Update on Transcatheter Device Closure of Congenital Septal Defects.

PURPOSE OF REVIEW: The goal of this paper is to review currently available devices for closure of atrial septal defects (ASDs) and ventricular septal defects (VSDs). RECENT FINDINGS: Favorable results from the ASSURED trial resulted in FDA approval for the most recently developed device for transcatheter ASD closure in the United States. Further studies are required to assist in the development or approval of safe devices for transcatheter perimembranous VSD closure in pediatric patients. Device closure is the less invasive and preferred management option for many ASDs, with multiple studies demonstrating lower complication rates, shorter hospital stays, and lower mortality than surgical repair. Complex ASDs that make device closure more difficult include large defects, rim deficiencies, fenestrated defects, multiple defects, and the presence of pulmonary arterial hypertension. Device closure has also become an accepted alternative to surgery for some types of ventricular septal defects VSDs, though challenges and limitations remain. Future innovations including novel devices and techniques are needed to further expand on the types of defects that can be safely closed via transcatheter approach.

Production and characterisation of modularly deuterated UBE2D1-Ub conjugate by small angle neutron and X-ray scattering.

This structural study exploits the possibility to use modular protein deuteration to facilitate the study of ubiquitin signalling, transfer, and modification. A protein conjugation reaction is used to combine protonated E2 enzyme with deuterated ubiquitin for small angle X-ray and neutron scattering with neutron contrast variation. The combined biomolecules stay as a monodisperse system during data collection in both protonated and deuterated buffers indicating long stability of the E2-Ub conjugate. With multiphase ab initio shape restoration and rigid body modelling, we reconstructed the shape of a E2-Ub-conjugated complex of UBE2D1 linked to ubiquitin via an isopeptide bond. Solution X-ray and neutron scattering data for this E2-Ub conjugate in the absence of E3 jointly indicate an ensemble of open and backbent states, with a preference for the latter in solution. The approach of combining protonated and labelled proteins can be used for solution studies to assess localization and movement of ubiquitin and could be widely applied to modular Ub systems in general.

Ionic group-dependent structure of complex coacervate hydrogels formed by ABA triblock copolymers.

This study investigates the nanostructure of complex coacervate core hydrogels (C3Gs) with varying compositions of cationic charged groups (i.e., ammonium and guanidinium) using small-angle X-ray/neutron scattering (SAX/NS). C3Gs were prepared by stoichiometric mixing of two oppositely charged ABA triblock copolymers in aqueous solvents, in which A end-blocks were functionalized with either sulfonate groups or a mixture of ammonium and guanidinium groups. Comprehensive small-angle X-ray/neutron scattering (SAX/NS) analysis elucidated the dependence of C3Gs structures on the fraction of guanidinium groups in the cationic end-block (x) and salt concentration (cs). As x increases, the polymer volume fraction in the cores, and interfacial tension (γcore) and salt resistance (c*) of the coacervate cores increase, which is attributed to the greater hydrophobicity and non-electrostatic association. Furthermore, we observed that the salt dependence of the interfacial tension follows γcore ∼ (1 - cs/c*)3/2 in all series of x. The results show that the variation of the ionic group provides a powerful method to control the salt-responsiveness of C3Gs as stimuli-responsive materials.

Polycation radius of gyration in a polymeric ionic liquid (PIL): the PIL melt is not a theta solvent.

The conformation of the polycation in the prototypical polymeric ionic liquid (PIL) poly(3-methyl-1-aminopropylimidazolylacrylamide) bis(trifluoromethylsulfonyl)imide (poly(3MAPIm)TFSI) was probed using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) at 25 °C and 80 °C. Poly(3MAPIm)TFSI contains microvoids which lead to intense low q scattering that can be mitigated using mixtures of hydrogen- and deuterium-rich materials, allowing determination of the polycation conformation and radius of gyration (Rg). In the pure PIL, the polycation adopts a random coil conformation with Rg = 52 ± 0.5 Å. In contrast to conventional polymer melts, the pure PIL is not a theta solvent for the polycation. The TFSI- anions, which comprise 48% v/v of the PIL, are strongly attracted to the polycation and act like small solvent molecules which leads to chain swelling analogous to an entangled, semi-dilute, or concentrated polymer solution in a good solvent.

Electrochemical Synthesis of Mesoporous Architectured Ru Films Using Supramolecular Templates.

The electrochemical synthesis of mesoporous ruthenium (Ru) films using sacrificial self-assembled block polymer micelles templates, and its electrochemical surface oxidation to RuOx is described. Unlike standard methods such as thermal oxidation, the electrochemical oxidation method described here retains the mesoporous structure. Ru oxide materials serve as high-performance supercapacitor electrodes due to their excellent pseudocapacitive behavior. The mesoporous architectured film shows superior specific capacitance (467 F g-1Ru ) versus a nonporous Ru/RuOx electrode (28 F g-1Ru ) that is prepared via the same method but omitting the pore-directing polymer. Ultrahigh surface area materials will play an essential role in increasing the capacitance of this class of energy storage devices because the pseudocapacitive redox reaction occurs on the surface of electrodes.

Mesoporous Metallic Iridium Nanosheets.

Two-dimensional (2D) metals are an emerging class of nanostructures that have attracted enormous research interest due to their unusual electronic and thermal transport properties. Adding mesopores in the plane of ultrathin 2D metals is the next big step in manipulating these structures because increasing their surface area improves the utilization of the material and the availability of active sites. Here, we report a novel synthetic strategy to prepare an unprecedented type of 2D mesoporous metallic iridium (Ir) nanosheet. Mesoporous Ir nanosheets can be synthesized with close-packed assemblies of diblock copolymer (poly-(ethylene oxide)- b-polystyrene, PEO- b-PS) micelles aligned in the 2D plane of the nanosheets. This novel synthetic route opens a new dimension of control in the synthesis of 2D metals, enabling new kinds of mesoporous architectures with abundant catalytically active sites. Because of their unique structural features, the mesoporous metallic Ir nanosheets exhibit a high electrocatalytic activity toward the oxygen evolution reaction (OER) in acidic solution as compared to commercially available catalysts.

A tethered bilayer lipid membrane that mimics microbial membranes.

A model membrane system has been developed, which mimics the outer membrane of Gram negative bacteria. The structure is based on a tethered monolayer which has been fused with vesicles containing lipopolysaccharide molecules. The effect of the composition of the monolayer and the lipids in the outer layer on the structural and electrical properties of the membrane has been investigated. By using electrochemical impedance spectroscopy as well as neutron scattering techniques, it could be shown that a relatively high tethering density and a small amount of diluting lipids in the outer membrane leaflet leads to the formation of a stable solid supported membrane. The influence of divalent ions on the membrane stability has been probed as well as the interaction of the bilayer with the antibiotic colistin. A number of different architectures were developed, suited to both the study of bacterial membrane proteins and the screening of antimicrobial activity of potential drug candidates.

Effect of protic ionic liquid nanostructure on phospholipid vesicle formation.

The formation of bilayer-based lyotropic liquid crystals and vesicle dispersions by phospholipids in a range of protic ionic liquids has been investigated by polarizing optical microscopy using isothermal penetration scans, differential scanning calorimetry, and small angle X-ray and neutron scattering. The stability and structure of both lamellar phases and vesicle dispersions is found to depend primarily on the underlying amphiphilic nanostructure of the ionic liquid itself. This finding has significant implications for the use of ionic liquids in soft and biological materials and for biopreservation, and demonstrates how vesicle structure and properties can be controlled through selection of cation and anion. For a given ionic liquid, systematic trends in bilayer thickness, chain-melting temperature and enthalpy increase with phospholipid acyl chain length, paralleling behaviour in aqueous systems.

