Pectin Conformation in Solution Alba, K; Bingham, R J; Gunning, P A ...
The journal of physical chemistry. B,
07/2018, Letnik:
122, Številka:
29
Journal Article
Recenzirano
Odprti dostop
The interplay of degree of methylesterification (DM), pH, temperature, and concentration on the macromolecular interactions of pectin in solution has been explored. Small-angle X-ray scattering ...complemented by atomic force microscopy and molecular dynamics was employed to probe chain dimensions and solution structure. Two length scales have been observed with the first level of structure characterising chain clusters with sizes ranging between 100-200 nm. The second level of structure arises from single biopolymer chains with a radius of gyration between ∼6 and 42 nm. The development of a range of macromolecular dimensions in vitro and in silico shows that the chain flexibility increases with DM and at acidic pH, whereas hydrogen bonding is the responsible thermodynamic driving force for cluster formation. High methyl pectins create structures of lower fractal dimension with less efficient packing. This work unveils pectin conformations covering most of its industrially and biologically relevant environments, enabling rational design of advanced biomaterials based on pectin.
Brain charts for the human lifespan Anderson, K M; Adamson, C; Adler, S ...
Nature (London),
04/2022, Letnik:
604, Številka:
7906
Journal Article
Recenzirano
Odprti dostop
Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual ...differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight
. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data ( http://www.brainchart.io/ ). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories
of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones
, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes.
Displacement of the proteins (β-lactoglobulin and β-casein) from air–water interfaces by non-ionic surfactants (Tween 20 and Tween 60) and ionic surfactants (Sodium Dodecyl Sulphate (SDS), ...Cetyl-Trimethyl-Ammonium Bromide (CTAB) and Lyso-Phosphatidyl-Choline-Lauroyl (LPC-L)) was studied. Interfacial structure was sampled using Langmuir–Blodgett deposition onto mica for imaging by atomic force microscopy. In all cases protein displacement was found to occur through an orogenic mechanism. For the non-ionic surfactants displacement involved nucleation and growth of surfactant domains, leading to failure of the protein network, and subsequent loss of protein into the bulk phase. The surface pressure dependences of surfactant domain growth, and the failure of the network, were found to be the same for Tween 20 and Tween 60. This suggests that protein network breakdown was dominated by the mechanical properties of the network, and unaffected by any protein–surfactant binding. Displacement of protein by ionic surfactants was found to be dominated by nucleation of surfactant domains, with little domain growth prior to failure of the network. The size of the domains formed by the ionic surfactants was found to be determined by the level of the intermolecular repulsive forces. Electrostatic screening of these charges led to an increase in the size of the domains. The surface pressure at which the networks failed was found to be dependent on the type of ionic surfactant and, in all cases, to occur at higher surface pressures than that required for non-ionic surfactants. This has been attributed to surfactant-protein binding that strengthens the protein network.
► Gal3 binds specifically to β-d-galactobiose. ► The lifetime of the interaction is 3.0s. ► Binding is consistent with a molecular model for the anti-cancer role of modified pectin.
Force ...spectroscopy has been used to investigate the interaction between the disaccharide β-galactobiose and the pro-metastatic regulatory protein galectin-3 (Gal3). The studies revealed specific interactions characterised by an off-rate dissociation constant koff=0.33s−1 and interaction distance x=0.2nm at zero applied force. These data suggest a lifetime for the interaction of 3.0s. The results are consistent with the hypothesis that oral consumption of modified citrus pectin controls cancer metastasis by inhibiting the role of Gal3. The modification is considered to facilitate binding of pectin-derived galactan sidechains to Gal3 and inhibition of the roles of Gal3 as a pro-metastatic regulatory protein.
A method has been developed for attaching oil (tetradecane) droplets to the end of an atomic force microscopy (AFM) cantilever and for immobilizing droplets on a glass substrate. This approach has ...permitted the monitoring of droplet-droplet interactions in aqueous solution as a function of interdroplet separation. Coating the droplet surfaces with added proteins or surfactants has allowed the production of model emulsions. We demonstrate that AFM measurements of droplet deformability are sensitive to interfacial rheology by modifying the interfacial film on a pair of droplets in situ. For droplets coated with the anionic surfactant sodium dodecyl sulfate, screening of the double layer has been found to facilitate coalescence. Direct imaging of the droplets has revealed the presence of regularly spaced concentric rings on the droplet surfaces. Careful experimental studies suggest that these structures may be imaging artifacts and are not perturbations of the droplet surface determined by the composition of the interface.
A STEM-based faculty in an Australian university leveraged online educational technology to help address student and academic concerns associated with team-based assessment. When engagement and ...contribution of all team members cannot be assured, team-based assessment can become an unfair and inaccurate measure of student competency. This case study explores the design and capacity of an online self and intra-team peer-assessment of teamwork strategy to measure student engagement and enable peers to hold each other accountable during team-based assessments. Analysis of student interactions across 39 subjects that implemented the strategy in 2020, revealed that an average of 94.4% of students completed the self and intra-team peer-assessment task when designed as part of a summative team-based assessment. The analysis also revealed that an average of 10.3% of students were held accountable by their peers, receiving feedback indicating their teamwork skills and behaviours were below the required minimum standard. Furthermore, the strategy was successfully implemented in cohorts ranging from seven to over 700 students, demonstrating scalability. Thus, this online self and intra-team peer-assessment strategy provided teaching teams with evidence of student engagement in a team-based assessment while also enabling students to hold each other accountable for contributing to the team task. Lastly, as the online strategy pairs with any discipline-specific team-based assessment, it provided the faculty with a method that could be used consistently across its schools to support management and engagement in team-based assessments.
