Determination of surface pKa values of surface-confined molecules derivatized with pH-sensitive pendant groups

Bryant, Mark A.; Crooks, Richard M.

doi:10.1021/la00026a005

Cited by 217 publications

(183 citation statements)

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“…[42][43][44] Considering the results presented in Figure 5 and those reported in the literature, [42][43][44] a model based on the resonance structures of the Hpyt molecules on gold is suggested in Scheme 1 to explain the changes in the voltammograms of the [Fe(CN) 6 ] 4-probe molecule. At pH > 4.0, two resonance forms, I and II, can be proposed, with the real structure between them.…”

Section: Inorganic Complexes As Probe Moleculesmentioning

confidence: 79%

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Paulo

Silva

Pinheiro

et al. 2008

J. Braz. Chem. Soc.

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O composto 5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) adsorve espontaneamente sobre ouro formando SAMs ("Self-Assembled Monolayers") que, de acordo com os resultados eletroquímicos e de STM ("Scanning Tunneling Microscopy"), contêm poros através dos quais as moléculas dos complexos [Fe(CN) 6 ] 4-, a dependência da corrente faradáica com o pH da solução eletrolítica permitiu o cálculo do pKa da molécula de Hpyt adsorvida sobre ouro (4,2). Os parâmetros termodinâmicos, H ads and G ads , para o processo de adsorção desta molécula foram estimados em -20,01 e -39,39 kJ mol -1 , respectivamente, utilizando-se o modelo de Langmuir. O processo redox da metaloproteína citocromo c foi estudado utilizando-se a SAM de Hpyt. A constante de velocidade heterogênea de transferência de elétrons foi calculada em 2,29 10 -3 cm s -1 .5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) spontaneously adsorbs on gold forming SAMs (self-assembled monolayers) that, based on STM (Scanning Tunneling Microscopy) and electrochemical data, contain pinholes through which [Fe(CN) 6 ] 4-and [Ru(NH 3 ) 6 ] 3+ probe molecules access the underlying gold electrode. For the former molecule, the dependence of the faradaic current on the electrolyte solution pH value allowed the evaluation of the surface pKa as 4.2. The thermodynamic parameters H ads and G ads for the Hpyt adsorption process could be described by the Langmuir model and were calculated as -20.01 and -39.39 kJ mol -1 , respectively. Electrodic redox reaction of cytochrome c metalloprotein was accessed by using the Hpyt SAM with a heterogeneous electron transfer rate constant of 2.29 10 -3 cm s -1 .

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Section: Inorganic Complexes As Probe Moleculesmentioning

confidence: 79%

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Paulo

Silva

Pinheiro

et al. 2008

J. Braz. Chem. Soc.

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“…In addition, the knowledge of the pKa of the terminal moieties allows chemical control on the electrode surface. As examples, pKa values of 6.0 [80] and 6.9 [81] for SAMs of 11-mercaptoundecanoic acid (MUA) and 4-aminothiophenol (4ATP) groups on gold were determined, respectively. Dependence of the pKa of -NH 2 -based SAMs on thiol chain length was also reported [82].…”

Section: Electrode Functionalizationmentioning

confidence: 99%

Controlling Redox Enzyme Orientation at Planar Electrodes

et al. 2018

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Abstract:Redox enzymes, which catalyze reactions involving electron transfers in living organisms, are very promising components of biotechnological devices, and can be envisioned for sensing applications as well as for energy conversion. In this context, one of the most significant challenges is to achieve efficient direct electron transfer by tunneling between enzymes and conductive surfaces. Based on various examples of bioelectrochemical studies described in the recent literature, this review discusses the issue of enzyme immobilization at planar electrode interfaces. The fundamental importance of controlling enzyme orientation, how to obtain such orientation, and how it can be verified experimentally or by modeling are the three main directions explored. Since redox enzymes are sizable proteins with anisotropic properties, achieving their functional immobilization requires a specific and controlled orientation on the electrode surface. All the factors influenced by this orientation are described, ranging from electronic conductivity to efficiency of substrate supply. The specificities of the enzymatic molecule, surface properties, and dipole moment, which in turn influence the orientation, are introduced. Various ways of ensuring functional immobilization through tuning of both the enzyme and the electrode surface are then described. Finally, the review deals with analytical techniques that have enabled characterization and quantification of successful achievement of the desired orientation. The rich contributions of electrochemistry, spectroscopy (especially infrared spectroscopy), modeling, and microscopy are featured, along with their limitations.

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“…34 However, Cha et al succeeded in forming lipid bilayers on gold decorated with alkanethiols functionalised with amino groups and negatively charged liposomes. 35 Accordingly, we studied the formation of a bilayer on a 4-ATP modified surface (at a pH lower than the pKa of its amino groups, 36 so that positive charges would be present in the gold surface) using negatively charged E. coli The ACS journal of surfaces and colloids 27: 6449-6457 (2011) 10 softer material (part of the curve marked with a square) are both compatible with the behavior described for a tip penetrating and breaking a 4 nm thick lipid bilayer deposited on a hard surface.…”

Section: Preparation Of Liposomesmentioning

confidence: 99%

Oriented Immobilization of a Membrane-Bound Hydrogenase onto an Electrode for Direct Electron Transfer

et al. 2011

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The ACS journal of surfaces and colloids 27: 6449-6457 (2011) 2 ABSTRACTThe interaction of redox enzymes with electrodes is of great interest for studying the catalytic mechanisms of redox enzymes and for bioelectronic applications. Efficient electron transport between the biocatalysts and the electrodes has achieved more success with soluble than with membrane enzymes due to the higher structural complexity and instability of the latter proteins. In this work we report a strategy for immobilizing a membrane-bound enzyme onto gold electrodes with a controlled orientation in its fully active conformation. The immobilized redox enzyme is the Ni-Fe-Se hydrogenase from Desulfovibrio vulgaris Hildenborough, which catalyzes H 2 -oxidation reversibly and is associated to the cytoplasmic membrane by a lipidic tail. Gold surfaces modified with this enzyme and phospholipids have been studied by atomic force microscopy (AFM) and electrochemical methods. The combined study indicates that by a two-step immobilization procedure the hydrogenase can be inserted via its lipidic tail onto a phospholipidic bilayer formed over the gold surface, only allowing mediated electron transfer between enzyme and electrode. On the other hand, a one-step immobilization procedure favours formation of a hydrogenase monolayer over the gold surface with its lipidic tail inserted in a phospholipid bilayer formed on top of the hydrogenase molecules. This latter method has allowed for the first time efficient electron transfer between a membrane-bound enzyme in its native conformation and an electrode.

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Determination of surface pKa values of surface-confined molecules derivatized with pH-sensitive pendant groups

Cited by 217 publications

References 0 publications

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Controlling Redox Enzyme Orientation at Planar Electrodes

Oriented Immobilization of a Membrane-Bound Hydrogenase onto an Electrode for Direct Electron Transfer

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