Quantification and origin of cooperativity: insights from density functional reactivity theory

Area of Science:

• * Chemical Physics
• * Computational Chemistry
• * Molecular Interactions

Background:

• * Cooperativity is a ubiquitous phenomenon in chemical and biological systems.
• * Quantification and understanding of cooperativity's origin remain challenging.
• * Existing methods lack a standardized quantitative approach for assessing cooperativity.

Purpose of the Study:

• * To propose a novel quantitative measurement for evaluating the cooperativity effect in molecular systems.
• * To investigate the presence and nature (positive/negative) of cooperativity in diverse molecular assemblies.
• * To elucidate the fundamental origins of cooperativity using theoretical chemistry principles.

Main Methods:

• * Calculation of interaction energies for molecular systems with varying numbers of building blocks (up to 20).
• * Application of a proposed quantitative cooperativity measurement to six distinct molecular systems.
• * Utilizing density functional theory (DFT) energy partition schemes and information-theoretic quantities (Shannon entropy, Fisher information).

Main Results:

• * Cooperativity was observed in all tested systems, including water, argon, and zinc clusters, as well as a water cluster on graphene and a glycine alpha-helix.
• * Both positive and negative cooperativity effects were identified across the studied molecular systems.
• * Strong linear correlations were found between the cooperativity measure and specific information-theoretic quantities, aiding in origin analysis.

Conclusions:

• * The developed quantitative approach successfully measures cooperativity in diverse molecular systems.
• * The study reveals complex interactions governing cooperativity and uncovers an opposite enthalpy-entropy compensation mechanism for positive and negative cooperativity.
• * Findings provide new perspectives on the nature and origin of cooperativity, enhancing understanding of this crucial chemical concept.