exercises:2017_ethz_mmm:alanine_dipeptide
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— | exercises:2017_ethz_mmm:alanine_dipeptide [2020/08/21 10:15] (current) – created - external edit 127.0.0.1 | ||
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+ | ====== Ramachandran plot for Alanine Dipeptide ====== | ||
+ | <note warning> | ||
+ | TO USE THE FUNCTION LIBRARY (VERSION UP TO DATE) IN THE INTERACTIVE SHELL: | ||
+ | you@eulerX ~$ module load courses mmm ; mmm-init | ||
+ | </ | ||
+ | |||
+ | |||
+ | Alanine dipeptide is often studied in theoretical work because it is among the simplest systems to exhibit some of the important features common to biomolecules. It has more than one long-lived conformational state. The relevant angles are the dihedral angles of the backbone, commonly called Φ and Ψ (see figure). In the following scheme, light blue atoms are carbons, white ones are hydrogens, red are oxygens, and blue are nitrogens. So the torsional angle Φ is C-N-C-C and Ψ is N-C-C-N along the backbone. | ||
+ | |||
+ | {{ alanine.png? | ||
+ | |||
+ | A detailed study of this system (see [[doi> | ||
+ | |||
+ | {{ screen_shot_2014-02-26_at_9.38.21_am.png? | ||
+ | |||
+ | The diagram represents the contour lines of the molecular energy as a function of the two dihedral angles. Contour lines are separated by 2 kcal/ | ||
+ | |||
+ | In this exercise you will obtain a simplified version of the above potential energy surface, obtained in a very similar way as in the paper. You will constrain the angles at fixed values using a strong harmonic potential, and optimize all other degrees of freedom. From this, a grid of energies will be built, and the energy diagram (Ramachandran plot) will be constructed. | ||
+ | |||
+ | Download the 2.2 exercise into your $HOME folder and unzip it. | ||
+ | |||
+ | < | ||
+ | you@eulerX ~$ wget http:// | ||
+ | you@eulerX ~$ unzip exercises: | ||
+ | </ | ||
+ | |||
+ | <note tip> All files of this exercise (** input and scripts are all commented **) can be downloaded from the wiki: {{exercise_2.2.zip|exercise_2.2.zip}}</ | ||
+ | |||
+ | Then go to the directory “exercise_2.2/ | ||
+ | < | ||
+ | you@eulerX ~$ cd exercise_2.2 | ||
+ | </ | ||
+ | |||
+ | The input file has a section concerning restrained optimization: | ||
+ | <code - inp.templ> | ||
+ | & | ||
+ | METHOD FIST ! Using Molecular Mechanics | ||
+ | &MM | ||
+ | & | ||
+ | parm_file_name ace_ala_nme.pot | ||
+ | ! This file contains force field parameters | ||
+ | parmtype CHM ! forcefield parameters has CHARMM format | ||
+ | & | ||
+ | ! in the nonboned interactions (both pair body potential and many body potential) | ||
+ | EMAX_SPLINE 1.0 ! Specify the maximum value of the potential up to which splines will be constructed | ||
+ | &END | ||
+ | &END FORCEFIELD | ||
+ | & | ||
+ | & | ||
+ | EWALD_TYPE ewald ! Standard non-fft based ewald method | ||
+ | ALPHA .36 | ||
+ | GMAX 29 ! Number of grid points | ||
+ | &END EWALD | ||
+ | &END POISSON | ||
+ | & | ||
+ | & | ||
+ | &END | ||
+ | & | ||
+ | &END | ||
