  We present experimental study of magnetization in $\lambda$-DNA in
conjunction with structural measurements. The results show the surprising
interplay between the molecular structures and their magnetic property. In the
B-DNA state, $\lambda$-DNA exhibits paramagnetic behaviour below 20 K that is
non-linear in applied magnetic field whereas in the A-DNA state, remains
diamagnetic down to 2 K. We propose orbital paramagnetism as the origin of the
observed phenomena and discuss its relation to the existence of long range
coherent transport in B-DNA at low temperature.
