The proton affinity of proline analogs, L-azetidine-2-carboxylic acid (Aze), L-proline (Pro), and L-pipecolic acid (Pip), have been measured using the Armentrout modification of the extended kinetic method in a quadrupole ion trap instrument. Experimental values of 223.0 Ϯ 1.5, 224.9 Ϯ 1.6, and 225.6 Ϯ 1.6 kcal/mol have been determined for the 298K proton affinities of Aze, Pro, and Pip respectively. High level theoretical calculations using both MP2 and B3LYP methods at a variety of basis sets were carried out in order to give theoretical predictions for the 298 K proton affinity and gas phase basicity of all three analogs. Recommended values for the gas phase basicity and proton affinity for proline based on our work and other recent determinations are 216 Ϯ 2 and 224 Ϯ 2 kcal/mol. (J Am Soc Mass Spectrom 2002, 13, 72-81)
Tibial fractures of the diaphysis are more frequently associated with development of compartment syndrome than proximal or distal tibial fractures. More specifically, young patients with diaphyseal fractures are at risk for developing this complication and warrant increased vigilance and suspicion for compartment syndrome. A prospective study with sufficient power is needed to further identify risk factors associated with compartment syndrome in tibial fractures.
In this model, immediate postoperative passive motion was found to be detrimental to passive shoulder mechanics. We speculate that passive motion results in increased scar formation in the subacromial space, thereby resulting in decreased range of motion and increased joint stiffness. Passive motion had no effect on collagen organization or tendon mechanical properties measured six weeks after surgery.
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