D1′ centers are less efficient than normal photosystem II centers

Differential D1 dephosphorylation in functional and photodamaged photosystem II centers. Dephosphorylation is a prerequisite for degradation of damaged D1.

Light dependence and kinetics of reversible phosphorylation of the D1 reaction center protein of Photosystem II was studied in pumpkin leaves. At growth light, maximal phosphorylation of D1 was observed after illumination of 1 h, with higher phosphorylation rates at stronger irradiances. 70-85% of D1 became phosphorylated, corresponding to the proportion of the protein in appressed thylakoid me...

Femtosecond photodichroism studies of isolated photosystem II reaction centers.

Photosynthetic conversion of light energy into chemical potential begins in reaction center protein complexes, where rapid charge separation occurs with nearly unit quantum efficiency. Primary charge separation was studied in isolated photosystem II reaction centers from spinach containing 6 chlorophyll a, 2 pheophytin a (Pheo), 1 cytochrome b559, and 2 beta-carotene molecules. Time-resolved pu...

Energy-Efficient Data Centers

Reducing Food Stamp and Welfare Caseloads in the South: Are Rural Areas Less Likely to Succeed Than Urban Centers? by

In this paper, tests are made for the effect that the spatial distribution of welfare and Food Stamp caseloads may have on caseload change in the South. Spatial effects are captured by contrasting caseload trends overtime in metropolitan (urban) counties and nonmetropolitan (rural) counties within two southern states, Mississippi and South Carolina. Tests for a location effect on caseload chang...

Energy and electron transfer in photosystem II reaction centers with modified pheophytin composition.

Energy and electron transfer in Photosystem II reaction centers in which the photochemically inactive pheophytin had been replaced by 13(1)-deoxo-13(1)-hydroxy pheophytin were studied by femtosecond transient absorption-difference spectroscopy at 77 K and compared to the dynamics in untreated reaction center preparations. Spectral changes induced by 683-nm excitation were recorded both in the Q...