Connective tissue polarity unraveled by a markov-chain mechanism of collagen fibril segment self-assembly.

The well-established occurrence of pyroelectricity (Lang, 1966) in tissues of living organisms has found a first explanation by a Markov-chain mechanism taking place during collagen fibril self-assembly in extracytoplasmic channels. Recently reported biochemical findings on the longitudinal fusion reactivity of small fibril segments (which undergo C-, N- and C-, C- but not N-, N-terminal fusions; see Graham et al., 2000; Kadler et al., 1996) may provide a mechanism by which a difference in the fusion probabilities P(CC), P(NN) drives the self-assembly into partial macroscopic polar order. In principle, a Markov-chain growth process can lower the noncentrosymmetric infinity 2 symmetry describing dielectric properties of a growing limb (as managed by fibroblasts) into the polar infinity group. It is proposed that macroscopically polar properties enter the biological world by a stochastic mechanism of unidirectional growth. Polarity formation in organisms shows similarity to effects reported for molecular crystals (Hulliger et al., 2002).