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Becucci L, Guryanov I, Maran F, Guidelli R. Effect of a strong interfacial electric field on the orientation of the dipole moment of thiolated aib-oligopeptides tethered to mercury on either the N- or C-terminus. J Am Chem Soc 2010; 132:6194-204. [PMID: 20392067 DOI: 10.1021/ja100486y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Four oligopeptides consisting of a sequence of alpha-aminoisobutyric acid (Aib) residues, thiolated at either the N- or C-terminus by means of a -(CH(2))(2)-SH anchor, were self-assembled on mercury, which is a substrate known to impart a high fluidity to self-assembled monolayers (SAMs). The surface dipole potential of these peptide SAMs was estimated in 0.1 M KCl aqueous solution at a negatively charged electrode, where the interfacial electric field is directed toward the metal. To the best of our knowledge, this is the first estimate of the surface dipole potential of peptide SAMs in aqueous solution. The procedure adopted consisted in measuring the charge involved in the gradual expansion of a peptide-coated mercury drop and then combining the resulting information with an estimate of the charge density experienced by diffuse layer ions. The dipole moment of the tethered thiolated peptides was found to be directed toward the metal, independent of whether they were thiolated at the C- or N-terminus. This result was confirmed by the effect of these SAMs on the kinetics and thermodynamics of the Eu(III)/Eu(II) redox couple. The combined outcome of these studies indicates that a strong interfacial electric field orients the dipole moment of peptide SAMs tethered to mercury, even against their "natural" dipole moment.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
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52
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Junghans A, Köper I. Structural analysis of tethered bilayer lipid membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11035-11040. [PMID: 20504013 DOI: 10.1021/la100342k] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Solid supported membrane systems have been established as biomimetic architectures, which allow for the systematic investigation of various membrane-related processes. Especially tethered bilayer lipid membranes have been a successful concept. They consist of a lipid bilayer that is covalently anchored to a solid substrate through a spacer group. The submembrane part, which is defined by the spacer group, is important especially for the biological activity of incorporated membrane proteins. Anchor lipids with different spacer and anchor groups have been synthesized, and the resulting membrane structures have been investigated by neutron reflectivity. The different molecular architectures had a significant effect on both the amount of water incorporated in the spacer region and the electrical properties of the bilayer. A detailed understanding of the structure-function relationship allows for an optimized design of the molecular architecture with respect to possible applications, for example an optimized protein incorporation.
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Affiliation(s)
- Ann Junghans
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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53
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Stammer X, Tonigold K, Bashir A, Käfer D, Shekhah O, Hülsbusch C, Kind M, Groß A, Wöll C. A highly ordered, aromatic bidentate self-assembled monolayer on Au(111): a combined experimental and theoretical study. Phys Chem Chem Phys 2010; 12:6445-54. [DOI: 10.1039/c002215m] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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54
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Sek S. EC-STM study of potential-controlled adsorption of substituted pyrimidinethiol on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:13488-13492. [PMID: 19715338 DOI: 10.1021/la901984v] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The ability of the pyrimidine derivatives to form numerous complexes and supramolecular assemblies makes them suitable for the construction of new functional surfaces. Therefore, in this paper, the adsorption behavior of 4-hydroxy-6-(trifluoromethyl)pyrimidine-2-thiol (HTPT) on a Au(111) surface has been investigated using electrochemical scanning tunneling microscopy (EC-STM). High-resolution imaging revealed that the HTPT molecules organize on a gold surface producing a highly ordered monolayer consistent with a (4 x radical3)R-30(0) superstructure. It has been observed that the arrangement of the molecules, as well as their orientation with respect to the substrate, remains stable over a relatively broad potential range from -0.40 to 0.55 V. It has been demonstrated that the presence of the functional groups attached to the aromatic ring affects the final structure of the HTPT adlayer, giving rise to the formation of the assembly with a uniform orientation of the molecules on the substrate.
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Affiliation(s)
- Slawomir Sek
- Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
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55
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Leitch J, Kunze J, Goddard JD, Schwan AL, Faragher RJ, Naumann R, Knoll W, Dutcher JR, Lipkowski J. In situ PM-IRRAS studies of an archaea analogue thiolipid assembled on a au(111) electrode surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:10354-10363. [PMID: 19499931 DOI: 10.1021/la900907d] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) has been applied to determine the conformation, orientation, and hydration of a monolayer of 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-dl-alpha-lipoic acid ester (DPTL) self-assembled at a gold electrode surface. This Archaea analogue thiolipid has been recently employed to build tethered lipid bilayers. By synthesizing DPT(d16)L, a DPTL molecule with a deuterium substituted tetraethylene glycol spacer, it was possible to differentiate the C-H stretch vibrations of the phytanyl chains from the tetraethylene glycol spacer and acquire the characteristic IR spectra for the chains, spacer, and lipoic acid headgroup separately. Our results show that the structure of the monolayer displays remarkable stability in a broad range of electrode potentials and that the phytanyl chains remain in a liquid crystalline state. The tetraethylene glycol chains are coiled, and the IR spectrum for this region shows that it is in the disordered state. The most significant result of this study is the information that in contrast to expectations the spacer region is poorly hydrated. Our results have implications for the design of a tethered lipid membrane based on this thiolipid.
