ORCID Profile
0000-0002-1786-3182
Current Organisation
University of York
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Publisher: American Chemical Society (ACS)
Date: 11-01-2008
DOI: 10.1021/AC701688Q
Abstract: We demonstrate the use of surface-immobilized, oriented peptide aptamers for the detection of specific target proteins from complex biological solutions. These peptide aptamers are target-specific peptides expressed within a protein scaffold engineered from the human protease inhibitor stefin A. The scaffold provides stability to the inserted peptides and increases their binding affinity owing to the resulting three-dimensional constraints. A unique cysteine residue was introduced into the protein scaffold to allow orientation-specific surface immobilization of the peptide aptamer and to ensure exposure of the binding site to the target solution. Using dual-polarization interferometry, we demonstrate a strong relationship between binding affinity and aptamer orientation and determine the affinity constant KD for the interaction between an oriented peptide aptamer ST(cys+)_(pep9) and the target protein CDK2. Further, we demonstrate the high selectivity of the peptide aptamer STM_(pep9) by exposing surface-immobilized ST(cys+)_(pep9) to a complex biological solution containing small concentrations of the target protein CDK2.
Publisher: American Chemical Society (ACS)
Date: 07-01-2011
DOI: 10.1021/LA103733J
Abstract: The structural stability of alkenthiolate monolayers assembled on gold surfaces is a result of the well-defined organization of the in idual molecules within the film. The formation of three-dimensional films assembled by stacking multiple molecular monolayers is substantially more challenging because the correct organization of the molecular components is required not only within the in idual monolayers but also between the monolayers of the film. In this paper we examine the structure of multilayer films based on mercaptoalkanoic acid monolayers in which ligation between adjacent monolayers is achieved using the interaction of carboxylic acid and thiol groups with a alent Cu ion. Using contact angle analysis and atomic force microscopy, we show that the use of Cu(2+) has profound implications on the properties and structure of the multilayer film. In particular, the alent ions effectively prohibit the complete assembly of the next monolayer. For multilayer SAMs assembled from short alkane chains with six methylene groups, we find that molecules in the incomplete adlayer organize themselves randomly over the underlying monolayer. However, as the number of methylene groups increases (11 and 16 methylene groups), the upper layer tends to fracture into discrete islands which cover around 50% of the surface. The height of these islands is found to be equal to that expected for a complete, well-ordered monolayer assembled from the equivalent mercaptoalkanoic acid molecules. This relationship between chain length and island growth results from the migration of molecules into ordered aggregates driven by the reduction of free energy associated with maximizing intermolecular interactions.
Publisher: American Chemical Society (ACS)
Date: 12-04-2012
DOI: 10.1021/LA300510X
Abstract: We discuss the assembly, structure, and stability of multilayer molecular films formed from multiple mercaptoalkanoic acid monolayers ligated via carboxyl and thiol interactions with alent copper ions. Using dual-polarization interferometry to study the assembly of multilayer films in real time, we observe a clear linear relationship between the number of layers within a film and the overall average film thickness. Unexpectedly, however, we find a restructuring of the lower monolayer upon association of the Cu(2+) ions to form the Cu carboxylate surface. In particular, the thickness of the lower monolayer was found to decrease significantly, accompanied by an increase in the film density. The conformation of the monolayer subsequently recovered to that observed originally following the reduction of the Cu ion to Cu(+) upon chemisorption of the adlayer. Comparable restructuring was also observed in molecular dynamics simulations of a bilayer film assembled on a gold surface. Our combined experimental and theoretical study suggests that the observed restructuring is a result of charge-charge interactions between adjacent Cu ions that exist in the +2 oxidation state in the copper carboxylate surface and in the +1 oxidation state following chemisorption of the adlayer.
Publisher: IOP Publishing
Date: 16-11-2012
Publisher: IOP Publishing
Date: 24-03-2009
DOI: 10.1088/0957-4484/20/15/155304
Abstract: We demonstrate a new process for fabricating embedded co-planar electrodes which combines top-down with bottom-up approaches to nanofabrication. The co-planarity of the electrodes with the substrate surface is achieved by deposition of a dielectric filling layer around a set of lithographically defined metallic electrodes. In order to prevent adhesion of the dielectric to the pre-defined electrodes, an adhesion inhibiting layer, based on a self-assembled monolayer, is formed specifically on the electrode surface prior to deposition of the dielectric. For monolayers with an acid functional group, this adhesion inhibitor yields almost complete non-adhesion of the dielectric filling layer.
Publisher: Springer Science and Business Media LLC
Date: 2008
DOI: 10.1186/JBIOL62
Publisher: American Chemical Society (ACS)
Date: 18-09-2012
DOI: 10.1021/LA3025149
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Steven David Johnson.