Publications by authors named "Frank Schreiber"

141 Publications

Polymorphism and structure formation in copper phthalocyanine thin films.

J Appl Crystallogr 2021 Feb 1;54(Pt 1):203-210. Epub 2021 Feb 1.

Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.

Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group 2/) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the 2/ structure by excluded-volume considerations. X-ray diffraction experiments and atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1107/S1600576720015472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7941321PMC
February 2021

Kinetics of Network Formation and Heterogeneous Dynamics of an Egg White Gel Revealed by Coherent X-Ray Scattering.

Phys Rev Lett 2021 Mar;126(9):098001

Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany.

The kinetics of heat-induced gelation and the microscopic dynamics of a hen egg white gel are probed using x-ray photon correlation spectroscopy along with ultrasmall-angle x-ray scattering. The kinetics of structural growth reveals a reaction-limited aggregation process with a gel fractal dimension of ≈2 and an average network mesh size of ca. 400 nm. The dynamics probed at these length scales reveals an exponential growth of the characteristic relaxation times followed by an intriguing steady state in combination with a compressed exponential correlation function and a temporal heterogeneity. The degree of heterogeneity increases with decreasing length scale. We discuss our results in the broader context of experiments and models describing attractive colloidal gels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevLett.126.098001DOI Listing
March 2021

Detection of Cerebral Microbleeds With Venous Connection at 7 Tesla MRI.

Neurology 2021 Mar 2. Epub 2021 Mar 2.

Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany.

Objective: Cerebral microbleeds (MBs) are a common finding in cerebral small vessel disease (CSVD) and Alzheimer's disease patients as well as in healthy elderly people, but their pathophysiology remains unclear. To investigate a possible role of veins in the development of MBs, we performed an exploratory study, assessing in vivo presence of MBs with a direct connection to a vein.

Methods: 7 Tesla (7 T) MRI was conducted and MBs were counted on Quantitative Susceptibility Mapping (QSM). A submillimeter resolution QSM-based venogram allowed identification of MBs with a direct spatial connection to a vein.

Results: 51 subjects (mean age [SD] 70.5[8.6] years, 37% females) participated in the study: 20 were patients with CSVD (cerebral amyloid angiopathy (CAA) with strictly lobar MBs (n=8), hypertensive arteriopathy (HA) with strictly deep MBs (n=5), and mixed lobar and deep MBs (n=7), 72.4 [6.1] years, 30% females) and 31 were healthy controls (69.4 [9.9] years, 42% females). In our cohort, we counted a total of 96 MBs with a venous connection, representing 14% of all detected MBs on 7T QSM. Most venous MBs (86%, n = 83) were observed in lobar locations and all of these were cortical. CAA subjects showed the highest ratio of venous to total MBs (19%) (HA=9%, mixed=18%, controls=5%) CONCLUSIONS: Our findings establish a link between cerebral MBs and the venous vasculature, pointing towards a possible contribution of veins to CSVD in general and to CAA in particular. Pathological studies are needed to confirm our observations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1212/WNL.0000000000011790DOI Listing
March 2021

Prevalent Synergy and Antagonism Among Antibiotics and Biocides in .

Front Microbiol 2020 4;11:615618. Epub 2021 Feb 4.

Division of Biodeterioration and Reference Organisms (4.1), Department of Materials and the Environment, Federal Institute for Materials Research and Testing (BAM), Berlin, Germany.

Antimicrobials can exert specific physiological effects when used in combination that are different from those when applied alone. While combination effects have been extensively mapped for antibiotic-antibiotic combinations, the combination effects of antibiotics with antimicrobials used as biocides or antiseptics have not been systematically investigated. Here, we investigated the effects of combinations of antibiotics (meropenem, gentamicin, and ciprofloxacin) and substances used as biocides or antiseptics [octenidine, benzalkonium chloride, cetrimonium bromide, chlorhexidine, Povidone-iodine, silver nitrate (AgNO), and Ag-nanoparticles] on the planktonic growth rate of . Combination effects were investigated in growth experiments in microtiter plates at different concentrations and the Bliss interaction scores were calculated. Among the 21 screened combinations, we find prevalent combination effects with synergy occurring six times and antagonism occurring 10 times. The effects are specific to the antibiotic-biocide combination with meropenem showing a tendency for antagonism with biocides (6 of 7), while gentamicin has a tendency for synergy (5 of 7). In conclusion, antibiotics and biocides or antiseptics exert physiological combination effects on the pathogen . These effects have consequences for the efficacy of both types of substances and potentially for the selection of antimicrobial resistant strains in clinical applications with combined exposure (e.g., wound care and coated biomaterials).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fmicb.2020.615618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7889964PMC
February 2021

High-Resolution Nerve Ultrasound Abnormalities in POEMS Syndrome-A Comparative Study.

