The
molecular mechanism of the microwave nonthermal effect is still
not clear. This work investigated the spatial orientation and kinetic
energy of active site collision of carnosine, a natural bioactive
dipeptide, under the weak microwave irradiation using the molecular
dynamics simulation. Our results showed the influences of the temperature,
microwave intensity, microwave frequency, and microwave polarization
mode (linear polarization and circular polarization) on the spatial
orientation and kinetic energy of active site collision of carnosine.
First, under the constant intensity and frequency of linear polarization
microwave irradiation, the increment of the collision probability
between the 6N atom of carnosine and the 28H atom of the other carnosine
at effective space angle decreases from 85.0% to 3.5% with increasing
temperature. Second, with the increase of microwave intensity, the
change of spatial orientation and kinetic energy becomes more and
more significant. However, the change of circular polarization microwaves
on the spatial orientation and kinetic energy of collision is weaker
than that of linear polarization. Third, under the constant intensity
of linear polarization microwave irradiation, the collision probability
between the 6N atom and the 28H atom at effective space angle decreases
from 70.2% to 14.7% with increasing frequency. Finally, under the
microwave polarization, the spatial orientation and kinetic energy
of molecular collision are changed, which is summarized as the microwave
postpolarization effect (MWPPE). The dependence of MWPPE on temperature,
microwave intensity, microwave frequency, and polarization mode is
very complicated. In the end, this effect can provide a new insight
into the molecular mechanism of the microwave nonthermal effect.