Writing through catalysis: A tape-reading molecular catalyst

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In 1936 Alan Turing published a concept for an automatic machine for abstract computing. Nowadays called a 'Turing machine', his proposal envisaged a device that featured a 'head' that could read and write symbols while moving along a tape. This influential thought experiment sparked the development of computer science. Although modern computers use a different design that employs random access memory, the resemblance of Turing's 'automatic machine' to information processing in biology is striking (the reading and writing of information by the ribosome, for example. Recently, the Leigh group reported an artificial molecular machine that is transported directionally along a molecular tape by chemical fuelling, changing the conformation of the reading head in response to chiral centres on the tape it encounters along the way. The conformational change results in changes to the circular dichroism response of the head, and so the sequence of symbols on the molecular tape can be read out as a string of data according to the changing CD response (+ve Cotton effect at 280 nm corresponds to the digit +1; -ve Cotton effect to -1, no Cotton effect to 0). This project will seek to extend this concept to the writing of information through catalysis, using the change in conformation to alter the handedness of asymmetric catalysis by the reading head as it moves along the track. We will first investigate this concept through step-wise operations (e.g. with Trost-like ligands, as depicted below) and, ultimately, extend it to the synthesis of polymers with encoded sequence information, a task analogous to that performed by the ribosome.The development of an artificial catalyst that changes the stereochemical outcome of catalytic transformations as it moves directionally along an information-encoded track would be a landmark achievement for the fields of both artificial molecular machinery and catalysis. It would enable the translation of molecular information from one form (the original tape) to another. This would be analogous to the function performed by the ribosome, but in a wholly artificial system not limited to peptides and featuring the reading of stereochemistry rather than nucleotide codons. The knowledge gained in this project will have impact in different areas. In addition to potentially improving the design of synthetic catalysts, the results may lead to the design of new, artificial, enzyme-like catalysts.