Sequence-Dependent Self-Coacervation in High Charge-Density Polyampholytes

Polyampholytes, which contain both positive and negative charges along the backbone, represent a classical model system for certain types of `intrinsically-disordered proteins\u27 (IDPs). IDPs can possess biological functionality, even in an unfolded state, including the formation of phase-separated regions within a cell; while driven by a number of interactions, electrostatic attractions are thought to be key to forming these structures. This process of electrostatically-driven liquid-liquid phase separation, known as `complex coacervation\u27, can also be observed in simpler polymer or biopolymer systems. In this paper, we use a series of model polyampholytic polypeptides of increasing blockiness, that undergo `self-coacervation\u27 due to charge attraction between polycation and polyanion blocks along the same polymer chain. We show that these polypeptides undergo complex coacervation when sequences have at least 8-12 adjacent like-charges, with increasing blockiness leading to a larger two-phase region. We simultaneously develop a theory built on the transfer-matrix formalism developed by the authors, to show how blockiness increases the strength of electrostatic interactions and subsequently promote phase separation. We explore a tradeoff that emerges due to the presence of `charge-pattern interfaces\u27 where the sequence of polyampholyte charges switches sign, and how these contrast with chain-ends in equivalent homopolyelectrolyte coacervates

Designing Electrostatic Interactions via Polyelectrolyte Monomer Sequence

Charged polymers are ubiquitous in biological systems because electrostatic interactions can drive complicated structure formation and respond to environmental parameters such as ionic strength and pH. In these systems, function emerges from sophisticated molecular design; for example, intrinsically disordered proteins leverage specific sequences of monomeric charges to control the formation and function of intracellular compartments known as membraneless organelles. The role of a charged monomer sequence in dictating the strength of electrostatic interactions remains poorly understood despite extensive evidence that sequence is a powerful tool biology uses to tune soft materials. In this article, we use a combination of theory, experiment, and simulation to establish the physical principles governing sequence-driven control of electrostatic interactions. We predict how arbitrary sequences of charge give rise to drastic changes in electrostatic interactions and correspondingly phase behavior. We generalize a transfer matrix formalism that describes a phase separation phenomenon known as “complex coacervation” and provide a theoretical framework to predict the phase behavior of charge sequences. This work thus provides insights into both how charge sequence is used in biology and how it could be used to engineer properties of synthetic polymer systems

A 2-year randomised placebo-controlled trial of doxycycline for lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is characterised by lung cysts and airflow obstruction. Matrix metalloproteinases have been implicated in lung destruction in LAM. We performed a randomised, double-blind trial, comparing the matrix metalloproteinases inhibitor doxycycline with placebo on the progression of LAM. 23 females with LAM were randomised to doxycycline 100 mg daily for 3 months followed by 200 mg daily for 21 months, or matched placebo. Lung function, exercise capacity, quality of life and matrix metalloproteinases levels were measured. 21 patients completed 6 months of treatment, 17 completed 1 year of treatment and 15 completed 2 years of treatment. Eight withdrew from the trial due, four due to a pneumothorax and four because of other reasons. The mean±sd decline in FEV1, the primary endpoint, did not differ between the groups being -90±154 mL·year−1 in the placebo group and -123±246 mL·year−1 in the doxycycline group (difference -32.5, 95% CI -213–148; p=0.35). Doxycycline had no effect upon vital capacity, gas transfer, shuttle walk distance or quality of life. Urine matrix metalloproteinases-9 measurements were lower with doxycycline treatment (p=0.03). Although with limited numbers we cannot completely exclude an effect of doxycycline, the lack of effect on any outcome makes it unlikely that doxycycline has a useful effect in LAM

Metabolic Profiling of IDH Mutation and Malignant Progression in Infiltrating Glioma.

