title: DEER in biological multispin-systems: a case study on the fatty acid binding to human serum albumin.
abstract: In this study, self-assembled systems of human serum albumin (HSA) and spin-labeled fatty acids are characterized by double electron-electron resonance (DEER). HSA, being the most important transport protein of the human blood, is capable to host up to seven paramagnetic fatty acid derivatives. DEER measurements of these self-assembled multispin clusters are strongly affected by correlations of more than two spins, the evaluation of the latter constituting the central topic of this paper. While the DEER modulation depth can be used to obtain qualitative information of the number of coupled spins, the quantitative analysis is hampered by the occurrence of cluster mixtures with different numbers of coupled spins and contributions from unbound spin-labeled material. Applying flip angle dependent DEER measurements, unwanted multispin correlations were found to lead not only to a broadening of the distance peaks but also to cause small distances to be overestimated and large distances to be suppressed. It is thus favorable to use spin-diluted systems with an average of two paramagnetic molecules per spin cluster when a quantitative analysis of the distance distribution is sought.
authors: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors: Matthias J N
authors: MJ
authors: Junk
authors: Hans W
authors: HW
authors: Spiess
authors: Dariush
authors: D
authors: Hinderberger
mesh_terms: D016477:Artifacts; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005227:Fatty Acids / Q000737:chemistry*; D006801:Humans; D011487:Protein Conformation; D012709:Serum Albumin / Q000737:chemistry*; D013113:Spin Labels; D013229:Stearic Acids / Q000737:chemistry
chemical_list: D003497:Cyclic N-Oxides; D005227:Fatty Acids; D012709:Serum Albumin; D013113:Spin Labels; D013229:Stearic Acids; C005072:5-doxylstearic acid; C031183:stearic acid; C032363:16-nitroxystearic acid