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1.
Nat Commun ; 15(1): 5120, 2024 Jun 15.
Article in English | MEDLINE | ID: mdl-38879623

ABSTRACT

Calmodulin transduces [Ca2+] information regulating the rhythmic Ca2+ cycling between the sarcoplasmic reticulum and cytoplasm during contraction and relaxation in cardiac and skeletal muscle. However, the structural dynamics by which calmodulin modulates the sarcoplasmic reticulum Ca2+ release channel, the ryanodine receptor, at physiologically relevant [Ca2+] is unknown. Using fluorescence lifetime FRET, we resolve different structural states of calmodulin and Ca2+-driven shifts in the conformation of calmodulin bound to ryanodine receptor. Skeletal and cardiac ryanodine receptor isoforms show different calmodulin-ryanodine receptor conformations, as well as binding and structural kinetics with 0.2-ms resolution, which reflect different functional roles of calmodulin. These FRET methods provide insight into the physiological calmodulin-ryanodine receptor structural states, revealing additional distinct structural states that complement cryo-EM models that are based on less physiological conditions. This technology will drive future studies on pathological calmodulin-ryanodine receptor interactions and dynamics with other important ryanodine receptor bound modulators.


Subject(s)
Calcium , Calmodulin , Fluorescence Resonance Energy Transfer , Muscle, Skeletal , Myocardium , Ryanodine Receptor Calcium Release Channel , Ryanodine Receptor Calcium Release Channel/metabolism , Ryanodine Receptor Calcium Release Channel/chemistry , Calmodulin/metabolism , Calmodulin/chemistry , Calcium/metabolism , Myocardium/metabolism , Kinetics , Animals , Muscle, Skeletal/metabolism , Humans , Protein Conformation , Protein Binding , Sarcoplasmic Reticulum/metabolism
2.
ACS Chem Biol ; 18(10): 2290-2299, 2023 10 20.
Article in English | MEDLINE | ID: mdl-37769131

ABSTRACT

Hyperactivity of cardiac sarcoplasmic reticulum (SR) ryanodine receptor (RyR2) Ca2+-release channels contributes to heart failure and arrhythmias. Reducing the RyR2 activity, particularly during cardiac relaxation (diastole), is a desirable therapeutic goal. We previously reported that the unnatural enantiomer (ent) of an insect-RyR activator, verticilide, inhibits porcine and mouse RyR2 at diastolic (nanomolar) Ca2+ and has in vivo efficacy against atrial and ventricular arrhythmia. To determine the ent-verticilide structural mode of action on RyR2 and guide its further development via medicinal chemistry structure-activity relationship studies, here, we used fluorescence lifetime (FLT)-measurements of Förster resonance energy transfer (FRET) in HEK293 cells expressing human RyR2. For these studies, we used an RyR-specific FRET molecular-toolkit and computational methods for trilateration (i.e., using distances to locate a point of interest). Multiexponential analysis of FLT-FRET measurements between four donor-labeled FKBP12.6 variants and acceptor-labeled ent-verticilide yielded distance relationships placing the acceptor probe at two candidate loci within the RyR2 cryo-EM map. One locus is within the Ry12 domain (at the corner periphery of the RyR2 tetrameric complex). The other locus is sandwiched at the interface between helical domain 1 and the SPRY3 domain. These findings document RyR2-target engagement by ent-verticilide, reveal new insight into the mechanism of action of this new class of RyR2-targeting drug candidate, and can serve as input in future computational determinations of the ent-verticilide binding site on RyR2 that will inform structure-activity studies for lead optimization.


