  Systems of quantum dots (QD) connected to leads exhibit periodic conductance
peaks as a function of gate voltage arising from the Coulomb blockade effect
\cite{review1,review2,review3}. Much effort goes into minimizing the size of
QDs and reaching the scale of single molecules
\cite{molecular1,molecular2,molecular3} which could serve as nanoelectronic
circuit components such as transistors. Connecting molecules or nanoparticles
to external leads cannot be achieved by the traditional methods used in
semiconductor based QDs, hence, controlling the coupling to nanoparticle QDs is
a major technical challenge.
  Here we present a novel technique by which we can explore electric properties
of a metallic nanoparticle while varying the coupling to leads. We find that
the conductance through the nanoparticle is characterized by \emph{two} gate
voltage periods. The relative strength of the periods depends both on the
dot-lead coupling and on the source-drain voltage. These surprising findings
may be a general property of strongly coupled metallic nanoparticles.
