Isolation of an androgen acceptor from salt extract of rat prostatic chromatin

The soluble androgen acceptor has been isolated from 0.35 M NaCl extract of rat prostatic chromatin by affinity chromatography on DNA-cellulose. The acceptor activity was assayed by interaction with 5α-dihydrotestosterone-receptor. Native DNA enhances this interaction. Polyacrylamide gel electrophoresis of the acceptor under denaturing conditions reveals a single polypeptide of molecular weight of 14,000. Amino acid analysis shows that the acceptor protein contains a higher content of acidic amino acid residues than basic amino acid residues. In an $\text{in}\text{vitro}$ RNA synthesizing system catalyzed by rat RNA polymerase II, addition of the acceptor stimulates RNA synthesis. Based on incorporation of [γ-³²P]ATP and [γ-³²P]GTP, the stimulation by the acceptor is mainly on the initiation of RNA chains.     

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.