The mechanism of O 2 -activation and oxygenation of CH 4 to CH 3 OH by soluble methane monooxygenase hydroxylase (sM-MOH) is of great current interest. 2 The diiron(II) center of sMMOH binds dioxygen to form a µ-peroxodiiron(III) intermediate P 3 via two transient intermediates O and P*, 4 and P is converted to an active intermediate Q. 5 P and Q have been studied spectroscopically 3-5 and followed by model studies. 6,7 A radicalrebound mechanism of the C-H oxygenation by Q has been proposed on the basis of product analysis and the kinetic isotope effect. 8 These results have been supported by DFT calculations. 9

In this study, the authors evaluated the distribution of low-abundance beauty ingredients in human skin tissues. The distribution of collagen tripeptide, a beauty ingredient, in the human skin was evaluated by applying multivariate curve resolution (MCR) to the time-of-flight secondary ion mass spectrometry mapping data, including reference information. The intensity of the secondary ion peaks was increased by the accumulation of secondary ion intensity in the depth direction obtained by argon cluster sputtering. Consequently, the collagen tripeptide distribution in the skin was evaluated by separating it from collagen peptide, although the conventional analysis was difficult because of the dilution of the collagen tripeptide in the skin. Additionally, the distribution of the collagen tripeptide in the skin may be determined with an autoencoder. In this study, the distribution of small amounts of beauty ingredients (the collagen tripeptide) in the skin was observed by integrating the secondary ion intensity in the depth direction with Ar cluster sputtering and applying MCR or autoencoder.

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