Skin aging and natural photoprotection

Aging of skin is a continuous process that may be enhanced by sun exposure. Photoaging may provoke changes different from aging. Epidermal changes involve thinning of stratum spinosum and flattening of the dermo-epidermal junction. The senescent keratinocytes becomes resistant to apoptosis and may survive for a long time giving time for DNA and protein damage to accumulate with possible implication for carcinogenesis. The numbers of melanocytes decrease with age with dysregulation of melanocyte density resulting in freckles, guttate hypo-melanosis, lentigines and nevi. The number of dendritic Langerhans cells also decreases with age and the cells get less dendrites and have reduced antigen-trapping capacity. Aging involves dermal changes such as damage to elastic and collagen fibers giving thickened, tangled, and degraded non-functional fibers. Collagen intermolecular cross-links are stable and essential for stability and tensile strength. Cross-links increase with age converting divalent cross-links into mature trivalent cross-links of, e.g. histidinohydroxylysinonorleucine. Two mechanisms are involved; an enzyme-controlled process of maturation and a non-enzymatic glycosylation, the Maillard reaction leading to cross-links in proteins such as in collagen between arginine and lysine. Such may be seen with age and in diabetes mellitus. However, autofluorescence studies have shown that UVR reduces collagen cross-links. Natural photoprotection involves thickening of stratum corneum by sunlight and increased pigmentation. This leads to a factor 2 increase in photoprotection from spring until after-summer. The constitutive pigmentation is independent of age and thickness of stratum corneum is likewise independent of age. The minimal erythema dose is thus the same through life, when corrected for pigmentation or measured in areas with constitutive pigmentation.     

Bioconversion of vanillin to vanillyl alcohol in a two-phase reactor

One of the next challenges in the use of biocatalysts (enzyme or microbial cells) is the upgrading of biological reactions of oxidoreduction. The oxidoreductases need cofactors that must be regenerated. Practical experience shows that this is most readily achieved by using living cells of microorganisms. Living cells ofSaccharomyces cerevisiae are able to bioconvert vanillin to vanillyl alcohol (1). By working with a two-phase reactor (dodecanol—feeding medium) it has been possible to use higher vanillin concentrations without inhibiting the bioconversion (2).     

Study on antiprotonic atoms of light nuclei and isotopes

New data on strong interaction effects in light antiprotonic atoms (N, ¹⁶O, ¹⁸O, S) are presented. For the first time an isotope effect could be observed in p?-¹⁶O/¹⁸O which is used to gain new information about the p?-n interaction in nuclei. A comparison between all existing p?-atomic data and an optical model calculation is performed, yielding a set of fit parameters for the potential.     

Quantitative imaging of 33P in plant materials using 14C polymer references

Analytical and Bioanalytical Chemistry - Phosphorus (P) research still lacks techniques for rapid imaging of P use and allocation in different soil, sediment, and biological systems in a...     

Rich coordination of Nd3+ in Mg2Nd13(BO3)8(SiO4)4(OH)3, derived from high-pressure/high-temperature conditions

A neodymium borosilicate, Mg(2)Nd(13)(BO(3))(8)(SiO(4))(4)(OH)(3) (MgNdBSi-1), was obtained from a high-temperature (1400 °C), solid-state reaction under high-pressure conditions (4.5 GPa). MgNdBSi-1 contains six different types of Nd(3+) coordination environments with three different ligands: BO(3), SiO(4), and OH groups. Mg(2+) cations are only bond to BO(3) groups and form porous two-dimensional layers based on 12-membered ring fragments. Surprisingly, the OH groups are retained at high temperature and reside at the center of Mg-BO(3) rings.     

On the spectrum of the Rayleigh piston

We make a rigorous study of the spectrum of the Rayleigh piston. Our main results are that one is dealing with a trace-class perturbation for all values of the mass ratio y between test particles and heat bath particles and that apart from the ground state the discrete spectrum is empty for y sufficiently near 1. We also show that the so-called Lorentz limit ( ) is mathematically well defined and derive a qualitative statement on the discrete spectrum of the scattering operator for 1.