Cooperative Weak Dispersive Interactions Actuate Catalysis in a Shape-Selective Abiological Racemase

Area of Science:

• Supramolecular Chemistry
• Catalysis
• Biomimetic Chemistry

Background:

• Enzymes achieve remarkable catalytic rates through specific active site interactions.
• Understanding non-enzymatic catalysis is key to designing artificial enzymes.
• Host-guest chemistry offers a platform for creating synthetic catalytic systems.

Purpose of the Study:

• To demonstrate racemase activity in a simple abiological host-guest system.
• To investigate the role of cooperative weak interactions and shape complementarity in catalysis.
• To explore the thermodynamic profile of non-enzymatic catalysis.

Main Methods:

• Design and synthesis of a "box-and-bowl" host-guest system.
• Kinetic studies to determine catalytic rate enhancements.
• Inhibition studies using a hapten resembling the transition state.
• Measurement of substrate binding affinity.

Main Results:

• Achieved catalytic rate enhancements of 10⁴ without traditional functional groups.
• Demonstrated that cooperative weak interactions and shape complementarity drive activity.
• Identified a potent transition-state-analog inhibitor, analogous to catalytic antibodies.
• Observed weak substrate binding (K_a ≈ 10² M^-1) and no substrate/product inhibition.

Conclusions:

• Shape selectivity from cooperative dispersive forces is sufficient for enzyme-like catalysis.
• This system provides a model for understanding enzyme catalytic mechanisms.
• Highlights the potential of supramolecular systems in artificial enzyme design.