Index

Macromolecular dictionary (mmCIF) version 2.0.09

_phasing_MIR_der_refln.HL_C_iso

Definition:

   The isomorphous Hendrickson-Lattman coefficient C~iso~ for this
   reflection for this derivative.

             -Fp~obs~^2^ * [sin(alphah~calc~)^2^
                         -  cos(alphah~calc~)^2^]
   C~iso~ =  ------------------------------------
                            E^2^

   E            = (Fph~obs~ - Fp~obs~ - Fh~calc~)^2^
                  for centric reflections
                = [(Fph~obs~ - Fp~obs~) * 2^1/2^ - Fh~calc~]^2^
                  for acentric reflections

   Fp~obs~      = the observed structure-factor amplitude of the
                  native
   Fph~obs~     = the observed structure-factor amplitude of the
                  derivative
   Fh~calc~     = the calculated structure-factor amplitude
                  from the heavy-atom model
   alphah~calc~ = the phase calculated from the heavy-atom model

   This coefficient appears in the expression for the phase
   probability of each isomorphous derivative:

   P~i~(alpha) = exp[k + A * cos(alpha) + B * sin(alpha)
                       + C * cos(2 * alpha) + D * sin(2 * alpha)]

   Ref: Hendrickson, W. A. & Lattman, E. E. (1970). Acta
        Cryst. B26, 136-143.

Type: float

Mandatory item: no

Category: phasing_MIR_der_refln