Effect of pH on the Enantiospecificity of Homocysteine Monolayer on Au(111) for the Redox Reaction of 3,4‐Dihydroxyphenylalanine

Matsunaga, Mariko; Nagasaka, Makoto; Nakanishi, Tetsuya; Sawaguchi, Takahiro; Osaka, Tetsuya

doi:10.1002/elan.200704110

Cited by 17 publications

(15 citation statements)

References 32 publications

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“…The magnitude of that peak is lower in Mefp-1 solution, indicating that less PtO is formed because the adsorbed Mefp-1 partially blocks active sites of Pt oxidation. Upon the anodic sweep, the presence of Mefp-1 leads to a slight increase in current density before 0.56 V (curve b, Figure ), which is probably due to the oxidation of the adsorbed DOPA content as reported in the literature. ,− On the other hand, at anodic potentials of 0.56 V and higher, the current density is lower for the sample in Mefp-1 solution than that in the buffer solution, suggesting some blocking effect of the adsorbed Mefp-1 as discussed above.…”

Section: Resultssupporting

confidence: 62%

Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control

2017

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Mussel adhesive proteins are of great interest in many applications because of their outstanding adhesive property and film-forming ability. Understanding and controlling the film formation and its performance is crucial for the effective use of such proteins. In this study, we focus on the potential controlled film formation and compaction of one mussel adhesive protein, Mefp-1. The adsorption and film-forming behavior of Mefp-1 on a platinum (Pt) substrate under applied potentials were investigated by cyclic voltammetry, potential-controlled electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Moreover, microfriction measurements were performed to evaluate the mechanical properties of the Mefp-1 films formed at selected potentials. The results led to the conclusion that Mefp-1 adsorbs on the Pt substrate through both electrostatic and nonelectrostatic interactions and shows an effective blocking effect for the electroactive sites on the substrate. The properties of the adsorbed Mefp-1 film vary with the applied potential, and the compactness of the adsorbed Mefp-1 film can be reversibly tuned by the applied potential.

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Section: Resultssupporting

confidence: 62%

Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control

2017

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“…5A, the current ratio of D-DOPA/L-DOPA (noted as cR) was greatest when the concentration of L-Trp-rGO@PtNPs was 0.5 mg mL À1 . 41 The electrochemical reaction of DOPA on the L-Trp-rGO@PtNPs interface at pH values of 0, 0.3, 0.6, 2, 3, 4 and 5.5 was investigated, and the results are shown in Fig. The maximum cR appeared at 8 mL (Fig.…”

Section: Optimization Of Experimental Conditionsmentioning

confidence: 99%

“…The electrochemical chiral sensing of DOPA enantiomers was sensitive to variations in the pH value of the solution. 41 The electrochemical reaction of DOPA on the L-Trp-rGO@PtNPs interface at pH values of 0, 0.3, 0.6, 2, 3, 4 and 5.5 was investigated, and the results are shown in Fig. 5C.…”

Section: Optimization Of Experimental Conditionsmentioning

confidence: 99%

The application of l-tryptophan functionalized graphene-supported platinum nanoparticles for chiral recognition of DOPA enantiomers

Cui

et al. 2015

New J. Chem.

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A new nanocomposite of L-tryptophan functionalized graphene-supported platinum nanoparticles (L-Trp-rGO@PtNPs) was synthesized utilizing a facile ultrasonic method via p-p conjugate action between graphenesupported platinum nanoparticles and L-tryptophan (L-Trp) molecules. The prepared nanomaterial, which dispersed well in water and presented excellent conductivity, was modified on a glassy carbon electrode (L-Trp-rGO@PtNPs/GCE) for the chiral sensing of DOPA enantiomers. The immobilization process of L-Trp-rGO@PtNPs/GCE was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, ultraviolet-visible (UV-vis) spectrometry and Raman spectroscopy. The electrochemical reactions of DOPA enantiomers were investigated via differential pulse voltammetry. The proposed electrochemical method showed excellent enantiospecificity for DOPA enantiomers and exhibited a stronger enantiospecificity for D-DOPA. In addition, the experimental parameters such as the concentration, the amount of L-Trp-rGO@PtNPs and the pH values were optimized. Under optimum conditions, the linear response ranges for the discrimination of DOPA were from 5.0 Â 10 À8 to 5.0 Â 10 À3 mol L À1 with a detection limit of 1.7 Â 10 À8 mol L À1 (S/N = 3).L-Trp-rGO@PtNPs with enantiomeric composition of L-and D-DOPA at different concentrations: (a) 2 Â 10 À3 mol L À1 and (b) 5 Â 10 À3 mol L À1 .

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“…10−12 One of the pH effects on discrimination efficiency is caused by pH dependence of the 2D arrangement stability of Hcy SAM on the gold surface. 15 Another pH effect is caused by pH dependence of stability of amino acid− metal complexes, which is relatively unknown. A few reports have indicated that amino acids can form complexes with metal ions in neutral pH solutions; 17 however, these studies refer to crystallographic information on amino acid complexes and a direct molecular-level understanding of the complexes in solution is not yet achieved.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, analyses using surfaces modified with a self-assembled monolayer (SAM) showed a capability to detect complexes with a high sensitivity. − Osaka et al proposed a solid–liquid interfacial system with SAM-modified substrate for the detection of amino acid complex − as a series of work developing enantio-sensing systems. − These past studies focused on Cu(II) complexes formed with enantiomeric amino acid and SAM constituents on gold substrates. Using this interfacial system, the enantiomeric form of the target amino acid in solution was discriminated with either cyclic voltammetry or a field-effect transistor (FET). , Because the SAM constituent is one of the ligands of the complex in this system, the characteristic of the SAM attached to the substrate should be a key factor in determining the ability of complex formation and efficiency of chiral discrimination.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study on the Formation Mechanism of Amino Acid–Cu(II) Complexes on an Enantio-Sensing Device Interface

et al. 2016

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Theoretical analyses of L-alanine (L-Ala)− and L-homocysteine (L-Hcy)−Cu(II) complexes in basic, neutral, and acidic solutions were carried out using density functional theory to investigate the pH dependence of the formation mechanism of amino acid−Cu(II) complexes. The calculated complex formation energies indicate that the amino acid−Cu(II) complexes were expected to form in basic and neutral solutions but not in acidic solutions. The factors that determine the stability of these complexes are the coordination ability of each amino acid and the significance of intramolecular interactions among ligands within the complexes. As predicted from the molecular structure, in neutral solutions, the coordination ability of amino acid becomes lower than that in basic solutions because of the inert structure of the protonated amino group, −NH 3 + ; however, the coordination ability originating from the −COO − group is estimated to be sufficient for stabilizing the entire complex system. Moreover, two H 2 O molecules coordinate with the central Cu 2+ ion from the equatorial direction and interact with the coordinating amino acids, providing additional stability within the complex. In contrast, in acidic solutions, the complex does not have either sufficient coordination ability of amino acids or effective intramolecular interactions within the complex.

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Effect of pH on the Enantiospecificity of Homocysteine Monolayer on Au(111) for the Redox Reaction of 3,4‐Dihydroxyphenylalanine

Cited by 17 publications

References 32 publications

Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control

Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control

The application of l-tryptophan functionalized graphene-supported platinum nanoparticles for chiral recognition of DOPA enantiomers

Theoretical Study on the Formation Mechanism of Amino Acid–Cu(II) Complexes on an Enantio-Sensing Device Interface

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