[en] The doubly closed-shell nucleus ₅₀¹⁰⁰Sn₅₀ has so far not been reached experimentally. The investigations of proton-rich nuclei in its neighbourhood, however, have made considerable progress in recent years. In this report, I would like to present results obtained at the GSI mass separator on-line to the heavy-ion accelerator UNILAC. In chapter 2 the measurements of decay properties and the interpretation of the resulting nuclear-structure information are described. Subsequently, properties of neutron-deficient isotopes of indium (Z=49), as deduced from collinear laser spectroscopy, are discussed (chapter 3). Chapter 4 deals with mass-excess value (''masses''), mass differences and the localization of the proton drip line in light odd-Z isotopes above tin. (orig.)