Decision-making, financial risk aversion, and behavioral biases: The role of testosterone and stress.

We examine the relation between testosterone, cortisol, and financial decisions in a sample of naïve investors. We find that testosterone level is positively related to excess risk-taking, whereas cortisol level is negatively related to excess risk-taking (correlation coefficient [r]: 0.75 and -0.

Comparison of the structural and physical properties of human hair eumelanin following enzymatic or acid/base extraction.

Eumelanin was isolated from a sample of black, Indonesian human hair using three different published procedures: two different acid/base extractions and an enzymatic extraction. The morphology and spectroscopic properties of the isolated pigments differ significantly. The acid/base procedures both yield an amorphous material, while enzymatic extraction yields ellipsoidal melanosomes.

Establishing structure-function relationships for eumelanin.

The aggregation-dependent optical properties of eumelanin from human hair are examined. When aggregation is increased, the absorption spectrum extends to lower energy. The absorption spectra of oligomers isolated from black human hair and Sepia officinalis are comparable and are in quantitative agreement with the reported action spectra for photoinduced oxygen consumption and free-radical generation by eumelanin.

Aggregation of eumelanin mitigates photogeneration of reactive oxygen species.

Melanins protect tissue by absorption and rapid nonradiative, nonreactive dissipation of ultraviolet (UV) light. However, melanins also produce reactive oxygen species (ROS) upon UV illumination. A chemical understanding of this dichotomy of photoprotection and phototoxicity has not been established.

Radiative relaxation of Sepia eumelanin is affected by aggregation.

The steady-state and time-resolved emission properties of aqueous solutions containing different aggregation state distributions of eumelanin are reported. Excitation spectra of the size-selected samples reveal, for the first time, differences in absorption bands due to varying levels of aggregation. These size-dependent absorption properties result in size-dependent emission band shapes and quantum yields.