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• W2027110562 abstract "Changes in the structural proteins and hydration during aging is responsible for altered skin morphologic and mechanical properties manifested as wrinkling, sagging, loss of elasticity, or apparent dryness. To gain insight into the age-related alterations in protein conformation and water structure, we obtained Raman spectra from the sun-protected buttock skin representing chronologic aging and the sun-exposed forearm skin representing combined effects of photoaging and chronologic aging. Ten aged individuals (five men, five women; age range 74–87) and 10 control young individuals (five men, five women; age range 22–29) entered the study. In the photoaged forearm skin the positions of protein-specific amide I, amide III, and CH stretching bands were shifted, suggesting increased protein folding. In contrast, major changes were seen only in the amide I peak in chronologically aged skin. The intensity of the 3250 cm–1 OH stretching band was increased in photoaged skin (but not in chronologically aged skin) indicating an increased water content. R(ν) representation of the low-frequency region of Raman spectra was applied to determine water structure. In the young skin and chronologically aged skin water was mostly present in the bound form. In the photoaged skin, however, an increase in intensity at 180 cm–1 was noted, which reflects an increase in the not-protein bound water (tetrahedron water clusters). In conclusion, it seems that proteins in the photoaged skin are more compact and interact with water to limited degree. Impairment in protein hydration may add to the understanding of ultrastructural, mechanical, and biochemical changes in structural proteins in the aged skin. Changes in the structural proteins and hydration during aging is responsible for altered skin morphologic and mechanical properties manifested as wrinkling, sagging, loss of elasticity, or apparent dryness. To gain insight into the age-related alterations in protein conformation and water structure, we obtained Raman spectra from the sun-protected buttock skin representing chronologic aging and the sun-exposed forearm skin representing combined effects of photoaging and chronologic aging. Ten aged individuals (five men, five women; age range 74–87) and 10 control young individuals (five men, five women; age range 22–29) entered the study. In the photoaged forearm skin the positions of protein-specific amide I, amide III, and CH stretching bands were shifted, suggesting increased protein folding. In contrast, major changes were seen only in the amide I peak in chronologically aged skin. The intensity of the 3250 cm–1 OH stretching band was increased in photoaged skin (but not in chronologically aged skin) indicating an increased water content. R(ν) representation of the low-frequency region of Raman spectra was applied to determine water structure. In the young skin and chronologically aged skin water was mostly present in the bound form. In the photoaged skin, however, an increase in intensity at 180 cm–1 was noted, which reflects an increase in the not-protein bound water (tetrahedron water clusters). In conclusion, it seems that proteins in the photoaged skin are more compact and interact with water to limited degree. Impairment in protein hydration may add to the understanding of ultrastructural, mechanical, and biochemical changes in structural proteins in the aged skin. glycosaminoglycan; near-infrared Fourier transform Altered texture and structure of aged skin is caused by molecular alterations in proteins, lipids, and water. Changes in dermal structural proteins have been extensively investigated, but there is still much debate about the molecular basis of observed age-related alterations. Changes in the amount and architecture of collagen (Shuster et al., 1975Shuster S. Black M.M. McVitie E. The influence of age and sex on skin thickness, skin collagen and density.Br J Dermatol. 