Subject(s)
Depsipeptides , Ryanodine Receptor Calcium Release Channel , Mice , Swine , Humans , Animals , Ryanodine/chemistry , Ryanodine/metabolism , Ryanodine/therapeutic use , Ryanodine Receptor Calcium Release Channel/chemistry , Ryanodine Receptor Calcium Release Channel/metabolism , Fluorescence Resonance Energy Transfer/methods , HEK293 Cells , Arrhythmias, Cardiac/drug therapy , Arrhythmias, Cardiac/metabolism , Depsipeptides/metabolism , Calcium/metabolism , Myocytes, Cardiac/metabolism
3.
Int J Mol Sci ; 24(16)2023 Aug 08.
Article in English | MEDLINE | ID: mdl-37628726

ABSTRACT

Ca2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide (DPc10) binding promotes leaky RyR2 in cardiomyocytes and reports on that endogenous state. Conversely, calmodulin (CaM) binding inhibits RyR2 leak and low CaM affinity is diagnostic of leaky RyR2. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. We used FRET to clarify the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca2+, DPc10 decreased both FRETmax (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca2+, DPc10 decreased FRETmax without affecting CaM/RyR2 binding affinity. This correlates with the analysis of fluorescence-lifetime-detected FRET, indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca2+ and lengthens D-FKBP/A-CaM distances independent of [Ca2+]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, with this effect being larger in micromolar versus nanomolar Ca2+. Moreover, A-DPc10/RyR2 binding is cooperative in a CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by the analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.


Subject(s)
Fluorescence Resonance Energy Transfer , Ryanodine Receptor Calcium Release Channel , Binding Sites , Drug Delivery Systems
4.
bioRxiv ; 2023 Jul 08.
Article in English | MEDLINE | ID: mdl-37461514

ABSTRACT

Ca 2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide, (DPc10) detects leaky RyR2 in cardiomyocytes. Conversely, calmodulin (CaM) inhibits RyR2 leak. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. Here we used FRET to understand the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca 2+ , DPc10 decreased both FRET max (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca 2+ , DPc10 decreased FRET max without affecting CaM/RyR2 binding affinity. This correlates with analysis of fluorescence-lifetime-detected FRET indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca 2+ and lengthens D-FKBP/A-CaM distances independent of [Ca 2+ ]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, this effect being larger in micromolar vs. nanomolar Ca 2+ . Moreover, A-DPc10/RyR2 binding is cooperative in CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.

5.
J Biol Chem ; 299(3): 102956, 2023 03.
Article in English | MEDLINE | ID: mdl-36731793

ABSTRACT

ß-III-Spectrin is a key cytoskeletal protein that localizes to the soma and dendrites of cerebellar Purkinje cells and is required for dendritic arborization and signaling. A spinocerebellar ataxia type 5 L253P mutation in the cytoskeletal protein ß-III-spectrin causes high-affinity actin binding. Previously we reported a cell-based fluorescence assay for identification of small-molecule actin-binding modulators of the L253P mutant ß-III-spectrin. Here we describe a complementary, in vitro, fluorescence resonance energy transfer (FRET) assay that uses purified L253P ß-III-spectrin actin-binding domain (ABD) and F-actin. To validate the assay for high-throughput compatibility, we first confirmed that our 50% FRET signal was responsive to swinholide A, an actin-severing compound, and that this yielded excellent assay quality with a Z' value > 0.77. Second, we screened a 2684-compound library of US Food and Drug Administration-approved drugs. Importantly, the screening identified numerous compounds that decreased FRET between fluorescently labeled L253P ABD and F-actin. The activity and target of multiple Hit compounds were confirmed in orthologous cosedimentation actin-binding assays. Through future medicinal chemistry, the Hit compounds can potentially be developed into a spinocerebellar ataxia type 5-specific therapeutic. Furthermore, our validated FRET-based in vitro high-throughput screening platform is poised for screening large compound libraries for ß-III-spectrin ABD modulators.


