scholarly journals Preparation and characterization of stable Core/Shell Fe3O4@Au ‎decorated with amine group for immobilization of lipase by covalent ‎attachment

2021 ◽  
Author(s):  
Marziyeh Aghamolaei ◽  
Amir Landarani-Isfahani ◽  
Mehrnaz Bahadori ◽  
Zahra Zamani Nori ◽  
Saghar Rezaei ◽  
...  
Keyword(s):  
Self Assembly ◽  
Immobilized Lipase ◽  
Residual Activity ◽  
Covalent Bond ◽  
Temperature Stability ◽  
Covalent Immobilization ◽  
Covalent Attachment ◽  
Core Shell ◽  
Amine Group ◽  
Wide Range

The self-assembly approach was used for amine decoration of core/shell Fe3O4@Au with 4-aminothiphenol. This structure was used for covalent immobilization of lipase using a Ugi 4-component reaction. The amine group on the structure and carboxylic group from lipase can react in the Ugi reaction and a firm and stable covalent bond creates between enzyme and support. The synthesized structure was fully characterized and its activity was explored in different situations. The results displayed the pH and temperature stability of immobilized lipase compared to free lipase in a wide range of pH and temperature. Also after 60 days, it showed excellent activity while residual activity for the free enzyme was only 10%. The synthesized structure was conveniently separated using an external magnetic field and reused 6 times without losing the activity of the immobilized enzyme.

scholarly journals Improving the Thermostability and Optimal Temperature of a Lipase from the Hyperthermophilic ArchaeonPyrococcus furiosusby Covalent Immobilization

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Roberta V. Branco ◽  
Melissa L. E. Gutarra ◽  
Jose M. Guisan ◽  
Denise M. G. Freire ◽  
Rodrigo V. Almeida ◽  
...  
Keyword(s):  
Pyrococcus Furiosus ◽  
Enzyme Stability ◽  
Enantiomeric Excess ◽  
Residual Activity ◽  
Covalent Bond ◽  
Covalent Immobilization ◽  
Covalent Attachment ◽  
Optimal Temperature ◽  
Thermostable Lipase ◽  
Multipoint Covalent Attachment

A recombinant thermostable lipase (Pf2001Δ60) from the hyperthermophilic ArchaeonPyrococcus furiosus(PFUL) was immobilized by hydrophobic interaction on octyl-agarose (octyl PFUL) and by covalent bond on aldehyde activated-agarose in the presence of DTT at pH = 7.0 (one-point covalent attachment) (glyoxyl-DTT PFUL) and on glyoxyl-agarose at pH 10.2 (multipoint covalent attachment) (glyoxyl PFUL). The enzyme’s properties, such as optimal temperature and pH, thermostability, and selectivity, were improved by covalent immobilization. The highest enzyme stability at 70°C for 48 h incubation was achieved for glyoxyl PFUL (around 82% of residual activity), whereas glyoxyl-DTT PFUL maintained around 69% activity, followed by octyl PFUL (27% remaining activity). Immobilization on glyoxyl-agarose improved the optimal temperature to 90°C, while the optimal temperature of octyl PFUL was 70°C. Also, very significant changes in activity with different substrates were found. In general, the covalent bond derivatives were more active than octyl PFUL. TheEvalue also depended substantially on the derivative and the conditions used. It was observed that the reaction of glyoxyl-DTT PFUL using methyl mandelate as a substrate at pH 7 presented the best results for enantioselectivityE=22and enantiomeric excess (ee (%) = 91).

scholarly journals Enzymatic Production of Biodiesel Using Immobilized Lipase on Core-Shell Structured Fe3O4@MIL-100(Fe) Composites

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 850 ◽  
Author(s):  
Xie ◽  
Huang
Keyword(s):  
Immobilized Lipase ◽  
Metal Organic Framework ◽  
Candida Rugosa ◽  
Covalent Immobilization ◽  
Molar Ratio ◽  
Core Shell ◽  
Enzymatic Production ◽  
Metal Organic ◽  
Significant Mass Loss ◽  
Significant Mass

In this research, core–shell structured Fe3O4@MIL-100(Fe) composites were prepared by coating Fe3O4 magnetite with porous MIL-100(Fe) metal-organic framework (MOF) material, which were then utilized as magnetic supports for the covalent immobilization of the lipase from Candida rugosa through amide linkages. By using the carbodiimide/hydroxysulfosuccinimide (EDC/NHS) activation strategy, the lipase immobilization efficiency could reach 83.1%, with an activity recovery of 63.5%. The magnetic Fe3O4@MIL-100(Fe) composite and immobilized lipase were characterized by several techniques. The characterization results showed that the Fe3O4 core was coated with MIL-100(Fe) shell with the formation of perfect core–shell structured composites, and moreover, the lipase was covalently tethered on the magnetic carrier. The immobilized lipase displayed a strong magnetic response and could be facilely separated by an external magnetic field. With this magnetic biocatalyst, the maximum biodiesel conversion attained 92.3% at a methanol/oil molar ratio of 4:1, with a three-step methanol addition manner, and a reaction temperature of 40 °C. Moreover, the biocatalyst prepared in the present study was recycled easily by magnetic separation without significant mass loss, and displayed 83.6% of its initial activity as it was reused for five runs, thus allowing its potential application for the cleaner production of biodiesel.

