Estimation of possible selectivity and sensitivity of a cooperative system to low-intensive microwave radiation

A cooperative bistable chemical system is considered as a possible mechanism for sensitive and selective reception of low-intensive microwaves in bio-objects. The mechanism is realized in a two-level hierarchical manner with a threshold for signal channeling from the first level to the second one. At the first stage the microwave signal is perceived in a population of primary receptors represented as molecules of definite species. Each primary receptor has an active and a non-active conformation. The subpopulations of active and non-active receptors are in thermal equilibrium at physiological temperatures, and thermal fluctuations are taken into account. The microwaves are expected to shift the equilibrium to the more active receptors when acting at the non-active receptor fundamental frequency of mechanical oscillations. If the concentration of the active receptors is high enough, the whole bistable system switches from one stable state to another. Due to thermal fluctuations the switching has a probabilistic nature, and is characterized via a mean waiting time for first switching. The whole system sensitivity is estimated in terms of the waiting time shortening due to microwaves. At the level of primary receptors the sensitivity is described as a relative increment of active receptors. It is expected that the individual receptor oscillations are overdamped with a quality factor Q = 1. The sensitivity to a 1 GHz field with power density 1 mW/cm2 is estimated. Sensitivity to this field at the level of the primary receptors is characterized by the factor ≈ 10−8, which is indistinguishable from thermal fluctuations at physiological temperatures. If the bistable system has maximum volume consistent with spatial homogeneity (the coherent volume), then its sensitivity is estimated as shortening of waiting time by a factor as high as exp(104). The system selectivity is also much better than that of the individual primary receptor, and may be expressed by an apparent quality factor Q ≃ 103.