Requesting for a single apartment in Jena

Hello, I am 27 year student living in Bielefeld Germany. I am doing a PhD student (doktorand) in Biology. As my PhD supervisor is moving to Jena, I have to move as well. I am looking for a single apartment in Jena from April 2016. The apartment should have a kitchenette and a bathroom. The maximum rent I can pay is 400 euros. I speak English. I am also a smoker and smoke in the room or on the balcony. A balcony would be nice but I am fine without it as well. It would be good if I get some place close to the main building of University of Jena.