Browsing by Subject "HIGHLY EFFICIENT"

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  • Shahbazi, Mohammad-Ali; Ghalkhani, Masoumeh; Maleki, Hajar (2020)
    Herein, the potential of directional freeze-casting techniques as a very generic, green, and straightforward approach for the processing of various functional porous materials is introduced. These materials include 3D monoliths, films, fibers, and microspheres/beads, which are obtained by the assembly of network building blocks originated from cryoassembly of the various aqueous-based systems. The process simply relies on 1) directional freezing of the slurry through contact with a cold surface, 2) maintaining the slurry at the frozen state for a particular time with controlling the freezing parameters and directions, and 3) sublimation of the created ice crystal templates inside the developed structure to translate the ice growth pattern to final porous structure. The materials developed with such a cryogenic process contain a highly complex porous structure, e.g., a hierarchical and well-aligned microstructure in different levels, which renders a high control over the physicochemical and mechanical functionalities. Due to the versatility and controllability of this technique, the process can also be extended for the mimicking of the structures found in natural materials to the bulk materials to assemble bioinspired porous composites with many useful mechanical and physical features. The aim, herein, is to give a brief overview of the recent advances in developing anisotropic porous inorganic, organic, hybrid, and carbonaceous materials with a particular emphasis on materials with biomimicking microstructure using directional ice templating approach and to highlight their recent breakthrough for different high-performance applications.
  • de Souza Rodrigues, Maria Paula; Dourado, Andre H. B.; Cutolo, Leonardo de O.; Parreira, Luanna S.; Alves, Tiago Vinicius; Slater, Thomas J. A.; Haigh, Sarah J.; Camargo, Pedro H. C.; Cordoba de Torresi, Susana Ines (2021)
    State of the art electrocatalysts for the hydrogen evolution reaction (HER) are based on metal nanoparticles (NPs). It has been shown that the localized surface plasmon resonance (LSPR) excitation in plasmonic NPs can be harvested to accelerate a variety of molecular transformations. This enables the utilization of visible light as an energy input to enhance HER performances. However, most metals that are active toward the HER do not support LSPR excitation in the visible or near-IR ranges. We describe herein the synthesis of gold-rhodium core-shell nanoflowers (Au@Rh NFs) that are composed of a core made up of spherical Au NPs and shells containing Rh branches. The Au@Rh NFs were employed as a model system to probe how the LSPR excitation from Au NPs can lead to an enhancement in the HER performance for Rh. Our data demonstrate that the LSPR excitation at 533 nm (and 405 nm) leads to an improvement in the HER performance of Rh, which depends on the morphological features of the Au Rh NFs, offering opportunities for optimization of the catalytic performance. Control experiments indicate that this improvement originates from the stronger interaction of Au@Rh NFs with H2O molecules at the surface, leading to an icelike configuration, which facilitated the HER under LSPR excitation.
  • Beyer, Hannes M.; Iwai, Hideo (2019)
    Protein-splicing domains are frequently used engineering tools that find application in the in vivo and in vitro ligation of protein domains. Directed evolution is among the most promising technologies used to advance this technology. However, the available screening systems for protein-splicing activity are associated with bottlenecks such as the selection of pseudo-positive clones arising from off-pathway reaction products or fragment complementation. Herein, we report a stringent screening method for protein-splicing activity in cis and trans, that exclusively selects productively splicing domains. By fusing splicing domains to an intrinsically disordered region of the antidote from the Escherichia coli CcdA/CcdB type II toxin/antitoxin system, we linked protein splicing to cell survival. The screen allows selecting novel cis- and trans-splicing inteins catalyzing productive highly efficient protein splicing, for example, from directed-evolution approaches or the natural intein sequence space.
