diff --git a/pymix/AminoAcidPropertyPrior.py b/pymix/AminoAcidPropertyPrior.py
index 56ae29b..25d3c7d 100644
--- a/pymix/AminoAcidPropertyPrior.py
+++ b/pymix/AminoAcidPropertyPrior.py
@@ -167,7 +167,7 @@ def readUCSCPrior(filename):
             s = m3.groups(1)[0]
             alpha = s.split(' ')
             alpha = map(float,alpha)
-            as =  alpha.pop(0) # first entry is the sum of the others -> remove
+            alpha.pop(0) # first entry is the sum of the others -> remove
             alpha_mat.append(alpha)
 
     # intergrate gap character '-' into the alphabet