Subject(s)
Actins , Spectrin , Spinocerebellar Ataxias , Humans , Actins/genetics , Actins/metabolism , Drug Discovery , Neurons/metabolism , Spectrin/metabolism , Spinocerebellar Ataxias/drug therapy , Spinocerebellar Ataxias/genetics , Spinocerebellar Ataxias/metabolism
6.
J Biol Chem ; 298(1): 101412, 2022 01.
Article in English | MEDLINE | ID: mdl-34793835

ABSTRACT

The N-terminal region (NTR) of ryanodine receptor (RyR) channels is critical for the regulation of Ca2+ release during excitation-contraction (EC) coupling in muscle. The NTR hosts numerous mutations linked to skeletal (RyR1) and cardiac (RyR2) myopathies, highlighting its potential as a therapeutic target. Here, we constructed two biosensors by labeling the mouse RyR2 NTR at domains A, B, and C with FRET pairs. Using fluorescence lifetime (FLT) detection of intramolecular FRET signal, we developed high-throughput screening (HTS) assays with these biosensors to identify small-molecule RyR modulators. We then screened a small validation library and identified several hits. Hits with saturable FRET dose-response profiles and previously unreported effects on RyR were further tested using [3H]ryanodine binding to isolated sarcoplasmic reticulum vesicles to determine effects on intact RyR opening in its natural membrane. We identified three novel inhibitors of both RyR1 and RyR2 and two RyR1-selective inhibitors effective at nanomolar Ca2+. Two of these hits activated RyR1 only at micromolar Ca2+, highlighting them as potential enhancers of excitation-contraction coupling. To determine whether such hits can inhibit RyR leak in muscle, we further focused on one, an FDA-approved natural antibiotic, fusidic acid (FA). In skinned skeletal myofibers and permeabilized cardiomyocytes, FA inhibited RyR leak with no detrimental effect on skeletal myofiber excitation-contraction coupling. However, in intact cardiomyocytes, FA induced arrhythmogenic Ca2+ transients, a cautionary observation for a compound with an otherwise solid safety record. These results indicate that HTS campaigns using the NTR biosensor can identify compounds with therapeutic potential.


Subject(s)
Biosensing Techniques , Ryanodine Receptor Calcium Release Channel , Animals , Calcium/metabolism , Fluorescence Resonance Energy Transfer , High-Throughput Screening Assays , Mice , Muscle, Skeletal/chemistry , Muscle, Skeletal/metabolism , Ryanodine Receptor Calcium Release Channel/analysis , Ryanodine Receptor Calcium Release Channel/metabolism
7.
Vet Sci ; 8(12)2021 Nov 23.
Article in English | MEDLINE | ID: mdl-34941816

ABSTRACT

We have analyzed the enzymatic activity of the sarcoplasmic reticulum (SR) Ca2+-transporting ATPase (SERCA) from the horse gluteal muscle. Horses are bred for peak athletic performance yet exhibit a high incidence of exertional rhabdomyolysis, with elevated levels of cytosolic Ca2+ proposed as a correlative linkage. We recently reported an improved protocol for isolating SR vesicles from horse muscle; these horse SR vesicles contain an abundant level of SERCA and only trace-levels of sarcolipin (SLN), the inhibitory peptide subunit of SERCA in mammalian fast-twitch skeletal muscle. Here, we report that the in vitro Ca2+ transport rate of horse SR vesicles is 2.3 ± 0.7-fold greater than rabbit SR vesicles, which express close to equimolar levels of SERCA and SLN. This suggests that horse myofibers exhibit an enhanced SR Ca2+ transport rate and increased luminal Ca2+ stores in vivo. Using the densitometry of Coomassie-stained SDS-PAGE gels, we determined that horse SR vesicles express an abundant level of the luminal SR Ca2+ storage protein calsequestrin (CASQ), with a CASQ-to-SERCA ratio about double that in rabbit SR vesicles. Thus, we propose that SR Ca2+ cycling in horse myofibers is enhanced by a reduced SLN inhibition of SERCA and by an abundant expression of CASQ. Together, these results suggest that horse muscle contractility and susceptibility to exertional rhabdomyolysis are promoted by enhanced SR Ca2+ uptake and luminal Ca2+ storage.

