6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes for signatures of adaptation revealed signals at several loci, with the strongest signal located in a cluster of fatty acid desaturases that determine PUFA levels. The selected alleles are associated with multiple metabolic and anthropometric phenotypes and have large effect sizes for weight and height, with the effect on height replicated in Europeans. By analyzing membrane lipids, we found that the selected alleles modulate fatty acid composition, which may affect the regulation of growth hormones. Thus, the Inuit have genetic and physiological adaptations to a diet rich in PUFAs.

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Greenlandic Inuit show genetic signatures of diet and climate adaptation.

Excimer and electron transfer quenching studies of a cyclometalated platinum complex

The role of Pleistocene forest refugia and rivers in the evolutionary diversification of tropical biota has been the subject of considerable debate. A range-wide analysis of gorilla mitochondrial and nuclear variation was used to test the potential role of both refugia and rivers in shaping genetic diversity in current populations. Results reveal strong patterns of regional differentiation that are consistent with refugial hypotheses for central Africa. Four major mitochondrial haplogroups are evident with the greatest divergence between eastern (A, B) and western (C, D) gorillas. Coalescent simulations reject a model of recent east–west separation during the last glacial maximum but are consistent with a divergence time within the Pleistocene. Microsatellite data also support a similar regional pattern of population genetic structure. Signatures of demographic expansion were detected in eastern lowland (B) and Gabon/Congo (D3) mitochondrial haplogroups and are consistent with a history of postglacial expansion from formerly isolated refugia. Although most mitochondrial haplogroups are regionally defined, limited admixture is evident between neighboring haplogroups. Mantel tests reveal a significant isolation-by-distance effect among western lowland gorilla populations. However, mitochondrial genetic distances also correlate with the distance required to circumnavigate intervening rivers, indicating a possible role for rivers in partitioning gorilla genetic diversity. Comparative data are needed to evaluate the importance of both mechanisms of vicariance in other African rainforest taxa.

https://www.pnas.org/content/pnas/104/51/20432.full.pdf

The role of Pleistocene refugia and rivers in shaping gorilla genetic diversity in central Africa.

Over the past few years, new high-throughput DNA sequencing technologies have dramatically increased speed and reduced sequencing costs. However, the use of these sequencing technologies is often challenged by errors and biases associated with the bioinformatical methods used for analyzing the data. In particular, the use of naive methods to identify polymorphic sites and infer genotypes can inflate downstream analyses. Recently, explicit modeling of genotype probability distributions has been proposed as a method for taking genotype call uncertainty into account. Based on this idea, we propose a novel method for quantifying population genetic differentiation from next-generation sequencing data. In addition, we present a strategy for investigating population structure via principal components analysis. Through extensive simulations, we compare the new method herein proposed to approaches based on genotype calling and demonstrate a marked improvement in estimation accuracy for a wide range of conditions. We apply the method to a large-scale genomic data set of domesticated and wild silkworms sequenced at low coverage. We find that we can infer the fine-scale genetic structure of the sampled individuals, suggesting that employing this new method is useful for investigating the genetic relationships of populations sampled at low coverage.

https://www.genetics.org/content/genetics/195/3/979.full.pdf

Quantifying Population Genetic Differentiation from Next-Generation Sequencing Data

Quenching of triplet states of organic compounds by chromium(III) tris(hexafluoroacetylacetonate) in benzene solution as a result of energy and electron transfer

Absolute excited state dipole moments from solvatochromic shifts

The shifts of absorption bands of a few polar molecules have been measured as a function of temperature in several non-polar and polar solvents. These shifts can be described adequately with the Onsager model of dielectrics provided both solute–solvent dipole–dipole interactions and dipole–induced-dipole interactions are included.Thermochromic shifts can be used to obtain excited state dipole moments in a way similar to constant temperature solvatochromic shifts; the two methods appear to be in general agreement.

Temperature effects in solvatochromic shifts

Electronic energy transfer for organic triplet states to chromium(III) complexes: the role of steric effects, spectroscopically forbidden excited states, and "plateau regions" for quenching

Quenching studies of triplet states of organic donors by chromium(III) complexes in benzene solution were carried out by nanosecond pulsed laser photolysis. Quenching of a series of well-characterized triplets by chromium(III)β-diketonates in benzene solution proceeds via electronic energy transfer. The quenching efficiency is associated with the energetically available doublet and quartet states of the central atom and the diffusion-controlled rate is modified by spin-statistical factors. Theoretical treatment of the quenching rates indicates that the free energy of activation for production of the distorted quartet states is at least five times higher than that for production of the undistorted doublet states. The transmission coefficient for energy transfer depends on the substituents in the ligands and increases as the nephelauxetic effect is enhanced.

Electronic energy transfer from triplet states of organic compounds to coordination compounds. Part 1.—Effects of spin-statistical factors on the efficiency of quenching by β-diketonato complexes of chromium(III)

Christos Tsiamis

Papers

Quenching of triplet states of organic compounds by chromium(III) tris(hexafluoroacetylacetonate) in benzene solution as a result of energy and electron transfer

Absolute excited state dipole moments from solvatochromic shifts

Temperature effects in solvatochromic shifts

Electronic energy transfer for organic triplet states to chromium(III) complexes: the role of steric effects, spectroscopically forbidden excited states, and "plateau regions" for quenching

Electronic energy transfer from triplet states of organic compounds to coordination compounds. Part 1.—Effects of spin-statistical factors on the efficiency of quenching by β-diketonato complexes of chromium(III)