Spectroscopic properties of the hydroxylase of methane monooxygenase

The hydroxylase component of methane monooxygenase (EC 1.14.13.25), which catalyzes the oxidation of methane to methanol, has been studied by visible, electron spin resonance and X-ray spectroscopies. The enzyme appears to possess a mu-oxo- or mu-hydroxo-bridged binuclear iron site, with no sulfur ligands to the cluster. Each Fe has 4-6 oxygen (or nitrogen) ligands, at an average distance of 1.92 +/- 0.03 A. The Fe-Fe distance is 3.05 +/- 0.05 A. Essentially all of the irons are in the Fe3+ state as the enzyme is prepared, but reduction with N-methylphenazonium methosulfate generates ESR-detectable states that appear to emanate from mixed-valence binuclear sites. One of these, with gav near 1.85, displays typical Curie law microwave saturation behavior, but the other, gav near 1.73, has a very potent method of spin-relaxation. Together they account for approximately 0.6 spins per molecule.     

Healing of specialized tongue epithelium following cryosurgery

Although cryosurgery of oral tissues has been extensively studied, there is little information concerning healing and repapillation of the dorsum of the tongue. Using light, transmission, and scanning electron microscopy, an investigation of the sequence of reformation of papillae was carried out in the hamster. Four days postoperatively there was mitotic activity and cell migration at the periphery of the wound. At the edge of the ulcer there were partially damaged tongue papillae with evidence of recovery. Damaged papillae had regenerated completely within 2 weeks. In the central ulcerated area, epithelium healed by migration and, within this new epithelium, tongue papillae commenced to form by a process similar to that seen in the fetal tongue. Repapillation of the central area of the lesion was complete 6 weeks after operation, leaving minimal scarring. The details of these processes are described.