Topological characterization and modeling of the 3D structure of lipase from Pseudomonas aeruginosa.

Lipase from Pseudomonas aeruginosa is a M(r) 29 kDa protein with a single functional disulfide bond as shown by a shift in electrophoretic mobility after treatment with dithiothreitol and iodoacetamide. Limited proteolysis of lipase with Staphylococcus aureus protease V8 resulted in cleavage after amino acid residues Asp38 and Glu46. Comparison of the lipase amino acid sequence with those of other hydrolases with known 3D structures indicated that the folding pattern might be compatible with the alpha/beta hydrolase fold, thereby allowing us to construct a 3D model which fitted the biochemical properties. The model predicts a catalytic triad consisting of Ser82, Asp229 and His251, and contains a disulfide bond connecting residues Cys183 and Cys235. Residues Asp38 and Glu46 are located at the surface of the enzyme, whereas the disulfide bond is rather inaccessible, which is in agreement with the finding that the protein needed to be partly unfolded before a reduction of the disulfide bond could take place. A striking prediction from the model was the lack of a lid-like alpha-helical loop structure covering the active site which confers to other well-characterized lipases a unique property known as interfacial activation. Experimental determination of lipase activity under conditions where the substrate existed either as monomeric solutions or aggregates confirmed the absence of interfacial activation.

The instructional media: an overview.

PIP: The advantages of using audiovisual instructional techniques in training programs for nurses were noted and administrative strategies for encouraging the effective use of educational technology were provided. Audiovisual instructional techniques can enhance classroom learning, create opportunity for individualized learning programs, and can serve as an effective tool for monitoring and supervising clinical training. In the classroom situation, audiovisual techniques should be incorporated as a basic instructional tool and not simply used to occasionally supplement traditional learning techniques. The use of these tools can free the teacher for more personalized teaching tasks. Educational technology permits instructors to develop individualized learning programs for their students. Students can progress at their own pace and students can learn to manage their own learning process. Audiovisual tools can be used to monitor student-patient interactions. Supervisors can monitor the work of a larger number of students with these devices. These devices also permit students to reexamine and to judge their own performance. Administrations should not view educational technology as a way to reduce costs. Costs will not decline and may, at least initially, increase. Administrators should purchase equipment to fit the needs of the faculty and the students instead of expecting the faculty to develop programs suited to particular types of equipment. The faculty should be provided with assistance to learn how to operate the new equipment.^ieng