UV-vis spectra as an alternative to the Lowry method for quantify hair damage induced by surfactants.

It is well known that long term use of shampoo causes damage to human hair. Although the Lowry method has been widely used to quantify hair damage, it is unsuitable to determine this in the presence of some surfactants and there is no other method proposed in literature. In this work, a different method is used to investigate and compare the hair damage induced by four types of surfactants (including three commercial-grade surfactants) and water.

Entropy and volume change of dissociation in tobacco mosaic virus probed by high pressure.

Virus dissociation and inactivation by high pressure have been extensively studied in recent decades. Pressure-induced dissociation of viral particles involves a reduction in the Gibbs free energy of dissociation and a negative change in volume. In this work, we investigated the combined effect of high pressure and temperature on the dissociation of tobacco mosaic virus (TMV).

Different urea stoichiometries between the dissociation and denaturation of tobacco mosaic virus as probed by hydrostatic pressure.

Viruses are very efficient self-assembly structures, but little is understood about the thermodynamics governing their directed assembly. At higher levels of pressure or when pressure is combined with urea, denaturation occurs. For a better understanding of such processes, we investigated the apparent thermodynamic parameters of dissociation and denaturation by assuming a steady-state condition.

Hair melanin content and photodamage.

The aim of this study was to compare the susceptibility of hair with different melanin content (virgin white, blond and dark-brown) to photodegradation, evaluating changes on hair color and mechanical properties. Light exposure was carried out with a mercury-vapor lamp for up to 1800h. It was observed that color changes are different for each hair type and dependent on the wavelength range.

Hair medulla morphology and mechanical properties.

The morphology of human hair was extensively discussed in the last century, except for hair medulla, mainly because it was believed to have little or no influence on any useful hair property. Early SEM results showed that medulla is formed by unorganized fibrilar material that could be macrofibrils randomly located in the fiber center. The present paper aims to correlate the fibrilar structures with the macrofibrils using transmission electron microscopy (TEM) and to evaluate the influence of medulla on the mechanical properties of hair.

Electron microscopic observations of human hair medulla.

In the study of human hair, medulla is the less studied structure because it is believed that it has no influence on the fibre properties. The aim of this paper is to contribute to the better understanding of medulla morphology. Using reproducible methods for hair samples preparations allowed observing the inner fibre by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Yeast cells long-term interaction with asbestos fibers.

Saccharomyces cerevisiae was supported on chrysotile, crocidolite and lixiviated chrysotile. Samples of the supported cells and free cells were observed by confocal laser scanning microscopy. After 30 days, the free cells showed no viability when stored at 30 degrees C, and a viability of 40% when stored at 4 degrees C.

Hair protein removal by sodium dodecyl sulfate.

The effect of sodium dodecyl sulfate (SDS) on protein loss was studied. Three kinds of human hair were tested by rubbing or immersion in water or immersion in SDS solution, at 25, 40 and 70 degrees C. Under friction, hair treated with SDS solution loses seven times more protein than in water, while by immersion, protein loss is roughly two times higher in SDS than in water.

Hair color changes caused by dyeing and thermal treatments.

The aim of this study was to show the effect of heat exposure, dyeing, and shampooing on hair color as measured by diffuse reflectance spectrophotometry. Successive dyeing of virgin hair with six permanent commercial formulations showed that color saturation was obtained after the first dyeing cycle. An unexpectedly high difference in hair color saturation, measured as DE* values, was obtained for virgin hair samples that differed only in cleansing history.

Extractable substances from human hair: a discussion about the origin of the holes.

The existence of holes in the endocuticle, in the inter-macrofibrilar matrix and in the cell membrane complex of hair fibers is described. In this paper, we show that these holes are absent in the hair follicle. However, cell remnants found in young hair inside the follicle are located in the same regions and are of the same dimensions as the holes observed in mature fibers.

Hair color changes and protein damage caused by ultraviolet radiation.

Ultraviolet and visible radiations are known to damage hair. However, quantitative data relating damage to hair type, proteins and color to the radiation wavelength are missing. We studied the effect of UV plus visible, UVA plus visible, visible mercury-vapor lamp radiation and sunlight on (blended) virgin dark-brown, blond and red hair and (one head) virgin black and curly dark-brown hair.