After graduating from University College Galway (UCG) with a first class Honours degree in Chemistry in 1989, Walsh remained at UCG for his PhD work which used X-ray crystallography to fully characterize the flavoprotein, flavodoxin. This work aided in providing a general model for how flavoproteins modulate the redox potentials of flavin mononucleotide (FMN). The work was a significant milestone for structural biology in Ireland, as it presented the first protein crystal structures determined from an Irish-based research group.
Early postdoctoral work at York and EMBL Hamburg concentrated on the development and determination of protein structures at atomic resolution which was being pioneered at that time in Hamburg. This work contributed to introducing routine refinement of structures at this resolution as well as providing experimental data on the stereochemistry of amino acids in proteins.
In 1997 Walsh moved to Argonne National Laboratory (ANL) where he worked primarily on chaperonins and contributed to the commissioning of the world’s first dedicated insertion device beamline for exploiting anomalous diffraction in macromolecular crystallography: ID19 at the Advance Photon Source (APS). Work and associated research carried out at Argonne in the late 1990’s contributed strongly to establishing the MAD technique. In 1999 he moved to IRBM in Rome where work focused on the structural biology of the hepatitis C virus.
In 2001 he was appointed MRC group leader for BM14, based at the ESRF. Key hardware and software solutions to crystallography were delivered – automation of sample handling through robotics and management of crystallographic data (ISPyB) which have changed the way crystallographers now approach macromolecular structure determination at synchrotron beamlines.
In 2009, he joined Diamond Light Source with responsibility for life science research.