Protein Self-Association Induced by Macromolecular Crowding: A Quantitative Analysis by Magnetic Relaxation Dispersion  Karim Snoussi, Bertil Halle  Biophysical Journal  Volume 88, Issue 4, Pages 2855-2866 (April 2005) DOI: 10.1529/biophysj.104.055871 Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 1 1H relaxation dispersion profiles from aqueous solutions of dextran at pH 4.5 and 27°C. The dextran concentrations for samples D1–D5 are given in Table 1. The curves were obtained by three-Lorentzian fits as described in the text. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 2 Dependence of the zero-frequency excess 1H relaxation rate, R1(0)−R1bulk, in dextran solutions D1–D5 on the dextran hydroxyl proton fraction, fIM. The bulk water relaxation rate at 27°C is R1bulk=0.272⁡s−1. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 3 1H difference relaxation dispersion profiles from aqueous solutions of BPTI and dextran at pH 4.5 and 27°C. BPTI and dextran concentrations for samples P0–P5 are given in Table 1. The curves were obtained by two-Lorentzian (samples P0–P3) or three-Lorentzian (samples p4 and p5) fits as described in the text. The data have been normalized to a water/BPTI mol ratio of NWBPTI=3500. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 4 The fraction, pB, of decamer-forming BPTI molecules as a function of dextran volume fraction, ϕM. The points were derived from the MRD data (samples P0–P3) and the curve resulted from a fit to the model described in the text (with δ=3.0Å). The dashed curve was calculated with the same model parameters, but without the nonideality contribution from BPTI. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 5 Variation of (A) the Kuhn length, λM, and (B) the natural logarithm of the ideal association constant, K0, with the thickness, δ, of the undisplacable water layer. The shaded regions correspond to one standard deviation in the fitted parameters. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions

Figure 6 Dependence of the natural logarithm of the nonideality factor, Γ, on the dextran volume fraction, ϕM. The solid curve was calculated from the model with the parameter values resulting from the fit in Fig. 4. The dashed curve was calculated with the same parameter values, but without the nonideality contribution from BPTI. Biophysical Journal 2005 88, 2855-2866DOI: (10.1529/biophysj.104.055871) Copyright © 2005 The Biophysical Society Terms and Conditions