The displacement of the proteins (beta-lactoglobulin and beta-casein) from an air-water interface by the nonionic (Tween 20 and Tween 60) and ionic (sodium dodecyl sulfate, cetyltrimethylammonium ...bromide, and lyso-phosphatidylcholine-lauroyl) surfactants has been visualized by atomic force microscopy (AFM). The surface structure has been sampled by the use of Langmuir-Blodgett deposition onto mica substrates to allow imaging in the AFM. In all cases, the displacement process was found to occur through the recently proposed orogenic mechanism (Mackie et al. J. Colloid Interface Sci. 1999, 210, 157-166). In the case of the nonionic surfactants, the displacement involved nucleation and growth of surfactant domains leading to failure of the protein network and subsequent loss of protein into the bulk phase. The surface pressure dependence of the growth of surfactant domains and the failure of the network were found to be the same for both Tween 20 and Tween 60, demonstrating that the breakdown of the protein film was dominated by the mechanical properties of the network. The displacement of protein by ionic surfactants was found to be characterized by nucleation of surfactant domains with little domain growth prior to failure of the network. The size of the domains formed by ionic surfactants was found to be limited by the strong intersurfactant repulsive forces between the charged headgroups. Screening of these charges led to an increase in the size of the domains. The surface pressure at which the network continuity was lost was found to be dependent on the type of surfactant and, in all cases, to occur at higher surface pressures than that required for nonionic surfactants. This has been attributed to surfactant-protein binding that initially strengthens the protein network at low surfactant concentrations. Evidence obtained from surface shear rheology supports this assertion.
The displacement of proteins from an air/water interface by surfactant has been visualized by atomic force microscopy (AFM) through the imaging of Langmuir–Blodgett films formed on mica. Three ...different proteins were studied: β-casein, a largely random coil protein, and two globular proteins, β-lactoglobulin and α-lactalbumin. The proteins were displaced from both spread and coadsorbed films using the nonionic surfactant Tween 20. The combined use of AFM with studies of surface tension and surface rheology have revealed the mechanism of protein desorption from the air/water interface. The surfactant is found to adsorb at defects in the protein network and these nucleated sites then grow, compressing the protein network. At sufficiently high surface pressures the network fails, releasing proteins that then desorb from the interface. We have called this mechanism orogenic displacement. Stress propagation through β-casein films is homogeneous resulting in the growth of circular surfactant domains. β-Lactoglobulin and α-lactalbumin form stronger networks and stress propagation is restricted resulting in the growth of irregular (fractal) surfactant domains. The AFM images also provide direct evidence for the formation of elastic (gel-like) protein networks at the air/water interface.
Displacement of sodium caseinate from the air-water interface by nonionic surfactants Tween 20 and Tween 60 was observed by atomic force microscopy (AFM). The interfacial structure was sampled by ...Langmuir-Blodgett deposition onto freshly cleaved mica substrates. Protein displacement occurred through an orogenic mechanism: it involved the nucleation and growth of surfactant domains within the protein network, followed by failure of the protein network. The surface pressure at which failure of the protein network occurred was essentially independent of the type of surfactant. The major component of sodium caseinate is beta-casein, and previous studies at the air-water interface have shown that beta-casein networks are weak, failing at surface pressures below that observed for sodium caseinate. The other components of sodium caseinate are alpha(s)- and kappa-caseins. Studies of the displacement of alpha(s)-caseins from air-water interfaces show that these proteins also form weak networks that fail at surface pressures below that observed for sodium caseinate. However, kappa-casein was found to form strong networks that resisted displacement and failed at surface pressures comparable to those observed for sodium caseinate. The AFM images of the displacement suggest that, despite kappa-casein being a minor component, it dominates the failure of sodium caseinate networks: alpha(s)-casein and beta-casein are preferentially desorbed at lower surface pressures, allowing the residual kappa-casein to control the breakdown of the sodium caseinate network at higher surface pressures.
To provide a comprehensive overview of cardiovascular disease (CVD) risk prediction models for women and models that include female-specific predictors.
We performed a systematic review of CVD risk ...prediction models for women in the general population by updating a previous review. We searched Medline and Embase up to July 2017 and included studies in which; (a) a new model was developed, (b) an existing model was validated, or (c) a predictor was added to an existing model.
A total of 285 prediction models for women have been developed, of these 160 (56%) were female-specific models, in which a separate model was developed solely in women and 125 (44%) were sex-predictor models. Out of the 160 female-specific models, 2 (1.3%) included one or more female-specific predictors (mostly reproductive risk factors). A total of 591 validations of sex-predictor or female-specific models were identified in 206 papers. Of these, 333 (56%) validations concerned nine models (five versions of Framingham, SCORE, Pooled Cohort Equations and QRISK). The median and pooled C statistics were comparable for sex-predictor and female-specific models. In 260 articles the added value of new predictors to an existing model was described, however in only 3 of these female-specific predictors (reproductive risk factors) were added.
There is an abundance of models for women in the general population. Female-specific and sex-predictor models have similar predictors and performance. Female-specific predictors are rarely included. Further research is needed to assess the added value of female-specific predictors to CVD models for women and provide physicians with a well-performing prediction model for women.
PDF