Determining the analytical specificity of PCR-based assays for the diagnosis of IA: What is Aspergillus?

A wide array of PCR tests has been developed to aid the diagnosis of invasive aspergillosis (IA), providing technical diversity but limiting standardisation and acceptance. Methodological recommendations for testing blood samples using PCR exist, based on achieving optimal assay sensitivity to help exclude IA. Conversely, when testing more invasive samples (BAL, biopsy, CSF) emphasis is placed on confirming disease, so analytical specificity is paramount. This multicenter study examined the analytical specificity of PCR methods for detecting IA by blind testing a panel of DNA extracted from a various fungal species to explore the range of Aspergillus species that could be detected, but also potential cross reactivity with other fungal species. Positivity rates were calculated and regression analysis was performed to determine any associations between technical specifications and performance. The accuracy of Aspergillus genus specific assays was 71.8%, significantly greater (P < .0001) than assays specific for individual Aspergillus species (47.2%). For genus specific assays the most often missed species were A. lentulus (25.0%), A. versicolor (24.1%), A. terreus (16.1%), A. flavus (15.2%), A. niger (13.4%), and A. fumigatus (6.2%). There was a significant positive association between accuracy and using an Aspergillus genus PCR assay targeting the rRNA genes (P = .0011). Conversely, there was a significant association between rRNA PCR targets and false positivity (P = .0032). To conclude current Aspergillus PCR assays are better suited for detecting A. fumigatus, with inferior detection of most other Aspergillus species. The use of an Aspergillus genus specific PCR assay targeting the rRNA genes is preferential.

Passive immunotherapy targeting amyloid-ß reduces cerebral amyloid angiopathy and improves vascular reactivity.

Prominent cerebral amyloid angiopathy is often observed in the brains of elderly individuals and is almost universally found in patients with Alzheimer's disease. Cerebral amyloid angiopathy is characterized by accumulation of the shorter amyloid-ß isoform(s) (predominantly amyloid-ß40) in the walls of leptomeningeal and cortical arterioles and is likely a contributory factor to vascular dysfunction leading to stroke and dementia in the elderly. We used transgenic mice with prominent cerebral amyloid angiopathy to investigate the ability of ponezumab, an anti-amyloid-ß40 selective antibody, to attenuate amyloid-ß accrual in cerebral vessels and to acutely restore vascular reactivity. Chronic administration of ponezumab to transgenic mice led to a significant reduction in amyloid and amyloid-ß accumulation both in leptomeningeal and brain vessels when measured by intravital multiphoton imaging and immunohistochemistry. By enriching for cerebral vascular elements, we also measured a significant reduction in the levels of soluble amyloid-ß biochemically. We hypothesized that the reduction in vascular amyloid-ß40 after ponezumab administration may reflect the ability of ponezumab to mobilize an interstitial fluid pool of amyloid-ß40 in brain. Acutely, ponezumab triggered a significant and transient increase in interstitial fluid amyloid-ß40 levels in old plaque-bearing transgenic mice but not in young animals. We also measured a beneficial effect on vascular reactivity following acute administration of ponezumab, even in vessels where there was a severe cerebral amyloid angiopathy burden. Taken together, the beneficial effects ponezumab administration has on reducing the rate of cerebral amyloid angiopathy deposition and restoring cerebral vascular health favours a mechanism that involves rapid removal and/or neutralization of amyloid-ß species that may otherwise be detrimental to normal vessel function.

Incidence and Predictors of Abnormal Anal Cytology Findings Among HIV-Infected Adults Receiving Contemporary Antiretroviral Therapy.

