Human serum albumin (HSA) was labeled in various ways and with different radioactive labels . Characterization with electrophoresis on polyacryl gel and immunoelectrophoresis did not reveal differences between labeled and nonlabeled HSA. The release of the label from labeled proteins in phosphate buffer (pH 7.4) was studied as a function of time. IzSI-labeled proteins were stable and 99mTc-labeled proteins showed different stabilities depending on the labeling method which was used. The adsorption behavior of labeled HSA and HSA onto polystyrene (PS) and silicon rubber (SR) was studied by using two methods. It appeared that all labeled HSA compounds showed a preferential adsorption onto PS (and SR) substrates. The 99mTc-labeled HSA showed a high value of the preferential adsorption factor (4~ >> 1). The value for 125I-labeled HSA was about 1.4. It was also shown that q~ was dependent on the kind of substrate used. The methods developed to determine preferential adsorption of labeled proteins compared to their nonlabeled analogs are also generally applicable for different types of compounds.

No abstract

Flocculation experiments on polystyrene latex (PSL) with human serum albumin (HSA) and human fibrinogen (HFb) have been performed above and below the iso-electric points (i.e.p.) of the proteins. The stability of the proteins (HFb, HSA) in solution has been determined as a function of salt concentration (NaCI, BaC12, La(NO&) and pH. Using a stopped flow spectrophotometer the rate constant of flocculation (or coagulation) kll has been measured at different protein and salt concentrations (BaC12, NaCl). A model is proposed and tested to explain the enhancement of kll above the value for bare PSL when bridging occurs at pH-values above the i.e.p. of the proteins. The observed enhancement of kll, being 20-30% for HSA and 5040% for HFb, is a result of two effects: reduced

SYNOPSISEarlier measurements of paraffin oil (PO)-water contact angles on protein layers [human serum albumin (HSA) or human fibrinogen (HFb)] adsorbed on polystyrene (PS) showed that HSA could be transferred from the PSlwater to the POlwater interface by a passing POwater front, while HFb could not. Interfacial association of adsorbed HF% molecules was adopted as an explanation for the irreversible localization of HFb at the PS surface. In the present work it is shown that aggregation by a heat treatment of adsorbed HSA molecules also causes an irreversible localization of the HSA at the PS surface. It is shown that advancing and receding PO-water contact angles on HSA-coated PS substrates have practically the same value. Variation of pH and NaCl concentration hardly shows any effect on these contact angles, indicating that in all cases the HSA coating behaves the same. The advancing and receding PO-water contact angles on HFb-coated substrates differ greatly. In analogy with ElShimi and Goddard we conclude that the natural HF% coating is able to adopt and retain a configuration compatible with the immediate environment.