How to reasonably determine backbone angle parameter

[gundalav]

Hi,

Thank you for making this great package.
First of all this is not about issue in the code. But a usage question.

AFAIK the key parameters in Peptide builder is the backbone angle parameter.
As defined by geo.phi and geo.psi in the code below.

from PeptideBuilder import Geometry
import PeptideBuilder
import Bio.PDB

# Useful description about PeptideBuilder, it's conceptual basis
# https://peerj.com/articles/80/

def split(word):
    return [char for char in word]

wanted_peptide = "GGGGGG"


res = split(wanted_peptide)
geo = Geometry.geometry(res[0])
geo.phi = -60
geo.psi_im1 = -40

structure = PeptideBuilder.initialize_res(geo)
nres = res[1:len(res)]

for r in nres: 
    # print(r)
    rgeo = Geometry.geometry(r)
    rgeo.phi = -60
    rgeo.psi_im1 = -40
    PeptideBuilder.add_residue(structure, rgeo)

PeptideBuilder.add_terminal_OXT(structure)

out = Bio.PDB.PDBIO()
out.set_structure(structure)
out.save("mypeptide.pdb")

My question are:

1. How can I reasonable determine the value for geo.phi and geo.psi?
2. Should it be defined differently for each residue in the peptide?

The final aim for me to construct the 3d model, is to dock it to some existing
protein structure.

Thanks and truly hope from you again.

G.V.