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Unaltered biological matter (biomatter) can be harnessed to fabricate cohesive, sustainable bioplastics. However, controlling the material properties of these bioplastics is challenging, as the contributions of different macromolecular building blocks to processability and performance are unknown. To deconvolute the roles of different classes of biomolecules, we developed experimental and computational methods to construct and analyze biomatter analogs composed of carbohydrates, proteins, and lipids. These analogs are intended to improve fundamental understanding of biomatter plastics. Spectroscopic analyses of biomatter analogs suggest that cohesion depends on protein aggregation during thermomechanical processing. Molecular dynamics simulations confirm that alterations to protein conformation and hydrogen bonding are likely the primary mechanisms underlying the formation of a cohesive, proteinaceous matrix. Simulations also corroborate experimental measurements highlighting the importance of hydrogen bonding and self-assembly between specific, small-molecule constituents. These conclusions may enable the engineering of next-generation biomatter plastics with improved performance. 

We report a detailed study of the synthesis, composition, magnetic structure, and transport properties of a quasi-one-dimensional antiferromagnet FeBi4S7 that contains chains of edge-sharing FeS6 octahedra. High-resolution powder X-ray diffraction (PXRD) analysis, aided by variation of synthetic conditions, suggests that the true formula of the material is Fe1.2Bi3.8S7, due to the minor substitution of Fe into Bi sites. This finding is in agreement with crystal structure refinement from neutron powder diffraction data as well as with the small band gap of 0.23 eV determined from electrical transport measurements. Analysis of the neutron diffraction pattern collected below the antiferromagnetic ordering temperature of 64 K revealed ferromagnetic coupling between the Fe moments in the chains of FeS6 octahedra. The overall ordering, however, is antiferromagnetic due to the antiparallel arrangement of moments on neighboring chains. The collinear spin arrangement is described by a k-vector (1, 0, 1/2), which indicates doubling of the unit cell in the c direction and the loss of the C-centering translation as compared to the nuclear cell. The ferromagnetic nature of the sulfidebridged chains of Fe2+ ions in FeBi4S7, in contrast to the antiferromagnetic coupling between Fe moments in compounds with similar structural fragments, can be justified by the analysis of metric parameters that characterize the Fe−S bonding in these materials. 

Abstract Flavodoxins (Flds) mediate the flux of electrons between oxidoreductases in diverse metabolic pathways. To investigate whether Flds can support electron transfer to a sulfite reductase (SIR) that evolved to couple with a ferredoxin, we evaluated the ability of Flds to transfer electrons from a ferredoxin‐NADP reductase (FNR) to a ferredoxin‐dependent SIR using growth complementation of anEscherichia colistrain with a sulfur metabolism defect. We show that Flds from cyanobacteria complement this growth defect when coexpressed with an FNR and an SIR that evolved to couple with a plant ferredoxin. When we evaluated the effect of peptide insertion on Fld‐mediated electron transfer, we observed a sensitivity to insertions within regions predicted to be proximal to the cofactor and partner binding sites, while a high insertion tolerance was detected within loops distal from the cofactor and within regions of helices and sheets that are proximal to those loops. Bioinformatic analysis showed that natural Fld sequence variability predicts a large fraction of the motifs that tolerate insertion of the octapeptide SGRPGSLS. These results represent the first evidence that Flds can support electron transfer to assimilatory SIRs, and they suggest that the pattern of insertion tolerance is influenced by interactions with oxidoreductase partners. 

Parents’ questions are an effective strategy for fostering the development of young children’s science understanding and discourse. However, this work has not yet distinguished whether the frequency of questions about scientific content differs between mothers and fathers, despite some evidence from other contexts (i.e., book reading) showing that fathers ask more questions than mothers. The current study compared fathers’ and mothers’ questions to their four- to six-year-old children ( N  = 49) while interacting with scientific stimuli at a museum research exhibit. Results indicated that fathers asked significantly more questions than mothers, and fathers’ questions were more strongly related to children’s scientific discourse. Results are discussed in terms of the importance of adult questions for the development of children’s scientific understanding as well as broadening research to include interlocutors other than mothers.