MATLAB Examples

# spce2tip4p.m

• This function converts a .gro or .pdb file with spc water to some tip4p water
• The coordinate of the new MW center is set to OW coordinates, thus must be properly energy minimized
• this could easliy be avoided if using an unwrapped structure...

## Dependent functions

• import_atom_gro.m
• write_atom_gro.m
• update_atom.m

## Examples

• tip4p_atom = spce2tip4p('SOL.pdb')
• tip4p_atom = spce2tip4p('SOL.gro')
```function tip4p_atom = spce2tip4p(filename) atom=import_atom(filename); % Import the gro file nAtoms=size(atom,2); % Total number of atoms Ow_ind=find(strcmpi([atom.type],'Ow')); % find the index of the water-Oxygens SOL_ind=sort([Ow_ind Ow_ind+1 Ow_ind+2]); % find the index of the water-Hydrogens SOL_atom=atom(SOL_ind); % Extract the water into a new atom struct (why not just use atom.resname?) [SOL_atom.resname]=deal({'SOL'}); % Set the new resname nSOL=size(SOL_atom,2); % Number of water atoms new_SOL=[SOL_atom(1:3:end) SOL_atom(1:3:end) SOL_atom(1:3:end) SOL_atom(1:3:end)]; % Create a new struct new_SOL(1:4:end)=SOL_atom(1:3:end); % assign Ow -> Ow new_SOL(2:4:end)=SOL_atom(2:3:end); % assign Hw -> Hw new_SOL(3:4:end)=SOL_atom(3:3:end); % assign Hw -> Hw new_SOL(4:4:end)=SOL_atom(1:3:end); % assign Ow -> Mw [new_SOL(4:4:end).type]=deal({'MW'}); % rename Ow -> Mw [new_SOL(4:4:end).fftype]=deal({'MW'}); % rename Ow -> Mw % Put the new_atom struct back again into the original atom struct if SOL_ind(end) == nAtoms; tip4p_atom=[atom(1:SOL_ind(1)-1) new_SOL]; else tip4p_atom=[atom(1:SOL_ind(1)-1) new_SOL atom(SOL_ind(end)+1:nAtoms)]; end % Update the atoms index and stuff tip4p_atom=update_atom(tip4p_atom); % Write the new .gro file write_atom_gro(tip4p_atom,Box_dim,strcat('tip4p_',filename)) ```