1975; 93: 639-643Crossref PubMed Scopus (388) Google Scholar;Lavker, 1979Lavker R.M. Structural changes in exposed and unexposed aged skin.J Invest Dermatol. 1979; 73: 59-66Abstract Full Text PDF PubMed Scopus (358) Google Scholar,Lavker, 1995Lavker R.M. Cutaneous aging: chronologic versus photoaging.in: Glichrest B.A. Photodamage. Blackwell, New York1995: 123-135Google Scholar;Bernstein et al., 1996aBernstein E.F. Chen Y.Q. Kopp J.B. et al.Long-term sun exposure alters the collagen of the papillary dermis. Comparison of sun-protected and photoaged skin by northen analysis, immunohistochemical staining, and confocal laser scanning microscopy.J Am Acad Dermatol. 1996 a; 34: 209-218Abstract Full Text PDF PubMed Scopus (168) Google Scholar), elastin (Braverman and Fonferko, 1982Braverman I.M. Fonferko E. Studies in cutaneous ageing. I. The elastic fiber network.J Invest Dermatol. 1982; 78: 434-443Abstract Full Text PDF PubMed Scopus (375) Google Scholar;Lavker, 1995Lavker R.M. Cutaneous aging: chronologic versus photoaging.in: Glichrest B.A. Photodamage. Blackwell, New York1995: 123-135Google Scholar;Bernstein et al., 1996aBernstein E.F. Chen Y.Q. Kopp J.B. et al.Long-term sun exposure alters the collagen of the papillary dermis. Comparison of sun-protected and photoaged skin by northen analysis, immunohistochemical staining, and confocal laser scanning microscopy.J Am Acad Dermatol. 1996 a; 34: 209-218Abstract Full Text PDF PubMed Scopus (168) Google Scholar), and glycosaminoglycans (GAG) (Uitto, 1989Uitto J. Connective tissue biochemistry of aging dermis.Clin Geriatr Med. 1989; 1989: 127-147Google Scholar;Wulf et al., 1989Wulf H.C. Poulsen T. Davies R.E. Urbach F. Narrow-band UV radiation and induction of dermal elastosis and skin cancer.Photochem Photomed Photobiol. 1989; 6: 44-51Google Scholar;Bernstein et al., 1996bBernstein E.F. Underhill C.B. Hahn P.J. Brown D.B. Uitto J. Chronic sun exposure alters both the content and distribution of dermal glycosaminoglycans.Br J Dermatol. 1996 b; 135: 255-262Crossref PubMed Scopus (131) Google Scholar) have been described in photoaged and in chronically aged skin protected from ultraviolet radiation. For example, in photoaged skin the collagen fibers are fragmented, thickened, and more soluble, elastin fibres form conglomerates, and the amount of GAG increases. The changes in chronically aged skin are more subtle: collagen seems to be less soluble, its fibers are thinner but increased in number with a relative increase in the collagen III/collagen I ratio (Lovell et al., 1987Lovell C.R. Smolenski K.A. Duance V.C. Light N.D. Young S. Dyson M. Type I and III collagen content and fibre distribution in normal human skin during aging.Br J Dermatol. 1987; 117: 419-428Crossref PubMed Scopus (184) Google Scholar;Vitellaro-Zuccarello et al., 1992Vitellaro-Zuccarello L. Garbelli R. Rossi V.D. Immunocytochemical localization of collagen types I, II, IV, and fibronection in the human dermis: modifications with aging.Cell Tissue Res. 1992; 268: 505-511Crossref PubMed Scopus (31) Google Scholar). The reason why observed architectonic, ultrastructural, and biochemical changes occur is not immediately obvious. Some changes, such as a decrease in collagen content and fiber fragmentation, may be explained by the activation of proteolitic enzymes by ultraviolet radiation (Fisher et al., 1996Fisher G.J. Datta S.C. Talwar H.S. Wang Z.Q. Varani J. Kang S. Voorhees J.J. Molecular bassis of sun-induced premature skin ageing and retinoid antagonism.Nature. 