+ | &END | ||
+ | &END MM | ||
+ | & | ||
+ | & | ||
+ | ABC 50.0 50.0 50.0 ! Lengths of the cell vectors A, B, and C | ||
+ | &END CELL | ||
+ | & | ||
+ | & | ||
+ | ATOMS 5 7 9 15 ! Four atoms specify torsion angle | ||
+ | & | ||
+ | & | ||
+ | & | ||
+ | &END | ||
+ | & | ||
+ | & | ||
+ | ATOMS 7 9 15 17 ! Four atoms specify torsion angle | ||
+ | & | ||
+ | & | ||
+ | & | ||
+ | &END | ||
+ | & | ||
+ | CONN_FILE_NAME ace_ala_nme.psf | ||
+ | ! File which contains the connectivity information | ||
+ | CONNECTIVITY psf ! Format of the connectivity file is PSF | ||
+ | COORD_FILE_NAME ini.pdb | ||
+ | ! File which contains atom's coordinates of the system | ||
+ | COORDINATE PDB ! Coordinates are in the PDB format | ||
+ | & | ||
+ | &END | ||
+ | & | ||
+ | &END | ||
+ | &END TOPOLOGY | ||
+ | |||
+ | & | ||
+ | AMBER_INFO | ||
+ | &END | ||
+ | &END | ||
+ | &END SUBSYS | ||
+ | &END FORCE_EVAL | ||
+ | & | ||
+ | PRINT_LEVEL LOW ! Global print level | ||
+ | PROJECT ch ! Name of the project. This word will appear as part of a name of all ouput files (except main ouput file, specified with -o option) | ||
+ | RUN_TYPE GEO_OPT | ||
+ | &END GLOBAL | ||
+ | & | ||
+ | & | ||
+ | & | ||
+ | INTERMOLECULAR T | ||
+ | COLVAR 1 ! Sequential number of the variable | ||
+ | & | ||
+ | K=5.0 ! U(x)=K*(x-x0)^2 | ||
+ | &END | ||
+ | TARGET [deg] _A1_ ! _A1_ will be changed to the number by an external scritp | ||
+ | &END | ||
+ | & | ||
+ | INTERMOLECULAR T | ||
+ | COLVAR 2 ! Sequential number of the variable | ||
+ | & | ||
+ | K=5.0 ! U(x)=K*(x-x0)^2 | ||
+ | & | ||
+ | TARGET [deg] _A2_ ! _A1_ will be changed to the number by an external scritp | ||
+ | &END | ||
+ | & | ||
+ | |||
+ | & | ||
+ | & | ||
+ | FORMAT PDB ! Format of the ouput trajectory is PDB | ||
+ | ADD_LAST NUMERIC | ||
+ | &EACH | ||
+ | | ||
+ | &END | ||
+ | & | ||
+ | & | ||
+ | & | ||
+ | OPTIMIZER BFGS ! Type of the optimizer | ||
+ | MAX_ITER 5000 ! Maximum number of optimization steps | ||
+ | MAX_FORCE 0.005 ! The value of maximal force | ||
+ | RMS_FORCE 0.003 ! The value of maximal force RMS | ||
+ | & | ||
+ | &END | ||
+ | |||
+ | </ | ||
+ | |||
+ | At this point submit the job grid, first loading the module for cp2k version 2.5 entering | ||
+ | |||
+ | < | ||
+ | you@eulerX exercise_2.2$ module load cp2k | ||
+ | you@eulerX exercise_2.2$ bsub < grid_alanine | ||
+ | </ | ||
+ | |||
+ | The file " | ||
+ | Using gnuplot, you can visualize the results | ||
+ | |||
+ | < | ||
+ | you@eulerX exercise_2.2$ gnuplot torsion.gnu | ||
+ | </ | ||
+ | |||
+ | <note important> | ||
+ | Changing into the directory **Logs** you fill find files of the kind **opt.? | ||
+ | m_pdbtorsion: | ||
+ | < | ||
+ | you@eulerX exercise_2.2/ | ||
+ | </ | ||
+ | |||
+ | for the two dihedral **Phi** and **Psi**. | ||
+ | |||
+ | |||
+ | </ | ||
+ | To clean the output and unnecessary files and do it again, | ||
+ | |||
+ | < | ||
+ | you@eulerX exercise_2.2$ ./cleanall | ||
+ | </ |
exercises/2017_ethz_mmm/alanine_dipeptide.txt · Last modified: 2020/08/21 10:15 by 127.0.0.1