O3) is a promising catalyst for selective CH3OH synthesis from CO2but displays insufficient activity at low reaction temperatures. By screening a range of promoters (Co, Ni, Cu, and Pd) in combination with In2O3using flame spray pyrolysis (FSP) synthesis, Ni is identified as the most suitable first-row transition-metal promoter with similar performance as Pd-In2O3. NiO-In2O3was optimized by varying the Ni/In ratio using FSP. The resulting catalysts including In2O3and NiO end members have similar high specific surface areas and morphology. The main products of CO2hydrogenation are CH3OH and CO with CH4being only observed at high NiO loading (≥75 wt %). The highest CH3OH rate (∼0.25 gMeOH/(gcath), 250 °C, and 30 bar) is obtained for a NiO loading of 6 wt %. Characterization of the as-prepared catalysts reveals a strong interaction between Ni cations and In2O3at low NiO loading (≤6 wt %). H2-TPR points to a higher surface density of oxygen vacancy (Ov) due to Ni substitution. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electron paramagnetic resonance analysis of the used catalysts suggest that Ni cations can be reduced to Ni as single atoms and very small clusters during CO2hydrogenation. Supportive density functional theory calculations indicate that Ni promotion of CH3OH synthesis from CO2is mainly due to low-barrier H2dissociation on the reduced Ni surface species, facilitating hydrogenation of adsorbed CO2on Ov © 2021 The Authors. Published by American Chemical Society
Podosome-Driven Defect Development in Lamellar Bone under the Conditions of Senile Osteoporosis Observed at the Nanometer Scale
2021, Simon, Paul, Pompe, Wolfgang, Bobeth, Manfred, Worch, Hartmut, Kniep, Rüdiger, Formanek, Petr, Hild, Anne, Wenisch, Sabine, Sturm, Elena
The degradation mechanism of human trabecular bone harvested from the central part of the femoral head of a patient with a fragility fracture of the femoral neck under conditions of senile osteoporosis was investigated by high-resolution electron microscopy. As evidenced by light microscopy, there is a disturbance of bone metabolism leading to severe and irreparable damages to the bone structure. These defects are evoked by osteoclasts and thus podosome activity. Podosomes create typical pit marks and holes of about 300-400 nm in diameter on the bone surface. Detailed analysis of the stress field caused by the podosomes in the extracellular bone matrix was performed. The calculations yielded maximum stress in the range of few megapascals resulting in formation of microcracks around the podosomes. Disintegration of hydroxyapatite and free lying collagen fibrils were observed at the edges of the plywood structure of the bone lamella. At the ultimate state, the disintegration of the mineralized collagen fibrils to a gelatinous matrix comes along with a delamination of the apatite nanoplatelets resulting in a brittle, porous bone structure. The nanoplatelets aggregate to big hydroxyapatite plates with a size of up to 10 x 20 μm2. The enhanced plate growth can be explained by the interaction of two mechanisms in the ruffled border zone: the accumulation of delaminated hydroxyapatite nanoplatelets near clusters of podosomes and the accelerated nucleation and random growth of HAP nanoplatelets due to a nonsufficient concentration of process-directing carboxylated osteocalcin cOC. © 2021 The Authors. Published by American Chemical Society.
Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins
2017, Liu, Kai, Ma, Chao, Göstl, Robert, Zhang, Lei, Herrmann, Andreas
ConspectusBiomacromolecules, such as nucleic acids, proteins, and virus particles, are persistent molecular entities with dimensions that exceed the range of their intermolecular forces hence undergoing degradation by thermally induced bond-scission upon heating. Consequently, for this type of molecule, the absence of a liquid phase can be regarded as a general phenomenon. However, certain advantageous properties usually associated with the liquid state of matter, such as processability, flowability, or molecular mobility, are highly sought-after features for biomacromolecules in a solvent-free environment. Here, we provide an overview over the design principles and synthetic pathways to obtain solvent-free liquids of biomacromolecular architectures approaching the topic from our own perspective of research. We will highlight the milestones in synthesis, including a recently developed general surfactant complexation method applicable to a large variety of biomacromolecules as well as other synthetic principles granting access to electrostatically complexed proteins and DNA.These synthetic pathways retain the function and structure of the biomacromolecules even under extreme, nonphysiological conditions at high temperatures in water-free melts challenging the existing paradigm on the role of hydration in structural biology. Under these conditions, the resulting complexes reveal their true potential for previously unthinkable applications. Moreover, these protocols open a pathway toward the assembly of anisotropic architectures, enabling the formation of solvent-free biomacromolecular thermotropic liquid crystals. These ordered biomaterials exhibit vastly different mechanical properties when compared to the individual building blocks. Beyond the preparative aspects, we will shine light on the unique potential applications and technologies resulting from solvent-free biomacromolecular fluids: From charge transport in dehydrated liquids to DNA electrochromism to biocatalysis in the absence of a protein hydration shell. Moreover, solvent-free biological liquids containing viruses can be used as novel storage and process media serving as a formulation technology for the delivery of highly concentrated bioactive compounds. We are confident that this new class of hybrid biomaterials will fuel further studies and applications of biomacromolecules beyond water and other solvents and in a much broader context than just the traditional physiological conditions. © 2017 American Chemical Society.