Covalent Attachment of a Single Dextran Polymer Between the Tip of an Atomic Force Microscope and a Gold Surface

1999 ◽  
Vol 576 ◽  
Author(s):  
M. Grandbois ◽  
R. Décor ◽  
M. Rief ◽  
A. Wagner ◽  
C. Mioskowski ◽  
...  
Keyword(s):  
Atomic Force Microscope ◽  
Covalent Bond ◽  
Gold Surface ◽  
Covalent Immobilization ◽  
Covalent Attachment ◽  
Amino Groups ◽  
Fly Fishing ◽  
Atomic Force ◽  
Carbodiimide Hydrochloride ◽  
Measuring Force

ABSTRACTA method for covalent immobilization of a single dextran polymer between a gold surface and the tip of an atomic force microscope (AFM) is presented. Carboxymethylated dextran immobilized on gold by epoxythiol chemistry was activated with N-hydroxysuccinimide (NHS) and N-ethyl-N'-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) in order to make the dextran polymer reactive for the amino groups present on the previously aminosilanized AFM tip. By measuring force vs extension curves we have shown that it is possible to catch such an activated dextran polymer with an AFM tip through the formation of a covalent bond. Dextran polymers were attached even without any detectable indentation of the tip in the dextran-coated gold surface. In this so-called fly-fishing mode, attachment of multiple dextran polymers, which typically occurs when the tip is indented into the surface, are efficiently avoided.

scholarly journals Self-Assembly of N-Heterocyclic Carbenes on Au(111)

2020 ◽  
Author(s):  
Alex Inayeh ◽  
Ryan Groome ◽  
Ishwar Singh ◽  
Alex Veinot ◽  
Felipe Iima ◽  
...  
Keyword(s):  
Self Assembly ◽  
Rational Design ◽  
Organic Molecules ◽  
Covalent Bond ◽  
Heterocyclic Carbenes ◽  
Metallic Surfaces ◽  
Surface Geometry ◽  
Wide Range ◽  
Structure Surface ◽  
Potential Applications

The production of ordered arrays of organic molecules on metallic surfaces by means of self-assembly is one of the most powerful methods for controlled patterning on the nanometer scale. Although the self-assembly of sulfurbased ligands has been studied for decades, the thermal and oxidative instability of these systems introduces challenges in many potential applications. In recent years, it has been shown that a new ligand class, N-heterocyclic carbenes (NHCs), bind to metal surfaces via a metal–carbon covalent bond, resulting in monolayers with much greater stability. However, fundamental questions surrounding self-assembly in this new ligand class remain unanswered, including the simple questions of what controls NHC orientation on the surface and under what conditions they self-assemble. Herein we describe how NHC structure, surface density, deposition temperature, and annealing temperature control mobility, thermal stability, NHC surface geometry, self-assembly, and the exact chemical nature of the surface structures. These data provide the first general set of guidelines to enable the rational design of highly ordered NHC-based monolayers. Considering that NHCs may supplant thiols as the functionalization agent of choice in a wide range of applications, a detailed understanding of their surface chemistry is crucial for the success of these next-generation monolayers.

Chemically Functional Semiconductor Nanocrystals: Electrochemistry and Self-Assembly on Surfaces

2002 ◽  
Vol 737 ◽  
Author(s):  
Benjamin M. Hutchins ◽  
Andrew H. Latham ◽  
Mary Elizabeth Williams
Keyword(s):  
Band Gap ◽  
Self Assembly ◽  
Semiconductor Nanocrystals ◽  
Band Gap Energy ◽  
Covalent Attachment ◽  
Core Shell ◽  
Metallic Surfaces ◽  
Shell Nanoparticles ◽  
Size Dependent ◽  
Core Shell Nanoparticles

ABSTRACTSemiconductor nanocrystals (i.e., Quantum Dots, QDs) exhibit size-dependent emission properties and have synthetically adjustable ligand shells, making them interesting materials for applications ranging from luminescent displays to biomolecular tags. In this paper, the electrochemical properties of two types of nanocrystal are studied with an emphasis on the effect of core/shell vs core structures. The band gap energy of CdSe particles, measured using optical spectroscopy, was shown to increase slightly with the application of a ZnSe shell, as expected based on the increased energy required to transfer an electron through the shell material. The electrochemically determined band gaps are overestimated in the case of CdSe/ZnSe core/shell nanoparticles, reflecting the band gap of the ZnSe shell. Finally, QDs were self-assembled onto gold surfaces by electrostatic and covalent attachment, and their presence confirmed by fluorescence spectroscopy. The high intensity of emitted light shows that the QDs can be self-assembly onto metallic surfaces, without energy transfer quenching of the luminescence.

scholarly journals Self-Assembly of N-Heterocyclic Carbenes on Au(111)

