Display omitted
•We grafted zwitterionic polymer brushes on UF membrane and pore surfaces via ATRP.•A large brush layer thickness (>100nm) is required to prevent fouling.•Both surface and interior ...pore modified membranes showed similar fouling behavior.•Pore size limits the efficacy of grafting non-fouling brushes to UF interior surface.
We studied the efficacy of grafting zwitterionic polymer brushes for the antifouling modification of ultrafiltration (UF) membranes. Poly(vinylidene fluoride) (PVDF) UF membranes were modified by surface initiated atom transfer radical polymerization (SI-ATRP) to graft poly(sulfobetaine methacrylate) (PSBMA) brushes to the membrane surface. Protein adsorption tests and chemical force microscopy show that a large brush layer thickness (greater than 100nm) is necessary in order to impart effective fouling resistance. In dynamic fouling experiments with bovine serum albumin (BSA) asa model foulant, however, the modified membranes exhibited only a slight increase of flux recovery after fouling compared to pristine PVDF membranes. Despite the thick PSBMA brush layer, this low water flux recovery indicates that internal fouling takes place within the membrane pores. To prevent internal fouling, we grafted PSBMA brushes to both the surface and internal structure of the membranes. Nevertheless, dynamic fouling experiments again showed only a minute improvement in water flux recovery. While a thick brush layer is required for effective fouling resistance, we note that the small pore size of UF membranes imposes a fundamental limit on the brush layer thickness inside the pores. Finally, we discuss the challenges of polymer brush grafting for antifouling UF membrane modification and suggest possible alternative methods to create fouling resistant UF membranes.
Architecture of the symmetric core of the nuclear pore Lin, Daniel H.; Stuwe, Tobias; Schilbach, Sandra ...
Science (American Association for the Advancement of Science),
04/2016, Letnik:
352, Številka:
6283
Journal Article
Recenzirano
Odprti dostop
The nuclear pore complex (NPC) controls the transport of macromolecules between the nucleus and cytoplasm, but its molecular architecture has thus far remained poorly defined. We biochemically ...reconstituted NPC core protomers and elucidated the underlying protein-protein interaction network. Flexible linker sequences, rather than interactions between the structured core scaffold nucleoporins, mediate the assembly of the inner ring complex and its attachment to the NPC coat. X-ray crystallographic analysis of these scaffold nucleoporins revealed the molecular details of their interactions with the flexible linker sequences and enabled construction of full-length atomic structures. By docking these structures into the cryoelectron tomographic reconstruction of the intact human NPC and validating their placement with our nucleoporin interactome, we built a composite structure of the NPC symmetric core that contains ~320,000 residues and accounts for ~56 megadaltons of the NPC's structured mass. Our approach provides a paradigm for the structure determination of similarly complex macromolecular assemblies.
In this work we present the first fully-integrated free-space beam-steering chip using the hybrid silicon platform. The photonic integrated circuit (PIC) consists of 164 optical components including ...lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens. The PIC exhibited steering over 23° x 3.6° with beam widths of 1° x 0.6°.
SIRT1 is a NAD+-dependent deacetylase that plays important roles in many cellular processes. SIRT1 activity is uniquely controlled by a C-terminal regulatory segment (CTR). Here we present crystal ...structures of the catalytic domain of human SIRT1 in complex with the CTR in an open apo form and a closed conformation in complex with a cofactor and a pseudo-substrate peptide. The catalytic domain adopts the canonical sirtuin fold. The CTR forms a β hairpin structure that complements the β sheet of the NAD+-binding domain, covering an essentially invariant hydrophobic surface. The apo form adopts a distinct open conformation, in which the smaller subdomain of SIRT1 undergoes a rotation with respect to the larger NAD+-binding subdomain. A biochemical analysis identifies key residues in the active site, an inhibitory role for the CTR, and distinct structural features of the CTR that mediate binding and inhibition of the SIRT1 catalytic domain.
Display omitted
•Crystal structures of the human SIRT1 catalytic domain in complex with its CTR.•Conformational changes upon substrate and cofactor binding elucidated.•Mutagenesis identifies key residues for catalysis and CTR-mediated inhibition.•CTR binding pocket provides opportunity for the development of novel therapeutics.
