Conversion of ortho-para H2O isomers in water and a jump in erythrocyte fluidity through a microcapillary at a temperature of 36.6±0.3°C

A mechanism is proposed for the previously observed [1] jump in erythrocyte fluidity through a microcapillary 1.3 µm in diameter at a temperature of 36.6±0.3°C. Our interpretation is based on the experimental evidence both for existence of ortho and para H2O isomers in water and on spin-selective interaction of proteins with para H2O isomers as hydration shells of biomolecules are being formed [2]. It is important that the formation of hydration shells of proteins and DNA in aqueous solutions is accompanied by an increase in the Brillouin shift to 0.4 cm−1 (≃0.25 cm−1 in water), which points to the formation of icelike structures. We believe that the coincidence of the translational energy kT of the Brownian motion and the energy of the rotational quanta for the 313–202 transition of para H2O isomers at the temperature 36.6°C increases the probability for excitation of para H2O isomers in collisions. Collisions mix quantum states of closely spaced levels in para H2O (313, 285.2 cm−1) and ortho H2O (330, 285.4 cm−1) and induce conversion of para isomers to ortho H2O. It is assumed that this conversion in the icelike hydration shell of hemoglobin (Hb) is accelerated under the catalyzing effect of oxygen and iron present in Hb and triggers a chain reaction: release of ortho H2O isomers through the erythrocyte membrane→compaction of Hb molecules and increase in concentration of catalysts→acceleration of conversion→structural gel-sol transition. It is the sequence of these processes that provides a jump in fluidity of erythrocytes through a microcapillary and the anomalous increase in fluidity of the aqueous solution of hemoglobin by almost an order of magnitude at temperatures close to 36.6°C and an increase in the solution concentration by a factor of 1.7.