8.
Work ; 69(3): 1053-1061, 2021.
Article in English | MEDLINE | ID: mdl-34219698

ABSTRACT

BACKGROUND: Lack of mental health literacy among rehabilitation professionals and employers in the return-to-work of persons with mental health problems resulted in the development of a three-day group training program, the Support to Employers from rehabilitation Actors about Mental health (SEAM) intervention. OBJECTIVE: To evaluate the impact of SEAM on rehabilitation professionals' knowledge and beliefs, attitudes, and supporting behaviors towards people with mental health problems and employers as part of the return-to-work process. METHODS: In this longitudinal study, 94 rehabilitation professionals were included. Data were collected prior to (T1), immediately after (T2) and 6 months after SEAM training (T3) using knowledge and attitude scales and a questionnaire on supporting behaviors. SEAM includes training in Mental Health First Aid, presentations and discussions on current research on work and mental health, and strategies and communication guidelines to use when meeting service users and employers as part of the return-to-work of persons with mental health problems. SEAM also includes a homepage with targeted employer information. Data were analyzed using non-parametric statistics. RESULTS: SEAM significantly increased rehabilitation professionals' knowledge of mental health (T1-T2: z = -2.037, p = 0.042; T2-T3: z = -5.093, p = 0.001), and improved their attitudes towards persons with mental health problems (T1-T2: z = 4.984, p = 0.001). Professionals (50-60%) also estimated that they had increased their use of supporting strategies towards service users and employers. CONCLUSIONS: The study suggests that SEAM can increase mental health literacy among rehabilitation professionals and lead to a greater focus on service users' resources and work ability, as well as on employers' support needs.


Subject(s)
Health Literacy , Humans , Longitudinal Studies , Mental Health , Rehabilitation, Vocational , Return to Work
9.
J Biol Chem ; 296: 100215, 2021.
Article in English | MEDLINE | ID: mdl-33839680

ABSTRACT

Numerous diseases are linked to mutations in the actin-binding domains (ABDs) of conserved cytoskeletal proteins, including ß-III-spectrin, α-actinin, filamin, and dystrophin. A ß-III-spectrin ABD mutation (L253P) linked to spinocerebellar ataxia type 5 (SCA5) causes a dramatic increase in actin binding. Reducing actin binding of L253P is thus a potential therapeutic approach for SCA5 pathogenesis. Here, we validate a high-throughput screening (HTS) assay to discover potential disrupters of the interaction between the mutant ß-III-spectrin ABD and actin in live cells. This assay monitors FRET between fluorescent proteins fused to the mutant ABD and the actin-binding peptide Lifeact, in HEK293-6E cells. Using a specific and high-affinity actin-binding tool compound, swinholide A, we demonstrate HTS compatibility with an excellent Z'-factor of 0.67 ± 0.03. Screening a library of 1280 pharmacologically active compounds in 1536-well plates to determine assay robustness, we demonstrate high reproducibility across plates and across days. We identified nine Hits that reduced FRET between Lifeact and ABD. Four of those Hits were found to reduce Lifeact cosedimentation with actin, thus establishing the potential of our assay for detection of actin-binding modulators. Concurrent to our primary FRET assay, we also developed a high-throughput compatible counter screen to remove undesirable FRET Hits. Using the FRET Hits, we show that our counter screen is sensitive to undesirable compounds that cause cell toxicity or ABD aggregation. Overall, our FRET-based HTS platform sets the stage to screen large compound libraries for modulators of ß-III-spectrin, or disease-linked spectrin-related proteins, for therapeutic development.


