Ultrasensitive optical detection of hydrogen peroxide by triggered activation of horseradish peroxidase.

Hydrogen peroxide is a very reactive byproduct of many metabolic pathways. We describe an ultra-sensitive colorimetric method to detect hydrogen peroxide based on the reconstitution of apo-horseradish peroxidase with the hemin derivative, hemin di(N,N'-acetyl-hydrazide). Oxidation of the latter by hydrogen peroxide yields hemin, which is able to reconstitute apo-horseradish peroxidase, forming an active peroxidase. We have also applied this analyte-triggered reconstitution of horseradish peroxidase to detect the activity of the enzyme glucose oxidase.

Postformation Modification of SAMs: using click chemistry to functionalize organic surfaces.

We have investigated a recently established strategy of modifying organic surfaces exposed by thiolate SAMs (self-assembled monolayers) deposited on Au substrates by employing so-called click chemistry. This term is used to denote a modified Huisgen 1,3-dipolar cycloaddition. We demonstrate the potential of this method by coupling ferrocene and azido acetic acid to alkyne/azide-terminated SAMs. After the surface reaction, the modified organic monolayers were analyzed using infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Under the conditions used in this study, only for the azide-terminated SAMs could successful grafting of the ferrocene be achieved whereas for the alkyne-terminated SAMs the spectroscopic studies reveal a rather low yield of the coupling reaction.

Peptide-based SAMs that resist the adsorption of proteins.

In this paper we present a modular approach for the fabrication of surfaces to characterize protein-protein interactions. The approach is based on azido peptides with an optimized sequence which are then thiol-functionalized using an alkynyl thiol and "click" chemistry. From these peptide thiols we fabricated SAMs on gold to evaluate the protein resistance, using surface plasmon resonance spectroscopy, toward streptavidin, bovin serum albumin (BSA), and fibronectin.