The study of a single well-chosen substance, here aspartate transcarb amylase, can provide an excellent basis for a laboratory course. The student is introduced to a variety of scientific ideas and to many experi mental and interpretive techniques. This enzyme is readily available, is relatively stable, has an extensive literature, and its behavior has many facets: substrate inhibition, a large change in structure upon homo tropic activation by substrates, allosteric stimulation by ATP, allosteric inhibition by CTP synergistic with VTP, positive cooperativity for sub strates, negative cooperativity for CTP binding, and dissociation and reassembly of subunits Cand R2 from the holoenzyme CI\5. In addition 3 6 to the known biochemical aspects of these properties, the results ob tained here can be interpreted in the light of the high-resolution X-ray diffraction structures of the T and R forms, the low-angle X-ray scattering results, and the large number of mutants now available by recombinant DNA methods. Future development of this course could also involve part of these methods, as well as the carefully chosen experiments described here. This approach resembles research more than the approaches one usually finds in biochemical laboratory courses. A consistent develop ment of ideas about a single enzyme, which shows so many facets in its behavior, is sure to hold the interest of the student. Moreover, one explores a depth, and reasons to move forward, that are an essential part of research."

The use of phosphine derivatives has historically induced the tremendous development of catalysis (both non-asymmetric and asymmetric). Although the chemistry of amines is more documented, the use of nitrogen-containing ligands only appeared recently. Nevertheless, during the last ten years, the results describing chiral diamine preparations and their uses in asymmetric catalysis and synthesis are increasing faster than their phosphorus counterparts. The reader will find in this volume the most recent methods for the synthesis of chiral diamines as well as their applications in asymmetric catalysis of CC bond formation. Particular attention will be given to spartein and derivatives of such diamines. Recently, the particular properties and the chemistry of amines allowed to obtain catalysts easy to separate and recycle and new types of ligands such as diaminocarbenes, ureas and thioureas. Finally, the complexing properties of some diamines allowed the formation of complexes with chirality "at the metal " which is of major theoretical interest and presents numerous potential applications.

The use of phosphine derivatives has historically induced the tremendous development of catalysis (both non-asymmetric and asymmetric). Although the chemistry of amines is more documented, the use of nitrogen-containing ligands only appeared recently. Nevertheless, during the last ten years, the results describing chiral diamine preparations and their uses in asymmetric catalysis and synthesis are increasing faster than their phosphorus counterparts. The reader will find in this volume the most recent methods for the synthesis of chiral diamines as well as their applications in asymmetric catalysis of CC bond formation. Particular attention will be given to spartein and derivatives of such diamines. Recently, the particular properties and the chemistry of amines allowed to obtain catalysts easy to separate and recycle and new types of ligands such as diaminocarbenes, ureas and thioureas. Finally, the complexing properties of some diamines allowed the formation of complexes with chirality "at the metal " which is of major theoretical interest and presents numerous potential applications.

1 Aspartate Transcarbamylase.- 2 Molecular Genetics: Regulation of Aspartate Transcarbamylase Biosynthesis.- 3 Purification of Aspartate Transcarbamylase and Its Subunits.- 4 Structural and Physicochemical Study of Aspartate Transcarbamylase.- 5 Enzymatic Catalysis and Regulation.- 6 Complementary Experiments.- 1. Equations and Units.- 2. Molar Mass and Molecular Mass.- 3. Units of Catalytic Activity.- 4. Units of Radioactivity.- 5. Units of Quantity.- 7. Calculation of Acceleration.- 8. Bacterial Strains.- 9. Solutions and Reagents.- 9.1. 0.8-M Tris-Acetate Buffer, pH 8.- 9.2. 0.2-M Acetic Acid.- 9.6. Elution Buffer for Chromatography: 10 x Stock Solution.- 9.7. 100-mM Aspartate, pH 8.- 9.8. 10-mM Carbamylaspartate, pH 8.- 9.9. 1-M Phosphate Buffer, pH 7.2.- 9.10. Buffer for Dilution of E.- 9.11. Buffer for Dilution of C.- 9.12. Buffer for Dilution of R and Recombination.- 9.13. 200-mM Cacodylate Buffer, pH 6, 7, and 7.5.- 9.14. 200-mM Tris-Acetate Buffer, pH 8 and 9.- 9.15. 200-mM Glycine Buffer, pH 10.- 9.16. 400-mM Succinate, pH 7.- 9.17. Reaction Medium: 20-mM CAP-200-mM Tris-Acetate, pH 8.- 10. Preparation of Standard Protein Mixtures for Column Calibration.- Answers To Questions.- References.