Subject(s)
Actins/metabolism , Binding Sites/drug effects , High-Throughput Screening Assays , Recombinant Fusion Proteins/metabolism , Spectrin/metabolism , Actins/chemistry , Actins/genetics , Fluorescence Resonance Energy Transfer , Gene Expression , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HEK293 Cells , Humans , Kinetics , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Marine Toxins/pharmacology , Models, Biological , Models, Molecular , Mutation , Neuroprotective Agents/pharmacology , Protein Binding/drug effects , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Reproducibility of Results , Spectrin/chemistry , Spectrin/genetics , Spinocerebellar Ataxias/genetics , Spinocerebellar Ataxias/metabolism , Spinocerebellar Ataxias/pathology , Red Fluorescent Protein
10.
Int J Drug Policy ; 87: 103013, 2021 01.
Article in English | MEDLINE | ID: mdl-33181448

ABSTRACT

BACKGROUND: Sweden regulates new psychoactive substances, including fentanyl analogs, individually. This reactive scheduling procedure enabled the existence of a recreational market for unscheduled fentanyl analogs sold from surface webshops. We measure the interest in 24 named fentanyl analogs and the impact of scheduling. METHODS: We scraped posts in threads on named fentanyl analogs from the Swedish internet forum Flashback.org, 2012-2019. The sample consists of 24 threads with a total of 8761 posts. We construct five measures of interest based on duration of threads, number of posts, and number of distinct posters, and fit a non-seasonal ARMA model to test if there was a change in mean activity after scheduling. RESULTS: Across the five measures, there was most interest in acryl fentanyl, butyr fentanyl, and acetyl fentanyl. The number of daily posts was significantly reduced in nine out of 13 threads after scheduling. CONCLUSION: The scheduling of fentanyl analogs impacted interest on Flashback.org. The biggest effect sizes were from the narcotics scheduling of 2-Me-MAF, acryl, and acetyl fentanyl, while furanyl fentanyl saw the biggest reduction after health scheduling. The reductions were bigger for narcotics scheduling compared to health scheduling.


Subject(s)
Analgesics, Opioid , Fentanyl , Diagnostic Tests, Routine , Humans , Narcotics , Sweden
11.
Nordisk Alkohol Nark ; 37(1): 69-85, 2020 Feb.
Article in English | MEDLINE | ID: mdl-32934594

ABSTRACT

AIMS: To examine parents' experiences of abuse directed at them by their adult children with drug problems. MATERIAL AND METHOD: The material consists of 32 qualitative interviews on child-to-parent abuse with 24 mothers and eight fathers. The interviewees had experienced verbal abuse (insults), emotional abuse (threats), financial abuse (damage to property and possessions) and physical abuse (physical violence). FINDINGS: In the parents' narratives, the parent-child interaction is dominated by the child's destructive drug use, which the parents are trying to stop. This gives rise to conflicts and ambivalence. The parents' accounts seem to function as explaining and justifying their children's disruptive behavior in view of the drug use. The fact that an external factor - drugs - is blamed seems to make it easier to repair the parent-child bonds. The parents differentiate between the child who is sober and the child who is under the influence of drugs, that is, between the genuine child and the fake, unreal child. The sober child is a person that the parent likes and makes an effort for. The child who is on drugs is erratic, at times aggressive and self-destructive. CONCLUSIONS: The interviewed parents' well-being is perceived as directly related to how their children's lives turn out. The single most important factor in improving the parents' situation is to find a way for their adult child to live their lives without drug problems.

12.
Cells ; 9(5)2020 05 08.
Article in English | MEDLINE | ID: mdl-32397211

ABSTRACT

We engineered a concatenated fluorescent biosensor and dual-wavelength fluorescence lifetime (FLT) detection, to perform high-throughput screening (HTS) in living cells for discovery of potential heart-failure drugs. Heart failure is correlated with insufficient activity of the sarcoplasmic reticulum Ca-pump (SERCA2a), often due to excessive inhibition by phospholamban (PLB), a small transmembrane protein. We sought to discover small molecules that restore SERCA2a activity by disrupting this inhibitory interaction between PLB and SERCA2a. Our approach was to fluorescently tag the two proteins and measure fluorescence resonance energy transfer (FRET) to detect changes in binding or structure of the complex. To optimize sensitivity to these changes, we engineered a biosensor that concatenates the two fluorescently labeled proteins on a single polypeptide chain. This SERCA2a-PLB FRET biosensor construct is functionally active and effective for HTS. By implementing 2-wavelength FLT detection at extremely high speed during primary HTS, we culled fluorescent compounds as false-positive Hits. In pilot screens, we identified Hits that alter the SERCA2a-PLB interaction, and a newly developed secondary calcium uptake assay revealed both activators and inhibitors of Ca-transport. We are implementing this approach for large-scale screens to discover new drug-like modulators of SERCA2a-PLB interactions for heart failure therapeutic development.


