JOURNAL OF COSMETIC SCIENCE 306 for the cumulative protein values (Table I). High inter-individual variability was found for protein levels from the torso (Table I). For tape 1, the jaw site had lower citrulline than the back, torso and calf, and lower serine than the calf. For the cumulative levels, the total FAA (log10 pmoles/μg protein) was lower for the jaw than for all other sites as fol- lows: 3.12 ± 0.1, jaw 3.41 ± 0.1 back 3.26 ± 0.1 torso 3.51 ± 0.1 calf (F = 2.9, p = 0.05). Citrulline was signifi cantly lower for the jaw than for all other sites, and arginine was signifi cantly lower for the calf (Figure 2). Cumulative citrulline (normalized to cumula- tive protein) for tape 1, sum 1+3, sum 1+3+5, sum 1+3+5+10, and the sum of all tapes is shown versus the respective cumulative protein amounts in Figure 3. Similar trends were observed for total FAA and individual amino acids. With SC depth, FAA fi rst in- creased and then leveled off for the back and torso. The increase continued throughout the sampled region for the jaw. In contrast, the calf site remained relatively constant. MAT was signifi cantly lower for the jaw than for either the torso or back ( p 0.05, Table I), but the jaw and calf were not different. There were no signifi cant correlations between FAAs and MAT values for either study, as indicated in Figure 3. At the outermost SC, the calf site had greater FAA than the forearm for comparable pro- tein removed. FAAs were lowest for the jaw compared to the torso, back, and calf. The outcomes do not support the study hypothesis, i.e., body site variations in skin hydration (MAT) could not be attributed to differences in FAA levels. One important limitation in this study is that we examined only about 40% of the components of NMF (14). We did Figure 2. Cumulative FAA by cumulative protein is shown as log10 pmoles of amino acid normalized to μg protein. Citrulline was signifi cantly lower for the jaw than for all other sites, and arginine was signifi cantly lower for the calf (*p 0.05). Table I Study 2 Protein Levels and Rate of Moisture Accumulation (MAT) for Back, Torso, Calf, and Jaw Sites Site Rate of moisture accumulation (MAT) (cru/sec) Protein tape 1 (μg/ml) Protein: Cumulative tapes 1,3,5,10,15 (μg/ml) Back 2.5 ± 1.2 8.5 ± 2.3 49.2 ± 22.3 Torso 3.4 ± 2.0 22.3 ± 15.7 81.4 ± 23.0 Calf 1.6 ± 0.9 18.8 ± 3.9** 107.2 ± 22.0 Jaw 0.9 ± 0.7* 14.1 ± 3.1 66.2 ± 21.9 * Signifi cant difference from back and torso (F = 5.06, p = 0.01). ** Calf and torso sites different by ANOVA on ranks, post hoc Dunn’s versus torso contol ( p 0.05).

REGIONAL VARIATION IN FAAs IN STRATUM CORNEUM 307 not measure PCA, urocanic acid, lactates, urea, sugars, or ions. Other NMF components such as lactates are positively correlated to SC hydration (24) and omission of lactate lev- els could account in part for the lack of correlation between putative NMF and MAT. Another potential source of protein that could account for higher citrulline levels in the samples is keratin 1. Peptidylarginine deiminase isoform 1 (PAD1) is responsible for deimination of K1 in the SC (25). Keratin 1 is expected to be present at higher levels in dry Figure 3. MAT was signifi cantly lower for the jaw than for either the torso or back, but the jaw and calf were not different. The total FAA levels were not correlated with skin hydration, measured as the rate of moisture accumulation (MAT), for the body sites as indicated here for Study 2. Figure 4. Cumulative citrulline (normalized to cumulative protein) for tape 1, sum 1+3, sum 1+3+5, sum 1+3+5+10, and the sum of all tapes is shown versus the respective cumulative protein amounts for the four sites. Similar trends were observed for total FAA and individual amino acids. With SC depth, FAA fi rst increased and then leveled off for the back and torso. The increase continued for the jaw but remained rela- tively constant for the calf.