Diagnostics (Basel) 2021 Feb 9;11(2). Epub 2021 Feb 9.

Center for Neurology, Tuebingen University Hospital and Hertie-Institute for Clinical Brain Research, Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany.

Background: High-resolution nerve ultrasound (HRUS) has been proven to be a valuable tool in the diagnosis of immune-mediated neuropathies, such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes) is an important differential diagnosis of CIDP. Until now, there have been no studies that could identify specific HRUS abnormalities in POEMS syndrome patients. Thus, the aim of this study was to assess possible changes and compare findings with CIDP patients.

Methods: We retrospectively analyzed HRUS findings in three POEMS syndrome and ten CIDP patients by evaluating cross-sectional nerve area (CSA), echogenicity and additionally calculating ultrasound pattern scores (UPSA, UPSB, UPSC and UPSS) and homogeneity scores (HS).

Results: CIDP patients showed greater CSA enlargement and higher UPSS (median 14 vs. 11), UPSA (median 11.5 vs. 8) and HS (median 5 vs. 3) compared with POEMS syndrome patients. However, every POEMS syndrome patient illustrated enlarged nerves exceeding reference values, which were not restricted to entrapment sites. In CIDP and POEMS syndrome, heterogeneous enlargement patterns could be identified, such as inhomogeneous, homogeneous and regional nerve enlargement. HRUS in CIDP patients visualized both increased and decreased echointensity, while POEMS syndrome patients pictured hypoechoic nerves with hyperechoic intraneural connective tissue. This is the first study to demonstrate HRUS abnormalities in POEMS syndrome outside of common entrapment sites. Although nerve enlargement was more prominent in CIDP, POEMS syndrome patients revealed distinct echogenicity patterns, which might aid in its differentiation from CIDP. Future studies should consider HRUS and its possible role in determining diagnosis, prognosis and treatment response in POEMS syndrome.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/diagnostics11020264DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7915164PMC
February 2021

Nanoscale Phase Segregation in Supramolecular π-Templating for Hybrid Perovskite Photovoltaics from NMR Crystallography.

J Am Chem Soc 2021 Jan 14;143(3):1529-1538. Epub 2021 Jan 14.

Laboratory of Magnetic Resonance, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.

The use of layered perovskites is an important strategy to improve the stability of hybrid perovskite materials and their optoelectronic devices. However, tailoring their properties requires accurate structure determination at the atomic scale, which is a challenge for conventional diffraction-based techniques. We demonstrate the use of nuclear magnetic resonance (NMR) crystallography in determining the structure of layered hybrid perovskites for a mixed-spacer model composed of 2-phenylethylammonium (PEA) and 2-(perfluorophenyl)ethylammonium (FEA) moieties, revealing nanoscale phase segregation. Moreover, we illustrate the application of this structure in perovskite solar cells with power conversion efficiencies that exceed 21%, accompanied by enhanced operational stability.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c11563DOI Listing
January 2021

Bulk Phase Behavior vs Interface Adsorption: Specific Multivalent Cation and Anion Effects on BSA Interactions.

Langmuir 2021 01 4;37(1):139-150. Epub 2021 Jan 4.

Institute for Applied Physics, University of Tübingen, 72076 Tübingen, Germany.

Proteins are ubiquitous and play a critical role in many areas from living organisms to protein microchips. In humans, serum albumin has a prominent role in the foreign body response since it is the first protein which will interact with, e.g., an implant or stent. In this study, we focused on the influence of salts (i.e., different cations (Y, La) and anions (Cl, I) on bovine serum albumin (BSA) in terms of its bulk behavior as well as the role of charges for protein adsorption at the solid-liquid interface in order to understand and control the underlying molecular mechanisms and interactions. This is part of our group's effort to gain a deeper understanding of protein-protein and protein-surface interactions in the presence of multivalent ions. In the bulk, we established two new phase diagrams and found not only multivalent cation-triggered phase transitions, but also a dependence of the protein behavior on the type of anion. The attractive interactions between proteins were observed to increase from Cl < NO < I, resulting in iodide preventing re-entrant condensation and promoting liquid-liquid phase separation in bulk. Using ellipsometry and a quartz-crystal microbalance with dissipation (QCM-D), we obtained insight into the growth of the protein adsorption layer. Importantly, we found that phase transitions at the substrate can be triggered by certain interface properties, whether they exist in the bulk solution or not. Through the use of a hydrophilic, negatively charged surface (native silica), the direct binding of anions to the interface was prevented. Interestingly, this led to re-entrant adsorption even in the absence of re-entrant condensation in bulk. However, the overall amount of adsorbed protein was enhanced through stronger attractive protein-protein interactions in the presence of iodide salts. These findings illustrate how carefully chosen surface properties and salts can directly steer the binding of anions and cations, which guide protein behavior, thus paving the way for specific/triggered protein-protein, protein-salt, and protein-surface interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.langmuir.0c02618DOI Listing
January 2021

Structural order enhances charge carrier transport in self-assembled Au-nanoclusters.