Subject(s)
Calcium/metabolism , High-Throughput Screening Assays/methods , Myocardium/cytology , Myocardium/metabolism , Biological Transport , Biosensing Techniques , Calcium-Binding Proteins/metabolism , Fluorescence Resonance Energy Transfer , HEK293 Cells , Humans , Organ Specificity , Recombinant Fusion Proteins/metabolism , Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism
13.
J Phys Chem B ; 123(48): 10131-10141, 2019 12 05.
Article in English | MEDLINE | ID: mdl-31693365

ABSTRACT

Direct time-domain simulation of continuous-wave (CW) electron paramagnetic resonance (EPR) spectra from molecular dynamics (MD) trajectories has become increasingly popular, especially for proteins labeled with nitroxide spin labels. Due to the time-consuming nature of simulating adequately long MD trajectories, two approximate methods have been developed to reduce the MD-trajectory length required for modeling EPR spectra: hindered Brownian diffusion (HBD) and hidden Markov models (HMMs). Here, we assess the accuracy of these two approximate methods relative to direct simulations from MD trajectories for three spin-labeled protein systems (a simple helical peptide, a soluble protein, and a membrane protein) and two nitroxide spin labels with differing mobilities (R1 and 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC)). We find that the HMMs generally outperform HBD. Although R1 dynamics partially resembles hindered Brownian diffusion, HMMs accommodate the multiple dynamic time scales for the transitions between rotameric states of R1 that cannot be captured accurately by a HBD model. The MD trajectories of the TOAC-labeled proteins show that its dynamics closely resembles slow multisite exchange between twist-boat and chair ring puckering states. This motion is modeled well by HMM but not by HBD. All MD-trajectory data processing, stochastic trajectory simulations, and CW EPR spectral simulations are implemented in EasySpin, a free software package for MATLAB.


Subject(s)
Calcium-Binding Proteins/chemistry , Cyclic N-Oxides/chemistry , Molecular Dynamics Simulation , Muramidase/chemistry , Nitrogen Oxides/chemistry , Peptides/chemistry , Diffusion , Electron Spin Resonance Spectroscopy , Markov Chains , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Quantum Theory , Software , Spin Labels , Staining and Labeling/methods , Thermodynamics
14.
J Phys Chem Lett ; 10(16): 4725-4730, 2019 Aug 15.
Article in English | MEDLINE | ID: mdl-31365264

ABSTRACT

Direct evidence of the formation of nitrogen molecules (N2) after ion implantion of ZnO has been revealed by an atomically resolved scanning transmission electron microscopy (STEM)-electron energy-loss spectroscopy (EELS) investigation. Taking advantage of the possibility of using multiple detectors simultaneously in aberration-corrected STEM, we utilize the detailed correlation between the atomic structure and chemical identification to develop a model explaining the formation and evolution of different defect types and their interaction with N. In particular, the formation of zinc vacancy (VZn) clusters filled with N2 after heat treatment at 650 °C was observed, clearly indicating that N has not been stabilized in the O substitution site, thus limiting p-type doping. Previous results showing an exceptional thermal stability of vacancy clusters only for the case of N-doped ZnO are supported. Furthermore, VZn-N2 stabilization leads to suppression of VZn-Zni recombination; hence, the highly mobile Zn interstitials preferentially condense on the basal planes promoting formation of extended defects (basal stacking faults and stacking mismatched boundaries). The terminations of these defects provide energetically favorable sites for further N2 trapping as a way to reduce local strain fields.

