TOPICAL HYDROCARBONS 9 ACKNOWLEDGMENTS This work was supported by NIH grant AR 19098 and the Medical Research Service, United States Veterans Administration. Annette Grimmert and Hans-Juergen Duesing provided skillful experimental assistance, and Angie Kho-Kim capably prepared the manuscript. REFERENCES (1) J. T. Bortz, P. W. Wertz, and D. T. Downing, The origin of alkanes found in human skin surface lipids, J. Invest. Dermatol. 93, 723-727 (1989). (2) P. M. Elias, M. L. Williams, and S. J. Rehfled, N-alkanes in the skin: Function or fancy? Arch. Dermatol., 126, 868-870 (1990). (3) D. E. Lester, Normal paraffins in living matter: Occurrence, metabolism, and pathology, Progr. Food N•tr. Sci., 3, 1-66 (1979). (4) M. K. Baldwin, P. H. Berry, D. J. Esdaile, S. L. Linnette, J. G. Martin, G. C. Peristianis, R. A. Priston, B. J. Simpson, and J. D. Smith, Feeding studies in rats with mineral hydrocarbon food grade white oils, Toxico/. Path., 20, 426-435 (1992). (5) CONCAWE: a 90-day feeding study in the rat with six different white mineral oils, N15(H), N70(H), N70(A), P15(H), N10(A), and P100(H), three different mineral waxes (a low melting point wax, a high melting point wax and a high sulfur wax) and coconut oil. BIBRA Toxicology Interna- tional (Sponsor: CONCAWE) (1992). (6) R. G. Ghadially, L. Halkier-Sorensen, and P. M. Elias, Effects of petrolatum on stratum corneum structure and function. J. Amer. Acad. Dermatol., 26, 387-396 (1992). (7) M. Mao-Qiang, B. E. Brown, S. Wu, K. R. Feingold, and P.M. Elias, Exogenous non-physiological vs. physiological lipids: Divergent mechanisms for correction of permeability barrier dysfunction, Arch. Dermato/. (in press). (8) P. M. Elias and B. E. Brown, The mammalian cutaneous permeability barrier: Defective barrier function in essential fatty acid deficiency correlates with abnormal intercellular lipid deposition, Lab. Invest., 39, 574-583 (1978). (9) J. J. Yang, T. A. Roy, W. Nell, A. J. Krueger, and C. R. Mackerer, Percutaneous and oral ab- sorption of chlorinated paraffins in the rat, Toxiol. Ind. Health, 3, 405-411 (1987).

jo Soc. Cosmet. Chem., 46, 11-28 (January/February 1995) An investigation into the action of transglutaminase on human hair JOHN M. GARDNER, PAUL E. SWANSON, and B. VIRGINIA TORRES-LOPEZ, Central Research and Development, The Dow Chemical Company, Midland, MI 48674. Received August 25, 1994. Synopsis Enzymes may offer an attractive alternative to traditional chemical approaches in permanent modification or conditioning of hair. The goal of this research was to determine if glutamine residues on the surface of human hair were recognized as a substrate for guinea pig liver transglutaminase. Optical and isotope assays were developed and used to monitor specific activity. Traditional amine donor substrates were used in conjunction with control treatments and rinsing procedures to seek evidence of covalent modification. No conclusive evidence was found for biocatalytic activity of transglutaminase with virgin hair. An estimate based on literature data from a nonsoluble glutamine substrate indicated that the detection limit of the isotope assay was approximately two orders of magnitude more sensitive than required to verify reaction. The results appear to contradict previous work in which it was thought that transglutaminase cross-links endogenous glutamine and lysine residues on the hair surface. Reaction with hair in the present work may have been limited by the presence of the proposed fatty acid layer (F-layer) on the hair surface. Future work with transglutaminase might be directed toward applications that do not require hair to donate endogenous residues to the reaction. INTRODUCTION The two primary morphological regions of human hair are the cuticle and the cortex. The cuticle is an external, layered network of flattened cells that protects the cortex from damage (1,2). Shampooing, wet combing, dry combing, toweling, styling, and weath- ering are all known to contribute to cuticle degradation (3-5). Wet combing is believed to be the most damaging hair care operation performed on a daily basis (6,7). Cell fragments are exfoliated during combing, gradually exposing cortex and creating an area subject to fibrillation or fracture. Functional polymers can be formulated into products to reduce wet combing damage by improving lubricity (8-10). These materials are deposited during shampooing or conditioning and have been designed to be substantive but not accumulate from repeated use. Some attempts have been made to "permanently condition" hair using reactive materials such as certain protein hydrolyzates and their derivatives (11,12). These are not in wide use, however, because the cystine in hair 11