1996; 379: 335-339Crossref PubMed Scopus (1120) Google Scholar). It is not known, however, whether the conformation is disturbed in structural proteins in photoaged skin. This is important because the mechanical properties of the proteins and the ability to form layer fibrillar structures strictly depend on conformation. Water is another skin component that has quantitative and structural changes with aging that are poorly understood. In most studies only stratum corneum water has been investigated (Hegner et al., 1981Hegner V.G. Wienert H.S. Gahlen W. Hautfeuchtigkeit und Lebesalter: alters- und geschlechtsbedingte Topographie der Hautfeuchtigkeit.Fortschr Med. 1981; 99: 486-490PubMed Google Scholar;Wiener et al., 1981Wiener V. Hegner G. Sick H. Ein Verfahren zur Bestimumung des relativen Wassergehaltes des stratum corneum der menschlichen Haut.Arch Dermatol Res. 1981; 270: 67-75Crossref Scopus (11) Google Scholar;Potts et al., 1984Potts R.O. Buras E.M. Chrisman D.A. Changes with age in the moisture content of human skin.J Invest Dermatol. 1984; 82: 97-100Abstract Full Text PDF PubMed Scopus (115) Google Scholar;Elsner et al., 1994Elsner P. Berardesca E. Maibach H.I. Bioengineering of the skin: water and the stratum corneum. CRC Press, Boca Raton1994Google Scholar;Aisen et al., 1997Aisen E. Shafran A. Gilhar A. Sebum and water content in the skin of aged immobilized patients.Acta Derm Venereol (Stockh). 1997; 77: 142-143PubMed Google Scholar). The general belief is that aged skin is “drier,” i.e., contains less water. Few substantive data can be found in the literature to support this hypothesis. It is difficult to explain why water content in the photoaged skin should be decreased, because GAG, which are important water-holding molecules in the skin and have potency to bind water up to 1000 times their volume, increase in amount in photoaged skin (Uitto, 1989Uitto J. Connective tissue biochemistry of aging dermis.Clin Geriatr Med. 1989; 1989: 127-147Google Scholar;Bernstein et al., 1996bBernstein E.F. Underhill C.B. Hahn P.J. Brown D.B. Uitto J. Chronic sun exposure alters both the content and distribution of dermal glycosaminoglycans.Br J Dermatol. 1996 b; 135: 255-262Crossref PubMed Scopus (131) Google Scholar). Thus, hydration of photoaged skin could be higher, a hypothesis that has been supported byKligman, 1979Kligman A.M. Perspectives and problems in cutaneous gerontology.J Invest Dermatol. 1979; 73: 39-46Abstract Full Text PDF PubMed Scopus (218) Google Scholar. An issue that is crucial for the understanding of the changes of hydration in aging skin is water structure. Water can bind to various proteins constituting so-called bound water. Presence of bound water is important for the maintenance of structural and mechanical properties of proteins and their mutual interactions. In young skin the majority of water molecules are found in the bound form (Gniadecka et al., 1998aGniadecka M. Faurskov Nielsen O. Christensen D.H. Wulf H.C. Structure of water, proteins and lipids in intact human skin, hair and nail.J Invest Dermatol. 1998 a; 110: 393-398Abstract Full Text Full Text PDF PubMed Scopus (268) Google Scholar). Water molecules that are not bound to other compounds are bound to each other, forming tetrahedron structures (so-called tetrahedron or bulk water) (Walrafen, 1972Walrafen G.E. Raman and infrared spectral investigations of water structure.in: Franks F. Water, a Comprehensive Treatise, Vol 1, Physiscs and Physical Chemistry of Water. Plenum Press, New York1972: 151-214Google Scholar;Nielsen, 1979Nielsen O.F. The structure of liquid water. A low-frequency (10–400cm–1) Raman study.Chem Phys Lett. 1979; 60: 515-517Crossref Scopus (65) Google Scholar,Nielsen, 