Orientation of Ordered Structures of Cytosine and Cytidine<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mn>5</mml:mn><mml:mo>′</mml:mo></mml:msup></mml:math>-Monophosphate Adsorbed at Au(110)/Liquid Interfaces

Weightman, P.; Dolan, G. J.; Cm, Smith; Cuquerella, M. Consuelo; Almond, Nick; Farrell, T.; Fernig, David G.; Edwards, C.; Martin, D. S.

doi:10.1103/physrevlett.96.086102

Cited by 51 publications

(112 citation statements)

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“…This might reflect conformational differences between wild-type and mutant proteins that affect the local environment around the FAD isoalloxazine ring [12]. As with the wild-type ETF, the ETF 1e /ETF 2e couple was ⪡ −250mV for the engineered ETF proteins and not accessible [9] using this method.RAS is a surface-sensitive optical technique that has been used to probe molecular assembly and changes in molecular orientation at metal/liquid interfaces [13][14][15][16][17]. The preparation of the Au(110) single crystal used to immobilize engineered variants of ETF together with a description of the electrochemical cell, potentiostat and RAS instrument [18] have been described previously [15].…”

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confidence: 99%

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Evidence for protein conformational change at a Au(110)/protein interface

Messiha

Scrutton

et al. 2008

Europhys. Lett.

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Evidence is presented that reflection anisotropy spectroscopy (RAS) can provide real-time measurements of conformational change in proteins induced by electron transfer reactions. A bacterial electron transferring flavoprotein (ETF) has been modified so as to adsorb on an Au(110) electrode and enable reversible electron transfer to the protein cofactor in the absence of mediators. Reversible changes are observed in the RAS of this protein that are interpreted as arising from conformational changes accompanying the transfer of electrons.While there has been considerable progress in the determination of the structures of biological molecules using techniques like X-ray diffraction, there has been very little progress in obtaining information on the time-dependent conformational changes that are the key to understanding the function of such molecules. The importance of extensive motion of protein domains coupled to biological electron transfer has come to light in recent years, primarily through structural analysis of redox proteins using crystallographic methods [1,2]. Domain motion shortens electron tunneling distances through conformational search mechanisms, thus increasing the probability of electron transfer by quantum-mechanical tunneling [3]. Despite these advances, real-time observation of conformational change coupled to electron transfer is difficult and we lack a method of directly probing conformational change linked to redox chemistry in real time that is generally applicable to biological macromolecules. In this work we show that the introduction of surface-exposed cysteine groups into proteins can lead to the creation of protein-Au(110) assemblies suitable for combined electrochemical and reflectance anisotropy spectroscopy (RAS) studies of conformational changes driven by electron transfer. We report real-time measurements of changes in RA spectra that are correlated with the changes in electrode potential. In natural systems such changes in electrode potential induce electron transfer interactions that lead to changes in the conformation of protein domains.The experiments were performed on the electron transfer flavoproteins (ETFs) that act as carriers of electrons between a number of donor and acceptor proteins [4]. They are dynamic molecules both in complex with donor proteins [1,2] and free in solution [5,6]. They have a 2-electron reduction capacity, but thermodynamically are restricted to 1-electron reduction/ oxidation in biological cells. The crystallographic structure of human and bacterial ETFs are known [1,7], thus facilitating a knowledge-based design of surface-exposed cysteine groups. Prior to the RAS experiments the mid-point reduction potential of the FAD cofactor in the engineered ETF proteins was determined as described previously for a wild-type ETF [9]. Enzyme solutions were electrochemically titrated using sodium dithionite as reductant and potassium ferricyanide as oxidant. The UV-visible spectra of ∼30 to 40 points from 300 to 800 nm (4.1 to 1.6 eV) across a whole ran...

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confidence: 99%

“…The preparation of the Au(110) single crystal used to immobilize engineered variants of ETF together with a description of the electrochemical cell, potentiostat and RAS instrument [18] have been described previously [15]. Electrolyte solutions were prepared from 0.1 M NaH 2 PO 4 and K 2 HPO 4 dissolved in ultra-pure water.…”

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confidence: 99%

Evidence for protein conformational change at a Au(110)/protein interface

Messiha

Scrutton

et al. 2008

Europhys. Lett.

