To detect labeled cell surface glycoproteins, we stained cells for 20min with Streptavidin Alexa Fluor 488 at 1:100 dilution in blocking solution and washed with PBS. Upon washing, cells were transferred onto cover slides and fixed with 4% paraformaldehyde for 10 min and subsequently washed with PBS. The nucleus was counterstained for five minutes with 1 µg/ml DAPI (Merck) and washed with PBS. To detect labeled cell surface glycoproteins and potentially labeled intracellular glycoproteins, cells were permeabilized for 5 min with 0.1% saponin. Permeabilized cells were stained for 20 min with Streptavidin Alexa Fluor 488 at 1:100 dilution in blocking solution and washed with PBS. In control experiments, Neuraminidase treated and untreated cells were stained with peanut agglutinin-Rhodamine (Axxora) according to the manufacturers instructions. Cover slides were mounted with Fluoromount-G (Southern Biotechnology). Confocal laser scan microscopy images were taken with a 64 × 1.4 oil objective using a Leica TCS SP2 AOBS and filters as follows: AF488 emission 501–554nm, excitation 490nm, DAPI emission 409–478nm, excitation 365nm. Images were merged with Photoshop 6.0 and LCS Lite (Leica) software.