  • Leung, Alan W.; Broton, Cayla; Bogacheva, Mariia S.; Xiao, Andrew Z.; Garcia-Castro, Martin I.; Lou, Yan-Ru (2020)
    Current approaches for Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-Associated-9 (Cas9)-mediated genome editing in human pluripotent stem (PS) cells mainly employ plasmids or ribonucleoprotein complexes. Here, we devise an improved transfection protocol of in vitro transcribed Cas9 mRNA and crRNA:tracrRNA duplex that can effectively generate indels in four genetic loci (two active and two inactive) and demonstrate utility in four human PS cell lines (one embryonic and three induced PS cell lines). Our improved protocol incorporating a Cas9-linked selection marker and a staggered transfection strategy promotes targeting efficiency up to 85% and biallelic targeting efficiency up to 76.5% of total mutant clones. The superior targeting efficiency and the non-integrative nature of our approach underscores broader applications in high-throughput arrayed CRISPR screening and in generating custom-made or off-the-shelf cell products for human therapy.
  • Oeemig, Jesper S.; Beyer, Hannes M.; Aranko, A. Sesilja; Mutanen, Justus; Iwai, Hideo (2020)
    Inteins catalyze self-excision from host precursor proteins while concomitantly ligating the flanking substrates (exteins) with a peptide bond. Noncatalytic extein residues near the splice junctions, such as the residues at the -1 and +2 positions, often strongly influence the protein-splicing efficiency. The substrate specificities of inteins have not been studied for many inteins. We developed a convenient mutagenesis platform termed "QuickDrop"-cassette mutagenesis for investigating the influences of 20 amino acid types at the -1 and +2 positions of different inteins. We elucidated 17 different profiles of the 20 amino acid dependencies across different inteins. The substrate specificities will accelerate our understanding of the structure-function relationship at the splicing junctions for broader applications of inteins in biotechnology and molecular biosciences.
  • Michael Beyer, Hannes; Malgorzata Mikula, Kornelia; Li, Mi; Wlodawer, Alexander; Iwaï, Hideo (2020)
    Abstract Protein trans-splicing catalyzed by split inteins has increasingly become useful as a protein engineering tool. We solved the 1.0 Å-resolution crystal structure of a fused variant from the naturally split gp41-1 intein, previously identified from environmental metagenomic sequence data. The structure of the 125-residue gp41-1 intein revealed a compact pseudo-C2-symmetry commonly found in the Hedgehog/Intein (HINT) superfamily with extensive charge-charge interactions between the split N- and C-terminal intein fragments that are common among naturally occurring split inteins. We successfully created orthogonal split inteins by engineering a similar charge network into the same region of a cis-splicing intein. This strategy could be applicable for creating novel natural-like split inteins from other, more prevalent cis-splicing inteins.
  • Zhang, Wenzhong; Avdibegovic, Dzenita; Koivula, Risto; Hatanpää, Timo; Hietala, Sami; Regadio, Mercedes; Binnemans, Koen; Harjula, Risto (2017)
    The separation of rare-earth elements (REEs) is usually carried out by a multi-stage solvent extraction process utilising organophosphorus extractants. Inspired by the structure of the solvating extractant tri-n-butyl phosphate (TBP), new sorbents were designed by covalently attaching short n-alkyl chains (ethyl, n-propyl and n-butyl) to titanium(IV) phosphate functionalised mesoporous MCM-41 silica by a layer-by-layer grafting route. Mesoporous MCM-41 silica served as a versatile porous support and the grafted titanium(IV) derivatives provided enhanced acid stability and solvating extraction capability. Various characterisation methods including solid-state C-13, Si-29 and P-31 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and simultaneous thermogravimetry and differential scanning calorimetry-mass spectroscopy (TG/DSC-MS) were used to confirm the ligand attachment. The hybrid materials showed a better uptake of rare-earth ions from nitrate feed solution than the unmodified inorganic material. The optimal separation factor (SF) obtained for scandium-lanthanum separation is in excess of 100 000 at pH 2.1. The SFs calculated for dysprosium-neodymium are approximately 3, which is comparable to that of TBP in a typical solvent extraction setup. This study provides a new strategy to design inorganic-organic hybrid sorbents based on the structure of organophosphorus extractants via metal(IV)-O-P bonds.