Table 1.

Biopolymer Universalities and Idiosyncrasies

Attribute	Polynucleotide	Polypeptide	Polyglucose
Primary proficiency	Maintain, record, and transduce information, catalyze chemical reactions	Catalyze and regulate chemical reactions, provide physical structure	Provide physical structure, energy storage, and recognition
Conditional self-complementarityU	Yes	Yes	Yes
Condition for self-complementarity	Nucleotide sequence	Amino acid composition	Linkage stereochemistry (β- vs. α-anomer)
Small number of types of folding elementsU	Yes	Yes	Yes
Folding element identities	Nitrogenous bases	Peptide linkage	Cyclic glucose
Enzymatic capability	Moderate	High	Low
Sidechain diversity	Low: four planer nitrogenous bases	High: 20 amino acid sidechains	N/A: no sidechains
Sidechain complementarity	Yes, base pairing	No	No
Backbone self-complementarity	No: anionic, self-repulsive backbone	Yes: neutral, cohesive backbone	Yes: neutral, cohesive backbone
Complementary hydrogen bondingU	Unipolar, coplanar	Unipolar, coplanar	Bipolar, non-planar
Net hydrogen bond polarity	Large excess of acceptors over donors	Equivalent number of acceptors and donors	Excess of acceptors over donors
Selective self-interaction of hydrolyzed monomersU	No	No	No
Backbone linearity	Yes	Yes	Sometimes
Strand directionalityU	Yes, 5′–3′	Yes, N to C	Yes, 1–4
Secondary structureU	Helices, bulges, stem-loops, pseudoknots, etc	α-Helices, β-sheets and turns	Elongated fibers
Conformational constraintsU	“Rigid nucleotides,” planar bases	Planar peptide, allowed regions of ϕφ space	Conformational preferences within and between cyclic glucose
Self-destruct mechanism	RNA: Yes (2′ hydroxyl) DNA: No	No	No
Required folding cofactors	Cations	None	None
Degradation by hydrolysisU	Yes	Yes	Yes
Polymerized by	Protein	Ribozyme RNP complex	Protein
Polymerization is dependent on divalent cationsU	Yes	Yes	Yes
Polymerization mechanismU	Condensation dehydration	Condensation dehydration	Condensation dehydration
Polymerization intermediatesU	Phosphorylated	Phosphorylated	Phosphorylated
Driver of polymerization motorU	Phosphate release	Phosphate release	Phosphate release
Retention of phosphate during polymerization	Yes	No	No

U indicates universal property of all biopolymers