1. Statistical and Biological Physics Group of the Hungarian Academy of Sciences, Pázmány P. s. 1A, H-1117 Budapest, Hungary.
2. Department of Genetics, Eötvös University, Pázmány P. s. 1C, H-1117 Budapest, Hungary.
3. Department of Medical Chemistry, Semmelweis University, 37-47 Tűzoltó Street, H-1094 Budapest, Hungary.
4. Department of Physics, Loránd Eötvös University, Pázmány P. s. 1/A, H-1117 Budapest, Hungary, and Research Institute for Solid State Physics and Optics, H-1525 Budapest, Post Office Box 49, Hungary.
5. Vanderbilt University, Nashville, TN 37240, USA.
6. Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA.