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1 Dynamic aggregation of the mid size gadolinium complex {Ph 4 [Gd(DTTA)(H O) ] 3} Hugues Jaccard, Pascal Miéville, Caroline Cannizzo, Cédric R. Mayer, Lothar Helm Electronic Supplementary Material Hugues Jaccard, Pascal Miéville, Caroline Cannizzo, Lothar Helm ( ) Institut des sciences et ingénierie chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), EPFL-BCH, CH-15 Lausanne, Switzerland lothar.helm@epfl.ch Tel: Fax: Cédric R. Mayer Laboratoire d Ingénierie des Systèmes de Versailles LISV EA 448,Université de Versailles Saint Quentin en Yvelines, /1 avenue de l Europe, F-7814 Vélizy, France 1

2 INDEX Fitting of NMR data 1 H relaxivity as a function of ph 3 1 H relaxivity in presence of phosphate buffer 3 1 H relaxivity in presence of human serum 4 Fitting of NMR data Different approaches have been used to analyse 1 H NMRD and 17 O NMR data. In all cases longitudinal relaxivities r 1 and reduced 17 O relaxation rates and chemical shifts are fitted. The relaxivity is given by the sum of inner sphere, second sphere and outer sphere contributions. r r r r r r 1 1is 1,nd 1os 1is 1os [1] As usual, the second sphere contribution is not explicitly calculated but included in r 1os. The inner H sphere term is given in Eq. [], where q is the number of inner sphere water molecules, T 1 M is the longitudinal relaxation time and τ M the residence time of bound water molecules. r 1is 1 q T H 1M M From the measured 17 O NMR relaxation rates and angular frequencies of the paramagnetic solutions, 1/T 1, 1/T and ω, and of the acidified water reference, 1/T 1A, 1/T A and ω A, one can calculate the reduced relaxation rates, 1/T 1r, 1/T r (Eq. [3] and [4]), where 1/T 1M, 1/T M are the relaxation rates of the bound water and ω M is the chemical shift difference between bound and bulk water, ω M is the mean residence time or the inverse of the water exchange rate k ex and P M is the mole fraction of the bound water. [] T P T T T T 1r M 1 1A 1M M 1OS T T 1 T P T T T 1 1 M M M M 1 1 r M A M M T M M OS [3] [4] The terms 1/T 1OS and 1/T OS describe relaxation contributions from water molecules not directly bound to the paramagnetic centre. In previous studies it has been shown that 17 O outer sphere relaxation terms due to water molecules freely diffusing on the surface of Gd-polyaminocarboxylate complexes are negligible. The approaches used in the fitting differ in the calculation of the inner-sphere contributions. For a detailed treatment of the approaches used we recommend the following references: J. Kowalewski, D. Kruk, G. Parigi, in Advances in Inorganic Chemistry, Vol. 57 (Eds.: R. Van Eldik, I. Bertini), Elsevier, San Diego, 5, pp L. Helm Prog. in NMR Spect. 6, 49,

3 E. Belorizky, P. H. Fries, L. Helm, J. Kowalewski, D. Kruk, R. R. Sharp, P.-O. Westlund, J. Chem. Phys. 8, 18, 537. É. Tóth, L. Helm, A. E. Merbach, in The Chemistry of COntrast Agents in Medical Magnetic Resonance Imaging, nd ed. (Eds.: A. E. Merbach, L. Helm, É. Tóth), John Wiley & Sons Ltd., Chichester, 13, pp H relaxivity as a function of ph Relaxivities of {Ph 4 [Gd(DTTA)(H O) ] - 3} ~.77 mm solutions at six different ph between 4 and 7 were measured at 5 C and 3 MHz. The relaxivities were proved to be unaffected by the ph throughout the working ph range (Figure S1). 4 r ph Figure S1 Relaxivity of {Ph 4 [Gd(DTTA)(H O) ] - 3}.8 mm as a function of ph 1 H relaxivity in presence of phosphate buffer Relaxivities of {Ph 4 [Gd(DTTA)(H O) ] - 3} ~.5 mm solutions containing, 11, 1, 51, 116, and 7 mm of phosphate buffer were measured at 5 C and 3 MHz minutes after phosphate addition and then every 4h. The phosphate buffer was prepared from mono and dibasic sodium phosphate in order to obtain a final ph 5.8 solution. This experiment was designed to break the aggregates, ideally until the total disaggregation of the system to leave the only monomer in solution. That was tried by adding from 5 to equivalents of phosphate buffer, which proved to be an efficient disaggregating agent for -stacking systems, 1, to a.5 mm solution of {Ph 4 [Gd(DTTA)(H O) ] - 3}. The relative high concentration of paramagnetic compound was necessary in order to induce aggregates. The evolution of the relaxivities with time for the different phosphate concentrations is presented on Figure S. Though a clear relaxivity drop is observed, this experiment turned out to be not quantitative, as the phosphate makes the compound precipitate, even in the sample most diluted in phosphate. The relaxivity decrease is therefore not only due to a disaggregation but also due to change in concentration due to precipitation. 3

4 r time / hrs 1 [PO 4 3- ] / mm Figure S Relaxivity evolution in time of.3 mm samples containing various concentrations of phosphate buffer 1 H relaxivity in presence of human serum The relaxivity of the.5 mm complex in human serum (3% w/w) (Human serum from human male AB plasma, Sigma-Aldrich) was measured at 5 C and 3 MHz minutes after phosphate addition and then every 4h for ~7 days. This experiment was designed to test if aggregates exist in human serum. A slight relaxivity decrease is observed (Figure S3). Because of the turbidity of the serum however, precipitation of the compound is not clearly distinguishable and cannot be excluded. The inorganic phosphate concentration in adult serum ranges to.8 to 1.45 mm, 3 which implies a concentration between.6 and.46 mm with dilution. In addition to phosphate ions the concentrations of other salts in the serum have to be taken into account to explain the small relaxivity drop. Sodium chloride can indeed play a role in disaggregation. 1 Lactates and carbonates can complex gadolinium in a mono-dentate fashion in the case of DTTA because the two free positions are not adjacent. 4 The higher initial relaxivities in serum compared to water are certainly due to the higher viscosity of the solution. 4

5 6 r time / hrs Figure S3 Relaxivity evolution in time of a.3 mm sample in human serum References 1. Laus, S.; Sitharaman, B.; Tóth, É.; Bolskar, R. D.; Helm, L.; Asokan, S.; Wong, M. S.; Wilson, L. J.; Merbach, A. E. J. Am. Chem. Soc. 5, 17, Laus, S.; Sitharaman, B.; Tóth, É.; Bolskar, R. D.; Helm, L.; Wilson, L. J.; Merbach, A. E. J. Phys. Chem. C 7, 111, Lewis, J. L. The Merck Manuals - Online Medical Library 9, sorders/disorders_of_phosphate_concentration.html 4. L. Moriggi, C. Cannizzo, C. Prestinari, F. Berrière, L. Helm, Inorg. Chem. 8, 47,