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PREDICCIÓN DE ESTRUCTURAS DE CRISTALES CON MOLÉCULAS FLEXIBES EN SU CELDA. V. Bazterra, M. B. Ferraro, J. C. Facelli. Departamento de Física Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires. 2007. AIM OF THE APPLICATION. Crystal engeneering. Pharmaceutical design.

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## PREDICCIÓN DE ESTRUCTURAS DE CRISTALES CON MOLÉCULAS FLEXIBES EN SU CELDA

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**PREDICCIÓN DE ESTRUCTURAS DE CRISTALES CON MOLÉCULAS**FLEXIBES EN SU CELDA V. Bazterra, M. B. Ferraro, J. C. Facelli Departamento de Física Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires 2007**AIM OF THE APPLICATION**• Crystal engeneering • Pharmaceutical design • Polymorphism • Application in materials.**Why GENETIC ALGORITHMS?**• Difficult crystal prediction from first principles. • Polymorphic forms in organic crystals • Useful to model atomic and molecular clusters.**MGAC Crystal Structure Prediction CapabilitiesVictor E.**Bazterra, Matthew Thorley, Marta B. Ferraro, and Julio C. FacelliJ. Chem. Theory Comput. 2007, 3, 201-209 • Search for crystal structures within any symmetry group and with an arbitrary number of molecules and molecular types per asymmetric unit. • Search structures using either the rigid or flexible molecule models. • Automatically generate the molecule’s force field using existing force field libraries. • Increase the sampling power and the complexity of molecules amenable to CSP studies using the parallel and distributed computing capabilities of the system. • Automatically compare, sort and archive the most relevant structures in a user database.**Molecular center of mass {R1, R2,…Rn} **Its orientations {1 , 2 ,…\n } Relevant dihedral angles {1 , 2 , …..n } Space group and lattice parameters {a,b,c,,,} GENETIC CODING (Rigid bodies)**SEMI-RIGID APPROXIMATION**-Crystallographic group DATA -Number of molecules in the cell MOLECULES: -center of mass positions -relative orientations PARAMETERS -Lattice axis a, b, c -Lattice angles, , , -AMBER FORCE FIELD -CHARMm FORCE FIELD in CHARMM code APTITUDE FUNCTION**SEMIRIGID APPROXIMATION**-crystallographic cell axes and angles. -positions of the center of masss of each molecule. -Euler angles respect to the unit cell. -Ndihe molecular angles. Rigid bodies with flexible chains K=6+Z(6+Ndihed.) Parameters to be optimized**Population analysis**Evolution of the population energy Hystogram of the evolution**CSP2007 Methodology**• Local optimization using CHARMM 6, 7 with the GAFF 14 parameters. cutoff of 14 Å, and the electrostatic interactions were calculated using the Ewald technique. • Atomic charges, , using the restrained electrostatic potential approach implemented on the RESP program. Gaussian03 32 package at HF/6-31G* level. • Restricted searches using 30 individuals in the population for up to 130 generations, for the 14 most common symmetry groups for organic molecules, P1, P-1, P21, C2, Pc, Cc, P21/c, C2/c, P212121, Pca21, Pna21, Pbcn, Pbca and Pnma. • For each molecule we performed between 150 and 200 runs leading to at least 100 complete runs with 130 generations. • From these short lists we manually detected clearly unphysical structures and duplicated ones that were not eliminated in the previous step that were identified by comparison of their XRPD spectra**Molecule XII**ACRY02 Space group: Pbca**Molecule XIV**P21/c**??????**• Test predictions of benchmark crystals • Prediction of experimental data • Incorporation of additional pseudopotentials • Cosmetics and website.**Marta Ferraro**Víctor Bazterra Departamento de Física University of Buenos Aires Argentina Center for High Performance Computing University of Utah Julio C. Facelli Martin Cuma

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