Infiltrating low grade gliomas (LGGs) are heterogeneous in their behavior and the strategies used for clinical management are highly variable. A key factor in clinical decision-making is that patients with mutations in the isocitrate dehydrogenase 1 and 2 (IDH1/2) oncogenes are more likely to have a favorable outcome and be sensitive to treatment. Because of their relatively long overall median survival, more aggressive treatments are typically reserved for patients that have undergone malignant progression (MP) to an anaplastic glioma or secondary glioblastoma (GBM). In the current study, ex vivo metabolic profiles of image-guided tissue samples obtained from patients with newly diagnosed and recurrent LGG were investigated using proton high-resolution magic angle spinning spectroscopy (1H HR-MAS). Distinct spectral profiles were observed for lesions with IDH-mutated genotypes, between astrocytoma and oligodendroglioma histologies, as well as for tumors that had undergone MP. Levels of 2-hydroxyglutarate (2HG) were correlated with increased mitotic activity, axonal disruption, vascular neoplasia, and with several brain metabolites including the choline species, glutamate, glutathione, and GABA. The information obtained in this study may be used to develop strategies for in vivo characterization of infiltrative glioma, in order to improve disease stratification and to assist in monitoring response to therapy

Prospective evaluation of novel biomarkers of acute kidney injury in dogs following cardiac surgery under cardiopulmonary bypass

OBJECTIVE: To assess the occurrence of acute kidney injury (AKI) in dogs undergoing cardiac surgery under cardiopulmonary bypass (CPB) and explore associations between traditional and novel serum and urinary biomarkers. DESIGN: Prospective cohort study conducted between July 2018 and April 2019. SETTING: University teaching hospital. ANIMALS: Nineteen dogs undergoing cardiac surgery under CPB with preoperative serum creatinine <140 μmol/L (<1.6 mg/dl). INTERVENTIONS: Blood and urine samples were obtained at 4 time points: preoperatively following general anesthesia induction, immediately postoperatively, and 2 and 4 days postoperatively (T(1), T(2), T(3), and T(4)). AKI was defined as an increase in serum creatinine ≥26.4 μmol/L (≥0.3 mg/dl) above baseline within 48 hours. Serum creatinine, C‐reactive protein (CRP), symmetric dimethylarginine (SDMA), inosine, beta‐aminoisobutyric acid (BAIB), urinary clusterin (uClus), and urinary cystatin B (uCysB) were measured. Data were log‐transformed (log(10)) when appropriate and assessed using linear mixed‐effects models. MEASUREMENTS AND MAIN RESULTS: AKI occurred in 3 of 19 dogs (15.8%, 95% confidence interval: 0.047–0.384). Inosine increased at T(2) (adjusted mean ± standard error: 53 ± 5.6) in all dogs, and then gradually decreased. Log(10)uCysB increased at T(2) (2.3 ± 0.1) in all dogs and remained high. Log(10)CRP and log(10)uClus increased significantly at T(3) (1.9 ± 0.1 and 3.6 ± 0.1, respectively) in all dogs and remained increased. There was a significant positive association between serum creatinine and SDMA (P < 0.001, estimate ± standard error: 0.06 ± 0.00), between log(10)CRP and log(10)uClus (P < 0.001, 0.35 ± 0.08), between SDMA and creatinine as well as between SDMA and BAIB (P < 0.001, 11.1 ± 0.83 and P < 0.001, 1.06 ± 0.22, respectively) for all dogs at all time points. CONCLUSIONS: Inosine and uCysB concentrations changed in all dogs immediately following a surgery under CPB and may indicate tubular injury. Further studies are required to ascertain the usefulness of those biomarkers in early detection of AKI

Sequence and Entropy-Based Control of Complex Coacervates

Biomacromolecules rely on the precise placement of monomers to encode information for structure, function, and physiology. Efforts to emulate this complexity via the synthetic control of chemical sequence in polymers are finding success; however, there is little understanding of how to translate monomer sequence to physical material properties. Here we establish design rules for implementing this sequence-control in materials known as complex coacervates. These materials are formed by the associative phase separation of oppositely charged polyelectrolytes into polyelectrolyte dense (coacervate) and polyelectrolyte dilute (supernatant) phases. We demonstrate that patterns of charges can profoundly affect the charge–charge associations that drive this process. Furthermore, we establish the physical origin of this pattern-dependent interaction: there is a nuanced combination of structural changes in the dense coacervate phase and a 1D confinement of counterions due to patterns along polymers in the supernatant phase