Nat Commun 2020 Dec 3;11(1):6188. Epub 2020 Dec 3.

Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Auf der Morgenstelle 18, D-72076, Tübingen, Germany.

The collective properties of self-assembled nanoparticles with long-range order bear immense potential for customized electronic materials by design. However, to mitigate the shortcoming of the finite-size distribution of nanoparticles and thus, the inherent energetic disorder within assemblies, atomically precise nanoclusters are the most promising building blocks. We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au(BuP)Cl nanoclusters into micro-crystals. This enables the determination of emergent optoelectronic properties which resulted from long-range order in such assemblies. Compared to the same nanoclusters in glassy, polycrystalline ensembles, we find a 100-fold increase in the electric conductivity and charge carrier mobility as well as additional optical transitions. We show that these effects are due to a vanishing energetic disorder and a drastically reduced activation energy to charge transport in the highly ordered assemblies. This first correlation of structure and electronic properties by comparing glassy and crystalline self-assembled superstructures of atomically precise gold nanoclusters paves the way towards functional materials with novel collective optoelectronic properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-19461-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7713068PMC
December 2020

Minimizing the Trade-Off between Photocurrent and Photovoltage in Triple-Cation Mixed-Halide Perovskite Solar Cells.

J Phys Chem Lett 2020 Dec 18;11(23):10188-10195. Epub 2020 Nov 18.

Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.

Its lower bandgap makes formamidinium lead iodide (FAPbI) a more suitable candidate for single-junction solar cells than pure methylammonium lead iodide (MAPbI). However, its structural and thermodynamic stability is improved by introducing a significant amount of MA and bromide, both of which increase the bandgap and amplify trade-off between the photocurrent and photovoltage. Here, we simultaneously stabilized FAPbI into a cubic lattice and minimized the formation of photoinactive phases such as hexagonal FAPbI and PbI by introducing 5% MAPbBr, as revealed by synchrotron X-ray scattering. We were able to stabilize the composition (FAMACs)Pb(IBr), which exhibits a minimal trade-off between the photocurrent and photovoltage. This material shows low energetic disorder and improved charge-carrier dynamics as revealed by photothermal deflection spectroscopy (PDS) and transient absorption spectroscopy (TAS), respectively. This allowed the fabrication of operationally stable perovskite solar cells yielding reproducible efficiencies approaching 22%.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpclett.0c02791DOI Listing
December 2020

An integrated model system to gain mechanistic insights into biofilm-associated antimicrobial resistance in Pseudomonas aeruginosa MPAO1.

NPJ Biofilms Microbiomes 2020 10 30;6(1):46. Epub 2020 Oct 30.

Research Group Molecular Diagnostics Genomics & Bioinformatics, Agroscope and SIB Swiss Institute of Bioinformatics, Wädenswil, Switzerland.

Pseudomonas aeruginosa MPAO1 is the parental strain of the widely utilized transposon mutant collection for this important clinical pathogen. Here, we validate a model system to identify genes involved in biofilm growth and biofilm-associated antibiotic resistance. Our model employs a genomics-driven workflow to assemble the complete MPAO1 genome, identify unique and conserved genes by comparative genomics with the PAO1 reference strain and genes missed within existing assemblies by proteogenomics. Among over 200 unique MPAO1 genes, we identified six general essential genes that were overlooked when mapping public Tn-seq data sets against PAO1, including an antitoxin. Genomic data were integrated with phenotypic data from an experimental workflow using a user-friendly, soft lithography-based microfluidic flow chamber for biofilm growth and a screen with the Tn-mutant library in microtiter plates. The screen identified hitherto unknown genes involved in biofilm growth and antibiotic resistance. Experiments conducted with the flow chamber across three laboratories delivered reproducible data on P. aeruginosa biofilms and validated the function of both known genes and genes identified in the Tn-mutant screens. Differential protein abundance data from planktonic cells versus biofilm confirmed the upregulation of candidates known to affect biofilm formation, of structural and secreted proteins of type VI secretion systems, and provided proteogenomic evidence for some missed MPAO1 genes. This integrated, broadly applicable model promises to improve the mechanistic understanding of biofilm formation, antimicrobial tolerance, and resistance evolution in biofilms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41522-020-00154-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7603352PMC
October 2020

MRI phenotyping of underlying cerebral small vessel disease in mixed hemorrhage patients.