Purpose To examine the effects of subconcussive impacts resulting from a single season of youth (age range, 8-13 years) football on changes in specific white matter (WM) tracts as detected with ...diffusion-tensor imaging in the absence of clinically diagnosed concussions. Materials and Methods Head impact data were recorded by using the Head Impact Telemetry system and quantified as the combined-probability risk-weighted cumulative exposure (RWE
). Twenty-five male participants were evaluated for seasonal fractional anisotropy (FA) changes in specific WM tracts: the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus, and superior longitudinal fasciculus (SLF). Fiber tracts were segmented into a central core and two fiber terminals. The relationship between seasonal FA change in the whole fiber, central core, and the fiber terminals with RWE
was also investigated. Linear regression analysis was conducted to determine the association between RWE
and change in fiber tract FA during the season. Results There were statistically significant linear relationships between RWE
and decreased FA in the whole (R
= 0.433; P = .003), core (R
= 0.3649; P = .007), and terminals (R
= 0.5666; P < .001) of left IFOF. A trend toward statistical significance (P = .08) in right SLF was observed. A statistically significant correlation between decrease in FA of the right SLF terminal and RWE
was also observed (R
= 0.2893; P = .028). Conclusion This study found a statistically significant relationship between head impact exposure and change of FA fractional anisotropy value of whole, core, and terminals of left IFOF and right SLF's terminals where WM and gray matter intersect, in the absence of a clinically diagnosed concussion.
RSNA, 2016.
Lateral inhibition at the first synapse in the retina is important for visual perception, enhancing image contrast, color discrimination, and light adaptation. Despite decades of research, the ...feedback signal from horizontal cells to photoreceptors that generates lateral inhibition remains uncertain. GABA, protons, or an ephaptic mechanism have all been suggested as the primary mediator of feedback. However, the complexity of the reciprocal cone to horizontal cell synapse has left the identity of the feedback signal an unsolved mystery.
Advancements in single-cell sequencing have transformed the genomics field by allowing researchers to delve into the intricate cellular heterogeneity within tissues at greater resolution. While ...single-cell omics are more widely applied in model organisms and humans, their use in livestock species is just beginning. Studies in cattle, sheep, and goats have already leveraged single-cell and single-nuclei RNA-seq as well as single-cell and single-nuclei ATAC-seq to delineate cellular diversity in tissues, track changes in cell populations and gene expression over developmental stages, and characterize immune cell populations important for disease resistance and resilience. Although challenges exist for the use of this technology in ruminant livestock, such as the precise annotation of unique cell populations and spatial resolution of cells within a tissue, there is vast potential to enhance our understanding of the cellular and molecular mechanisms underpinning traits essential for healthy and productive livestock. This review intends to highlight the insights gained from published single-cell omics studies in cattle, sheep, and goats, particularly those with publicly accessible data. Further, this manuscript will discuss the challenges and opportunities of this technology in ruminant livestock and how it may contribute to enhanced profitability and sustainability of animal agriculture in the future.
The degree of dietary generalism among consumers has important consequences for population, community, and ecosystem processes, yet the effects on consumer fitness of mixing food types have not been ...examined comprehensively. We conducted a meta-analysis of 161 peer-reviewed studies reporting 493 experimental manipulations of prey diversity to test whether diet mixing enhances consumer fitness based on the intrinsic nutritional quality of foods and consumer physiology. Averaged across studies, mixed diets conferred significantly higher fitness than the average of single-species diets, but not the best single prey species. More than half of individual experiments, however, showed maximal growth and reproduction on mixed diets, consistent with the predicted benefits of a balanced diet. Mixed diets including chemically defended prey were no better than the average prey type, opposing the prediction that a diverse diet dilutes toxins. Finally, mixed-model analysis showed that the effect of diet mixing was stronger for herbivores than for higher trophic levels. The generally weak evidence for the nutritional benefits of diet mixing in these primarily laboratory experiments suggests that diet generalism is not strongly favored by the inherent physiological benefits of mixing food types, but is more likely driven by ecological and environmental influences on consumer foraging.
PDF
