  Many of the concepts which are at the basis of the development associated
with a quantitative treatment of the variety of phenomena associated with the
spontaneous breaking of gauge symmetry in nuclei have been instrumental in
connection with novel studies of soft matter, namely of protein evolution and
protein folding. Although the route to these subjects and associated
development does not necessarily imply the nuclear physics connection, such a
connection has proven qualitatively and quantitatively inspiring. In particular
to model protein evolution in terms of the alignment of quasispins displaying
twenty different projections, one for each of the twenty amino acids occurring
in nature, and the associated symmetry breaking in information (sequence)
space. Emergent properties of the corresponding phase transition are domain
walls which stabilize local elementary structures (LES), few groups of 10-20
aminoacids which become structured already in the denatured state provide the
molecular recognition directing protein folding. In fact, their docking is
closely related to the transition state of the process. While the two-step, yes
or no, folding process, does not provide direct information concerning LES, one
can force LES from virtual to become real, observable final state entities.
Getting again inspiration from the nuclear case (virtual processes contributing
to pair correlations can be forced to become real with the help of a probe
which itself changes particle number by two), one would expect that to make
real virtual LES, that is segments of the protein which already at an early
stage of the folding process flicker in and out of their native conformation,
one needs a probe which itself displays a similar behaviour. Peptides
displaying a sequence identical to LES are such probes.
