All-derivable points in matrix algebras

Let Mn be the algebra of all n×n matrices. We say that an element G∈Mn is an all-derivable point in Mn if every derivable linear mapping φ at G (i.e. φ(ST)=φ(S)T+Sφ(T) for any S,T∈Mn with ST=G) is a derivation. We mainly show in this paper that a matrix G is an all-derivable point in Mn if and only if G≠0.