Segregated Network Polymer Composites with High Electrical Conductivity and Well Mechanical Properties based on PVC, P(VDFTFE), UHMWPE, and rGO
2020, Shiyanova, Kseniya A., Gudkov, Maksim V., Gorenberg, Arkady Ya, Rabchinskii, Maxim K., Smirnov, Dmitry A., Shapetina, Maria A., Gurinovich, Tatiana D., Goncharuk, Galina P., Kirilenko, Demid A., Bazhenov, Sergey L., Melnikov, Valery P.
The formation of a segregated network structure (wittingly uneven distribution of a filler) is one of the most promising strategies for the fabrication of electrically conductive polymer composites at present. However, the simultaneous achievement of high values of electrical conductivity with the retention of well mechanical properties within this approach remains a great challenge. Here, by means of X-ray photoelectron spectra (XPS), near-edge X-ray absorption fine structure (NEXAFS) spectra, scanning electron microscopy (SEM), dielectric spectroscopy, and compression engineering stress-strain curve analysis, we have studied the effect of a segregated network structure on the electrical conductivity and mechanical properties of a set of polymer composites. The composites were prepared by applying graphene oxide (GO) with ultralarge basal plane size (up to 150 μm) onto the surface of polymer powder particles, namely, poly(vinyl chloride) (PVC), poly(vinylidene fluoride-co-tetrafluoroethylene) (P(VDF-TFE)), and ultrahigh-molecular-weight poly(ethylene) (UHMWPE) with the subsequent GO reduction and composite hot pressing. A strong dependence of the segregated network polymer composites' physical properties on the polymer matrix was demonstrated. Particularly, 12 orders of magnitude rise of the polymers' electrical conductivity up to 0.7 S/m was found upon the incorporation of the reduced GO (rGO). A 17% increase in the P(VDF-TFE) elastic modulus filled by 1 wt % of rGO was observed. Fracture strength of PVC/rGO at 0.5 wt % content of the filler was demonstrated to decrease by fourfold. At the same time, the change in strength was not significant for P(VDF-TFE) and UHMWPE composites in comparison with pure polymers. Our results show a promise to accelerate the development of new composites for energy applications, such as metal-free supercapacitor plates and current collectors of lithium-ion batteries, bipolar plates of proton-exchange membrane fuel cells, antistatic elements of various electronic devices, etc. © 2020 American Chemical Society.
Self-Regenerating Soft Biophotovoltaic Devices
2018, Qiu, Xinkai, Castañeda Ocampo, Olga, de Vries, Hendrik W., van Putten, Maikel, Loznik, Mark, Herrmann, Andreas, Chiechi, Ryan C.
This paper describes the fabrication of soft, stretchable biophotovoltaic devices that generate photocurrent from photosystem I (PSI) complexes that are self-assembled onto Au electrodes with a preferred orientation. Charge is collected by the direct injection of electrons into the Au electrode and the transport of holes through a redox couple to liquid eutectic gallium-indium (EGaIn) electrodes that are confined to microfluidic pseudochannels by arrays of posts. The pseudochannels are defined in a single fabrication step that leverages the non-Newtonian rheology of EGaIn. This strategy is extended to the fabrication of reticulated electrodes that are inherently stretchable. A simple shadow evaporation technique is used to increase the surface area of the Au electrodes by a factor of approximately 106 compared to planar electrodes. The power conversion efficiency of the biophotovoltaic devices decreases over time, presumably as the PSI complexes denature and/or detach from the Au electrodes. However, by circulating a solution of active PSI complexes the devices self-regenerate by mass action/self-assembly. These devices leverage simple fabrication techniques to produce complex function and prove that photovoltaic devices comprising PSI can retain the ability to regenerate, one of the most important functions of photosynthetic organisms. © 2018 American Chemical Society.
Present and future of surface-enhanced Raman scattering
2020, Langer, Judith, de Aberasturi, Dorleta Jimenez, Aizpurua, Javier, Alvarez-Puebla, Ramon A., Auguié, Baptiste, Baumberg, Jeremy J., Bazan, Guillermo C., Bell, Steven E.J., Boisen, Anja, Brolo, Alexandre G., Choo, Jaebum, Cialla-May, Dana, Deckert, Volker, Fabris, Laura, Faulds, Karen, de Abajo, F. Javier García, Goodacre, Royston, Graham, Duncan, Haes, Amanda J., Haynes, Christy L., Huck, Christian, Itoh, Tamitake, Käll, Mikael, Kneipp, Janina, Kotov, Nicholas A., Kuang, Hua, Le Ru, Eric C., Lee, Hiang Kwee, Li, Jian-Feng, Ling, Xing Yi, Maier, Stefan A., Mayerhöfer, Thomas, Moskovits, Martin, Murakoshi, Kei, Nam, Jwa-Min, Nie, Shuming, Ozaki, Yukihiro, Pastoriza-Santos, Isabel, Perez-Juste, Jorge, Popp, Juergen, Pucci, Annemarie, Reich, Stephanie, Ren, Bin, Schatz, George C., Shegai, Timur, Schlücker, Sebastian, Tay, Li-Lin, Thomas, K. George, Tian, Zhong-Qun, Van Duyne, Richard P., Vo-Dinh, Tuan, Wang, Yue, Willets, Katherine A., Xu, Chuanlai, Xu, Hongxing, Xu, Yikai, Yamamoto, Yuko S., Zhao, Bing, Liz-Marzán, Luis M.
