Ordered arrays of proteins on graphite observed by scanning tunneling microscopy

Haggerty, L.; Watson, Brian A.; Barteau, Mark A.; Lenhoff, Abraham M.

doi:10.1116/1.585208

Cited by 48 publications

(26 citation statements)

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“…This was the standard calibration procedure to test the tips in our STM measurements. The STM image of H 3 -PMo 12 O 40 deposited on HOPG is shown in Figure 2a and clearly indicates the formation of an ordered structure on the surface. difference in the sizes of the cations leads to differences in the lattice constants of these materials 25 Acidic protons, water of crystallization, and cations exist in the interstices between polyanions in the solid state as shown schematically in Figure 1.…”

Section: Resultsmentioning

confidence: 99%

“…31 It has been found that when the identity of the countercation of the heteropoly anion (12-molybdophosphate) is fixed and the extent of exchange is varied, the oxidation activity for methacrolein varies significantly in a manner that is distinctly different from the acidity of the catalyst measured by means of the adsorption of NH 3 . 28 The reducibilities of salts of 12-molybdophosphoric acid, M x/n H 3-x PMo 12 O 40 (where M is an n-valent cation), were measured by Ai in a closed system using H 2 . 3 The temperature at which H 2 consumption reached 0.3 mol per mole of 12-molybdophosphoric acid (denoted as "the reduction temperature") was employed as the index of reducibility.…”

Section: Effect Of Countercation On Ndrmentioning

confidence: 99%

“…10 STM can provide real space images of catalyst surfaces with angstrom scale resolution. 11 Insulating materials have been imaged using STM by depositing thin films on a conducting substrate such as graphite, 12 and several models 13,14 have been proposed to explain the significant tunneling current measured in these systems. STM images for several heteropoly and isopoly acids deposited on conductive substrates have been reported by various researchers.…”

Section: Introductionmentioning

confidence: 99%

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Ordered Array Formation and Negative Differential Resistance Behavior of Cation-Exchanged Heteropoly Acids Probed by Scanning Tunneling Microscopy

1996

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Cation-exchanged 12-molybdophosphates deposited on a graphite surface were imaged by scanning tunneling microscopy (STM), and their current-voltage behavior in tunneling spectroscopy (TS) measurements was examined. The periodicity of the polyanion arrays in the STM images was ca. 11-14 Å, and the spacing was dependent on the identity of the countercation. It was also observed that the characteristic negative differential resistance (NDR) behavior of 12-molybdophosphates, observed in TS measurements, is closely related to the reduction potential of the polyoxometalate and to the electronegativity of the countercation. The applied potential (sample to tip) at which NDR behavior was observed decreased with increases in the reduction potential of the HPA as well as with increases in electronegativity of the countercation. More electronegative countercations facilitated electron transfer between the cation and the heteropoly anion, apparently by acting as electron reservoirs, leading to NDR behavior at lower applied voltages and generating higher reduction potentials. This work demonstrates the first correlation between tunneling spectra measured by STM and the chemical properties of polyoxometalates.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Countercation On Ndrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ordered Array Formation and Negative Differential Resistance Behavior of Cation-Exchanged Heteropoly Acids Probed by Scanning Tunneling Microscopy

1996

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“…However, in fact the cleaved HOPG surface exhibits hydrophobic property and is not beneficial for hydrophilic organic and biological materials to combine with it. Only few kinds of proteins, such as lysozyme and chymotrypsinogen A, can be dispersed uniformly and adsorbed orderly on HOPG surface [34]. In our preliminary experiments, catalase was directly deposited onto a freshly cleaved HOPG.…”

Section: Stm Image Of Catalase On Freshly Cleaved Hopg Surfacementioning

confidence: 99%

Molecular Characterization of Beef Liver Catalase by Scanning Tunneling Microscopy

Zhang¹,

Chi²,

Zhang³

et al. 1998

Electroanalysis

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Beef liver catalase molecules can stick tenaciously to the highly oriented pyrolytic graphite (HOPG) surface which has been activated by electrochemical anodization. The immobilized sample is stable enough for high resolution scanning tunneling microscope (STM) imaging. When the anodized conditions are controlled properly, the HOPG surface will be covered with a very thin oxide layer which can bind the protein molecules. Individual molecules of native beef liver catalase are directly observed in detail by STM, which shows an oval-shape structure with a waist. The dimensions of one catalase molecule in this study are estimated as 9.0 × 6.0 × 2.0 nm 3 , which are in good agreement with the known data obtained from X-ray analysis, except the height can not be exactly determined from STM. Electrochemical results confirm that the freshly adsorbed catalase molecules maintain their native structures with biological activities. However, the partly unfolding structure of catalase molecules is observed after the sample is stored for 15 days, this may be caused by the long-term interaction between catalase molecules and the anodized HOPG surface.

