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 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 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 Experimental and Theoretical Study of the Covalent Grafting of Triazole Layer onto the Gold Surface

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2927
Author(s):  
Nimet Orqusha ◽  
Sereilakhena Phal ◽  
Avni Berisha ◽  
Solomon Tesfalidet
Keyword(s):  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Electrochemical Impedance ◽  
Gold Surface ◽  
Covalent Attachment ◽  
Force Microscopy ◽  
Atomic Force ◽  
Covalent Grafting ◽  
Before And After

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Site-Specific Attachment of Gold Nanoparticles to DNA Templates

2001 ◽  
Vol 635 ◽  
Author(s):  
Karen A. Stevenson ◽  
Govindarajan Muralidharan ◽  
Leon Maya ◽  
Jack C. Wells ◽  
Jacob Barhen
Keyword(s):  
Gold Nanoparticles ◽  
Amino Groups ◽  
Dna Templates ◽  
Force Microscopy ◽  
Atomic Force ◽  
Carbodiimide Hydrochloride ◽  
Transmission Electron ◽  
Specific Attachment ◽  
Chemical Technique ◽  
Dna Template

AbstractDNA was used as a scaffold for the binding of gold nanoparticles using a standard chemical technique. A DNA template was designed with amino-modified thymines located every 3.7 nm, which would allow the attachment of the carboxylic acid functionalized gold nanoparticles. The gold particles were covalently bound to the amino groups on the DNA using standard 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) chemistry in the presence of a competitor to block excess gold binding sites. The products were analyzed by transmission electron microscopy (TEM) and atomic force microscopy (AFM).

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

Imaging polymers, proteins and dna in aqueous solutions with the atomic force microscope

1989 ◽  
Vol 47 ◽  
pp. 32-33
Author(s):  
S.A.C. Gould ◽  
B. Drake ◽  
C.B. Prater ◽  
A.L. Weisenhorn ◽  
S.M. Lindsay ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dna Sequencing ◽  
Aqueous Solutions ◽  
Atomic Force Microscope ◽  
Piezoelectric Crystal ◽  
Atomic Force ◽  
Structure Of Molecules ◽  
Optical Lever

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

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