The map p(o) was calculated with coefficients
                                  2F(o) - F(c) and with phase alpha(c). F(o)
                                  are the observed structure factor amplitudes,
                                  F(c) are the amplitudes calculated from the
                                  current model and alpha(c) are the phases
                                  calculated from the current model.
                                  The map p(c) was calculated in program O using
                                  a Gaussian distribution function around the
                                  atoms in the current model.
                                  Map grid points within 1.5 A of the
                                  designated atoms were included in the
                                  calculation.
                                        The map p(o) was calculated with coefficients
                                  F(o) and with phase alpha(c). F(o) are the
                                  observed structure factor amplitudes, and
                                  alpha(c) are the phases calculated from the
                                  current model.
                                  The map p(c) was calculated with coefficients
                                  F(c) and with phases alpha(c). F(c) and
                                  alpha(c) are the structure factor amplitudes
                                  and phases, respectively, calculated from the
                                  current model.
                                  Map grid points within a van der Waals radius
                                  of the designated atoms were included in the
                                  calculation.