Change in the surface density of immobilized enzyme molecules induced by photoelectron processes in a silicon substrate

Scanning probe microscopy techniques were used to study immobilized enzyme molecules of glucose oxidase (GOD) on a biosensor surface. The study was carried out in order to optimize atomic force microscopy (AFM) imaging and reveal themolecular resolution of individual GOD molecules. Chemically modified AFM tips and the light tapping mode were found to be the optimal conditions for imaging soft biomolecules such as GOD. The information obtained from the AFM images included spatial distribution and organization of the enzyme molecules on the surface, surface coverage and shape, size and orientation of individual molecules. Two typical shapes of GOD molecules were found, spherical and butterfly, which are in accordance with the shapes obtained from scanning tunnelling microscopy (STM) images. Using a model of the orientation of the GOD molecules on the surface, these shapes are assigned to the enzyme standing and lying on the surface. After AFM tip deconvolution, the size of the spherical shaped GOD molecules was found to be 12 ?2.1 nm in diameter, whereas the butterfly shapes were 16.5 ? 3.3 nm x10.2 ? 2.5 nm. Corresponding STM images showed smaller lateral dimensions of 10 _1nm_ 6 ?1nm and 6.5 ? 1 nm x5 ? 1 nm. The disagreement between these two techniques is attributed to the deformation of the GOD molecules caused by the tapping process.

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Toward controlled geometric structure and surface property heterogeneities of TiO2 for lipase immobilization

10.22541/au.160791614.41920343/v1 ◽

2020 ◽

Author(s):

Wenfeng Zhou ◽

Xiaohong Zhou ◽

Wei Zhuang ◽

Rijia Lin ◽

Ye Zhao ◽

...

Keyword(s):

Synergistic Effect ◽

Pore Size ◽

Surface Properties ◽

Geometric Structure ◽

Immobilized Enzyme ◽

Immobilized Lipase ◽

Immobilized Enzymes ◽

Relative Activity ◽

Lipase Immobilization ◽

Enzyme Molecules

Immobilized enzymes as biocatalysts are expected to solve issues of pollution and economic inefficiency in industrial catalysis. In order to obtain an immobilized enzyme with high activity and stability, the design of substrate geometric structure and surface properties is desirable. Here, TiO2 with controlled pore size and surface properties was designed and synthesized for lipase immobilization, resulting in an efficient biocatalyst. The activity of TiO2 immobilized lipase is improved with the increasing pore size of TiO2 from 10 to 100 nm. Compared to geometric structure impact, regulation of surface properties plays a greater role on the immobilization of lipase on TiO2. Among them, the relative activity of ethenyl triethoxy silane (ETS) modified TiO2 immobilized lipase is as high as 365.85 % over the pristine lipase. This research provides experimental evidence for studying the adsorption of enzyme molecules on the supports under the synergistic effect of geometric structure and surface properties.

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Motions of neutral hydrogen at high latitudes

Symposium - International Astronomical Union ◽

10.1017/s0074180900101068 ◽

1967 ◽

Vol 31 ◽

pp. 265-278 ◽

Cited By ~ 1

Author(s):

A. Blaauw ◽

I. Fejes ◽

C. R. Tolbert ◽

A. N. M. Hulsbosch ◽

E. Raimond

Keyword(s):

Surface Density ◽

Velocity Dispersion ◽

Neutral Hydrogen ◽

Hydrogen Gas ◽

High Latitudes ◽

Low Velocity

Earlier investigations have shown that there is a preponderance of negative velocities in the hydrogen gas at high latitudes, and that in certain areas very little low-velocity gas occurs. In the region 100° <l< 250°, + 40° <b< + 85°, there appears to be a disturbance, with velocities between - 30 and - 80 km/sec. This ‘streaming’ involves about 3000 (r/100)2solar masses (rin pc). In the same region there is a low surface density at low velocities (|V| < 30 km/sec). About 40% of the gas in the disturbance is in the form of separate concentrations superimposed on a relatively smooth background. The number of these concentrations as a function of velocity remains constant from - 30 to - 60 km/sec but drops rapidly at higher negative velocities. The velocity dispersion in the concentrations varies little about 6·2 km/sec. Concentrations at positive velocities are much less abundant.

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Analyzing reactions of single mechanoenzyme molecules by light microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122538 ◽

1992 ◽

Vol 50 (1) ◽

pp. 426-427

Author(s):

Jeff Gelles

Keyword(s):

Image Processing ◽

Reaction Mechanisms ◽

Transient State ◽

Nanometer Scale ◽

Reaction Intermediates ◽

Enzyme Molecule ◽

Directed Movement ◽

Enzyme Molecules ◽

Individual Enzyme ◽

Single Reaction

Mechanoenzymes are enzymes which use a chemical reaction to power directed movement along biological polymer. Such enzymes include the cytoskeletal motors (e.g., myosins, dyneins, and kinesins) as well as nucleic acid polymerases and helicases. A single catalytic turnover of a mechanoenzyme moves the enzyme molecule along the polymer a distance on the order of 10−9 m We have developed light microscope and digital image processing methods to detect and measure nanometer-scale motions driven by single mechanoenzyme molecules. These techniques enable one to monitor the occurrence of single reaction steps and to measure the lifetimes of reaction intermediates in individual enzyme molecules. This information can be used to elucidate reaction mechanisms and determine microscopic rate constants. Such an approach circumvents difficulties encountered in the use of traditional transient-state kinetics techniques to examine mechanoenzyme reaction mechanisms.

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On the Preparation of Bovine α-Thrombin

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646669 ◽

1978 ◽

Vol 39 (01) ◽

pp. 193-200 ◽

Cited By ~ 7

Author(s):

Erwin F Workman ◽

Roger L Lundblad

Keyword(s):

Immobilized Enzyme ◽

Catalytic Properties ◽

Specific Activity ◽

Guanidine Hydrochloride ◽

Low Molecular Weight ◽

Reversible Process ◽

Gel Beads ◽

Tissue Thromboplastin ◽

C 50 ◽

Hydrolysis Of

SummaryAn improved method for the preparation of bovine α-thrombin is described. The procedure involves the activation of partially purified prothrombin with tissue thromboplastin followed by chromatography on Sulfopropyl-Sephadex C-50. The purified enzyme is homogeneous on polyacrylamide discontinuous gel electrophoresis and has a specific activity toward fibrinogen of 2,200–2,700 N.I.H. U/mg. Its stability on storage in liquid media is dependent on both ionic strenght and temperature. Increasing ionic strength and decreasing temperature result in optimal stability. The denaturation of α-thrombin by guanidine hydrochloride was found to be a partially reversible process with the renatured species possessing properties similar to “aged” thrombin. In addition, the catalytic properties of a-thrombin covalently attached to agarose gel beads were also examined. The activity of the immobilized enzyme toward fibrinogen was affected to a much greater extent than was the hydrolysis of low molecular weight, synthetic substrates.

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