def get_backbone_atoms_nucleicacids (chain):
	""" This function returns a list of nucleic acids' backbone atoms (C4') from a given chain. """

	c4_atoms = []
	for residue in chain:
		if residue.get_id()[0] == " " and residue.has_id("C4\'"):
			c4_atoms.append(residue["C4\'"])
	return c4_atoms