15.
Nanotechnology ; 30(22): 225702, 2019 May 31.
Article in English | MEDLINE | ID: mdl-30743257

ABSTRACT

Functionalizing transparent conducting oxides (TCOs) is an intriguing approach to expand the tunability and operation of optoelectronic devices. For example, forming nanoparticles that act as quantum wells or barriers in zinc oxide (ZnO), one of the main TCOs today, may expand its optical and electronic tunability. In this work, 800 keV Ge ions have been implanted at a dose of 1 × 1016 cm-2 into crystalline ZnO. After annealing at 1000 °C embedded disk-shaped particles with diameters up to 100 nm are formed. Scanning transmission electron microscopy shows that these are particles of the trigonal Zn2GeO4 phase. The particles are terminated by atomically sharp facets of the type {11 [Formula: see text] 0}, and the interface between the matrix and particles is decorated with misfit dislocations in order to accommodate the lattice mismatch between the two crystals. Electron energy loss spectroscopy has been employed to measure the band gap of individual nanoparticles, showing an onset of band-to-band transitions at 5.03 ± 0.02 eV. This work illustrates the advantages of using STEM characterization methods, where information of structure, growth, and properties can be directly obtained.

16.
Materials (Basel) ; 11(12)2018 Dec 19.
Article in English | MEDLINE | ID: mdl-30572661

ABSTRACT

Silicon-based tandem solar cells incorporating low-cost, abundant, and non-toxic metal oxide materials can increase the conversion efficiency of silicon solar cells beyond their conventional limitations with obvious economic and environmental benefits. In this work, the electrical characteristics of a metal oxide thin-film heterojunction solar cell based on a cuprous oxide (Cu2O) absorber layer were investigated. Highly Al-doped n-type ZnO (AZO) and undoped p-type Cu2O thin films were prepared on quartz substrates by magnetron sputter deposition. The electrical and optical properties of these thin films were determined from Hall effect measurements and spectroscopic ellipsometry. After annealing the Cu2O film at 900 °C, the majority carrier (hole) mobility and the resistivity were measured at 50 cm²/V·s and 200 Ω·cm, respectively. Numerical modeling was carried out to investigate the effect of band alignment and interface defects on the electrical characteristics of the AZO/Cu2O heterojunction. The analysis suggests that the incorporation of a buffer layer can enhance the performance of the heterojunction solar cell as a result of reduced conduction band offset.

17.
Int J Integr Care ; 18(4): 11, 2018 Dec 06.
Article in English | MEDLINE | ID: mdl-30532665

ABSTRACT

INTRODUCTION: There is increasing interest in implementing evidence-based integrated models of care in community-based mental health service systems. Assertive Community Treatment (ACT) is seen as an attractive, and at the same time challenging, model to implement in sectored service settings. This study investigates the implementation process of such an initiative. METHODS: Interviews were conducted with ACT team members, the process leader, steering group members, and collaboration partners. The "Sustainable Implementation Scale" helped to identify critical implementation components, and these were further explored using the qualitative interview data. The "Tool for Measuring Assertive Community Treatment" addressed programme fidelity, and the initiative's sustainability was assessed. RESULTS: High-fidelity implementation of ACT in a sectored service setting is possible. Prominent components that facilitated implementation were careful preparations, team members' characteristics, and efforts by the process leader and the steering group to improve networking. Implementation was hampered by conflicting goals among the involved authorities and a mismatch between the ACT model's characteristics and existing organisational traditions and regulations. DISCUSSION AND CONCLUSIONS: Reducing the uncertainty caused by conflicting goals is an important step in improving the implementation of ACT. In order to facilitate implementation, the goals, regulations, and availability of resources should be aligned horizontally and vertically through the involved organisations.