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“…We identify it with the phase reported in STM studies in electrochemical cells 22,28 , and by optical studies in solution 26 . In the last study, the measurements were performed in situ, and the molecules were found to be perpendicular to the surface and oriented along [1 1 0], whereas we found an intermediate angle.…”

Section: Adsorption Modelmentioning

confidence: 60%

“…The adsorption of cytosine on gold has been the subject of numerous studies using a wide range of techniques, such as STM, theoretical calculations, infrared and surface enhanced Raman spectroscopy and cyclic voltammetry [18][19][20][21][22][23][24][25][26][27] . Adsorption has been carried out in vacuum, in solution and in electrochemical cells, and on single crystals, thin films and nanoparticles of gold.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Cytosine and AZA Derivatives of Cytidine on Au Single Crystal Surfaces

et al. 2013

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ABSTRACT. The adsorption of cytosine, 6-azacytosine, 6-azacytidine and 5-azacytidine on the Au(111) surface has been studied by soft X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). Monolayer films of these molecules were adsorbed on Au(111) from aqueous solution, and the nature of bonding with this surface has been determined. Cytosine was adsorbed from the gas phase by evaporation, as well as from solution, on both the Au(111) and Au (110) through the N (3) atom of the pyrimidine ring dominates, but a second state is also 2 present. For deposition from solution, this second state dominates, and the molecular plane is no longer parallel to the surface. This state also bonds through the N (3) atom, but in addition interacts with the surface via the amino group. Two tautomers of 6-azacytosine were observed, and they and 6-azacytidine adsorb with similar geometries and chemical bonding via the azacytosine ring. The ribose ring does not appear to perturb the adsorption of azacytidine compared with azacytosine. The azacytosine ring is nearly but not perfectly parallel to the surface. 5-azacytidine adsorbs with the azacytosine ring very nearly parallel to the surface, as an imino tautomer.3

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“…This is one of relatively few anisotropic metal substrates that can be prepared under ambient conditions using the flame annealing technique developed and used successfully by electrochemists. An example of the potential of RAS in exploring this electrochemical interface is a study of the adsorption of the DNA base cytosine and cytidine 5 -monophosphate from solutions of NaH 2 PO 4 and K 2 HPO 4 [58]. Ordered structures were formed on the Au surface, and analysis of the RAS results showed that the plane of the nucleic acid base was oriented vertically and was parallel to the [110] axis of the Au(110) surface.…”

Section: Solid-liquid Interfacesmentioning

confidence: 99%

Probing surface and interface structure using optics

McGilp

2010

J. Phys.: Condens. Matter

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Optical techniques for probing surface and interface structure are introduced and recent developments in the field are discussed. These techniques offer significant advantages over conventional surface probes: all pressure ranges of gas-condensed matter interfaces are accessible and liquid-liquid, liquid-solid and solid-solid interfaces can be probed, due to the large penetration depth of the optical radiation. Sensitivity and discrimination from the bulk are the two challenges facing optical techniques in probing surface and interface structure. Where instrumental improvements have resulted in enhanced sensitivity, conventional optical techniques can be used to characterize heterogeneous adsorbed layers on a substrate, often with sub-monolayer resolution. Nanoscale lateral resolution is possible using scanning near-field optics. A separate class of techniques, which includes reflection anisotropy spectroscopy, and nonlinear optical probes such as second-harmonic and sum-frequency generation, uses the difference in symmetry between the bulk and the surface or interface to suppress the bulk contribution. A perspective is presented of likely future developments in this rapidly expanding field.

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Orientation of Ordered Structures of Cytosine and Cytidine5′-Monophosphate Adsorbed at Au(110)/Liquid Interfaces

Cited by 51 publications

References 19 publications

Evidence for protein conformational change at a Au(110)/protein interface

Evidence for protein conformational change at a Au(110)/protein interface

Adsorption of Cytosine and AZA Derivatives of Cytidine on Au Single Crystal Surfaces

Probing surface and interface structure using optics

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