Continuity conditions and torsion angles from ssNMR orientational restraints.

The backbone torsion angle pair (varphi,psi) at each amino acid of a polypeptide is a descriptor of its conformation. One can use chemical shift and dipolar coupling data from solid-state NMR PISEMA experiments to directly calculate the torsion angles for the membrane-spanning portion of a protein. However, degeneracies inherent in the data give rise to multiple potential torsion angles between two adjacent peptide planes (a diplane). The molecular backbone structure can be determined by gluing together the consecutive diplanes, as in the PIPATH algorithm [T. Asbury, J.R. Quine, S. Achuthan, J. Hu, M.S. Chapman, T.A. Cross, R. Bertram, PIPATH: an optimized alogrithm for generating alpha-helical structures from PISEMA data, J. Magn. Reson. 183 (2006) 87-95.]. The multiplicities in torsion angles translate to multiplicities in diplane orientations. In this paper, we show that adjacent diplanes can be glued together to form a permissible structure only if they satisfy continuity conditions, described quantitatively here. These restrict the number of potential torsion angle pairs. We rewrite the torsion angle formulas from [J.R. Quine, M.T. Brenneman, T.A. Cross, Protein structural analysis from solid-state NMR-drived orientational constraints, Biophys. J. 72 (1997) 2342-2348.] so that they automatically satisfy the continuity conditions. The reformulated torsion angle formulas have been applied recently in the PIPATH algorithm [T. Asbury, J.R. Quine, S. Achuthan, J. Hu, M.S. Chapman, T.A. Cross, R. Bertram, PIPATH: an optimized alogrithm for generating alpha-helical structures from PISEMA data, J. Magn. Reson. 183 (2006) 87-95.] and will be helpful in other applications in which diplane gluing is used to construct a protein backbone model.

PIPATH: an optimized algorithm for generating alpha-helical structures from PISEMA data.

An optimized algorithm for finding structures and assignments of solid-state NMR PISEMA data obtained from alpha-helical membrane proteins is presented. The description of this algorithm, PIPATH, is followed by an analysis of its performance on simulated PISEMA data derived from synthetic and experimental structures. pipath transforms the assignment problem into a path-finding problem for a directed graph, and then uses techniques of graph theory to efficiently find candidate assignments from a very large set of possibilities.

Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR.

The solid-state NMR experiment PISEMA, is a technique for determining structures of proteins, especially membrane proteins, from oriented samples. One method for determining the structure is to find orientations of local molecular frames (peptide planes) with respect to the unit magnetic field direction, B0. This is done using equations that compute the coordinates of this vector in the frames. This requires an analysis of the PISEMA function and its degeneracies. As a measure of the sensitivity of peptide plane orientations to the data, we use these equations to derive a formula for the intensity function in the powder pattern. With this function and other measures, we investigate the effect of small changes in peptide plane orientations depending on the location of the resonances in the powder pattern spectrum. This gives us an indication of the change in lineshape due to mosaic spread and a way to interpret these in terms of an orientational error bar.

A condensed history of ophthalmology in Cincinnati (1827-1999).

The history of ophthalmology in Cincinnati dates back to 1827, when Dr. Daniel Drake founded the Eye Institute of Cincinnati. Since that time, many other individuals have influenced the course of ophthalmology in the city and region. Included among these were Elkanah Williams, first chairman of the Department of Ophthalmology at Miami Medical College of Ohio (the forerunner of the University of Cincinnati), William Seeley, Robert Sattler, Christian Holmes, Derrick T. Vail and his illustrious son Derrick T. Vail, Jr., Clarence King, Karl Ascher, Donald Lyle, and Mary Knight Asbury. The author presents brief biographical summaries and interesting anecdotes about each of these individuals and several others of importance to Cincinnati ophthalmology.

System of notation for photocoagulation in the presumed ocular histoplasmosis syndrome.

Using a notation system for evaluation of photocoagulatin of the choroidal neovascular membrane (CNVM) in presumed ocular histoplasmosis syndrome (POHS) demonstrated several advantages, which are: (1) a projector system which allowed excellent magnification of the CNVM and its distance from the foveal avascular zone (FAZ); (2) direct study of fluorescein angiographic negatives; (3) good comparison of pretreatment of posttreatment lesions in relation to FAZ; (4) a precise measurement of the surface area of each CNVM and its distance from the FAZ; and (5) an accurate and rapid way of recording and comparing data. This notation system appears valuable as a means of standardizing the examination and photographic findings from multiple institutions. Results of photocoagulatin of the CNVM are presented. Photocoagulatin of the entire CNVM appeared more effective than partial photocoagulatin of the CNVM.

Cystic retinoblastoma.

A grossly cystic retinoblastoma, presumably a form of the diffuse infiltrating type, mimicked uveitis in an 81/2-year-old boy. A review of 44 cases indicated that grossly (clinically) detectably cysts are rare in this neoplasm, although microcysts are relatively common. Lesions of this nature, especially if presenting with a history of trauma, as in our patient, may lead the ophthalmologist to diagnose uveitis. The diagnosis of retinoblastoma may thus be unduly delayed.