- Email: [email protected]
A novel fixed-bed raney catalyst
N19
106 Fulton Street, New York, NY 10038, U.S.A. Abzymea or Catalytic Antibodies Designer Enzymes Workers at Sheffield University, U.K., have written a review on this subject (AS Kang, G.A. Kingsbury, G.M. Blackburn and D.R. Burton, Chem. Britain, 28 (1990) 128), which is comprehensible to catalytic chemists who have no biological training. The tailoring of an antibody ta provide a synthetic mimic of a transition state of a reaction, and so obtaining a new enzyme, has aroused much excitement since it was first achieved three years ago. The procedure is complex. Small molecules do not usually stimulate the formation of antibodies, so the small molecule must be ~ovalently attached to a larger molecule, usually a protein, which is immunogenic, i.e. antibody stimulating, This conjugate is used to immunise mice and, in response to immunisation, B lympho~~es (plasma cells), which are abundant in the spleen secrete antibodies against the added molecule. Isolating a pure strain of antibody is done by a technology for which Milstein and Kohler were awarded the Nobel prize in 1985 and then the different antibodies have to be assessed for catalytic activity (probably only l-10% of the small proportion which bind the reactant will posses catalytic activity). Reactions which have been investigated with abzyme catalysts include ester hydrolysis, amide hydrolysis, intermolecular rearrangements, photochemical reactions, redox reactions and elimination reactions. enhancements The rate achieved are impressive: the abzyme esterases made so far have given enhancements over the uncatalysed rates of ester hydrolysis of almost lo’, close to those of
applied catalysis - Volume 59 No 2 --
natural enzymes with the same substrates.The authors believe that catalytic antibodies are still at an early stage of development and they foresee much further refinement in designing molecules to stimulate better antibodies and in the use of recombinant DNA technology to the antibody binding site. A Novel Fixed-bed Raney Catalyst Workers at W.R. Grace (W.C. Cheng, L.J. Czarnecki and G,J. Pereira, Ind. Eng. Chem. Res., 28(1989)1784) have produced an interesting variation on the familiar Raney nickel catalyst. The Raney alloy powder is extruded with a polymer and a plasticiser, the piasticiser is extracted and the solid dried to form a rigid pellet. Calcination in air at 1173 K replaces the polymer support with a-alumina. This is followed by conventional activation by leaching with sodium hydroxide solution, Catalysts prepared in this way by compounding a mixture of powdered 42% NilAl alloy with 2 wt.-% polyethylene and 20% mineral oil (the plasticiser) and treating as above were more active and selective than nickel/silica, nickel/silica-alumina or conventional granular Raney nickel catalysts in the hydrogenation of toluene to methylcyclohexane. Catalyst Materials as Reference Standards Through a series of round-robin tests conducted by pa~icipat~ng laboratories, the American Standards for Testing Materials (ASTM) Committee D-32 on Catalysts has characterized a variety of catalyst materials using standard test methods (R.A. Haines, ACS Symposium Series, 411 (1989)430). Materials tested include fluidcracking catalysts, zeolites, silicas, alumi-
2 Aprif 7990
106 Fulton Street, New York, NY 10038, U.S.A. Abzymea or Catalytic Antibodies Designer Enzymes Workers at Sheffield University, U.K., have written a review on this subject (AS Kang, G.A. Kingsbury, G.M. Blackburn and D.R. Burton, Chem. Britain, 28 (1990) 128), which is comprehensible to catalytic chemists who have no biological training. The tailoring of an antibody ta provide a synthetic mimic of a transition state of a reaction, and so obtaining a new enzyme, has aroused much excitement since it was first achieved three years ago. The procedure is complex. Small molecules do not usually stimulate the formation of antibodies, so the small molecule must be ~ovalently attached to a larger molecule, usually a protein, which is immunogenic, i.e. antibody stimulating, This conjugate is used to immunise mice and, in response to immunisation, B lympho~~es (plasma cells), which are abundant in the spleen secrete antibodies against the added molecule. Isolating a pure strain of antibody is done by a technology for which Milstein and Kohler were awarded the Nobel prize in 1985 and then the different antibodies have to be assessed for catalytic activity (probably only l-10% of the small proportion which bind the reactant will posses catalytic activity). Reactions which have been investigated with abzyme catalysts include ester hydrolysis, amide hydrolysis, intermolecular rearrangements, photochemical reactions, redox reactions and elimination reactions. enhancements The rate achieved are impressive: the abzyme esterases made so far have given enhancements over the uncatalysed rates of ester hydrolysis of almost lo’, close to those of
applied catalysis - Volume 59 No 2 --
natural enzymes with the same substrates.The authors believe that catalytic antibodies are still at an early stage of development and they foresee much further refinement in designing molecules to stimulate better antibodies and in the use of recombinant DNA technology to the antibody binding site. A Novel Fixed-bed Raney Catalyst Workers at W.R. Grace (W.C. Cheng, L.J. Czarnecki and G,J. Pereira, Ind. Eng. Chem. Res., 28(1989)1784) have produced an interesting variation on the familiar Raney nickel catalyst. The Raney alloy powder is extruded with a polymer and a plasticiser, the piasticiser is extracted and the solid dried to form a rigid pellet. Calcination in air at 1173 K replaces the polymer support with a-alumina. This is followed by conventional activation by leaching with sodium hydroxide solution, Catalysts prepared in this way by compounding a mixture of powdered 42% NilAl alloy with 2 wt.-% polyethylene and 20% mineral oil (the plasticiser) and treating as above were more active and selective than nickel/silica, nickel/silica-alumina or conventional granular Raney nickel catalysts in the hydrogenation of toluene to methylcyclohexane. Catalyst Materials as Reference Standards Through a series of round-robin tests conducted by pa~icipat~ng laboratories, the American Standards for Testing Materials (ASTM) Committee D-32 on Catalysts has characterized a variety of catalyst materials using standard test methods (R.A. Haines, ACS Symposium Series, 411 (1989)430). Materials tested include fluidcracking catalysts, zeolites, silicas, alumi-
2 Aprif 7990