the line is analyzed and can be used to determine the propensity of the peptide to self associate using the computer program origin because of the large diffusion coefficients of small peptides synthetic boundary centerpieces can be used to obtain an initial sharp boundary between peptide and solvent band forming centerpieces can be used depending on preliminary results the initial concentrations of peptide may vary between 0 01 and 100 u03bcg ml diffusion coefficients can be obtained from boundary spreading experiments while these can be obtained from the high speed synthetic boundary experiments generally the determinations can be made at low speed where sedimentation will be small initially the rotor speed can be set low and adjusted upward during the experiment depending on the determined concentration gradient in this way a range of concentrations can be generated in a single experiment and any pressure dependencies can then be identified due to the high diffusion coefficient of the peptides equilibrium can be attained rapidly equilibrium can be defined as lack of at detectable difference in measurements of the concentration gradient taken 1 hour apart in cases where self association of peptide is observed in the analytical ultracentrifuge chromatography can be used to extend analysis to lower concentrations which may be more relevant to those used for measurement of biological activity the total volume of a column v t v 0 v i v g where v 0 is the void volume v i is the interior volume and v g is the volume of the.