Energy transfer and connectivity in chloroplasts: Competition between trapping and annihilation in pulsed fluorescence induction experiments.

Despite the fact that fluorescence induction is a very complicated process, the technique is used to obtain information regarding connectivity in photosynthetic systems. The models generally used for the analysis are oversimplified, which in some cases has led to questionable interpretations. Here we describe the effects of nonlinear loss processes in (pulsed) induction experiments and how they obscure the features attributed to large-scale connectivity in chloroplasts. We simulate the fluorescence induction process for finite size domains (1-4 reaction centers per domain) and describe both the trapping process and the generation of triplets by a discrete state model. From our numerical calculations it is demonstrated that singlet-triplet annihilation is unavoidable when using microsecond pulses for actinic illumination

Singlet-singlet annihilation kinetics in aggregates and trimers of LHCII.

Singlet-singlet annihilation experiments have been performed on trimeric and aggregated light-harvesting complex II (LHCII) using picosecond spectroscopy to study spatial equilibration times in LHCII preparations, complementing the large amount of data on spectral equilibration available in literature. The annihilation kinetics for trimers can well be described by a statistical approach, and an annihilation rate of (24 ps)(-1) is obtained. In contrast, the annihilation kinetics for aggregates can well be described by a kinetic approach over many hundreds of picoseconds, and it is shown that there is no clear distinction between inter- and intratrimer transfer of excitation energy. With this approach, an annihilation rate of (16 ps)(-1) is obtained after normalization of the annihilation rate per trimer. It is shown that the spatial equilibration in trimeric LHCII between chlorophyll a molecules occurs on a time scale that is an order of magnitude longer than in Photosystem I-core, after correcting for the different number of chlorophyll a molecules in both systems. The slow transfer in LHCII is possibly an important factor in determining excitation trapping in Photosystem II, because it contributes significantly to the overall trapping time

Investigation of the Dietary Intake and Health Status in East Africa in the 1960s: A Systematic Review of the Historic Oltersdorf Collection

We have recently reported on the myriad health benefits of traditional East African foods and food habits. However, this region continues to experience a nutrition transition whereby traditional, well-tried foods have been systematically replaced with the products of multinational corporations. The health-related impact has been devastating, as evidenced by current non-communicable disease (NCD) trends. The purpose of the present investigation was to review the historic Oltersdorf Collection (data collated by the Max-Planck Nutrition Research Unit, Bumbuli Tanzania from the 1930s to 1960s) to determine if adherence to traditional East African food habits was positively associated with health status indices in populations residing in Tanzania, Kenya and Uganda during this period. The systematic review process resulted in six investigations being identified. Published between 1963 and 1969, these are likely the first investigations to provide original data pertaining to dietary intake/adequacy and health status indices within specific East African cohorts. Overall, the review revealed that many ethnic groups did not exhibit adequate dietary intake and did not consume a diversity of traditional whole foods representative of the wide spectrum of food choices available within the region at this time. NCDs such as obesity, hypertension, and type 2 diabetes were not reported in any investigation. However, there was substantial reporting of malnutrition-related and infectious diseases, particularly among children. The present review supports the contention that the shift from a traditional, diversified diet to a simplified, monotonous diet may have occurred with the onset of cash-crop farming. For resolution of nutrition-related epidemics currently plaguing Africa, including NCDs and malnutrition-related diseases (i.e., the double burden) it is critically important to investigate and disseminate evidence related to the fundamental contributors to the nutrition transition