Effect of Humidity on Photoinduced Esr Signal From Human Hair

Jahan, M. S.; Drouin, T. R.; Sayre, Robert M.

doi:10.1111/j.1751-1097.1987.tb05416.x

Cited by 13 publications

(9 citation statements)

References 16 publications

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“…This observation together with our results suggests that the photodegradation of melanin inside the skin and feathers could be strongly affected by the humidity of the external environment. This hypothesis is supported by several studies dealing with the effect of humidity on photobleaching of hair (26,27). While the light intensities used in this work (0.1-10 mW mm )2 ) are 100-1000 times greater than the terrestrial solar radiation flux in visible and UV spectral ranges (28), they are several orders of magnitude smaller than those used for laser ablation of organic films (29).…”

Section: Resultssupporting

confidence: 76%

Effect of Ambient Humidity on UV/Visible Photodegradation of Melanin Thin Films

Sharma

2010

Photochem & Photobiology

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Photodegradation of spin-coated thin films of melanin is investigated using UVA and visible light from light-emitting diodes. The gradual increase in transmitted light through the film is measured as melanin photodegrades over the course of several hours. The photodegradation rate is measured for wavelengths in the 365-600 nm range. It is found that the increase in ambient humidity significantly accelerates the photodegradation process. Implications of these observations for evolution of melanism in biological systems are discussed.

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Section: Resultssupporting

confidence: 76%

Effect of Ambient Humidity on UV/Visible Photodegradation of Melanin Thin Films

Sharma

2010

Photochem & Photobiology

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“…The ESR method is one of the most productive methods in the study of melanin contained in hair and skin. [5, 8–21]…”

Section: Introductionmentioning

confidence: 99%

ESR study of photoinduced free radicals by visible light in hair and the effects of ascorbic acid (vitamin C)

Chikvaidze

Khachatryan

2011

Intern J of Cosmetic Sci

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The ESR spectra of melanin's free radicals in natural black and red hair have been investigated. It is shown that the ESR spectrum of black hair is slightly asymmetric singlet with g=2.0037 and ΔH=0.5 mTl. The ESR spectrum of red hair with g=2.0053 differs from the spectrum of black hair. Using the method of saturation was shown that ESR spectrum of red hair represents a superposition of two signals: a singlet, relating to the black hair, and a triplet from red hair's pheomelanin. Under the influence of visible light (blue with λ(max) =450 nm, green with λ(max) =510 nm and red with λ(max) =650 nm) in both types of hair (black and red), the photoinduced free radicals appear, which indicates an increase in the intensity of already existing ESR spectrum of hair. It should be noted that the ESR spectra of red hair from various donors are different. The antioxidant ascorbic acid (vitamin C) has the different effect on the photoinduced free radicals. In particular, in the case of black hair, the concentration of photoinduced free radicals is slightly reduced, whereas in red hair, the disappearance of the triplet in the spectrum is observed, and at the same time, the spectrum becomes a singlet, the intensity of which increases sharply. It is assumed that the antioxidants, effective for black hair, may be ineffective for red hair and vice versa. Therefore, in each, specific case is necessary to investigate the effectiveness of an antioxidant separately.

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“…The fibres were placed in the EPR tubes and dried in an oven at 100°C overnight to remove most of the adsorbed water before measurement. It has been reported that hydration of keratin fibres reduces their intrinsic EPR intensity . Most of the EPR signal originates from free radicals in the melanin pigments, and in particular eumelanin, which is why Asian black hair has the strongest EPR signal.…”

Section: Resultsmentioning

confidence: 99%

UV damage to hair and the effect of antioxidants and metal chelators

Millington

Marsh

2020

Intern J of Cosmetic Sci

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Objective To study the effects of addition of a redox metal, copper, antioxidants and metal chelators on the formation of free radicals in natural white Caucasian hair subsequently exposed to UV light. Three different methods, electron paramagnetic resonance (EPR), a fluorescent probe for hydroxyl radical formation (terephthalate) and free radical photoyellowing, were used. These methods utilized different UV sources and reaction conditions, and so can give insights into the different mechanisms of action occurring during UV oxidation of hair. In addition, this study demonstrates how antioxidants and chelators can be screened to determine whether they can protect hair from UV damage. Results The three methods gave somewhat different results, illustrating the importance of reaction conditions and wavelength on the photochemical mechanisms, and the efficacy of additives to influence these reactions. EPR results showed that N‐acetylcysteine (NAC) pre‐treatment eliminated the intensity of the signal because of sulphur and carbon free radicals in white hair both before and after exposure to UVB radiation. Doping the hair with copper ions had no effect on the intensity of the EPR signal under dry conditions. Terephthalate fluorescent probe data showed that under wet conditions, irradiation of white hair with UVA produced significant amounts of hydroxyl radicals. Pre‐treatment of hair with NAC reduced the number of •OH radicals produced by natural white hair compared to an untreated control. In contrast to the EPR result, white hair doped with copper ions produced significantly higher levels of •OH radicals under wet conditions. It appears that the ability of copper ions to catalyse the photogeneration free radicals in hair is highly dependent on water content. Photoyellowing data showed a benefit for oxalic acid but no difference for NAC and an increase in yellowing for EDTA. Conclusion The micro‐EPR and terephthalate fluorescent probe methods are both effective techniques to study production of free radicals by hair exposed to UV light under wet and dry conditions, respectively. Both assays are simple methods for determining the effectiveness of potential protective hair treatments against UV damage, but because they assess free radical damage under dry vs wet conditions, the chemistry created on UV exposure is different. This gives insights into mechanism of action, but results may not be consistent between the two methods for actives added for reduction of UV damage. NAC pre‐treatment did reduce free radical generation in UV‐exposed hair under both wet and dry conditions. Photoyellowing data are more complicated as it is a less direct measure of UV damage and is highly dependent on irradiation source. Using UVB irradiation is experimentally convenient but may not be appropriate, because UVB wavelengths comprise only 0.3% of terrestrial sunlight. The photochemistry of hair exposed to sunlight involves concurrent photobleaching and photoyellowing processes and is far more complex. Under UVB irradiation condit...

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Effect of Humidity on Photoinduced Esr Signal From Human Hair

Cited by 13 publications

References 16 publications

Effect of Ambient Humidity on UV/Visible Photodegradation of Melanin Thin Films

Effect of Ambient Humidity on UV/Visible Photodegradation of Melanin Thin Films

ESR study of photoinduced free radicals by visible light in hair and the effects of ascorbic acid (vitamin C)

UV damage to hair and the effect of antioxidants and metal chelators

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