2020 ◽  
Author(s):  
Alex Inayeh ◽  
Ryan Groome ◽  
Ishwar Singh ◽  
Alex Veinot ◽  
Felipe Iima ◽  
...  
Keyword(s):  
Self Assembly ◽  
Rational Design ◽  
Organic Molecules ◽  
Covalent Bond ◽  
Heterocyclic Carbenes ◽  
Metallic Surfaces ◽  
Surface Geometry ◽  
Wide Range ◽  
Structure Surface ◽  
Potential Applications

The production of ordered arrays of organic molecules on metallic surfaces by means of self-assembly is one of the most powerful methods for controlled patterning on the nanometer scale. Although the self-assembly of sulfurbased ligands has been studied for decades, the thermal and oxidative instability of these systems introduces challenges in many potential applications. In recent years, it has been shown that a new ligand class, N-heterocyclic carbenes (NHCs), bind to metal surfaces via a metal–carbon covalent bond, resulting in monolayers with much greater stability. However, fundamental questions surrounding self-assembly in this new ligand class remain unanswered, including the simple questions of what controls NHC orientation on the surface and under what conditions they self-assemble. Herein we describe how NHC structure, surface density, deposition temperature, and annealing temperature control mobility, thermal stability, NHC surface geometry, self-assembly, and the exact chemical nature of the surface structures. These data provide the first general set of guidelines to enable the rational design of highly ordered NHC-based monolayers. Considering that NHCs may supplant thiols as the functionalization agent of choice in a wide range of applications, a detailed understanding of their surface chemistry is crucial for the success of these next-generation monolayers.

Factors Affecting Molecular Self-Assembly and Its Mechanism

2012 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Hueyling Tan
Keyword(s):  
Self Assembly ◽  
Building Blocks ◽  
Molecular Engineering ◽  
Molecular Structures ◽  
Polymer Science ◽  
New Approach ◽  
Factors Affecting ◽  
Dna Structures ◽  
Self Assembling ◽  
Wide Range

Molecular self-assembly is ubiquitous in nature and has emerged as a new approach to produce new materials in chemistry, engineering, nanotechnology, polymer science and materials. Molecular self-assembly has been attracting increasing interest from the scientific community in recent years due to its importance in understanding biology and a variety of diseases at the molecular level. In the last few years, considerable advances have been made in the use ofpeptides as building blocks to produce biological materials for wide range of applications, including fabricating novel supra-molecular structures and scaffolding for tissue repair. The study ofbiological self-assembly systems represents a significant advancement in molecular engineering and is a rapidly growing scientific and engineering field that crosses the boundaries ofexisting disciplines. Many self-assembling systems are rangefrom bi- andtri-block copolymers to DNA structures as well as simple and complex proteins andpeptides. The ultimate goal is to harness molecular self-assembly such that design andcontrol ofbottom-up processes is achieved thereby enabling exploitation of structures developed at the meso- and macro-scopic scale for the purposes oflife and non-life science applications. Such aspirations can be achievedthrough understanding thefundamental principles behind the selforganisation and self-synthesis processes exhibited by biological systems.

scholarly journals Real-time observation of tetrapyrrole binding to an engineered bacterial phytochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yusaku Hontani ◽  
Mikhail Baloban ◽  
Francisco Velazquez Escobar ◽  
Swetta A. Jansen ◽  
Daria M. Shcherbakova ◽  
...  
Keyword(s):  
Real Time ◽  
Rational Design ◽  
Near Infrared ◽  
Fluorescent Proteins ◽  
Covalent Bond ◽  
Binding Pocket ◽  
Tissue Imaging ◽  
Covalent Attachment ◽  
Time Resolved

AbstractNear-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes are widely used for structural and functional deep-tissue imaging in vivo. To fluoresce, NIR FPs covalently bind a chromophore, such as biliverdin IXa tetrapyrrole. The efficiency of biliverdin binding directly affects the fluorescence properties, rendering understanding of its molecular mechanism of major importance. miRFP proteins constitute a family of bright monomeric NIR FPs that comprise a Per-ARNT-Sim (PAS) and cGMP-specific phosphodiesterases - Adenylyl cyclases - FhlA (GAF) domain. Here, we structurally analyze biliverdin binding to miRFPs in real time using time-resolved stimulated Raman spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. Biliverdin undergoes isomerization, localization to its binding pocket, and pyrrolenine nitrogen protonation in <1 min, followed by hydrogen bond rearrangement in ~2 min. The covalent attachment to a cysteine in the GAF domain was detected in 4.3 min and 19 min in miRFP670 and its C20A mutant, respectively. In miRFP670, a second C–S covalent bond formation to a cysteine in the PAS domain occurred in 14 min, providing a rigid tetrapyrrole structure with high brightness. Our findings provide insights for the rational design of NIR FPs and a novel method to assess cofactor binding to light-sensitive proteins.

Core/Shell Dual‐Responsive Nanocarriers via Iron‐Mineralized Electrostatic Self‐Assembly for Precise Pesticide Delivery

2021 ◽  
pp. 2102027
Author(s):  
Da‐xia Zhang ◽  
Jiang Du ◽  
Rui Wang ◽  
Jian Luo ◽  
Tong‐fang Jing ◽  
...  
Keyword(s):  
Self Assembly ◽  
Core Shell ◽  
Dual Responsive
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