Associate Professor
Richard M Hartshorn
Position
Associate Professor
Fields of Study
Bioinorganic / Inorganic Chemistry
Qualifications
B.Sc.(Hons), Ph.D. (A.N.U.)
Room
830, Chemistry Building
Contact Details
Telephone: +64 3 364 2874
Fax: +64 3 364 2110
Email: richard.hartshorn@canterbury.ac.nz
Research Interests
General Area of Research
The reactivity of small, biologically relevant molecules when they are bound to metal ions. The reactivities of small molecules are modified when they are coordinated to metal ions. Nature exploits these effects on reactivity in the construction of many enzyme active sites, and thereby achieves catalysis of reactions which would otherwise proceed too slowly to be useful in a living system. As a result of our studies, we hope to gain insights in to the ways in which nature achieves and controls such chemical reactions. These studies may also point to the ways in which such chemistry may go astray, for example through undesirable reactions induced by UV light.
Projects
Research Poster (pdf)
Functional models for hydrolytic enzymes.
Hydrolytic enzymes are responsible for the cleavage of amide and ester groups in biological systems. Studies with model compounds have established that the rate accelerations observed for the enzymatic hydrolysis of carboxylic esters and amides, can be accounted for through the effect of the metal ion acting either as a Lewis acid catalyst (by coordinating the carbonyl oxygen atom and thereby polarising the carbonyl group), or as a source of a nucleophile (coordinated hydroxide). This project is aimed at developing molecules which can catalyse the reaction through the simultaneous use of both mechanisms.
Photoactivated cytotoxins.
This research project is aimed at developing molecules which will release and activate a cytotoxin when they are hit by light of a particular wavelength. This project is centred around the synthesis and study of multi-component molecules. They will be made up of: an antenna or electron donor unit, which will release an electron when it absorbs a photon of the appropriate wavelength; an acceptor unit which will release a cytotoxin when it is reduced by the electron; and a linking unit through which the electron will be passed. The cytotoxin should be inactive while it is still bound to the acceptor.
Photochemistry of metal complexes of amino acids and peptides.
It is well known that exposure to UV light results in DNA damage and, eventually, to diseases such as cancer in living organisms, but it is far less clear how UV irradiation affects other biomolecules, particularly when metal ions are present to catalyse redox processes. We have been studying the UV induced photochemistry of amino acid and peptide complexes in order to assess the degree to which UV photodamage of such biological molecules may be a problem. This involves establishing the mechanism(s) by which these reactions occur, and also looking at the reactivities of the resulting compounds.
Polydentate ligand construction.
Synthetic organic chemists have a wide range of methods and techniques available to them for the synthesis of complex organic molecules. This is not so true of inorganic chemists. This project is an attempt to explore the factors which are important in determining the course of reactions where a polydentate ligand is constructed on a metal complex. The reactions of interest involve the condensation of a carbonyl group in one ligand with a coordinated amine in another ligand to produce a new polydentate ligand, still bound to the metal ion. The metal ion holds the reacting molecules close together, and may control the stereochemistry of the reaction so that only a particular diastereoisomer is produced. The purpose of this project is to identify whether factors such as the relative locations in the complex of the reacting ligands, the conformational flexibility of the ligands, and the bond lengths and geometry of the metal ion are important.
Reactions of coordinated peptides.
Binding an amino acid to a metal ion both protects the parts of the molecule that are bound to the metal ion and activates other parts of the molecule towards reaction with a variety of reagents. In particular the high charge of a metal ion like cobalt(III) can make some protons in the molecule significantly more acidic. A proton can therefore be relatively easily removed in order to give a reactive intermediate which can be transformed in a variety of ways (see `Representative Papers' below). This chemistry is now being extended to larger molecules. Compounds made up of two or three amino acids (dipeptides and tripeptides) are being coordinated to metal ions and then treated with a variety of reagents in order to explore the types of chemistry that such molecules can undergo.