1993Nielsen O.F. Low frequency spectroscopic studies of interactions in liquids.Annu Rep Prog Chem Sec C Phys Chem. 1993; 90: 3-44Crossref Google Scholar,Nielsen, 1997Nielsen O.F. Low frequency spectroscopic studies of intermolecular vibrational energy transfer in liquids.Annu Rep Prog Chem Sec C Phys Chem. 1997; 93: 57-99Crossref Scopus (35) Google Scholar;Maeda and Kitano, 1995Maeda Y. Kitano H. The structure of water in polymer systems as revealed by Raman spectroscopy.Spectrochim Acta. 1995; 51: 2433-2446Crossref Scopus (119) Google Scholar;Nielsen et al., 1997Nielsen O.F. Christensen D.H. Trandum C. Gniadecka M. Wulf H.C. Studies of water structure by low-frequency Raman spectroscopy.in: Caramona P. Navarro R. Hernanz A. Spectrosc Biol Molecul: Modern Trends. Kluwer Acad Publishers, Dortrecht, The Netherlands1997: 593-594Google Scholar). An understanding of the changes in water structure in aged skin may be helpful in elucidating the molecular basis of mechanical alterations in aging skin. Raman spectroscopy has increasingly been used for studying molecular structure of various tissues and other biomaterials (reviewed inSchrader, 1995Schrader B. Infrared and Raman Spectroscopy. Methods and Applications. Weinheim., New York1995Google Scholar;Mahadevan-Jansen and Richards-Kortum, 1996Mahadevan-Jansen A. Richards-Kortum R. Raman spectroscopy for the detection of cancers and precancers.J Biomed Optics. 1996; 1: 31-70Crossref PubMed Scopus (395) Google Scholar;Brennan et al., 1997Brennan J.F. Wang Y. Dasari R.R. Feld M.S. Near infrared Raman spectrometer systems for human tissue studies.Appl Spectrosc. 1997; 51: 210-217Crossref Scopus (116) Google Scholar;Lawson et al., 1997Lawson E.E. Edwards Hgm Williams A.C. Barry B.W. Applications of Raman spectroscopy to skin research.Skin Res Technol. 1997; 3: 147-154Crossref Scopus (12) Google Scholar). Investigations by Edwardset al. (Barry et al., 1992Barry B.W. Edwards Hgm Williams A.C. Fourier transform Raman and infrared vibrational study of human skin: assignment of spectral bands.J Raman Spectrosc. 1992; 23: 641-645Crossref Scopus (208) Google Scholar;Williams et al., 1994Williams A.C. Edwards Hgm Barry B.W. Raman spectra of hyman keratotic biopolymers: skin, callus, hair and nail.J Raman Spectrosc. 1994; 25: 95-98Crossref Scopus (118) Google Scholar;Edwards et al., 1995Edwards Hgm Williams A.C. Barry B.W. Potential applications of FT-Raman spectroscopy for dermatological diagnosis.J Mol Struct. 1995; 347: 379-388Crossref Scopus (67) Google Scholar;Akhtar and Edwards, 1997Akhtar W. Edwards HgM Fourier-transform Raman spectroscopy of mammalian and avian keratotic biopolymers.Spectrochim Acta Part a. 1997; 53: 81-90Google Scholar;Barron, 1998Barron L.D. Raman optical activity: an incisive new probe of the struture and dynamics of biomolecules.Sci Prog. 1998; 81: 17-34Google Scholar) and our own group (Gniadecka et al., 1997aGniadecka M. Wulf H.C. Nymark Mortensen N. Faurskov Nielsen O. Christensen D.H. Diagnosis of basal cell carcinoma by Raman spectroscopy.J Raman Spectroscopy. 1997 a; 28: 125-129Crossref Google Scholar,Gniadecka et al., 1997bGniadecka M. Wulf H.C. Nielsen O.F. Christensen D.H. Hercogova J. Distinctive molecular abnormalities in benign and malignant skin lesions: studies by Raman spectroscopy.Photochem Photobiol. 1997 b; 66: 418-423Crossref PubMed Scopus (139) Google Scholar,Gniadecka et al., 1998aGniadecka M. Faurskov Nielsen O. Christensen D.H. Wulf H.C. Structure of water, proteins and lipids in intact human skin, hair and nail.J Invest Dermatol. 