Superior thermal stability and fast crystallization behavior of a novel, biodegradable α-methylated bacterial polyester

AbstractGiven their ubiquity in modern society, the development of biodegradable and renewably sourced plastics is essential for the creation of an environmentally sustainable society. One of the drawbacks for currently available biodegradable plastics such as poly(l-lactic acid) (PLLA) and polyhydroxyalkanoates (PHAs) is that it is difficult to simultaneously achieve mechanical flexibility and certain crystallization behavior in these materials, which limits their use as replacements for established petroleum-based plastics such as isotactic polypropylene (iPP). Here, we report the synthesis and characterization of a new biodegradable plastic, poly(3-hydroxy-2-methylbutyrate) [P(3H2MB)], which is a member of the bacterial PHA family whose members include an α-methylated monomer unit. Biosynthesis of P(3H2MB) was achieved using recombinant Escherichiacoli expressing an engineered pathway. Biosynthesized P(3H2MB) exhibited the highest melting temperature (197 °C) among the biosynthesized PHAs and improved thermal resistance. It also exhibited improved crystallization behavior and mechanical flexibility nearly equal to those of iPP. The primary nucleation rate of P(3H2MB) was faster than that of P(3HB), and the spherulite morphology of P(3H2MB) was much finer than that of P(3HB). This crystal morphology may result in more rapid crystallization behavior, increased transparency, and enhanced mechanical properties. The superior physical properties of P(3H2MB) have the potential to open new avenues for the production of high-performance biodegradable plastics for replacing petroleum-based bulk commodity plastics.

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Preparation and Characterization of NH2-Terminal Fibrinogen Bβ Fragments from N-DSK of Human Fibrinogen

Thrombosis and Haemostasis ◽

10.1055/s-0038-1660999 ◽

1984 ◽

Vol 51 (01) ◽

pp. 016-021 ◽

Cited By ~ 2

Author(s):

S Birken ◽

G Agosto ◽

B Lahiri ◽

R Canfield

Keyword(s):

High Performance ◽

Gel Filtration ◽

Ion Exchange Chromatography ◽

Exchange Chromatography ◽

Reverse Phase ◽

Human Fibrinogen ◽

Human Volunteers ◽

Cnbr Cleavage ◽

Two Peaks

SummaryIn order to investigate the early release of NH2-terminal plasmic fragments from the Bβ chain of fibrinogen, substantial quantities of Bβ 1-42 and Bβ 1-21 are required as immunogens, as radioimmunoassay standards and for infusion into human volunteers to determine the half-lives of these peptides. Towards this end methods that employ selective proteolytic cleavage of these fragments from fibrinogen have been developed. Both the N-DSK fragment, produced by CNBr cleavage of fibrinogen, and Bβ 1-118 were employed as substrates for plasmin with the finding of higher yields from N-DSK. Bβ 1-42 and Bβ 1-21 were purified by gel filtration and ion-exchange chromatography on SP-Sephadex using volatile buffers. When the purified preparation of Bβ 1-42 was chromatographed on reverse-phase high performance liquid chromatography, two peaks of identical amino acid composition were separated, presumably due either to pyroglutamate or to amide differences.

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Experimental and Numerical Characterization of Pullout Behavior of Hooked Steel Fibers in Ultra-High Performance Cementitious Matrix

10.21838/uhpc.2016.14 ◽

2016 ◽

Author(s):

Congrui Jin ◽

Mengxi Du ◽

Jun Feng ◽

Xinwei Zhou ◽

Gianluca Cusatis

Keyword(s):

High Performance ◽

Steel Fibers ◽

Cementitious Matrix ◽

Numerical Characterization

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Preparation and Characterization of the High Molecular Weight [3H]Hyaluronic Acid

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19922151 ◽

1992 ◽

Vol 57 (10) ◽

pp. 2151-2156 ◽

Cited By ~ 2

Author(s):

Peter Chabreček ◽

Ladislav Šoltés ◽

Hynek Hradec ◽

Jiří Filip ◽

Eduard Orviský

Keyword(s):

