PHO13 phosphoglycolate phosphatase from Saccharomyces cerevisiae (baker’s yeast), a member of the p-nitrophenylphosphatase family of the haloalkanoic acid dehalogenase (HAD) superfamily

The function of phosphoglycolate phosphatase (PGPase) in photosynthetic organisms such as green algae (Chlamydomonas reinhardti) is to recycle the 2-phosphoglycolate that is formed as a by-product of the Calvin cycle. The role of PGPase in nonphotosynthetic organisms is less understood, but one potential role that has been suggested is to remove the 2-phosphoglycolate that is formed as a result of DNA repair. This may be the biological role of PHO13 PGPase in Saccharomyces cerevisiae as well. PHO13 PGPase from S. cerevisiae is a member of the PGPase subfamily within the p-nitrophenylphosphatase (p-NPPase) family, which is within the Haloalkanoic Acid Dehalogenase (HAD) superfamily. pho13 has been subcloned into pET19b to create PHO13(His*Tag). PHO13(HT) was overexpressed and found to be soluble. It purified well by Ni2+-NTA affinity chromatography followed by size-exclusion chromatography. Its expression, solubility, and activity appeared comparable to the native PHO13, but PHO13(HT) was easier to purify due to the histidine tag. Both enzymes had comparable specific activities for both p-nitrophenylphosphate (p-NPP) and 2-phosphoglycolate (PG), pH optima around pH 8.0, optimal activity with ≥ 7 mM Mg2+, activity with Co2+ and Mn2+, negligible activity in the presence of Zn2+, and no activity for Ca2+. PHO13(HT) is now ready for x-ray crystal structure determination with our collaborator, Joseph Wedekind, at the University of Rochester

Modeling human color categorization: color discrimination and color memory

Color matching in Content-Based Image Retrieval is done using a color space and measuring distances between colors. Such an approach yields non-intuitive results for the user. We introduce color categories (or focal colors), determine that they are valid, and use them in two experiments. The experiments conducted prove the difference between color categorization by the cognitive processes color discrimination and color memory. In addition, they yield a Color Look-Up Table, which can improve color matching, that can be seen as a model for human color matching

Changes in salivary estradiol predict changes in women’s preferences for vocal masculinity

Although many studies have reported that women’s preferences for masculine physical characteristics in men change systematically during the menstrual cycle, the hormonal mechanisms underpinning these changes are currently poorly understood. Previous studies investigating the relationships between measured hormone levels and women’s masculinity preferences tested only judgments of men’s facial attractiveness. Results of these studies suggested that preferences for masculine characteristics in men’s faces were related to either women’s estradiol or testosterone levels. To investigate the hormonal correlates of within-woman variation in masculinity preferences further, here we measured 62 women’s salivary estradiol, progesterone, and testosterone levels and their preferences for masculine characteristics in men’s voices in five weekly test sessions. Multilevel modeling of these data showed that changes in salivary estradiol were the best predictor of changes in women’s preferences for vocal masculinity. These results complement other recent research implicating estradiol in women’s mate preferences, attention to courtship signals, sexual motivation, and sexual strategies, and are the first to link women’s voice preferences directly to measured hormone levels

Changes in salivary estradiol predict changes in women’s preferences for vocal masculinity

Although many studies have reported that women’s preferences for masculine physical characteristics in men change systematically during the menstrual cycle, the hormonal mechanisms underpinning these changes are currently poorly understood. Previous studies investigating the relationships between measured hormone levels and women’s masculinity preferences tested only judgments of men’s facial attractiveness. Results of these studies suggested that preferences for masculine characteristics in men’s faces were related to either women’s estradiol or testosterone levels. To investigate the hormonal correlates of within-woman variation in masculinity preferences further, here we measured 62 women’s salivary estradiol, progesterone, and testosterone levels and their preferences for masculine characteristics in men’s voices in five weekly test sessions. Multilevel modeling of these data showed that changes in salivary estradiol were the best predictor of changes in women’s preferences for vocal masculinity. These results complement other recent research implicating estradiol in women’s mate preferences, attention to courtship signals, sexual motivation, and sexual strategies, and are the first to link women’s voice preferences directly to measured hormone levels

Noise-induced pulse-timing statistics in an integrated two-section semiconductor laser with saturable absorber

We have analyzed and explained the generation of irregularly timed, spontaneous-emission triggered optical pulses from a two-section semiconductor laser with saturable absorber, operating near threshold in a regime of excitability. Here we focus on the statistics of the spontaneously emitted pulses. The numerical simulations and analytical theory are based on the Yamada model. The observed irregular pulse train intervals exhibit an initial refractory time, followed by a time interval until the next emitted pulse. The latter is analyzed in terms of a first-passage-time distribution for the intensity to diffuse from its equilibrium value to hit a larger threshold intensity for the first time. Analytic asymptotic short-time and long-time approximations have been derived