Interaction of shikimic acid with shikimate kinase (Retracted Article. See vol 334, pg 967, 2005)

The crystal structure of shikimate kinase from Mycobacterium tuberculosis (MtSK) complexed with MgADP and shikimic acid (shikimate) has been determined at 2.3 Angstrom resolution, clearly revealing the amino acid residues involved in shikimate binding. In MtSK, the Glu61 strictly conserved in SK forms a hydrogen bond and salt-bridge with Arg58 and assists in positioning the guanidinium group of Arg58 for shikimate binding. The carboxyl group of shikimate interacts with Arg58, Gly81, and Arg136, and hydroxyl groups with Asp34 and Gly80. The crystal structure of MtSK-MgADP-shikimate will provide crucial information for elucidation of the mechanism of SK-catalyzed reaction and for the development of a new generation of drugs against tuberculosis. (C) 2004 Elsevier B.V. All rights reserved.

External apical root resorption in retracted incisors

AIM: To evaluate the occurrence of external apical root resorption (EARR) in the incisors after anterior retraction in corrective orthodontic treatment with first premolar extractions and whether it was related with the type of root apex movement and its inclination. METHOD: The maxillary and mandibular incisors of 22 patients (12 to 25 years of age; 9 males and 13 females) were treated with fixed appliances and premolar extraction. EARR was defined as the difference in root length before and after incisal retraction on periapical radiographs. Distortion of radiographic images and changes due to incisal tipping were controlled for. Pre- and post-incisal retraction lateral cephalometric radiographs established the relationship between EARR and the tipping of the incisors, along with the vertical, horizontal, and total movement of the root apex. RESULTS: There was significant EARR (1.51 to 2.37 mm) during incisor retraction, but this was not related to the movement or the tipping of the root apex of almost all teeth. It was observed that after the retraction stage, EARR occurred in all evaluated incisors, but it was more significant (P < .05) in the mandibular right lateral incisor. CONCLUSION: The EARR that did occur was unrelated to movement or tipping of the root apex, except for the vertical root apex movement of the mandibular left central incisor and the inclination of the maxillary right lateral incisor.