BACKGROUND: Anal cancer rates are higher for human immunodeficiency virus (HIV)-infected adults than for uninfected adults. Limited published data exist characterizing the incidence of precursor lesions detected by anal cytology. METHODS: The Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy was a prospective cohort of 700 HIV-infected participants in 4 US cities. At baseline and annually thereafter, each participant completed a behavioral questionnaire, and healthcare professionals collected anorectal swabs for cytologic examination and human papillomavirus (HPV) detection and genotyping. RESULTS: Among 243 participants with negative baseline results of anal cytology, 37% developed abnormal cytology findings (incidence rate, 13.9 cases/100 person-years of follow-up; 95% confidence interval [CI], 11.3-16.9) over a median follow-up duration of 2.1 years. Rates among men having sex with men, among women, and among men having sex with women were 17.9 cases/person-years of follow-up (95% CI, 13.9-22.7), 9.4 cases/person-years of follow-up (95% CI, 5.6-14.9), and 8.9 cases/person-years of follow-up (95% CI, 4.8-15.6), respectively. In multivariable analysis, the number of persistent high-risk HPV types (adjusted hazard ratio [aHR], 1.17; 95% CI, 1.01-1.36), persistent high-risk HPV types except 16 or 18 (aHR, 2.46; 95% CI, 1.31-4.60), and persistent types 16 or 18 (aHR, 3.90; 95% CI, 1.78-8.54) remained associated with incident abnormalities. CONCLUSIONS: The incidence of abnormal anal cytology findings was high and more likely to develop among persons with persistent high-risk HPV.

Apolipoprotein C-II Adopts Distinct Structures in Complex with Micellar and Submicellar Forms of the Amyloid-Inhibiting Lipid-Mimetic Dodecylphosphocholine.

The formation of amyloid deposits is a common feature of a broad range of diseases, including atherosclerosis, Alzheimer's disease, and Parkinson's disease. The basis and role of amyloid deposition in the pathogenesis of these diseases is still being defined, however an interesting feature of amyloidogenic proteins is that the majority of the pathologically associated proteins are involved in lipid homeostasis, be it in lipid transport, incorporation into membranes, or the regulation of lipid pathways. Thus, amyloid-forming proteins commonly bind lipids, and lipids are generally involved in the proper folding of these proteins. However, understanding of the basis for these lipid-related aspects of amyloidogenesis is lacking. Thus, we have used the apolipoprotein C-II amyloid model system in conjunction with x-ray and neutron scattering analyses to address this problem. Apolipoprotein C-II is a well-studied model system of systemic amyloid fibril formation, with a clear and well-defined pathway for fibril formation, where the effects of lipid interaction are characterized, particularly for the lipid mimetic dodecylphosphocholine. We show that the micellar state of an inhibitory lipid can have a very significant effect on protein conformation, with micelles stabilizing a particular α-helical structure, whereas submicellar lipids stabilize a very different dimeric, α-helical structure. These results indicate that lipids may have an important role in the development and progression of amyloid-related diseases.

Discovery of indole-derived pyridopyrazine-1,6-dione γ-secretase modulators that target presenilin.

Herein we describe design strategies that led to the discovery of novel pyridopyrazine-1,6-dione γ-secretase modulators (GSMs) incorporating an indole motif as a heterocyclic replacement for a naphthyl moiety that was present in the original lead 9. Tactics involving parallel medicinal chemistry and in situ monomer synthesis to prepare focused libraries are discussed. Optimized indole GSM 29 exhibited good alignment of in vitro potency and physicochemical properties, and moderate reduction of brain Aß42 was achieved in a rat efficacy model when dosed orally at 30mg/kg. Labeling experiments using a clickable, indole-derived GSM photoaffinity probe demonstrated that this series binds to the presenilin N-terminal fragment (PS1-NTF) of the γ-secretase complex.

Guanidine hydrochloride denaturation of dopamine-induced α-synuclein oligomers: a small-angle X-ray scattering study.