1998 a; 110: 393-398Abstract Full Text Full Text PDF PubMed Scopus (268) Google Scholar) showed that the structure of proteins and water can also be studied in the intact skin by near-infrared Fourier-transform (NIR-FT) Raman spectroscopy. In NIR-FT Raman spectroscopy a sample is irradiated with a monochromoatic light that results in light scattering. The majority of scattered light has unchanged frequency (so-called Rayleigh line), whereas the rest is shifted in frequency (Raman effect). Those frequency shifts of the scattered light in the skin can be analyzed and presented as Raman spectra. The Raman effect is caused by vibrations of chemical bonds in molecules in an irradiated sample, and thus gives information about the structure of molecules. In the skin, vibrations of chemical bonds in water, protein, and lipid molecules can be analyzed. In normal young skin the majority of Raman scatter, especially in protein specific regions, is gathered from the dermis (Fendel, 1997Fendel S. NIR-FT-Raman-Spektroskopie zur Untersuchung von Haut und ihren pathologischen Veränderungen. PhD Thesis, University of Essen1997Google Scholar;Fendel and Schrader, 1998Fendel S. Schrader B. Investigation of skin and skin lesions by NIR-FT-Raman spectroscopy.Fresenius J Anal Chem. 1998; 360: 609-613Crossref Scopus (87) Google Scholar). The protein that mostly contributes to the spectra is collagen, which is understandable in view of the fact that it constitutes 70% of the skin dry mass.Gniadecka et al., 1998aGniadecka M. Faurskov Nielsen O. Christensen D.H. Wulf H.C. Structure of water, proteins and lipids in intact human skin, hair and nail.J Invest Dermatol. 1998 a; 110: 393-398Abstract Full Text Full Text PDF PubMed Scopus (268) Google Scholar analyzed the position of amide I and amide III bands (originating from vibrations in peptide bonds) and confirmed the helical conformation of collagen in the young skin. Moreover, their study documented higher fluidity of lipids in the whole skin than in the stratum corneum, and showed that almost all water molecules are bounded. Here, we show marked alterations in water and protein structure in photoaged in comparison with the chronically aged skin and young skin. Ten healthy young individuals (five men, five women; age range 22–29) and 10 aged individuals (five men, five women; age range 74–87) were enrolled in the study. This study was carried out in the winter season in Denmark where environmental exposure to solar UV is negligible (Wulf, 1994Wulf H.C. Sol og solbeskyttelse.Ugeskr Læger. 1994; 156: 3760-3764Google Scholar). None of the investigated persons gave a history of sunbathing 5 mo prior to the study, and none used to sunbathe nude exposing their buttocks. Enrolled persons gave no history of atopy or skin disease affecting the investigated regions. The protocol was accepted by the Ethics Committee of Copenhagen, Denmark. Three millimeter punch biopsies of normal sun-exposed dorsal forearm and sun-protected buttock skin were collected in all volunteers. The samples were kept at 4°C and analyzed within 30 min. Samples were carefully placed in a Raman sample holder (a stainless-steel cup with a 3 mm diameter hole for punch biopsy). Subcutis was facing the bottom of the cup, whereas epidermis was facing the incoming laser beam in the Raman instrument. Sample handling does not influence Raman spectra because it has been shown that spectra from the biopsies and spectra collected directly from the skin via optic fibers are virtually identical (Gniadecka et al., 1998bGniadecka M. Wessel S. Nielsen O.F. Christensen D.H. Hercogova J. Rossen J.K. Wulf H.C. Potential of Raman spectroscopy forin vitro andin vivo diagnosis of malignant melanoma.in: Heynes E.M. Proceedings of the Xvith International Conference on Raman Spectroscopy. John Wiley, Chichester1998 b: 764-765Google Scholar). No sample pretreatment of any kind was performed. A Bruker (Karlsruhe, Germany) IFS 66 interferometer equipped with a FRA 106 module or a 100 FRA-Raman spectrometer were used. The 1064 line at 300 mW from a Nd:YAG laser was the excitation source. A liquid nitrogen-cooled Ge detector was used. The laser beam was focused to a spot of ≈100 μm diameter on the epidermal site of the skin biopsy. Two hundred and fifty scans at a 4 cm–1 spectral resolution were collected from each sample and averaged. Wave numbers were accurate to ±1 cm–1. The total registration time was 10 min. The radiation scattered by the sample contains the frequency of the incident radiation (Rayleigh line) and a number of lines of other frequencies characteristic of the molecular vibrations (Raman lines). Frequency shifts of Raman lines relative to the exciting line are presented in the spectrum. The spectral range of the acquired spectra was from 0 to 3500 cm–1. OPUS software (Bruker) was used to evaluate spectral characteristics. To compare intensity of bands in the region of 0–1800 cm–1 spectra were equalized for the 1450 cm–1 band intensity, whereas in the region 2500–3500 cm–1 spectra were equalized for the 2940 cm–1 band intensity as a reference. The C–H bands (at 1450 cm–1 and 2940 cm–1) protrude outside the protein chain and do not take part in strong intermolecular interactions, therefore the C–H band is not modified by alterations in secondary protein structure and is used for equalization of the spectra. It is necessary to equalize the spectra in two different ranges using both 1450 cm–1 and 2940 cm–1 bands because of the fact that self-absorption of water in investigated tissue influences spectral regions differently. The water absorption is higher in the 2500–3500 cm–1 region than in the 0–2500 cm–1 region, which means that in tissue containing more water the 2940 cm–1 band would be absorbed more than the 1450 cm–1 band, leading to false differences in relative intensity between these two bands. Moreover, the 1450 cm–1 and 2940 cm–1 bands have highest intensity in the respective spectral regions, and thus are least sensitive to influences of noise. These two bands are usually used for equalization of the spectra (Liu et al., 1992Liu C.H. Das B.B. Sha Glassman W.L. et al.Raman, fluorescence, and time-resolved light scattering as optical diagnostic techniques to separate diseased and normal biomedical media.J Photochem Photobiol B Biol. 1992; 16: 187-209Crossref PubMed Scopus (203) Google Scholar;Schrader, 1995Schrader B. Infrared and Raman Spectroscopy. Methods and Applications. Weinheim., New York1995Google Scholar;Fendel, 1997Fendel S. NIR-FT-Raman-Spektroskopie zur Untersuchung von Haut und ihren pathologischen Veränderungen. PhD Thesis, University of Essen1997Google Scholar;Schallreuter et al., 1998Schallreuter K.U. Zeschiesche M. Moore J. et al.In vivo evidence for compromised phenyloalanine metabolsim in vitiligo.Biochem Biophys Res Commun. 1998; 243: 395-399Crossref PubMed Scopus (49) Google Scholar). In no case were smoothing procedures used. The ratio of intensities of C–H (around 2940 cm–1) and O–H stretching bands (around 3250 cm–1) is related to hydrogen bonding or hydration between protein and water (Cavotorta et al., 1976Cavotorta F. Fontana M.P. Vecli A. Raman spectroscopy of protein–water interactions in aqueous solutions.J Chem Phys. 1976; 65: 3635Crossref Scopus (26) Google Scholar;Samanta and Walfaren, 1978Samanta S.R. Walfaren G.E. Raman intensities and interactions in aqueous lysosyme solutions.J Chem Phys. 1978; 68: 3313-3315Crossref Scopus (11) Google Scholar). We determined skin water content by estimating the ratio I2940/I3250 (peak intensities of the 2940 cm–1 band to the 3250 cm–1 band) (Gniadecka et al., 1998aGniadecka M. Faurskov Nielsen O. Christensen D.H. Wulf H.C. Structure of water, proteins and lipids in intact human skin, hair and nail.J Invest Dermatol. 