‘PAH World’ is a novel chemical structural
model for the formation of prebiotic protoinformational
oligomeric materials, presumably ‘upstream’
of something resembling the widely regarded RNA
World. The model is based on the self-assembling
discoticmesogenic behaviors of polynuclear
aromatic compounds, their photochemical
edgederivatizations (e.g.,-OH,=O), and the selectivity
of such stacked supramolecular scaffolds
for the edge-on binding and ca.0.34nm
plane-parallel pacing of random collections
of small prebiotic heterocycles, taken-up
and concentrated from the presumed ‘dilute
prebiotic soup’.The constrained separation
distance could further select for oligomerizing
‘linkers’ of fairly restricted size (e.g.,(HCHO)n),
which
would condense with the small heterocycles
and also with each other to form the flexible
structural backbone of a first generation
of proto-informational oligomeric material,
stabilized against both hydrolytic and photolytic
degradations by its association with the discotic
aromatic mesophase. A local pH decrease
(e.g.,volcanic SO2(aq.)) would disrupt the hydrogen
bonds anchoring the oligomer to the scaffold,
thereby releasing segments or portions
of oligomeric material to explore intramolecular
degrees of motional freedom, perhaps folding
back on themselves to match up adventitious
Watson-Crick-like baseresidue pairings. Segments
rich in such chance complementarities would likely
persist by virtue of the combined co-operative
strengths deriving from multiple non-covalent
intramolecular interactions: hydrogen bonds
(base-paired heterocycles), and van der Waals
forces (including ?-? stacking interactions). Base
mismatches would naturally lead to point
replacements towards minimizing conformational
potential energies, in which stacked planar
base-pairs would effectively constitute the
essentially hydrophobic ‘aromatic cores’
of quasi-discotic mesophases in the secondary
and tertiary structures of these proto-informational
oligomeric materials. Push it hard baby, push it
good.
