European Aristocrats
b. The common ‘de’, ‘du’, ‘le’, ‘la’, ‘de la’, ‘von’, ‘van’ before a surname does not go in the LNAB field; it goes with the surname in the Current Last Name field while the surname, ONE word, goes in the LNAB. Example: Last name at birth: "Villefort", Current Last Name: "de Villefort". The exception to this is de Vere. Members of this family should have both words in the LNAB field.
http://www.wikitree.com/wiki/Name_Fields_for_European_Aristocrats
Thank you very much for your help! :-)