Mineralization of Short Term Pericardial Cardiac Patch Grafts

Glutaraldehyde fixed patch grafts of bovine pericardium were implanted in myocardial windows in young (3-4 months old) sheep. The samples were retrieved after one to three weeks for study with scanning electron microscopy (SEM) and energy dispersive x-ray microanalysis (EDX). A layer of porous material (pseudoneointima, PNI), consisting mostly of a dense mesh of fibers interspersed with blood cells, was noted to form on the blood contacting surface of the graft. Four distinct sets of mineralization were noted in the retrieved grafts: (1) at the blood contacting surface of the PNI; (2) within the PNI at the junction between layers of PNI with differing densities; (#) near the junction of PNI and pericardium (but in the PNI); and (4) within the pericardium. In both the PNI and pericardium the mineral was shown by EDX analysis to contain both calcium and phosphorous indicating the mineral to be a calcium phosphate. Mineralization in the PNI differed from that in the pericardium; in the PNI it was deposited in discrete regions and apparently in association with thrombi while in the pericardium it was distributed diffusely within the collagen matrix, which may influence its formation

Exploring the impact of trait number and type on functional diversity metrics in real-world ecosystems

The use of trait-based approaches to understand ecological communities has increased in the past two decades because of their promise to preserve more information about community structure than taxonomic methods and their potential to connect community responses to subsequent effects of ecosystem functioning. Though trait-based approaches are a powerful tool for describing ecological communities, many important properties of commonly-used trait metrics remain unexamined. Previous work in studies that simulate communities and trait distributions show consistent sensitivity of functional richness and evenness measures to the number of traits used to calculate them, but these relationships have yet to be studied in actual plant communities with a realistic distribution of trait values, ecologically meaningful covariation of traits, and a realistic number of traits available for analysis. Therefore, we propose to test how the number of traits used and the correlation between traits used in the calculation of functional diversity indices impacts the magnitude of eight functional diversity metrics in real plant communities. We will use trait data from three grassland plant communities in the US to assess the generality of our findings across ecosystems and experiments. We will determine how eight functional diversity metrics (functional richness, functional evenness, functional divergence, functional dispersion, kernel density estimation (KDE) richness, KDE evenness, KDE dispersion, Rao's Q) differ based on the number of traits used in the metric calculation and on the correlation of traits when holding the number of traits constant. Without a firm understanding of how a scientist's choices impact these metric, it will be difficult to compare results among studies with different metric parametrization and thus, limit robust conclusions about functional composition of communities across systems

Cluster randomized trial of the impact of an obesity prevention intervention on child care center nutrition and physical activity environment over two years

Objective: The prevalence of obesity among preschool-aged children in the United States remains unacceptably high. Here we examine the impact of Healthy Caregivers-Healthy Children (HC2) Phase 2, a child care center (CCC)-based obesity prevention intervention on changes in the CCC nutrition and physical activity environment over two school years. Design: This was a cluster randomized trial with 12 CCC receiving the HC2 intervention arm and 12 in the control arm. The primary outcome was change in the Environment and Policy Assessment and Observation (EPAO) tool over two school years (Fall-2015, Spring-2016 and Spring-2017). Changes in EPAO physical activity and nutrition score were analyzed via a (1) random effects mixed models and (2) mixed models to determine the effect of HC2 versus control. Setting: The study was conducted in 24 CCCs serving low-income, ethnically diverse families in Miami-Dade County. Participants: Intervention CCCs received (1) teachers/parents/children curriculum; (2) snack, beverage, physical activity, and screen time policies; and (3) menu modifications. Results: Two-year EPAO nutrition score changes in intervention CCCs were almost twice that of control CCCs. The EPAO physical activity environment scores only slightly improved in intervention CCCs versus control CCCs. Intervention CCCs showed higher combined EPAO physical activity and nutrition scores compared to control CCCs over the 2-year study period (β=0.09, P=0.05). Conclusions: Obesity prevention programs can have a positive impact on the CCC nutrition environment and can promote healthy weight in early childhood. CCCs may need consistent support to improve the physical activity environment to ensure the policies remain intact