  Paramagnetic alignment of fractal suprathermally rotating grains is
discussed. It is shown that if the concentration of H$_{2}$formation sites is
low and resurfacing is active, fractal structure of grains enhances their
alignment. Studying the influence of grain surface physics and chemistry on the
alignment we found that there exist two critical values of grain sizes, and the
alignment of smaller grains is expected to decrease as compared to the
predictions of the Purcell's theory (1979). One of the critical sizes is due to
intensified poisoning of active sites, while the other is a result of a finite
value of the imaginary part of magnetic susceptibility in the limit of high
angular velocities. On the contrary, if active sites completely cover grain
surface, suprathermal rotation, and therefore efficient alignment, is possible
only for a limited range of grain sizes.
