University of Kaiserslautern View Institution's Website 2 articles published in JoVE Bioengineering Aqueous Droplets Used as Enzymatic Microreactors and Their Electromagnetic Actuation Huschyar Al-Kaidy1, Kai Kuthan1, Thomas Hering1, Nils Tippkötter1,2 1Institute of Bioprocess Engineering, University of Kaiserslautern, 2Bioprocess Engineering, University of Applied Sciences, FH Aachen Lab-in-a-drop reaction systems allow the versatile implementation of complex reactions in a microfluidic scale. An automated actuation platform consisting of a 3 x 3 matrix of electromagnetic coils was developed and successfully used to merge two 10 µL microreactors and thereby initiate an enzymatic reaction in the resulting liquid marbles. Biology A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation Stefan Schmollinger1,2, Daniela Strenkert1,2, Vittoria Offeddu1,2, André Nordhues1,2, Frederik Sommer1,2, Michael Schroda1,2 1Max Planck Institute of Molecular Plant Physiology, 2University of Kaiserslautern We present a variation of the QUICK (QUantitative Immunoprecipitation Combined with Knockdown) approach that was introduced previously to distinguish between true and false protein-protein interactions. Our approach is based on 15N metabolic labeling, the modulation of affinities of protein-protein interactions by the presence/absence of ATP, immunoprecipitation, and quantitative mass spectrometry.