1 Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN, 55108, USA.
2 Barshop Institute for Longevity and Aging Studies, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229-3900, USA.
3 University Imaging Centers, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA.
4 Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota-Twin Cities, Minneapolis, MN, 55455, USA.
5 Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN, 55108, USA. xlchen@umn.edu.