  In this paper, I tentatively put forward a new hypothesis that the emergence
of a single chiral form of biomolecules in living organisms is specifically
determined by the electron spin state during their enzyme-catalyzed synthesis
processes. Specifically speaking, the electrons released from the coenzyme
NAD(P)H of amino acid synthase are heterogeneous in spin states; however, when
they pass through the chiral alpha-helix structure of the enzymes to the site
of amino acid synthesis at the other end of the helix, their spin states are
filtered and polarized, producing only spin up electrons; once the
spin-polarized electrons participate in the reductive reaction between
alpha-oxo acid and ammonia, only L-amino acids are formed according to the
Pauli exclusion principle.
