An "autorating" (peer rating) system designed to account for individual performance in team projects was used in two sophomorelevel chemical engineering courses in which the students did their homework in cooperative learning teams. Team members confidentially rated how well they and each of their teammates fulfilled their responsibilities, the ratings were converted to individual weighting factors, and individual project grades were computed as the product of the team project grade and the weighting factor. Correlations were computed between ratings and grades, self-ratings and ratings from teammates, and ratings received and given by men and women and by ethnic minorities and non-minorities. Incidences of "hitchhikers" (students whose performance was considered less than satisfactory by their teammates), "tutors" (students who received top ratings from all of their teammates), dysfunctional teams, and teams agreeing on a common rating were also determined. The results suggest that the autorating system works exceptionally well as a rule, and the benefits it provides more than compensate for the relatively infrequent problems that may occur in its use.

An affinity resin containing the peptide ligand Phe-Leu-Leu-Val-Pro-Leu (FLLVPL) has been developed for the purification of fibrinogen. The ligand was identified by screening a solid-phase combinatorial peptide library using an immunostaining technique. The specific binding of fibrinogen to the ligand has been characterized by isothermal calorimetry and adsorption isotherms and is dominated by both hydrophobic interactions and ionic interactions with the N-terminal free amino group. The effective association constant of fibrinogen was substantially higher when the peptide was immobilized on the resin than in solution; moreover, it increased with increasing peptide density, suggesting a cooperative binding effect. A low ionic strength buffer at pH 4 was used successfully to elute adsorbed fibrinogen from the column with high purity, retention of factor XIII crosslinking activity, and minimal, if any, loss of biological function. This general approach to ligand selection and characterization can be used to develop peptide ligands for the affinity purification of diverse proteins on a large scale.

Peptides deduced from peptide libraries may serve as affinity ligands for protein purification. Identification of a ligand that binds the protein of interest depends highly on the screening method used. One approach which offers simple and direct detection involves screening a solid‐phase peptide library against a radiolabeled target protein. We have developed a radiological screening method, using 14C as a radioactive label, that offers high resolution and sensitivity. Less than 100 DPM/bead are detectable after a one‐day exposure using autoradiography. The validity of the technique was illustrated by screening a solid‐phase hexameric‐peptide library spiked with YNFEVL‐beads against 14C‐labeled ribonuclease S‐protein. For this particular system, the amount of protein bound to a single bead was estimated to be in the femtomolar range with a peptide:protein ratio of 500:1. Finally, a portion of the library was screened against 14C‐labeled fibrinogen. Three peptides deduced from the library, WQEHYN, WQEHYN, and YENYGY, purified fibrinogen from a mixture with albumin.

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