I am an engineer working in the university as postdoc with TVL based salary. I have been offered a position in industry which I wish to take up from January 2011. According to my present contract with Uni, I can give Kündigung in any given quarter of the year by giving notice 6 weeks in advance (this means in the quarter Oct-Dec, to finish by Dec 31, I have to give notice before Nov 15.). I wish to take one month urlaub before taking up the new position.

Now the question: can I end my contract by Dec 31 by giving notice as above, but take leave for the entire month (= all working days in December) on a loss-of-pay basis, assuming my professor won't have any problem?

You do not have to go for a “loss of pay basis”. If you still have vacations left, you can apply for leave and exhaust the holidays you still have. The employer needs to grant the leave. If he does not and you are unable to exhaust the holidays during the remaining time of your contract, the employer would have to pay you out. If you do not have any holidays left it depends on the employer whether he grants you leave without pay.

Thanks for your reply vakalat. I don't have that many holidays. Either I have to take "unbezahlte Urlaub" for the remaining days or mutually dissolve the contract (which is also possible under TVL), both subject to approval by the professor. Is a normal Kündigung better than dissolving in any respect (career or legal), in the above scenario? (I am not thinking about ALG here.)
If I take the former route, what happens to social contributions AV, KV and RV from the salary, for the unpaid days? I have an NE from the highly qualified category.

MB