Showing papers by "Robert McKenna published in 2003"

The refined atomic structure of carbonic anhydrase II at 1.05 A resolution: implications of chemical rescue of proton transfer.

Abstract: Using synchrotron radiation and a CCD detector, X-ray data have been collected at 100 K for the His64Ala mutant of human carbonic anhydrase II complexed with 4-methylimidazole (4-MI) to a maximal 1.05 A resolution, allowing full anisotropic least-squares refinement. The refined model has a conventional R factor of 15.7% for all reflections. The Cα coordinates of the model presented here have an r.m.s. deviation of 0.10 A relative to the previously determined structure at 1.6 A resolution. Several amino-acid residues (six of the 255 observed) have been identified with multiple rotamer side-chain conformations. C, N and O atoms can be differentiated with selective electron-density map contouring. The estimated standard deviations for all main-chain non-H atom bond lengths and angles are 0.013 and 0.030 A, respectively, based on unrestrained full-matrix least-squares refinement. This structure gives detailed information about the tetrahedrally arranged zinc ion coordinated by three histidine N atoms (His94 N∊2, His96 N∊2 and His119 Nδ1) and a water/hydroxide, the multiple binding sites of the proton chemical rescue molecule 4-MI and the solvent networks linking the zinc-bound water/hydroxide and 4-MI molecules. This structure presents the highest resolution structure of a carbonic anhydrase isozyme so far determined and adds to the understanding of proton-transfer processes.

Thoracoscopic sympathectomy: the U.S. experience.

Abstract: Objective: 48 patients underwent TSSYM. Charts of patients undergoing thoracoscopy were reviewed to assess the safety and efficacy of thoracoscopic sympathectomy (TSSYM). Design: A retrospective review was undertaken at four United States medical centers. Results: TSSYM was performed for reflex sympathetic dystrophy in 27 patients, hyperhydrosis palmaris in 15 patients, and Raynaud's upper extremity ischemia and splanchnic pain in 2 patients each. Anesthesia with one lung ventilation was used. 2.9 ports were used per patient and 0.8 chest tubes were placed per patient. All patients underwent resection of the sympathetic chain, usually with a clip along the bottom of the resected chain. Laser, electro-ablation and electroresection were not used by any of the surgeons in his series. The mean length of hospital stay was 1.8 days. Conclusions: TSSYM is a safe and effective technique for treatment of a variety of thoracic disorders. Copyright © 1998 Taylor and Francis Ltd.

Malignant monotypic epithelioid angiomyolipoma of the retroperitoneum.

Abstract: Monotypic epithelioid angiomyolipoma (EAML) is an uncommon variant of angiomyolipoma, occurring primarily in the kidney and characterized by a predominance of HMB-45-positive epithelioid cells. EAML is generally considered a benign neoplasm, though rare cases exhibiting malignant behavior have been reported. We describe a patient with a primary retroperitoneal monotypic EAML, composed exclusively of atypical epithelioid cells, which metastasized to the liver and the mediastinum. This case represents, to our knowledge, the first description of metastatic disease occurring in an EAML of this particular site

Molecular modeling of the rabbit colonic (HKα2a) H+, K+ ATPase

Abstract: A model of the HKα2a subunit of the rabbit colonic H+, K+ ATPase has been generated using the crystal structure of the Ca+2 ATPase as a template. A pairwise sequence alignment of the deduced primary sequences of the two proteins demonstrated that they share 29% amino acid sequence identity and 47% similarity. Using O (version 7) the model of HKα2a was constructed by interactively mutating, deleting, and inserting the amino acids that differed between the pairwise sequence alignment of the Ca+2 ATPase and HKα2a. Insertions and deletions in the HKα2a sequence occur in apparent extra-membraneous loop regions. The HKα2a model was energy minimized and globally refined to a level comparable to that of the Ca+2 ATPase structure using CNS. The charge distribution over the surface of HKα2a was evaluated in GRASP and possible secondary structure elements of HKα2a were visualized in BOBSCRIPT. Conservation and placement of residues that may be involved in ouabain binding by the H+, K+ ATPase were considered and a putative location for the β subunit was postulated within the structure.