Purification of allantoicase fromPseudomonas aeruginosa

Cells ofPseudomonas aeruginosa were grown in a synthetic medium containing allantoin as the sole source of carbon, nitrogen and energy. The specific activity of allantoicase in the cell-free extract amounted to 7 units/mg protein. The enzyme was purified 190 times by treatment of the extract at 72 C in the presence of Mn²⁺ions and chromatography on Ecteola-cellulose.     

Rheological properties of cross-linked hyaluronan-gelatin hydrogels for tissue engineering

Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component.