1998 a; 110: 393-398Abstract Full Text Full Text PDF PubMed Scopus (268) Google Scholar). The low frequency region (10–300 cm–1) of the Raman spectra can be conveniently studied by employing the R(ν) representation (Nielsen, 1979Nielsen O.F. The structure of liquid water. A low-frequency (10–400cm–1) Raman study.Chem Phys Lett. 1979; 60: 515-517Crossref Scopus (65) Google Scholar,Nielsen, 1993Nielsen O.F. Low frequency spectroscopic studies of interactions in liquids.Annu Rep Prog Chem Sec C Phys Chem. 1993; 90: 3-44Crossref Google Scholar,Nielsen, 1997Nielsen O.F. Low frequency spectroscopic studies of intermolecular vibrational energy transfer in liquids.Annu Rep Prog Chem Sec C Phys Chem. 1997; 93: 57-99Crossref Scopus (35) Google Scholar;Brooker et al., 1988Brooker M.H. Faurskov Nielsen O. Praestgaard E. Assessment of correction procedures for reduction of Raman spectra.J Raman Spectrosc. 1988; 19: 71-78Crossref Scopus (114) Google Scholar;Nielsen et al., 1997Nielsen O.F. Christensen D.H. Trandum C. Gniadecka M. Wulf H.C. Studies of water structure by low-frequency Raman spectroscopy.in: Caramona P. Navarro R. Hernanz A. Spectrosc Biol Molecul: Modern Trends. Kluwer Acad Publishers, Dortrecht, The Netherlands1997: 593-594Google Scholar), where the Rayleigh line is converted into a plateau according to the formula: RV¯=V¯1−exp−hcV¯/kTIV¯(1) where I(ν) is the intensity in the Raman spectrum at a Raman shift on ν cm–1, c is the velocity of light, T is the absolute temperature, h is Planck’s constant, and k is Boltzmann’s constant. To measure relative changes in the amide III band intensity, the ratio of peak intensities of the amide III band (around 1270 cm–1) and the band around 1300 cm–1 of the vibrations in lipids (most probably CH2 twisting and wagging vibrations) (I1270/I1300) was calculated. Data are presented as mean ± SD. Data were found to deviate from normal distribution (tested with Shapiro–Wilk test) and therefore a nonparametric Wilcoxon test was used to compare the groups. p < 0.05 was considered significant. Raman vibrations sensitive to protein conformation are those of the peptide bonds. Among seven important vibrations, two are clearly represented in Raman spectra of the skin: the amide I and the amide III vibrations (Tu, 1982Tu A.T. Proteins.Raman Spectroscopy in Biology. Principles and Applications. John Wiley, New York1982: 66-113Google Scholar,Tu, 1986Tu A.T. Peptide backbone conformation and microenvironment of protein side chains.in: Clark R.J.H. Hester R.E. Spectroscopy of Biological Systems. John Wiley, Chichester1986: 47-113Google Scholar;Miura and Thomas, 1995Miura T. Thomas Jr, G. Raman spectroscopy of proteins and their assemblies.in: Biswas B.B. Siddhartha R. Subcellular Biochemistry, Vol. 24, Proteins: Structure, Function and Engineering. Plenum Press, New York1995: 55-99Google Scholar). Amide I mainly reflects the C=O stretching vibrations, whereas the amide III band is a more complex mode involving several chemical bonds (Tu, 1986Tu A.T. Peptide backbone conformation and microenvironment of protein side chains.in: Clark R.J.H. Hester R.E. Spectroscopy of Biological Systems. John Wiley, Chichester1986: 47-113Google Scholar). Major spectral amide band shapes of dorsal forearm and buttock skin in the young group were identical (Figure 1a, b). Moreover positions of amide I and III peaks did not differ significantly (band position shown inTable 1), indicating similar protein structure in both investigated regions. These data support previous findings that proteins in young skin are in the helical conformation (Gniadecka et al., 1998aGniadecka M. Faurskov Nielsen O. Christensen D.H. Wulf H.C. Structure of water, proteins and lipids in intact human skin, hair and nail.J Invest Dermatol. 