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Affiliation(s)
- Jay Leitch
- Department of Chemistry, University of Guelph, Guelph, Ontario, N1G2W1 Canada
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56
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Becucci L, Schwan AL, Sheepwash EE, Guidelli R. A new method to evaluate the surface dipole potential of thiol and disulfide self-assembled monolayers and its application to a disulfidated tetraoxyethylene glycol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1828-1835. [PMID: 19170650 DOI: 10.1021/la803282w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A procedure to evaluate the surface dipole potential chi of thiol and disulfide self-assembled monolayers (SAMs) is described. The procedure consists of self-assembling the monolayers on a hanging mercury drop electrode and of measuring the charge involved in a progressive expansion of the mercury drop. This measurement is then combined with an estimate of the charge density q experienced by diffuse layer ions, obtained by measuring the diffuse layer capacitance of the SAM at different electrolyte concentrations by electrochemical impedance spectroscopy. These chi measurements, combined with chronocoulometric measurements of the total charge density sigma(M) against potential, indicate that SAMs of tetraoxyethylene glycol-D,L-alpha-lipoic acid ester (TEGL), 2,3-di-O-phytanyl-sn-glycerol-1-tetraoxyethylene glycol-D,L-alpha-lipoic ester (DPTL), and trioxyethyleneoxythiol (EO3) on mercury may undergo a reversal in the surface dipole potential of their polyoxyethylene chain with a change in the interfacial electric field. Moreover, TEGL and EO3 form stable SAMs without electron transfer to the metal, while no such conclusion can be drawn for DPTL.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
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57
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Weidner T, Bretthauer F, Ballav N, Motschmann H, Orendi H, Bruhn C, Siemeling U, Zharnikov M. Correlation between the molecular structure and photoresponse in aliphatic self-assembled monolayers with azobenzene tailgroups. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:11691-11700. [PMID: 18823085 DOI: 10.1021/la802454w] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have compared the structural and photoisomerization properties of self-assembled monolayers (SAMs) comprising either the trans or cis isomers of azobenzene terminated dithiolane with in-chain amide unit, viz., 4-(phenyldiazenyl)phenyl-4-(1,2-dithiolane-3-yl)-butylcarboxamide ( 1). These films were prepared on Au(111) from solutions of both isomers. Structure and composition of the SAMs were studied by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The photoresponse of the films was monitored in real time by ellipsometry. SAMs fabricated from the trans isomer were found to be densely packed and highly ordered. These films did not show any discernible photoresponse upon irradiation with UV light, which, under favorable conditions, triggers the trans- cis isomerization. In contrast, films prepared from solutions containing predominantly the cis isomer were loosely packed and mostly disordered but exhibited reversible photoreactivity. The results confirm that steric effects, i.e., available free volume, play a dominant role for the photoresponse of aliphatic SAMs bearing the photoactive azobenzene group. The crystal structure of 1 ( trans isomer) exhibits a row-like aggregation of neighboring molecules by weak hydrogen bonds and can be taken as a model for the arrangement of 1 in the monolayer films. Further, in addition to the surface coordination behavior, we have also mimicked the chemisorption of the 1,2-dithiolane moiety onto the gold substrate in molecular coordination chemistry in oxidative addition reactions with the zero-valent platinum complex [Pt(PPh 3) 4].
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Affiliation(s)
- Tobias Weidner
- Angewandte Physikalische Chemie, Universitat Heidelberg, 69120 Heidelberg, Germany.
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58
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Zangmeister C, Bertocci U, Beauchamp C, Stafford G. In situ stress measurements during the electrochemical adsorption/desorption of self-assembled monolayers. Electrochim Acta 2008. [DOI: 10.1016/j.electacta.2007.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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59
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Santos E, Avalle L, Pötting K, Vélez P, Jones H. Experimental and theoretical studies of l-cysteine adsorbed at Ag(111) electrodes. Electrochim Acta 2008. [DOI: 10.1016/j.electacta.2007.12.080] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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60
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Atanasova PP, Atanasov V, Köper I. Anchor-lipid monolayers at the air-water interface; prearranging of model membrane systems. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:7672-8. [PMID: 17559241 DOI: 10.1021/la7002854] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Model membrane systems are gaining more and more interest both for basic studies of membrane-related processes as well as for biotechnological applications. Several different model systems have been reported among which the tethered bilayer lipid membranes (tBLMs) form a very attractive and powerful architecture. In all the proposed architectures, a control of the lateral organization of the structures at a molecular level is of great importance for an optimized preparation. For tBLMs, a homogeneous and not too dense monolayer is required to allow for the functional incorporation of complex membrane proteins. We present here an alternative approach to the commonly used self-assembly preparation. Lipids are spread on the air-water interface of a Langmuir film balance and form a monomolecular film. This allows for a better control of the lateral pressure and distribution for subsequent transfer to solid substrates. In this paper, we describe the properties of the surface monolayer, in terms of surface pressure, structure of the lipid molecule, content of lipid mixtures, temperature, and relaxations features. It is shown that a complete mixing of anchor-lipids and free lipids can be achieved. Furthermore, an increase of the spacer lengths and a decrease of the temperature lead to more compact films. This approach is a first step toward the fully controlled assembly of a model membrane system.
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Affiliation(s)
- Petia P Atanasova
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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61
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Köper I. Insulating tethered bilayer lipid membranes to study membrane proteins. MOLECULAR BIOSYSTEMS 2007; 3:651-7. [PMID: 17882328 DOI: 10.1039/b707168j] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tethered bilayer lipid membranes are stable and promising model systems that mimic several properties of biological membranes. They provide an electrically insulating platform for the incorporation and study of functional membrane proteins, especially ion channels. Covalently linked to a solid support, they also offer enhanced stability compared with other model architectures. If the support can be used as an electrode, electrical characterisation of the system is possible and biosensing applications can be envisioned.Here, we will review some tethered bilayer structures developed in the past and show some examples of functional protein incorporation, both on oxide and gold substrates.
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Affiliation(s)
- Ingo Köper
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
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