pdb1 ='/home/devanandt/Documents/VMD/1UBQ.pdb';
x=pdbread(pdb1);
atom={x.Model.Atom.AtomName};
n_i=find(strcmp(atom,'N')); % Find indices of atoms
X = [x.Model.Atom.X];
Y = [x.Model.Atom.Y];
Z = [x.Model.Atom.Z];
X_n = X(n_i); % X Y Z coordinates of N atoms
Y_n = Y(n_i);
Z_n = Z(n_i);