Alpha-synuclein (α-syn) forms the amyloid-containing Lewy bodies found in the brain in Parkinson's disease. The neurotransmitter dopamine (DA) reacts with α-syn to form SDS-resistant soluble, non-amyloid, and melanin-containing oligomers. Their toxicity is debated, as is the nature of their structure and their relation to amyloid-forming conformers of α-syn. The small-angle X-ray scattering technique in combination with modeling by the ensemble optimization method showed that the un-reacted native protein populated three broad classes of conformer, while reaction with DA gave a restricted ensemble range suggesting that the rigid melanin molecule played an important part in their structure. We found that 6 M guanidine hydrochloride did not dissociate α-syn DA-reacted dimers and trimers, suggesting covalent linkages. The pathological significance of covalent association is that if they are non-toxic, the oligomers would act as a sink for toxic excess DA and α-syn; if toxic, their stability could enhance their toxicity. We argue it is essential, therefore, to resolve the question of whether they are toxic or not.

Temperature- and pH-responsive micelles with collapsible poly(N-isopropylacrylamide) headgroups.

We have studied the micelle formation and phase behavior of a series of temperature- and pH-responsive surfactants prepared by controlled radical (RAFT) polymerization. These C12NIPAMm surfactants consist of a dodecyl tail, a poly(N-isopropylacrylamide) (polyNIPAM) headgroup with average degrees of polymerization of between 7 and 96, and an ionizable carboxylate group. In the un-ionized state, these surfactants phase separate on warming toward a lower critical solution temperature (LCST), which decreases as the length of the NIPAM group is decreased. This is in agreement with the behavior of conventional nonionic poly(ethylene oxide)-based surfactants but is very different from that of polyNIPAM oligomer solutions. Small angle neutron scattering (SANS) shows that these surfactants self-assemble into micelles consisting of a nearly spherical hydrophobic core surrounded by a "hairy" polyNIPAM shell far below their LCST. Upon warming, the micelles undergo a sphere-to-rod transition induced by the collapse of the polyNIPAM shell, causing a reduction in the headgroup area. In the un-ionized state the demixing follows at the LCST, but a single charge on the free polymer end completely suppresses phase separation, allowing micelles to undergo a shape change but remain dissolved.

Inelastic neutron scattering and spectroscopy methods to characterize dynamics in colloidal and soft matter systems.

Colloidal systems and soft materials are well suited to neutron scattering, and the community has readily adopted elastic scattering techniques to investigate their structure. Due to their unique properties, neutrons may also be used to characterize the dynamics of soft materials over a wide range of length and time scales in situ. Both static structures and an understanding of how molecules move about their equilibrium positions is essential if we are to deliver on the promise of rationally designing soft materials. In this review we introduce the basics of neutron spectroscopy and explore the ways in which inelastic neutron scattering can be used to study colloidal and soft materials. Illustrative examples are chosen that highlight the phenomena suitable for investigation using this suite of techniques.

H-bond network, interfacial tension and chain melting temperature govern phospholipid self-assembly in ionic liquids.

HYPOTHESIS: The self-assembly structures and phase behaviour of phospholipids in protic ionic liquids (ILs) depend on intermolecular forces that can be controlled through changes in the size, polarity, and H-bond capacity of the solvent. EXPERIMENTS: The structure and temperature stability of the self-assembled phases formed by four phospholipids in three ILs was determined by a combination of small- and wide-angle X-ray scattering (SAXS and WAXS) and small-angle neutron scattering (SANS). The phospholipids have identical phosphocholine head groups but different alkyl tail lengths and saturations (DOPC, POPC, DPPC and DSPC), while the ILs' amphiphilicity, H-bond network density and polarity are varied between propylammonium nitrate (PAN) to ethylammonium nitrate (EAN) to ethanolammonium nitrate (EtAN). FINDINGS: The observed structures and phase behaviour of the lipids becomes more surfactant-like with decreasing average solvent polarity, H-bond network density and surface tension. In PAN, all the investigated phospholipids behave like surfactants in water. In EAN they exhibit anomalous phase sequences and unexpected transitions as a function of temperature, while EtAN supports structures that share characteristics with water and EAN. Structures formed are also sensitive to proximity to the lipid chain melting temperature.

