  Energy spectra and transport properties of armchair nanotubes with curvature
induced spin-orbit interaction are investigated thoroughly. The spin-orbit
interaction consists of two terms: the first one preserves the spin symmetry in
rotating frame, while the second one breaks it. It is found that the both terms
are equally important: i)at scattering on the potential step which mimics a
long-range potential in the nanotubes; ii)at transport via nanotube quantum
dots. It is shown that an armchair nanotube with the first spin-orbit term
works as an ideal spin-filter, while the second term produces a parasitic
inductance.