Molecular Weight ◽

Hyaluronic Acid ◽

High Molecular Weight ◽

Methyl Bromide ◽

High Performance ◽

Hydrogen Atoms ◽

Isolation And Characterization ◽

Labelling Procedure ◽

Enzymatic Depolymerization

Two methods for the preparation of high molecular weight [3H]hyaluronic acid were investigated. In the first one, hydrogen atoms in the molecule were replaced by tritium. This isotopic substitution was performed in aqueous solution using Pd/CaCO3 as the catalyst. In the second method, the high molecular weight hyaluronic acid was alkylated with [3H]methyl bromide in liquid ammonia at a temperature of -33.5 °C. High-performance gel permeation chromatographic separation method was used for the isolation and characterization of the high molecular weight [3H]hyaluronic acid. Molecular weight parameters for the labelled biopolymers were Mw = 128 kDa, Mw/Mn = 1.88 (first method) and Mw = 268 kDa, Mw/Mn = 1.55 (second method). The high molecular weight [3H]hyaluronic acid having Mw = 268 kDa was degraded further by specific hyaluronidase. Products of the enzymatic depolymerization were observed to be identical for both, labelled and cold biopolymer. This finding indicates that the described labelling procedure using [3H]methyl bromide does not induce any major structural rearrangements in the molecule.

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Fabrication and characterization of buried-gate fin and recess channel MOSFET for high performance and low GIDL current

2009 International Semiconductor Device Research Symposium ◽

10.1109/isdrs.2009.5378069 ◽

2009 ◽

Author(s):

Jae Young Song ◽

Jong Pil Kim ◽

Sang Wan Kim ◽

Jeong-Hoon Oh ◽

Kyung-Chang Ryoo ◽

...

Keyword(s):

High Performance ◽

Fabrication And Characterization

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Development and characterization of Nb3Sn/Al2O3 superconducting multilayers for particle accelerators

Scientific Reports ◽

10.1038/s41598-021-87119-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Chris Sundahl ◽

Junki Makita ◽

Paul B. Welander ◽

Yi-Feng Su ◽

Fumitake Kametani ◽

...

Keyword(s):

High Performance ◽

High Energy ◽

Particle Accelerators ◽

Quality Factors ◽

Critical Fields ◽

Linear Accelerators ◽

Cross Sectional ◽

Low Field ◽

Superconducting Radio Frequency

AbstractSuperconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 1010 at 1–2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200–240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb3Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration field in Nb3Sn, it has been proposed to coat Nb cavities with thin film Nb3Sn multilayers with dielectric interlayers. Here, we report the growth and multi-technique characterization of stoichiometric Nb3Sn/Al2O3 multilayers with good superconducting and RF properties. We developed an adsorption-controlled growth process by co-sputtering Nb and Sn at high temperatures with a high overpressure of Sn. The cross-sectional scanning electron transmission microscope images show no interdiffusion between Al2O3 and Nb3Sn. Low-field RF measurements suggest that our multilayers have quality factor comparable with cavity-grade Nb at 4.2 K. These results provide a materials platform for the development and optimization of high-performance SIS multilayers which could overcome the intrinsic limits of the Nb cavity technology.

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Enzymatic Synthesis and Characterization of Different Families of Chitooligosaccharides and Their Bioactive Properties

Applied Sciences ◽

10.3390/app11073212 ◽

2021 ◽

Vol 11 (7) ◽

pp. 3212

Author(s):

Noa Miguez ◽

Peter Kidibule ◽

Paloma Santos-Moriano ◽

Antonio O. Ballesteros ◽

Maria Fernandez-Lobato ◽

...

Keyword(s):

High Performance ◽

Chemical Characterization ◽

Amperometric Detection ◽

Anion Exchange Chromatography ◽

Exchange Chromatography ◽

Enzymatic Production ◽

Bioactive Properties ◽

Substrate Properties ◽

Chitin Hydrolysis

Chitooligosaccharides (COS) are homo- or hetero-oligomers of D-glucosamine (GlcN) and N-acetyl-D-glucosamine (GlcNAc) that can be obtained by chitosan or chitin hydrolysis. Their enzymatic production is preferred over other methodologies (physical, chemical, etc.) due to the mild conditions required, the fewer amounts of waste and its efficiency to control product composition. By properly selecting the enzyme (chitinase, chitosanase or nonspecific enzymes) and the substrate properties (degree of deacetylation, molecular weight, etc.), it is possible to direct the synthesis towards any of the three COS types: fully acetylated (faCOS), partially acetylated (paCOS) and fully deacetylated (fdCOS). In this article, we review the main strategies to steer the COS production towards a specific group. The chemical characterization of COS by advanced techniques, e.g., high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and MALDI-TOF mass spectrometry, is critical for structure–function studies. The scaling of processes to synthesize specific COS mixtures is difficult due to the low solubility of chitin/chitosan, the heterogeneity of the reaction mixtures, and high amounts of salts. Enzyme immobilization can help to minimize such hurdles. The main bioactive properties of COS are herein reviewed. Finally, the anti-inflammatory activity of three COS mixtures was assayed in murine macrophages after stimulation with lipopolysaccharides.

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