J Neurol Sci 2020 Dec 9;419:117173. Epub 2020 Oct 9.

Department of Neurology, Otto-von-Guericke University, Leipziger Straße 44, 39120 Magdeburg, Germany; German Center for Neurodegenerative Diseases (DZNE), Leipziger Straße 44, 39120 Magdeburg, Germany; Center for Behavioral Brain Sciences (CBBS), Universitätsplatz 2, 39106 Magdeburg, Germany. Electronic address:

Objective: To investigate underlying cerebral small vessel disease (CSVD) in patients with mixed cerebral hemorrhages patterns and phenotype them according to the contribution of the two most common sporadic CSVD subtypes: cerebral amyloid angiopathy (CAA) vs. hypertensive arteriopathy (HA).

Methods: Brain MRIs of patients with intracerebral hemorrhages (ICHs) and/or cerebral microbleeds (CMBs) were assessed for the full spectrum of CSVD markers using validated scales: ICHs, CMBs, cortical superficial siderosis (cSS), white matter hyperintensities, MRI-visible perivascular spaces (PVS). PVS predominance pattern was grouped as centrum-semiovale (CSO)-PVS predominance, basal-ganglia (BG)-PVS predominance, CSO-PVS and BG-PVS equality. Patients with mixed cerebral hemorrhages were classified into mixed CAA-pattern or mixed HA-pattern according to the existence of cSS and/or a CSO-PVS predominance pattern and comparisons were performed.

Results: We included 110 patients with CAA (strictly lobar ICHs/CMBs), 33 with HA (strictly deep ICHs/CMBs) and 97 with mixed lobar/deep ICHs/CMBs. Mixed patients were more similar to HA with respect to their MRI-CSVD markers, vascular risk profile and cerebrospinal fluid (CSF) measures. In the mixed patients, 33 (34%) had cSS, a CSO-PVS predominance pattern, or both, and were defined as mixed CAA-pattern cases. The mixed CAA-pattern patients were more alike CAA patients regarding their MRI-CSVD markers, CSF and genetic profile.

Conclusion: Our findings suggest that the heterogeneous group of patients with mixed cerebral hemorrhages distribution can be further phenotyped according to the predominant underlying CSVD. cSS presence and a CSO-PVS predominance pattern could serve as strongly suggestive markers of a contribution from CAA among patients with mixed hemorrhages.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jns.2020.117173DOI Listing
December 2020

Impact of fluorination on interface energetics and growth of pentacene on Ag(111).

Beilstein J Nanotechnol 2020 8;11:1361-1370. Epub 2020 Sep 8.

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, People's Republic of China.

We studied the structural and electronic properties of 2,3,9,10-tetrafluoropentacene (F4PEN) on Ag(111) via X-ray standing waves (XSW), low-energy electron diffraction (LEED) as well as ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS). XSW revealed that the adsorption distances of F4PEN in (sub)monolayers on Ag(111) were 3.00 Å for carbon atoms and 3.05 Å for fluorine atoms. The F4PEN monolayer was essentially lying on Ag(111), and multilayers adopted π-stacking. Our study shed light not only on the F4PEN-Ag(111) interface but also on the fundamental adsorption behavior of fluorinated pentacene derivatives on metals in the context of interface energetics and growth mode.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3762/bjnano.11.120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7492695PMC
September 2020

Interplay between Glass Formation and Liquid-Liquid Phase Separation Revealed by the Scattering Invariant.

J Phys Chem Lett 2020 Sep 20;11(17):7273-7278. Epub 2020 Aug 20.

Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany.

The interplay of the glass transition with liquid-liquid phase separation (LLPS) is a subject of intense debate. We use the scattering invariant to probe how approaching the glass transition affects the shape of LLPS boundaries in the temperature/volume fraction plane. Two protein systems featuring kinetic arrest with a lower and an upper critical solution temperature phase behavior, respectively, are studied varying the quench depth. Using we noninvasively identify system-dependent differences for the effect of glass formation on the LLPS boundary. The glassy dense phase appears to enter the coexistence region for the albumin-YCl system, whereas it follows the equilibrium binodal for the γ-globulin-PEG system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpclett.0c02110DOI Listing
September 2020

Evolution of the structure and dynamics of bovine serum albumin induced by thermal denaturation.

