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Phase problem solved !!!
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Dear protein crystallographer !
The Uppsala Software Factory is proud to announce the
release of a new program, called APRIL. APRIL stands
for "Ab-initio Phasing using Rotationally Induced
Likelihood". The program can be used to solve the
phase problem in cases where you have two or more
non-isomorphous crystal forms of the same (or related,
e.g. mutants, complexes) compound.
The program exploits the inherent geometric redundancies
(Bricogne, 1974) to extract phase information, after
first solving the self-rotation (in case any of your
crystal forms contain NCS) and cross-rotation functions.
Trial phases are optimised using a maximum likelihood-based
Initial tests (using different lysozymes) have
given excellent results, confirming previous
models for the structure of this protein.
Now, I would like to invite you to become a
beta-testing site in order to help optimise
and debug the software.
Executables of APRIL (release 1) are available for
SGI, OSF1, HP-UX, Solaris, Linux, and ZX-81. The
program is CCP4-compatible. It requires at least two
MTZ files as input (one for each crystal form),
and some control information (e.g., number
of molecules per asymmetric unit for each crystal
form, resolution limits, etc.).
For more information about the program and
downloading instructions, please point your
The beta version of APRIL will only be available
today so as to limit the number of bonafide
beta testers to a manageable number.
Happy phasing !
CEO, Uppsala Software Factory
("21st century software with a 19th century interface,
but, hey, it's free !")