Toward Intelligent Materials - Molecular Self-Assembly: Advances and Applications - page 2

total synthesis [3] and functional transplantation [4] of an entire
genome.
This genome transplantation establishes that synthetic
biopolymers can be more than static materials, or even merely
responsive to a changing physical environment, they can profit from
the experience. These synthetic genomes can adapt and change,
evolve in response to pressure, i.e., learn from experience, such that
the system they direct can behave intelligently. Charles Darwin first
recognized the idea of molecular systems being intelligent when
he imagined a chemically rich “warm pond” from which evolution
originated [5], an idea published decades before the duplex structure
of DNA was proposed [6]. A population of simple molecules, storing
and copying information to ensure their own survival [7], suggests
that intelligent behavior is not restricted to complex genomes [8]
but is an inherent property of matter that could be translated into
new intelligent materials through a bottom-up design of synthetic
chemical evolution.
Already several examples of molecular information transfer have
appeared using template-directed syntheses on natural biopolymer
templates [9-12]. While nature's biopolymer catalysts that ensure
the accurate replication of present day genomes are highly regulated,
the nucleic acid polymerases, in their simplest form, couple the
thermodynamic condensation of monomers on the template with
a subsequent removal of the pyrophosphate product to drive the
reaction forward. Extending this process by combining reversible
imine condensation on a template with kinetic reductive amination
has been achieved for both chain-length and sequence-specific
template-directed polymerization of functional length polymers [13-
16]. This process has proven to be quite general [17,18], establishing
that a critical step in synthetic chemical evolution can be achieved
with very different reaction schemes on DNA templates.
If chemical evolution and intelligent behavior are inherent
properties of matter, they should be commonly observed today. The
protein-only infectious particles known as prions may represent
an early stage in biopolymer evolution [19]. While these epigenetic
elements [20] survive by templating the folding of complementary
peptide strands, their covalent structure evolves through nucleic
acid -amino acid

polyamides most interesting is their access to an incredible diversity
of precisely folded architectures and polymorphic assemblies. Even

replication. However, what makes these

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