diff --git a/deeprank2/molstruct/residue.py b/deeprank2/molstruct/residue.py
index e9938b219..552d1a015 100644
--- a/deeprank2/molstruct/residue.py
+++ b/deeprank2/molstruct/residue.py
@@ -97,7 +97,7 @@ def __repr__(self) -> str:
 
     @property
     def position(self) -> np.array:
-        return np.mean([atom.position for atom in self._atoms], axis=0)
+        return self.get_center()
 
     def get_center(self) -> NDArray:
         """Find the center position of a `Residue`.
diff --git a/deeprank2/utils/graph.py b/deeprank2/utils/graph.py
index 174eeb41c..4c51624e5 100644
--- a/deeprank2/utils/graph.py
+++ b/deeprank2/utils/graph.py
@@ -59,7 +59,6 @@ def __init__(self, id_: Atom | Residue):
             raise TypeError(type(id_))
 
         self.id = id_
-
         self.features = {}
 
     @property
@@ -319,8 +318,10 @@ def get_all_chains(self) -> list[str]:
         return list(chains)
 
 
-def build_atomic_graph( # pylint: disable=too-many-locals
-    atoms: list[Atom], graph_id: str, max_edge_distance: float
+def build_atomic_graph(
+    atoms: list[Atom],
+    graph_id: str,
+    max_edge_distance: float,
 ) -> Graph:
     """Builds a graph, using the atoms as nodes.
 
@@ -333,19 +334,18 @@ def build_atomic_graph( # pylint: disable=too-many-locals
 
     distances = distance_matrix(positions, positions, p=2)
     neighbours = distances < max_edge_distance
+    atom_index_pairs = np.transpose(np.nonzero(neighbours))
 
     graph = Graph(graph_id)
-    for atom1_index, atom2_index in np.transpose(np.nonzero(neighbours)):
-        if atom1_index != atom2_index:
+    for index1, index2 in atom_index_pairs:
+        if index1 != index2:
 
-            atom1 = atoms[atom1_index]
-            atom2 = atoms[atom2_index]
-            contact = AtomicContact(atom1, atom2)
+            node1 = Node(atoms[index1])
+            node2 = Node(atoms[index2])
+            contact = AtomicContact(node1.id, node2.id)
 
-            node1 = Node(atom1)
-            node2 = Node(atom2)
-            node1.features[Nfeat.POSITION] = atom1.position
-            node2.features[Nfeat.POSITION] = atom2.position
+            node1.features[Nfeat.POSITION] = node1.id.position
+            node2.features[Nfeat.POSITION] = node2.id.position
 
             graph.add_node(node1)
             graph.add_node(node2)
@@ -355,7 +355,9 @@ def build_atomic_graph( # pylint: disable=too-many-locals
 
 
 def build_residue_graph( # pylint: disable=too-many-locals
-    residues: list[Residue], graph_id: str, max_edge_distance: float
+    residues: list[Residue],
+    graph_id: str,
+    max_edge_distance: float,
 ) -> Graph:
     """Builds a graph, using the residues as nodes.
 
@@ -379,8 +381,6 @@ def build_residue_graph( # pylint: disable=too-many-locals
         positions[atom_index] = atom.position
 
     distances = distance_matrix(positions, positions, p=2)
-
-    # determine which atoms are close enough
     neighbours = distances < max_edge_distance
 
     atom_index_pairs = np.transpose(np.nonzero(neighbours))
@@ -390,26 +390,20 @@ def build_residue_graph( # pylint: disable=too-many-locals
 
     # build the graph
     graph = Graph(graph_id)
-    for residue1_index, residue2_index in residue_index_pairs:
-
-        residue1: Residue = residues[residue1_index]
-        residue2: Residue = residues[residue2_index]
+    for index1, index2 in residue_index_pairs:
+        if index1 != index2:
 
-        if residue1 != residue2:
+            node1 = Node(residues[index1])
+            node2 = Node(residues[index2])
+            contact = ResidueContact(node1.id, node2.id)
 
-            contact = ResidueContact(residue1, residue2)
+            node1.features[Nfeat.POSITION] = node1.id.position
+            node2.features[Nfeat.POSITION] = node2.id.position
 
-            node1 = Node(residue1)
-            node2 = Node(residue2)
-            edge = Edge(contact)
-
-            node1.features[Nfeat.POSITION] = residue1.get_center()
-            node2.features[Nfeat.POSITION] = residue2.get_center()
-
-            # The same residue will be added  multiple times as a node,
+            # The same residue will be added multiple times as a node,
             # but the Graph class fixes this.
             graph.add_node(node1)
             graph.add_node(node2)
-            graph.add_edge(edge)
+            graph.add_edge(Edge(contact))
 
     return graph