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Electrochemistry of Immobilized Hemes and Heme Proteins

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Electrochemistry of Immobilized Hemes and Heme Proteins Electrochemistry of immobilized hemes and heme proteins Citation for published version (APA): Groot, de, M. T. (2007). Electrochemistry of immobilized hemes and heme proteins. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR626249 DOI: 10.6100/IR626249 Document status and date: Published: 01/01/2007 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 06. Oct. 2021 Electrochemistry of Immobilized Hemes and Heme Proteins PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de Rector Magnificus, prof.dr.ir. C.J. van Duijn, voor een commissie aangewezen door het College voor Promoties in het openbaar te verdedigen op donderdag 14 juni 2007 om 16.00 uur door Matheus Theodorus de Groot geboren te Deurne Dit proefschrift is goedgekeurd door de promotoren: prof.dr. M.T.M. Koper en prof.dr. R.A. van Santen Copromotor: dr. M. Merkx A catalogue record is available from the Library Eindhoven University of Technology ISBN: 978-90-386-0985-0 Copyright © 2007 by Matheus T. de Groot The work described in this thesis has been carried out at the Schuit Institute of Catalysis within the Laboratory of Inorganic Chemistry and Catalysis, Eindhoven University of Technology and the Leiden Institute of Chemistry, Leiden University, The Netherlands. Financial support has been supplied by the National Research School Combination Catalysis (NRSC-C). Design cover: Thijs de Groot and Paul Verspaget Printed at the Universiteitsdrukkerij, Eindhoven University of Technology Life is not measured by the number of breaths you take, but by the number of moments that take your breath away. —————————————————————————————————————————— Contents —————————————————————————————————————————— Chapter 1 Introduction 1 Chapter 2 Electrochemical reduction of NO by hemin adsorbed at pyrolitic 11 graphite Chapter 3 Heme release in myoglobin-DDAB films and its role in 33 electrochemical NO reduction A. Heme release in myoglobin-DDAB films and its role in 35 electrochemical NO reduction B. Additional evidence for heme release in myoglobin-DDAB 61 films on pyrolitic graphite Chapter 4 Heme release and adsorption in layer-by-layer assemblies of 73 polystyrenesulfonate and myoglobin on pyrolitic graphite Chapter 5 Electron transfer and ligand binding to cytochrome c’ 85 immobilized on self-assembled monolayers Chapter 6 Reorganization of immobilized horse and yeast cytochrome c 109 induced by pH changes or nitric oxide binding Chapter 7 Redox transitions of chromium, manganese, iron, cobalt and 131 nickel protoporphyrins in aqueous solution Chapter 8 Conclusions and future prospects 161 Summary 16 5 Samenvatting 168 List of publications 170 Curriculum vitae 171 Dankwoord 172 ————————————————————————————————————————————— Chapter 1 ————————————————————————————————————————————— Introduction 1.1 The search for better catalysts Catalysts are of great value to mankind, since they enable reactions that would otherwise not occur or would occur at a very slow rate. The best-known example of a catalyst is the catalytic converter located in the exhaust of a car. It converts toxic gases such as carbon monoxide (CO), nitric oxide (NO) and nitrogen dioxide (NO 2), which are formed in the car engine, into the relatively harmless gases nitrogen (N 2) and carbon dioxide (CO 2). In this way the catalytic converter contributes to the improvement of the air quality in urban areas, which in turn has a positive influence on public health. The catalytic converter consists of a support with small metal particles, on which the reaction occurs in three steps (Figure 1.1). Firstly, the toxic gas molecules are adsorbed on the metal particles, next the reaction occurs, and finally the molecules are desorbed from the particles. The metal particles play an important role in the reaction, but they are not consumed. Therefore, the metal particles can in principle be used to convert an infinite number of toxic molecules and do not have to be replaced over the lifetime of a car. Without the metal particles the reaction would either not occur or occur at a very slow rate. This is the essence of every catalyst, which is defined as a substance that increases the rate of a reaction without being consumed. Although less known to the general public, catalysts are being used in many other processes. These include oil refinery, production of fertilizers, production of plastics and the production of drugs. Figure 1.1 The catalytic converter in a car. The figure depicts its location (top left), its macroscopic shape (bottom left) and a schematic representation of the reactions that occur on the small metal particles of the catalytic converter (right). 2 Chapter 1 ————————————————————————————————————————————— Catalysis is big business, as reflected in the fact that the global catalyst market is worth $ 210 billion annually. 1 Finding the right catalyst for an industrial process can determine whether such a process is economically feasible. Therefore, there is a continuous search for better and cheaper catalysts to improve the competitiveness of chemical processes. When considering the use of a catalyst for a particular reaction, one has to take into account the following important properties: • Activity. This corresponds to the rate of the reaction that occurs on the catalyst. Ideally, a catalyst should be very active, which means that only a small amount of catalyst is needed to convert many molecules in a relatively short time. • Selectivity. The selectivity of a catalyst indicates what products are formed in the reaction. In many chemical reactions more than one product can be formed and normally only one of the products is desired. Selectivity is of particular importance in the drug industry, where one reaction product might be a good drug and another product might be toxic. • Stability. This relates to the lifetime of a catalyst. Ideally, a catalyst should be able to catalyze an endless number of reactions, but in practice the catalyst becomes inactive after a certain time. The lifetime of a catalyst depends on its specific properties, but also on the temperature and pressure of the reaction. • Ease of separation. This corresponds to the ease of separation of the catalyst from the final reaction products. Catalysts that are dissolved in solutions are more difficult to separate compared to catalysts immobilized on a support, such as the catalyst used in a car. • Cost. Many industrial catalysts are made of relatively expensive noble metals, such as platinum and palladium. These metals generally determine the overall cost price of a catalyst. Replacing these metals by cheaper materials with similar catalytic properties, can improve the economic competitiveness of a process. Introduction 3 ————————————————————————————————————————————— 1.2 Nature’s catalysts Catalysts also play an important role in many natural processes. These natural catalysts are called enzymes and are found in every living cell. Enzymes catalyze a wide variety of reactions that enable vital biological processes such as respiration, processing of food, building of organs and photosynthesis. Most enzymes are proteins, which are complex organic molecules made of amino acids. The catalytic reaction occurs at a particular place in the enzyme, the so-called active site. At this place the reacting molecules interact with the enzyme. As an example the enzyme cytochrome c oxidase is depicted in Figure 1.2. This enzyme catalyzes the reaction of oxygen to water and is part of the respiration process. Apart from the enzyme’s amino acids, the active site of cytochrome c oxidase has incorporated iron and copper atoms, which play an important role in the reaction. Therefore cytochrome c oxidase is a so-called metalloenzyme. Similar to the industrial catalysts enzymes increase the rate of a reaction without being consumed.
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