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The dynamics of the PYP photocycle have been studied using time-resolved optical rotatory dispersion (TRORD) spectroscopy in the visible and far-UV spectral regions to probe the changes in the chromophore configuration and the protein secondary structure, respectively. The changes in the secondary structure in PYP upon photoisomerization of the chromophore can be described by two exponential lifetimes of 2 +/- 0.8 and 650 +/- 100 ms that correspond to unfolding and refolding processes, respectively. The TRORD experiments that follow the dynamics of the chromophore report three exponential components, with lifetimes of 10 +/- 3 micros, 1.5 +/- 0.5 ms, and 515 +/- 110 ms. A comparison of the kinetic behaviors of the chromophore and protein shows that during the decay of pR(465) an initial relaxation that is localized to the chromophore hydrophobic pocket precedes the formation of the chromophore and protein structures found in pB(355). In contrast, the protein and chromophore processes occur with similar time constants during inactivation of the signaling state.

The authors argue that white racial attitudes have shifted from a universal rejection of blacks as potential neighbors to an acceptance of open housing in principle—but not in practice. As a result, 1970-1980 declines in racial segregation were confined to metropolitan areas where the number of blacks was so small that desegregation could be accommodated without threatening white preferences for limited interracial contact. Although new housing construction created an impetus for integration in some areas by increasing the proportion of homes built under the Fair Housing Act, most urban blacks lived in older urban areas where new housing was quite limited.

BackgroundChagas disease is a parasitic infection transmitted to humans and mammals by the Triatominae insect. If untreated, Chagas disease can lead to heart failure and death. Previous publications highlighted the potential public health risk of disease transmission among hunters in the United States.FindingsWe further investigated this population’s risk by administering a knowledge, attitudes, and practices questionnaire. Responses from hunters detailed the vector exposure and hunting practices unique to this population that might lead to their increased risk of disease transmission.ConclusionsHunters should be aware of their potential risk for exposure to the insect that could be infected with the parasite that causes Chagas disease.