Toward a quantum-mechanical description of metal-assisted phosphoryl transfer in pyrophosphatase

The wealth of kinetic and structural information makes inorganic pyrophosphatases (PPases) a good model system to study the details of enzymatic phosphoryl transfer. The enzyme accelerates metal-complexed phosphoryl transfer 1010-fold: but how? Our structures of the yeast PPase product complex at 1.15 Å and fluoride-inhibited complex at 1.9 Å visualize the active site in three different states: substrate-bound, immediate product bound, and relaxed product bound. These span the steps around chemical catalysis and provide strong evidence that a water molecule (Onu) directly attacks PPi with a pKa vastly lowered by coordination to two metal ions and D117. They also suggest that a low-barrier hydrogen bond (LBHB) forms between D117 and Onu, in part because of steric crowding by W100 and N116. Direct visualization of the double bonds on the phosphates appears possible. The flexible side chains at the top of the active site absorb the motion involved in the reaction, which may help accelerate catalysis. Relaxation of the product allows a new nucleophile to be generated and creates symmetry in the elementary catalytic steps on the enzyme. We are thus moving closer to understanding phosphoryl transfer in PPases at the quantum mechanical level. Ultra-high resolution structures can thus tease out overlapping complexes and so are as relevant to discussion of enzyme mechanism as structures produced by time-resolved crystallography.

Washington, D.C., 1815 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Territory of Columbia, drawn by And'w Ellicott ; engraved by P.A.F. Tardieu, Paris, 1815. It was published in 1815. Scale [ca. 1:63,360]. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Maryland State Plane Coordinate System Meters NAD83 (Fipszone 1900). All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as roads, drainage, district boundaries, government buildings, parks and more. Relief is shown by hachures. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.

Georges Bank, 1837 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of Georges Shoal & Bank, surveyed by Charles Wilkes, Lieut. Commandant ... [et al.] in U.S. brig Porpoise, schooners Maria & Hadassah, by order of the Hon. Mahlon Dickerson, Secretary of the Navy ; drawn by J. Alden and W. May ; engraved by S. Stiles, Sherman & Smith, New-York. It was published under direction of the Navy Commissioners in 1837. Scale [ca. 1:62,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows hydrographic features such as as banks, shoals, bottom soil types, tide information, and more. Relief shown by soundings. Includes notes. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

The Journal of philosophy.

Vols. 31- include "A Bibliography of philosophy," 1933-

The works of Thomas Middleton, now first collected,

Imperfect: frontpiece wanting. cf. v.1, p. 4211.

Report of the Commissioners appointed to inquire into the several matters relating to coal in the United Kingdom.

Duke of Argyll, chairman.

Practical discourses on the leading truths of the gospel. ...

Mode of access: Internet.

The collected works of Henrik Ibsen.

Title vignette.

The Tasmanian law reports : cases determined in the Supreme Court of Tasmania.

Earlier reports in: Reports of cases determined in the Supreme Court of Tasmania / Herbert Nicholls and W. J. T. Stops.

The collected works of Henrik Ibsen.

"Entirely revised and edited by William Archer."

Liber fratrum cruciferorum Leodiensium : [1617].

Comprises 54 organ compositions, chiefly by anonymous composers, but including a few works by A. Gabrielli, P. Philipps, J. Swelinck, C. Merlu, and W. Brwon, transcribed from ms. 888 of University Library. Liège.

The vegetables of New York ...

Vol. I, pt. I- issued as a report of the New York Agricultural Experiment Station at Geneva for the year ending June 30, 1928;June 30, 1931; June 30, 1934

Records relating to the early history of Boston ...

Editors: 1876-1890, W. H. Whitmore and W. S. Appleton, record commissioners; 1893-1896, W. H. Whitmore, city registrar; 1894, W. S. Appleton; 1898, E. W. McGlenen; 1900-1909, E. W. McGlenen, city registrar; 1903 (v. 32) W. H. Whitmore, W. K. Watkins, and E. W. McGlenen.

Alaska /

Vol. XIV- are of Smithsonian issue.

Udder diseases of dairy cows /

"Revision of former editions by H. Bunyea and W.T. Miller."