Experimental Evidence for the Role of Dynamics in pH-Dependent Enzymatic Activity.

Enzymatic activity is heavily influenced by pH, but the rationale for the dynamical mechanism of pH-dependent enzymatic activity has not been fully understood. In this work, combined neutron scattering techniques, including quasielastic neutron scattering (QENS) and small angle neutron scattering (SANS), are used to study the structural and dynamic changes of a model enzyme, xylanase, under different pH and temperature environments. The QENS results reveal that xylanase at optimal pH exhibits faster relaxational dynamics and a lower energy barrier between conformational substates. The SANS results demonstrate that pH affects both xylanase's stability and monodispersity. Our findings indicate that enzymes have optimized stability and function under their optimal pH conditions, with both structure and dynamics being affected. The current study offers valuable insights into enzymatic functionality mechanisms, allowing for broad industrial applications.

Polyelectrolyte-protein synergism: pH-responsive polyelectrolyte/insulin complexes as versatile carriers for targeted protein and drug delivery.

The co-assembly of polyelectrolytes (PE) with proteins offers a promising approach for designing complex structures with customizable morphologies, charge distribution, and stability for targeted cargo delivery. However, the complexity of protein structure limits our ability to predict the properties of the formed nanoparticles, and our goal is to identify the key triggers of the morphological transition in protein/PE complexes and evaluate their ability to encapsulate multivalent ionic drugs. A positively charged PE can assemble with a protein at pH above isoelectric point due to the electrostatic attraction and disassemble at pH below isoelectric point due to the repulsion. The additional hydrophilic block of the polymer should stabilize the particles in solution and enable them to encapsulate a negatively charged drug in the presence of PE excess. We demonstrated that diblock copolymers, poly(ethylene oxide)-block-poly(N,N-dimethylaminoethyl methacrylate) and poly(ethylene oxide)-block-poly(N,N,N-trimethylammonioethyl methacrylate), consisting of a polycation block and a neutral hydrophilic block, reversibly co-assemble with insulin in pH range between 5 and 8. Using small-angle neutron and X-ray scattering (SANS, SAXS), we showed that insulin arrangement within formed particles is controlled by intermolecular electrostatic forces between protein molecules, and can be tuned by varying ionic strength. For the first time, we observed by fluorescence that formed protein/PE complexes with excess of positive charges exhibited potential for encapsulating and controlled release of negatively charged bivalent drugs, protoporphyrin-IX and zinc(II) protoporphyrin-IX, enabling the development of nanocarriers for combination therapies with adjustable charge, stability, internal structure, and size.

Discovery of Clinical Candidate PF-06648671: A Potent γ-Secretase Modulator for the Treatment of Alzheimer's Disease.

Herein, we describe the design and synthesis of γ-secretase modulator (GSM) clinical candidate PF-06648671 (22) for the treatment of Alzheimer's disease. A key component of the design involved a 2,5-cis-tetrahydrofuran (THF) linker to impart conformational rigidity and lock the compound into a putative bioactive conformation. This effort was guided using a pharmacophore model since crystallographic information was not available for the membrane-bound γ-secretase protein complex at the time of this work. PF-06648671 achieved excellent alignment of whole cell in vitro potency (Aß42 IC50 = 9.8 nM) and absorption, distribution, metabolism, and excretion (ADME) parameters. This resulted in favorable in vivo pharmacokinetic (PK) profile in preclinical species, and PF-06648671 achieved a human PK profile suitable for once-a-day dosing. Furthermore, PF-06648671 was found to have favorable brain availability in rodent, which translated into excellent central exposure in human and robust reduction of amyloid ß (Aß) 42 in cerebrospinal fluid (CSF).