dist_4gbx.py

#! /usr/bin/env python

from MDAnalysis import *
#from MDAnalysis.analysis.align import *
import numpy
import math

u = Universe("init.pdb","sampled.pos.pdb")
v = Universe("init.pdb")

# residues
a1 = u.selectAtoms("segid A and resid 46")
b1 = u.selectAtoms("segid B and resid 90")
a2 = u.selectAtoms("segid A and resid 69")
b2 = u.selectAtoms("segid B and resid 62")
a3 = u.selectAtoms("segid A and resid 77")
b3 = u.selectAtoms("segid B and resid 51")

# helices
a4 = u.selectAtoms("segid A and resid 46:77")
b4 = u.selectAtoms("segid B and resid 51:90")


f = open('helix_dist','w')
g = open('angle','w')

for ts in u.trajectory:
        
        distance1 = numpy.linalg.norm(a1.centerOfMass() - b1.centerOfMass())
        distance2 = numpy.linalg.norm(a2.centerOfMass() - b2.centerOfMass())
        distance3 = numpy.linalg.norm(a3.centerOfMass() - b3.centerOfMass())
	distance4 = numpy.linalg.norm(a4.centerOfMass() - b4.centerOfMass())
	
	a4_1,a4_2,a4_3 = a4.principalAxes()
	b4_1,b4_2,b4_3 = b4.principalAxes()
       # helix12_1,helix12_2,helix12_3 = helix12.principalAxes()
       # helix21_1,helix21_2,helix21_3 = helix21.principalAxes()
       # helix22_1,helix22_2,helix22_3 = helix22.principalAxes()

	angle = math.degrees(math.acos(numpy.dot(a4_1,b4_1)))
       # angle2 = math.degrees(math.acos(numpy.dot(helix21_1,helix22_1)))

	if angle > 90:
		angle = 180-angle
                
       # print "%6i %7.3f %7.3f %7.3f %7.3f %7.3f %7.3f %7.3f" % (ts.frame,rmsd0,rmsd1,rmsd2,distance1,distance2,angle1,angle2)

	f.write('%7.3f %7.3f % 7.3f % 7.3f\n' % (distance1,distance2,distance3,distance4))
	g.write('%7.3f\n' % angle)

f.close()
g.close()