We also investigated the angiogenic response of the nonrubber constituents of natural rubber, ie. the serum fraction
in the absence of rubber particles. The latex stabilized with
ammonium was submitted to a coagulation process by addition of acetic acid (2.0% v/v). The coagulation takes place
when pH falls below 5.0, and the latex is separated into two
parts: the rubber fraction and the serum fraction (nonrubber
constituents). The serum fraction was purified in a column
of DEAE-cellulose (5 × 40 cm) eluted with stepwise gradient of NH4HCO3/NaCl. From this purification, three fractions were obtained by exclusion based on the charge affinity with the DEAE column. Each fraction was dialyzed and
lyophilized