diff --git a/prody/atomic/flags.py b/prody/atomic/flags.py
index cee3c466a..56d9c4701 100644
--- a/prody/atomic/flags.py
+++ b/prody/atomic/flags.py
@@ -67,6 +67,8 @@
 NONSTANDARD = {
     'ASX': set(['acyclic', 'surface', 'polar', 'medium']),
     'GLX': set(['acyclic', 'surface', 'large', 'polar']),
+    'ASH': set(['acyclic', 'acidic', 'surface', 'polar', 'medium']),
+    'GLH': set(['acyclic', 'acidic', 'surface', 'large', 'polar']),
     'CSO': set(['acyclic', 'neutral', 'surface', 'medium', 'polar']),
     'CYX': set(['acyclic', 'neutral', 'buried', 'medium', 'polar']),
     'HIP': set(['cyclic', 'basic', 'surface', 'large', 'polar']),
@@ -75,6 +77,12 @@
     'HSD': set(['cyclic', 'basic', 'surface', 'large', 'polar']),
     'HSE': set(['cyclic', 'basic', 'surface', 'large', 'polar']),
     'HSP': set(['cyclic', 'acidic', 'surface', 'large', 'polar']),
+    'HISD': set(['cyclic', 'basic', 'surface', 'large', 'polar']),
+    'HISE': set(['cyclic', 'basic', 'surface', 'large', 'polar']),
+    'HISP': set(['cyclic', 'acidic', 'surface', 'large', 'polar']),
+    'LYN': set(['acyclic', 'neutral', 'surface', 'large', 'polar']),
+    'TYM': set(['cyclic', 'aromatic', 'surface', 'basic', 'large', 'polar']),
+    'ARN': set(['acyclic', 'neutral', 'surface', 'large', 'polar']),
     'MSE': set(['acyclic', 'neutral', 'buried', 'large']),
     'CME': set(['acyclic', 'neutral', 'buried', 'large']),
     'SEC': set(['acyclic', 'neutral', 'buried', 'polar', 'medium']),