Coulomb and Overlap Self-Similarities:  A Comparative Selectivity Analysis of Structure−Function Relationships for Auxin−like Molecules

Abstract

Auxins are defined mainly by a set of physiological actions, but the structure-effect relationship still is based on chemical intuition. Currently a well-defined auxin molecular structure is not available. The existence of different auxin binding proteins and mechanisms of auxin action, the wide diversity of the auxin molecules, and the pleiotropic effects of auxin imply a completely different mechanism as described for the animal hormone concept. Here, we present a computational approach dealing with semiempirical optimizations of the auxin molecules themselves, which represent a number of about 250 different chemical structures. Our approach uses molecular quantum similarity measures and additional quantum variables for the analysis of auxin-like molecules. The finding of similarities in molecules by focusing basically on their electron structure results in new insights in the relationship of the different auxin groups. Additional statistical analysis allows the identification of relationships between similarity groups and their biological activity, respectively. It is postulated that the auxin-like molecular recognition depends more on specific molecular assembling states than on a specific ring system or side chain.

Humic and fulvic acids as biostimulants in horticulture

“…These support the acid growth theory (Hager, 2003) and is agreement with previous reports suggesting that intrinsic IAA-like molecules are clustered within HA supramolecular arrangements (Muscolo et al, 1998). The existence of more than 240 auxin-like molecules has been described within the literature (Ferro et al, 2006). Some of these auxin-like molecules are likely to be present in HS and be able to access receptors outside or inside the cell.…”

Defining Binding Efficiency and Specificity of Auxins for SCFTIR1/AFB-Aux/IAA Co-receptor Complex Formation

“…10−12 Early work classified auxins by chemical structure. 26,10 Later, molecular interaction energy fields correlated with biological activity were used to group 53 compounds into 4 classes.…”

Assessment of quantum‐chemical methods for electronic properties and geometry of signaling biomolecules

“…PM3 shows somewhat larger deviations already known for indole due to the geometry of the pyrrol ring. 2,78 Significant deviations from the crystal structure obtained with all methods in certain molecular regions indicate that the intermolecular interactions forces are influencing the intermolecularbonding orientation of the concerned atoms.…”

“…Generally, molecule2biopolymer or biopolymer2biopolymer interactions are weak and therefore most investigations focused on the statistical regularities of the biomolecular contributions as active units. 1,2 In this context, it is more important to analyze the trends in properties of classes of compounds, rather than specific bonds of individual molecules. An accurate representation of physicochemical properties with respect to their degree of reproducibility 3 is needed to clarify possible misinterpretations in the sequence of interacting levels of structure and function, which are commonly reorganized in biology.…”

“…nism in the auxin binding site of a receptor 18 could be explained based on quantum-chemical results. 2,21 The bioactivity and toxicity of auxins, 1 as well as the cytotoxicity of similar substances, 22 depend linearly on the energy difference between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gap). The accurate determination of these electronic structure parameters is therefore crucial for the theoretical description of these phenomena.…”