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Using the energy components associated with density-functional theory (DFT) calculations and various descriptors from the density-functional reactivity theory (conceptual DFT), we explore which chemical effects are most important for determining the ordering the conformers of the twenty natural amino acids in terms of their relative energetic stability. Electrostatic and steric (alternatively, electrostatic and exchange–correlation) interactions are found to be most descriptive of conformer stability. We also introduce an approach for determining how well one or more descriptors order the conformers, without requiring a linear (or any other) correlation between the descriptors. This ordering/ranking paradigm is likely to be useful in many other contexts also. [ABSTRACT FROM AUTHOR]