18.
J Phys Condens Matter ; 30(7): 075702, 2018 02 21.
Article in English | MEDLINE | ID: mdl-29363624

ABSTRACT

Cuprous oxide (Cu2O) is a promising material for large scale photovoltaic applications. The efficiencies of thin film structures are, however, currently lower than those for structures based on Cu2O sheets, possibly due to their poorer transport properties. This study shows that post-deposition rapid thermal annealing (RTA) of Cu2O films is an effective approach for improving carrier transport in films prepared by reactive magnetron sputtering. The as-deposited Cu2O films were poly-crystalline, p-type, with weak near band edge (NBE) emission in photoluminescence spectra, a grain size of ~100 nm and a hole mobility of 2-18 cm2 V-1 s-1. Subsequent RTA (3 min) at a pressure of 50 Pa and temperatures of 600-1000 °C enhanced the NBE by 2-3 orders of magnitude, evidencing improved crystalline quality and reduction of non-radiative carrier recombination. Both grain size and hole mobility were increased considerably upon RTA, reaching values above 1 µm and up to 58 cm2 V-1 s-1, respectively, for films annealed at 900-1000 °C. These films also exhibited a resistivity of ~50-200 Ω cm, a hole concentration of ~1015 cm-3 at room temperature, and a transmittance above 80%.

19.
Nord J Psychiatry ; 72(3): 226-231, 2018 Apr.
Article in English | MEDLINE | ID: mdl-29373933

ABSTRACT

BACKGROUND: Flexible Assertive Community Treatment (Flexible ACT) has been implemented in Sweden during recent years due to increasing interest in integrated services for people with severe mental illness. To date, few studies have been done on Flexible ACT effectiveness. AIMS: The overall aim of this study was to explore the extent to which clients assigned to the Flexible ACT board for ACT intensive care were stabilized with improved everyday functioning, social outcomes, and changes in healthcare use. METHODS: Ninety-three participants with psychosis, in need of ACT from six newly started Flexible ACT teams, were included. Data were collected using the Social Outcome Index scale (SIX), Practical and Social Functioning Scale, and a healthcare usage questionnaire. RESULTS: There was a significant positive change in everyday functioning and in the SIX-item 'friendship' at 18-months follow-up. A positive correlation was also found between everyday functioning and the SIX-item 'friendship' and a negative correlation between duration of ACT and everyday functioning. A significant increase in number of inpatient hospital days and psychiatric outpatient visits also occurred. CONCLUSION: Clients with psychosis who need ACT may benefit from Flexible ACT through improved social functioning. Being involved in meaningful activities and supported by others are key aspects of recovering from mental illness and are enhanced by Flexible ACT.


Subject(s)
Community Mental Health Services/trends , Critical Care/trends , Mental Disorders/epidemiology , Mental Disorders/therapy , Patient Care Team/trends , Adult , Community Mental Health Services/methods , Critical Care/methods , Female , Follow-Up Studies , Humans , Longitudinal Studies , Male , Mental Disorders/psychology , Middle Aged , Sweden/epidemiology , Treatment Outcome
20.
J Ment Health ; 27(5): 395-401, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29252043

ABSTRACT

BACKGROUND: An important aspect of research regarding the implementation of evidence-based practice is the sustainability and long-term stability of a programme. There is a need to measure these critical components for establishing successful programmes. AIM: The aim was to develop and pilot test the sustainable implementation scale (SIS) for measuring the critical components in the sustainable implementation of community mental health services. METHOD: The scale was based on implementation research and consisted of three subscales regarding (1) the organisational level, (2) the team level and (3) continuous support. Data from interviews and documents were collected from 14 programmes implementing the Individual Placement and Support model of supported employment. RESULTS: Internal consistency was acceptable for all subscales and for the scale as a whole. Regarding the scale, an analysis of the differences between fully established programmes and the programmes that were not established or were or only partially established after three years showed statistically significant differences, indicating that a greater number of implementation components were present in the fully established programmes. CONCLUSIONS: SIS showed both good reliability and acceptable internal consistency as well as the ability to predict programme survival.


Subject(s)
Community Mental Health Services/organization & administration , Program Evaluation , Evidence-Based Practice , Health Services Research , Humans
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