Determining the forces that conserve amino acid positions in proteins across species is a fundamental pursuit of molecular evolution. Evolutionary conservation is driven by either a protein's function or its thermodynamic stability. Highly conserved histone proteins offer a platform to evaluate these driving forces. While the conservation of histone H3 and H4 “tail” domains and surface residues are driven by functional importance, the driving force behind the conservation of buried histone residues has not been examined. Using a computational approach, we determined the thermodynamically preferred amino acids at each buried position in H3 and H4. In agreement with what is normally observed in proteins, we find a significant correlation between thermodynamic stability and evolutionary conservation in the buried residues in H4. In striking contrast, we find that thermodynamic stability of buried H3 residues does not correlate with evolutionary conservation. Given that these H3 residues are not post-translationally modified and only regulate H3-H3 and H3-H4 stabilizing interactions, our data imply an unknown function responsible for driving conservation of these buried H3 residues.

Purpose Many coastal areas in the Baltic Sea are contaminated with wood fiber and pollutants from pulp and paper industries. These anthropogenic, organic-rich, sediments (fiberbanks) have not been characterized and knowledge about their role as secondary sources for dispersal of persistent organic pollutants (POPs) is limited. Hence, the aim of this study was to elucidate the fate of POPs and the relationships between sorption (K D and K TOC), sediment type, and compound hydrophobicity (K OW) in fiber-contaminated sediments. Materials and methods Paired sediment and pore water samples (n = 24 sites) from three fiber-contaminated areas, located in the Ångermanälven river estuary in northern Sweden, were analyzed for POPs (viz. PCBs, DDT, and HCB) in sediment types representing different fiber content (i.e., fiberbanks, fiber-rich sediments, and natural less fiber impacted sediments). The freely dissolved concentration in sediment pore water was determined by sediment-polyoxymethylene (POM) partitioning. Instrumental analysis was performed using gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). Results and discussion Higher levels of total organic carbon (TOC) were found in the fiberbank sediment (range 8.6-37%) than in fiber-rich sediment (range 2.0-6.5%) and more natural sediment (range 2.0-2.9%). The sediment concentrations of POPs (dry weight basis) were also found to be significantly (p < 0.05) elevated in fiberbanks compared to the other sediment types. The fraction of DDD (48-66% of Σ 6 DDX) was larger in fiberbanks than in the other sediment types, likely due to anoxic conditions favoring reductive dechlorination of DDT. When sediment levels were normalized to TOC, HCB displayed similar levels across sediment type, suggesting a more diffuse source pattern than for PCB and DDT. Although significantly higher sorption (K D) of POPs was observed in fiberbanks, pore water levels were still elevated due to high bulk concentrations. Conclusions This study shows that fiberbanks are coastal hot spots for POPs in the Baltic Sea and that the levels are of ecotoxicological concern. Although the POPs are more strongly sorbed (K D) to this type of organic rich sediment, the high pore water concentrations in fiberbanks compared to the other sediment types investigated show that the risk of contaminant dispersal via pore water is elevated for fiberbanks.

Determining the forces that conserve amino acid positions in proteins across species is a fundamental pursuit of molecular evolution. Evolutionary conservation is driven by either a protein's function or its thermodynamic stability. Highly conserved histone proteins offer a platform to evaluate these driving forces. While the conservation of histone H3 and H4 “tail” domains and surface residues are driven by functional importance, the driving force behind the conservation of buried histone residues has not been examined. Using a computational approach, we determined the thermodynamically preferred amino acids at each buried position in H3 and H4. In agreement with what is normally observed in proteins, we find a significant correlation between thermodynamic stability and evolutionary conservation in the buried residues in H4. In striking contrast, we find that thermodynamic stability of buried H3 residues does not correlate with evolutionary conservation. Given that these H3 residues are not post‐translationally modified and only regulate H3‐H3 and H3‐H4 stabilizing interactions, our data imply an unknown function responsible for driving conservation of these buried H3 residues.

No abstract

Individuals differ in how positively vs. negatively they judge others when providing ratings of first impressions. Here, we investigated whether these rating tendencies reflect conscious choices to be polite and benevolent vs. authentic and critical or whether positivity differences are rooted more deeply in basic information processing. To this end, we developed a procedure in which participants first familiarize themselves with vignettes of unknown targets which contain both desirable and undesirable personality information and later complete a surprise recognition task asking whether or not specific traits had been mentioned in the vignettes. In Study 1 (n = 312) participants differed considerably in the valence of traits they recognized as having been mentioned such that some recognized more positive than negative traits and others more negative than positive traits. Participants with a tendency to recognize mostly positive traits indicated greater liking for the targets and were more agreeable, more conscientious, and older. These results were replicated in Study 2 (n = 837). Study 2 further established that positivity differences occurred during encoding rather than recall and were moderately associated with positivity differences measured with a classic rating-based procedure. The present work expands the understanding of perceiver positivity by differentiating between judgment and perception phenomena.