The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.
Dehydroabietylamine-Based Cellulose Nanofibril Films: A New Class of Sustainable Biomaterials for Highly Efficient, Broad-Spectrum Antimicrobial Effects
2019, Hassan, Ghada, Forsman, Nina, Wan, Xing, Keurulainen, Leena, Bimbo, Luis M., Johansson, Leena-Sisko, Sipari, Nina, Yli-Kauhaluoma, Jari, Zimmermann, Ralf, Stehl, Susanne, Werner, Carsten, Saris, Per E.J., Österberg, Monika, Moreira, Vânia M.
The design of antimicrobial surfaces as integral parts of advanced biomaterials is nowadays a high research priority, as the accumulation of microorganisms on surfaces inflicts substantial costs on the health and industry sectors. At present, there is a growing interest in designing functional materials from polymers abundant in nature, such as cellulose, that combine sustainability with outstanding mechanical properties and economic production. There is also the need to find suitable replacements for antimicrobial silver-based agents due to environmental toxicity and spread of resistance to metal antimicrobials. Herein we report the unprecedented decoration of cellulose nanofibril (CNF) films with dehydroabietylamine 1 (CNF-CMC-1), to give an innovative contact-active surface active against Gram-positive and Gram-negative bacteria including the methicillin-resistant S. aureus MRSA14TK301, with low potential to spread resistance and good biocompatibility, all achieved with low surface coverage. CNF-CMC-1 was particularly effective against S. aureus ATCC12528, causing virtually complete reduction of the total cells from 10 5 colony forming units (CFU)/mL bacterial suspensions, after 24 h of contact. This gentle chemical modification of the surface of CNF fully retained the beneficial properties of the original film, including moisture buffering and strength, relevant in many potential applications. Our originally designed surface represents a new class of ecofriendly biomaterials that optimizes the performance of CNF by adding antimicrobial properties without the need for environmentally toxic silver. © Copyright 2019 American Chemical Society.
Biochemical Characterization of Mouse Retina of an Alzheimer's Disease Model by Raman Spectroscopy
2020, Stiebing, Clara, Jahn, Izabella J., Schmitt, Michael, Keijzer, Nanda, Kleemann, Robert, Kiliaan, Amanda J., Drexler, Wolfgang, Leitgeb, Rainer A., Popp, Jürgen
The presence of biomarkers characteristic for Alzheimer's disease in the retina is a controversial topic. Raman spectroscopy offers information on the biochemical composition of tissues. Thus, it could give valuable insight into the diagnostic value of retinal analysis. Within the present study, retinas of a double transgenic mouse model, that expresses a chimeric mouse/human amyloid precursor protein and a mutant form of human presenilin 1, and corresponding control group were subjected to ex vivo Raman imaging. The Raman data recorded on cross sections of whole eyes highlight the layered structure of the retina in a label-free manner. Based on the Raman information obtained from en face mounted retina samples, a discrimination between healthy and Alzheimer's disease retinal tissue can be done with an accuracy of 85.9%. For this a partial least squares-linear discriminant analysis was applied. Therefore, although no macromolecular changes in form of, i.e., amyloid beta plaques, can be noticed based on Raman spectroscopy, subtle biochemical changes happening in the retina could lead to Alzheimer's disease identification. ©
Rapid Colorimetric Detection of Pseudomonas aeruginosa in Clinical Isolates Using a Magnetic Nanoparticle Biosensor
2019, Alhogail, Sahar, Suaifan, Ghadeer A.R.Y, Bikker, Floris J., Kaman, Wendy E., Weber, Karina, Cialla-May, Dana, Popp, Jürgen, Zourob, Mohammed M.
A rapid, sensitive, and specific colorimetric biosensor based on the use of magnetic nanoparticles (MNPs) was designed for the detection of Pseudomonas aeruginosa in clinical samples. The biosensing platform was based on the measurement of P. aeruginosa proteolytic activity using a specific protease substrate. At the N-terminus, this substrate was covalently bound to MNPs and was linked to a gold sensor surface via cystine at the C-terminus of the substrates. The golden sensor appears black to naked eyes because of the coverage of the MNPs. However, upon proteolysis, the cleaved peptide–MNP moieties will be attracted by an external magnet, revealing the golden color of the sensor surface, which can be observed by the naked eye. In vitro, the biosensor was able to detect specifically and quantitatively the presence of P. aeruginosa with a detection limit of 102 cfu/mL in less than 1 min. The colorimetric biosensor was used to test its ability to detect in situ P. aeruginosa in clinical isolates from patients. This biochip is anticipated to be useful as a rapid point-of-care device for the diagnosis of P. aeruginosa-related infections.