I need to perform fibrogenesis study of an acid soluble protein (Collagen type II) using turbidity measurements. I have been looking through the literature for an efficient way to prepare the sample for the study. Most of the literature that dissolves the purified lyophilized dry protein in either 0.005 M Acetic acid or 0.001 M HCl (in a solution of ~ pH = 2 ) After that depending on the paper varying ratios of this solution and a stock buffer of pH 7.3-7.5 containing phosphates are mixed. The buffers are typically ~ 150 mM - 80 mM Phosphates in stock, and on preparing the final fibrogensis sample have a concentration of 15mM - 65 mM phosphates. As you must have expected, the buffering capacity of these buffers is so low that the pH is invariably not what is expected(between 7.2 -7.5).. Is there a standard way of studying such acid soluble proteins under various buffered conditions?

p.s. I tried dialysis and the result is image 3 (the fibers formed as soon as the buffer changed)

Image 1 is a method mentioned in the literature- in this method also, the final pH on mixing appropriate amounts of acid solublized collagen and fibber is ~ 6.8 (experimentally observed).

Image2 is another literature subscribed method of sample preparation. Here Acid-collagen solution:buffer solution ratio is (9:1) and the experimentally observed pH is ~5.8.