1. Institute
of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria
2. National Specialized Hospital for Active Treating of Haematological Diseases, Sofia 1756, Bulgaria
3. Unidad
de Biofísica (CSIC/UPV-EHU) and Departamento de Bioquímica
y Biología Molecular, Universidad del País Vasco, POB 644, 48080 Bilbao, Spain