The propagation of elementary layers over the (010) face of orthorhomb
ic lysozyme crystal is examined at a molecular-scale resolution by the
method of atomic force microscopy. The steps have a small number of k
inks spaced by about 100 growth units. The step motion occurs via succ
essive deposition of rows of growth units. The data obtained are discu
ssed in terms of the model of one-dimensional nucleation.