1 Department of Biochemistry, Middle East Technical University, Ankara, Turkey.
2 Section On Growth and Obesity, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
3 Department of Chemistry, Middle East Technical University, Ankara, Turkey.
4 Department of Biological Sciences, Middle East Technical University, 06800, Ankara, Turkey. tyanik@metu.edu.tr.