Dear Anna, I had some replies and most seem to agree that PE is not suitable for the double labeling tests I am trying to perform. Thanks for your tip. It seems someone from Hampstead will be coming down here soon. All the best Renato Dr. Renato Arruda Mortara Division of Parasitology Universidade Federal de Sao Paulo ESCOLA PAULISTA DE MEDICINA Rua Botucatu, 862 6o. andar 04023-062 Sao Paulo SP Brasil Email [log in to unmask] Fax : 55 11 571-1095 Fone: 55 11 570-8306