We present new results from an energetic surface imprinting method which allows us to outline the general conformation of protein ions in vacuo. Both disulfide-bond-intact and disulfide-bond-reduced gasphase lysozyme ions were produced by electrospray ionization and were accelerated and impacted onto graphite surfaces. The resulting surface defects, each created by a single incident ion, were imaged with scanning force microscopy. Disulfide-intact lysozyme ions created compact, slightly elliptical hillocks on the surfaces, whereas disulfide-reduced lysozyme produced more oblong, elongated hillocks. By employing a thermal model describing the response of graphite to energy deposited by an elongated incident energetic projectile, we calculated from the hillock sizes for disulfide-reduced lysozyme (Q = 14+) an overall length of 32.1 +/- 1.6 nm. This value is close to the length we observe for apomyoglobin (Q = 14+), 35.5 +/- 2.4 nm, although apomyoglobin and lysozyme possess significantly different numbers of amino acid residues. Based on these results, we hypothesize that aspects of a protein＇s native secondary structure are preserved in the gas phase, even if the tertiary structure might be non-native. We have unfolded disulfide-intact lysozyme computationally and find a qualitatively good agreement with the experimentally obtained length of disulfide-intact (Q = 9+) lysozyme.