1998 a; 110: 393-398Abstract Full Text Full Text PDF PubMed Scopus (268) Google Scholar).Table 1Major vibrational mode changes identified in NIR-FT spectra of the samples of sun-exposed and sun-protected skin in young and aged individuals. Mean peak position(cm–1) n with SD are showbuttock skin(chronologic aging)arm dorsal skin(photoaging)youngagedyoungagedν(C=O) amide Iaν, stretching mode, νas, asymmetric stretching mode.1663 ± 1.01659 ± 2.131661 ± 1.171657 ± 1.60p = 0.008p = 0.01δ(NH) and ν(C–N) amide IIIaν, stretching mode, νas, asymmetric stretching mode.1272 ± 4.581270 ± 2.371271 ± 4.301268 ± 3.35NSp = 0.05νas(CH3) in proteinsaν, stretching mode, νas, asymmetric stretching mode.2942 ± 1.942940 ± 3.292942 ± 1.662938 ± 2.94NSp = 0.002a ν, stretching mode, νas, asymmetric stretching mode. Open table in a new tab The intramolecular vibrations of hydrogen-bonded water include two O–H stretching bands in the 3000–3400 cm–1 region, and the bending band near 1645 cm–1 (Maeda and Kitano, 1995Maeda Y. Kitano H. The structure of water in polymer systems as revealed by Raman spectroscopy.Spectrochim Acta. 1995; 51: 2433-2446Crossref Scopus (119) Google Scholar;Walrafen and Chu, 1995Walrafen G.E. Chu Y.C. Linearity between structural correlation length and correlated-proton intensity from amorphous ice and supercooled water up to dense supercritical steam.J Phys Chem. 1995; 99: 11225-11229Crossref Scopus (116) Google Scholar). The bending mode is weaker in intensity than the stretching bands, and therefore it is hidden by the amide I vibrations around 1650 cm–1. The symmetric O–H stretching [νs(OH)] is found around 3250 cm–1, whereas the Raman component near 3400 cm–1 has been assigned to the asymmetric O–H stretching [νas(OH)]. The latter band has not been distinctively resolved in our spectra because of a drop of the detector sensitivity in this region. The estimate of total hydrogen-bonded water can be obtained by calculating I2940/I3250. No statistical differences in water content were found between sun-exposed and sun-protected skin in young individuals (I2940/I3250; dorsal forearm, 2.89 ± 0.44; buttock, 2.78 ± 0.51) (Figure 1c). Tetrahedron (bulk) water is reflected by a band at ≈180 cm–1, mainly representing motions of the oxygen atoms. This mode contains some hydrogen bond stretching (Walrafen, 1972Walrafen G.E. Raman and infrared spectral investigations of water structure.in: Franks F. Water, a Comprehensive Treatise, Vol 1, Physiscs and Physical Chemistry of Water. Plenum Press, New York1972: 151-214Google Scholar;Maeda and Kitano, 1995Maeda Y. Kitano H. The structure of water in polymer systems as revealed by Raman spectroscopy.Spectrochim Acta. 1995; 51: 2433-2446Crossref Scopus (119) Google Scholar;Nielsen, 1997Nielsen O.F. Low frequency spectroscopic studies of intermolecular vibrational energy transfer in liquids.Annu Rep Prog Chem Sec C Phys Chem. 1997; 93: 57-99Crossref Scopus (35) Google Scholar;Nielsen et al., 1997Nielsen O.F. Christensen D.H. Trandum C. Gniadecka M. Wulf H.C. Studies of water structure by low-frequency Raman spectroscopy.in: Caramona P. Navarro R. Hernanz A. Spectrosc Biol Molecul: Modern Trends. Kluwer Acad Publishers, Dortrecht, The Netherlands1997: 593-594Google Scholar). This band can be visualized employing the R(ν) representation of the spectra (eqn 1). The absence of the 180 cm–1 band indicated that most of the wa" @default.
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• W2027110562 title "Water and Protein Structure in Photoaged and Chronically Aged Skin" @default.
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