scientificprotocols

Authors: Giorgio Pochetti & Roberta Montanari

Abstract

It could be very useful in drug development to determine the relative affinities of a ligand that can bind to a protein with two (or more) different and specific binding sites. X-ray crystallography is a very powerful technique to determine the locations and describe the features of each binding site but it is unuseful to establish their relative affinities. Moreover, the stoichiometry of binding observed in the crystal structure of a complex could be an artifact of the crystallization conditions.

On the contrary, isothermal titration calorimetry (ITC) can be used to assign the correct stoichiometry of the association, depending on the initial and final concentration ratio between ligand and protein, and to establish the affinity for each specific binding site, if combined with structural information from X-ray crystallography.

andersx

import openbabel as ob

# Standard openbabel molecule load
conv = ob.OBConversion()
conv.SetInAndOutFormats('xyz','xyz')
mol = obOBMol()
conv.ReadFile(mol,'my_mol.xyz')

# Define constraints
constraints = ob.OBFFConstraints()

rmcgibbo

from __future__ import division
import numpy  as np
import IPython as ip
import matplotlib.pyplot as pp
import warnings
from collections import namedtuple
import scipy.optimize

#symbolic algebra
import theano

baoilleach

import math
import pybel

def sqr_dist(a, b):
    ac = a.coords
    bc = b.coords
    return (ac[0]-bc[0])**2 + (ac[1]-bc[1])**2 + (ac[2]-bc[2])**2

# Definitions taken from
#    http://baoilleach.blogspot.com/2007/07/pybel-hack-that-sd-file.html