RESUMO
Objective: To construct the three dimensional models of L. chuanxiong caffeic acid-3-O-methyltransferase (LCCOMT) and verify the model using site-directed mutagenesis technology. Methods: The three-dimensional model was constructed by homology modeling using the crystal structure of COMT from Medicago sativa as a temple. Caffeic acid was docked into the optimized model of LCCOMT to predict the active site. The predicted site was mutated using site-directed mutagenesis technology. Then, the activity of mutant enzyme was detected. Results: The molecular docking, which showed there were hydrogen bonds between His268 and 3-OH of caffeic acid, was successful. Two mutant enzymes, H268N and H268Q, lost 94.85% and 95.28% of their activity respectively. Conclusion: The His268 is confirmed as one of the key residues of LCCOMT. It may play a role as a base in the deprotonation reaction of the 3-OH of caffeic acid.
RESUMO
<p><b>OBJECTIVE</b>To investigate the biomechanical effect of anterior screw fixation on the type II fractured odontoid process.</p><p><b>METHODS</b>Twenty fresh human C1-C2 vertebrae specimens were harvested and randomly divided into three groups. The angle of type II fracture line was 0 degree in group I (n=6), 17 degrees in group II (n=8) and 25 degrees in group III (n=6). The fractures were treated by anterior screw fixation. Insertion torque,maximal axial pullout force and stiffness of the bone-screw were tested.</p><p><b>RESULTS</b>There was no significant difference of screw insertion torque and the pull-out strength between each group. The displacement of the odontoid fragment had an association to the angle of the fracture line,the displacement of the small angle was significantly higher than that of the large one (P < 0.5). No significant difference of structure stiffness of the bone-screw was found between each group.</p><p><b>CONCLUSION</b>Anterior screw fixation is feasible for type II odontoid fracture with certain fracture line extends from anteroinferior to posterosuperior.</p>