My research focuses on the geometric and electronic structures of the key reaction intermediates of the multicopper oxidases, which includes laccase, ascorbate oxidase, ceruloplasmin, Fet3p, CueO, CotA, etc. Moreover, the magnetic and optical properties of the related model complexes are extensively studied and correlated to those of the protein active site. The information gained from these studies is then implemented in the fundamental understanding of the reaction mechanism of the catalytic O-O bond cleavage and O₂ reduction to H₂O in the multicopper oxidases.

My recent accomplishments include:

• Elucidation of the unique magnetic and spectral features of the transiently-lived native intermediate form of the multicopper oxidases via extended application of the above magnetic phenomena.
• Determination of the geometric structure of the trinuclear Cu cluster sites by elucidating the physical origin of the characteristic features in their MCD spectra.
• Spectroscopic demonstration and theoretical/computational interpretation of the magnetic spin-canting and antisymmetric/anisotropic exchange phenomena in the trinuclear Cu(II) cluster systems that exhibit spin-frustration found prevalently in magnetic materials

1. Jungjoo Yoon, Edward I. Solomon, "Ground State Electronic and Magnetic Properties of a m₃-Oxo Bridged Trinuclear Cu(II) Complex: Correlation to the Native Intermediate of the Multicopper Oxidases" Inorg. Chem. 2005, 44 (22), 8076-8086.
2. Liliana Quintanar, Jungjoo Yoon, Constantino P. Aznar, Amy E. Palmer, K. Kristoffer Andersson, R. David Britt, Edward I. Solomon, "Spectroscopic and Electronic Structure Studies of the Trinuclear Cu Cluster Active Site of the Multicopper Oxidase Laccase: Nature of Its Coordination Unsaturation" J. Am. Chem. Soc. 2005, 127 (40), 13832-13845.
3. Jungjoo Yoon, Liviu M. Mirica, T. Daniel P. Stack, Edward I. Solomon, "Variable-Temperature Variable-Field Magnetic Circular Dichroism Studies of Tris-Hydroxy and m₃-Oxo Bridged Trinuclear Cu(II) Complexes: Evaluation of Proposed Structures of the Native Intermediate of the Multicopper Oxidases" J. Am. Chem. Soc. 2005, 127 (39), 13680-13693.
4. Jungjoo Yoon, Liviu M. Mirica, T. Daniel P. Stack, Edward I. Solomon, "Spectroscopic Demonstration of a Large Antisymmetric Exchange Contribution to the Spin-Frustrated Ground State of a D₃ Symmetric Hydroxy-Bridged Trinuclear Cu(II) Complex: Ground-to-Excited State Superexchange Pathways" J. Am. Chem. Soc. 2004, 126 (39), 12586-12595.