971 resultados para siglo 21


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Two enzyme mechanisms were examined: the 21-dehydroxylation of corticosteroids by the anaerobe Eubacterium l en tum, and the hydroxylation of steroids by fungal cytochrome P450. Deuterium labelling techniques were used to study the enzymic dehydroxylation. Corticosteroids doubly labelled (2H) at the C-21 position were incubated with a culture of Eubacterium lentum. It was found that t he enzymic dehydroxylation proceeded with the loss of one 2H f rom C-21 per molecule of substrate. The kinetic isotope ef fect f or the reaction was found to be k~kD = 2. 28. These results suggest that enzyme/substr ate binding in this case may proceed via t he enol form of the substrate. Also , it appears that this binding is, at least in part, the rate determining step of t he reaction. The hydroxylation of steroids by fungal cytochrome P450 was examined by means of a product study. Steroids with a double bond at the A8 (9), ~( lO ), or ~ (ll) position were synthesized. These steroids were then incubated with fungal strains known to use a cytochrome P450 monooxygenase to hydroxylate at positions allylic to these doubl e bonds. The products formed in these incubations indicated that the double bonds had migrated during allylic hydroxylat ion. This suggests that a carbon centred radical or ion may be an intermediate i n the cytochrome P450 cat alytic cycle.

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Two enzyme mechanisms were investigated: the 21-dehydroxylation of corticosteroids by Eubacterium lentum and the dehalogenation of 4-chlorobenzoic acid by Pseudomonas sp. CBS 3. , Chemical and enzymic methods of reduction of 21-oxo steroids were used to generate C-21-d1 compounds of tetrahydrodeoxycorticosterone, with both predominant stereochemistries. It was found that during the dehydroxylation the pro-S hydrogen at the C-21 position was lost preferentially. This suggests that the enzyme removes the pro-S hydrogen during binding to the active site as the ene-diol. To study the hydrolytic replacement of chlorine by hydroxyl , p-chlorobenzoic acid-d4 was prepared and sent to Germany for an ~ncubation with an enzyme preparation of 4-Chlorobenzo~te Dehalogenase. Results suggests the possible loss of deuterium during the conversion of p-chlorobenzoate to p-hydroxybenzoate, from all four ring positions. Many methods of preparing the control compound p-hydroxybenzoic acid-d4 were investigated.

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Survey map of the Second Welland Canal created by the Welland Canal Company showing south Merritton along the boundary between the Grantham and Thorold Townships. Identified structures associated with the Canal include Locks 19, 20, 21, and 22, Lock Tenders House, and the towing path. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks are also identified and include streets and roads (ex. Pine Street and Macadamized Road), J. Brown Cement Mill, W. B. Hendershot Saw Mill, W. Parnall Spoke and Sash Factory, W. Beatty Saw Mill, W. Beatty Tannery, a number of structures (possibly houses) belonging to: Mrs. Aikins, J. Battle, and E. Keefer, and a foundry, smithy, and machine shop (all of which possible belonged to J. Dobbie). Properties and property owners of note are: Concession 10 Lots 9 and 10, W. C. Loan Company, P.H. Ball, and J. Keefer. Two small properties belonging to W. B. Hendershot and W. Beatty exist and are outlined in red. A half acre property reserved for a lock lot exists and is outlined in blue. An additional property reserved for a quarry is also identified, but not outlined.

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Survey map of the Second Welland Canal created by the Welland Canal Company showing the areas in and around Port Colborne. Identified structures associated with the Canal include Lighthouse, Pier Light, Old Lock House, Collector's Office, Harbour Master's House, Canal Boundary, Back Ditch, Reserved Back Ditch, Basin, Light-Keeper's House and Ferry Recess. The surveyors' measurements and notes can be seen in red and black ink and pencil. Local area landmarks and businesses are also identified and include Gordon's Woodyard, Welland Rail Road, Welland Railway Elevator and Proposed Elevator, W.R.R. Flour Shed, Roman Catholic Church, School House, Sandhills, Lake Erie, and the High Water Mark. Streets running parallel to Canal include King St., West St., East St., Queen St., Hamilton St., and the Road Allowance are labelled. Streets running perpendicular to Canal include Kent St., Victoria St., Adelaide St., SugarLoaf St., George St., Alexandrina St., William St., Fort Erie St., Lake Rd., and New Road to Dutch Settlement are also labelled. Property owners and leasers as well as buildings on lots are also idenitified and noted as follows: Adams estate, J. Towhig, J.C. Kerr, Mrs. Hill, S. Cooke, Mrs. Yocum, W.T. Cooke, P. Wintermute, J. Shickluna, William Cooke, J. McChesney, John Beatty, W. Robertson, John Gordon, T. Armstrong, John Harper, George Keefer, Estate of James Black, Thomas Park, N. Higgins, S. Hopkins, and L.G. Cartier. Map of the Village of Port Colborne. Being Lot No. 27 and part of Lot No. 28 in the 1st Con. Township of HUMBERSTONE. Scale 2 Chs. per Inch. land shaded in RED Owned by DEPT. Do. Do. BLUE Sold to the COUNTY of WELLAND