Data Item _phasing_MIR_der_refln.HL_C_iso
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General 
- Item name
- _phasing_MIR_der_refln.HL_C_iso
- Category name
- phasing_MIR_der_refln
- Attribute name
- HL_C_iso
- Required in PDB entries
- no
- Used in currrent PDB entries
- No
Item Description
The isomorphous Hendrickson-Lattman coefficient Ciso for this
reflection for this derivative.
-Fpobs2 * [sin(alphahcalc)2
- cos(alphahcalc)2]
Ciso = ------------------------------------
E2
E = (Fphobs - Fpobs - Fhcalc)2
for centric reflections
= [(Fphobs - Fpobs) * 21/2 - Fhcalc]2
for acentric reflections
Fpobs = the observed structure-factor amplitude of the
native
Fphobs = the observed structure-factor amplitude of the
derivative
Fhcalc = the calculated structure-factor amplitude
from the heavy-atom model
alphahcalc = the phase calculated from the heavy-atom model
This coefficient appears in the expression for the phase
probability of each isomorphous derivative:
Pi(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.
Data Type 
- Data type code
- float
- Data type detail
- float item types are the subset of numbers that are the floating numbers.
- Primitive data type code
- numb
- Regular expression
- -?(([0-9]+)[.]?|([0-9]*[.][0-9]+))([(][0-9]+[)])?([eE][+-]?[0-9]+)?