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“…Further, the amount of adsorbed enzyme increases with the acidic conditions. 12 Previously, densely packed lysozyme molecules were observed in molecular-resolution STM images. Under high-surface-pressure conditions, formation of the same type of assembled structure is predicted.…”

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confidence: 99%

Nanostructural and Morphological Control of Biological Molecules Arranged by Using Langmuir–Blodgett Films of Organo-modified Aluminosilicate as Templates

Arai

Kusaka

Kubota³

et al. 2012

Chemistry Letters

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Clay LangmuirBlodgett (LB) films play the role of a template in the formation of lysozyme thin layers. Chemisorption of biological molecules onto the anionic montmorillonite surface is confirmed by comparing the IR spectra of organoclay multilayers and the chemisorbed lysozyme. The difference between the height of the monolayers for the organo-modified aluminosilicates and that for their adsorbed lysozyme is about 9 nm. This value is almost twice the length of the lysozyme along the long axis.Layered silicates, clay minerals, have played important roles in modern technology.1 These materials have received considerable attention because of their potential use in numerous applications, ranging from nanocomposite materials to biomedical and personal care products.2 Clays are unique in the sense that they consist of negatively charged aluminosilicate layers held together by exchangeable interlayer cations. Hence, a large number of alkylammonium-modified layered silicates (organomodified clays) have been developed, which are now widely used to form a large variety of nanocomposite materials with enhanced material properties. Organo-modified montmorillonites are post-petroleum resources; it may be possible to form next-generation eco-materials from them. In addition, thin films of clay minerals have been studied for application to modified electrodes, (bio)sensors, photochromic devices, nonlinear optical devices, and so on. 4 The LangmuirBlodgett (LB) method is one of the most useful techniques to prepare ultrathin films.5 In this method, floating molecular monolayers formed at an air/water interface are deposited on a solid substrate in a layer-by-layer manner. Recently, clay LB films have been hybridized with alkylammonium cations. Previously, the authors have developed organomodified montmorillonite (MMT) with extremely high surface coverage and localized negative charges in the bottom, by modification at an oil/water interface. 610In this study, floating monolayers and multilayered films on the solid of preformed organo-modified MMTs with high coverage and localized negative charges in the bottom were constructed by the Langmuir and LB method. In this case, buffer solution containing a lysozyme as the cationic biomolecule was used as the subphase. The organo-modified aluminosilicate LB films play the role of a template in the formation of the adsorbed lysozyme array. These LB multilayers of organo-modified MMTs on which an enzyme was adsorbed were characterized by the ³A isotherm method, infrared (IR) spectroscopy, and atomic force microscopy (AFM) observation.Natural Na + montmorillonite with a cation-exchange capacity of 108.6 mequiv/100 g was supplied by Kunimine Co. The organophilic clay was prepared by cation-exchange reactions of natural clay (aqueous dispersion) with a 0.1% aqueous solution of dimethyldioctadecylammonium chloride. Four kinds of quaternary ammonium cations based on long alkyl chains were used for the hydrophobic parts of the clays. In order to estimate the hydrophobicity and the ability of f...

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Ordered arrays of proteins on graphite observed by scanning tunneling microscopy

Cited by 48 publications

References 0 publications

Ordered Array Formation and Negative Differential Resistance Behavior of Cation-Exchanged Heteropoly Acids Probed by Scanning Tunneling Microscopy

Ordered Array Formation and Negative Differential Resistance Behavior of Cation-Exchanged Heteropoly Acids Probed by Scanning Tunneling Microscopy

Molecular Characterization of Beef Liver Catalase by Scanning Tunneling Microscopy

Nanostructural and Morphological Control of Biological Molecules Arranged by Using Langmuir–Blodgett Films of Organo-modified Aluminosilicate as Templates

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