The fracture lines associated with posterior malleolar fractures appear to be highly variable. A large fragment extending to the medial malleolus existed in almost 20% of the posterior malleolar fractures in the current study, and some fragments involved almost the entire medial malleolus. Because of the great variation in fracture configurations, preoperative use of computed tomography may be justified. The information obtained from this study will be helpful for conducting basic research of this condition and for determining appropriate surgical approaches.

SUMMARY Macrolide antibiotics are a class of valuable anti-infective agents that include a macrolactone ring, at least one appended sugar unit, and in most cases, additional functionalization in the form of hydroxyl and/or epoxide groups. There is a significant body of work to understand assembly of the polyketide derived aglycone for this class of compounds, particularly for erythromycin and pikromycin that are generated through the action of a modular polyketide synthases. In addition, the mode of assembly of deoxysugars and aminosugars as well as their transfer to the aglycone has been reported over the past decade. However, much less information exists for the final tailoring reactions, typically mediated by P450 enzymes that are capable of regio- and stereospecific oxidations to add hydroxyl or epoxide functionality. Herein, we have characterized in vitro two P450 enzymes from the mycinamicin biosynthetic gene cluster of Micromonospora griseorubida. Cloning, overexpression and purification of MycCI revealed its selectivity for C21 methyl group hydroxylation. The natural substrate for this P450 enzyme is mycinamicin VIII, the earliest macrolide form in the post-PKS tailoring pathway appended with desosamine at C5 OH. Moreover, we found the optimal activity of MycCI is dependent on the native ferredoxin MycCII. The second and third oxidation reactions including hydroxylation and epoxidation respectively are mediated by MycG with mycinamicin IV as initial substrate. This reaction requires prior dimethylation of the second deoxysugar residue (e.g., 6-deoxyallose to mycinose) for effective conversion by the dual function MycG P450, the first natural product biosynthetic monooxygenase characterized with an ability to catalyze both hydroxylation and epoxidation steps.

Background: A hierarchy of catalytic steps characterizes multifunctional cytochrome P450 enzymes. Results: In the post-polyketide oxidative tailoring of mycinamicins by MycG, the two methoxy groups of mycinose are sensors that mediate initial recognition and discriminate between closely related molecules. Conclusion: Bulky and conformationally restrained macrolide substrates advance to the catalytically productive mode through multiple steps. Significance: Protein engineering facilitating substrate progression may enhance catalysis.

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Changes in hydrogen environments in porous silicon prepared from a p-type silicon wafer with thermal annealing were studied to make an exact assignment of the infrared absorption spectrum and to clarify the fine structures of hydrogen in porous silicon. Annealing makes it possible to desorb the SiH3 and Sill2 states from porous silicon. The results, with the help of the vibrational analysis by molecular orbital calculations, revealed the following. First, an absorption band at 2100 cm' is composed of seven fine structures and their assignment is clarified. Second, the wagging mode of SiH., contributes an absorption band at 667 cm', and finally it is confirmed that the strongest absorption band at 626 cm