Phys Chem Chem Phys 2020 Sep 11;22(33):18507-18517. Epub 2020 Aug 11.

Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France.

Protein denaturation in concentrated solutions consists of the unfolding of the native protein structure, and subsequent cross-linking into clusters or gel networks. While the kinetic evolution of structure has been studied for some cases, the underlying microscopic dynamics of proteins has so far been neglected. However, protein dynamics is essential to understand the specific nature of assembly processes, such as diffusion-limited growth, or vitrification of dense liquids. Here, we present a study on thermal denaturation of concentrated solutions of bovine serum albumin (BSA) in DO with and without NaCl. Using small-angle scattering, we provide information on structure before, during and after denaturation. Using quasi-elastic neutron scattering, we monitor in real-time the microscopic dynamics and dynamical confinement throughout the entire denaturation process covering protein unfolding and cross-linking. After denaturation, the protein dynamics is slowed down in salty solutions compared to those in pure water, while the stability and dynamics of the native solution appears unaffected by salt. The approach presented here opens opportunities to link microscopic dynamics to emerging structural properties, with implications for assembly processes in soft and biological matter.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0cp01857kDOI Listing
September 2020

Textural markers of ultrasonographic nerve alterations in amyotrophic lateral sclerosis.

Muscle Nerve 2020 11 7;62(5):601-610. Epub 2020 Sep 7.

Department of Neurology, Otto von Guericke University, Magdeburg, Germany.

Ultrasound has revealed cross-sectional nerve area (CSA) reduction in amyotrophic lateral sclerosis (ALS), but little is known about the sonographic nerve texture beyond CSA alterations. In a large cohort of 177 ALS patients and 57 control subjects, we investigated the covariance and disease-specific signature of several sonographic texture features of the median and ulnar nerves and their relationship to the patients' clinical characteristics. ALS patients showed atrophic nerves, a loss of the intranerve structures' echoic contrast, elevated coarseness, and a trend toward lower cluster shading compared with controls. A reduction in intranerve echoic contrast was related to longer disease duration and poorer functional status in ALS. Sonographic texture markers point toward a significant reorganization of the deep nerve microstructure in ALS. Future studies will be needed to further substantiate the markers' potential to assess peripheral nerve alterations in ALS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mus.27043DOI Listing
November 2020

Peripheral Nerve Imaging Aids in the Diagnosis of Immune-Mediated Neuropathies-A Case Series.

Diagnostics (Basel) 2020 Jul 30;10(8). Epub 2020 Jul 30.

Department of Neurology, Otto-von-Guericke University, 39120 Magdeburg, Germany.

Background: Diagnosis of immune-mediated neuropathies and their differentiation from amyotrophic lateral sclerosis (ALS) can be challenging, especially at early disease stages. Accurate diagnosis is, however, important due to the different prognosis and available treatment options. We present one patient with a left-sided dorsal flexor paresis and initial suspicion of ALS and another with multifocal sensory deficits. In both, peripheral nerve imaging was the key for diagnosis.

Methods: We performed high-resolution nerve ultrasound (HRUS) and 7T or 3T magnetic resonance neurography (MRN).

Results: In both patients, HRUS revealed mild to severe, segmental or inhomogeneous, nerve enlargement at multiple sites, as well as an area increase of isolated fascicles. MRN depicted T2 hyperintense nerves with additional contrast-enhancement.

Discussion: Peripheral nerve imaging was compatible with the respective diagnosis of an immune-mediated neuropathy, i.e., multifocal motor neuropathy (MMN) in patient 1 and multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) in patient 2. Peripheral nerve imaging, especially HRUS, should play an important role in the diagnostic work-up for immune-mediated neuropathies and their differentiation from ALS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/diagnostics10080535DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7459443PMC
July 2020

Packing and dynamics of a protein solution approaching the jammed state.

Soft Matter 2020 Aug;16(33):7751-7759

Institut für Angewandte Physik, Universtitat Tübingen, 70276, Tübingen, Germany.

The packing of proteins and their collective behavior in crowded media is crucial for the understanding of biological processes. Here we study the structural and dynamical evolution of solutions of the globular protein bovine serum albumin with increasing concentration via drying using small angle X-ray scattering and dynamic light scattering. We probe an evolving correlation peak on the scattering profile, corresponding to the inter-protein distance, ξ, which decreases following a power law of the protein volume fraction, φ. The rate of decrease in ξ becomes faster above a protein concentration of ∼200 mg ml-1 (φ = 0.15). The power law exponent changes from 0.33, which is typical of colloidal or protein solutions, to 0.41. During the entire drying process, we observe the development and the growth of two-step relaxation dynamics with increasing φ as revealed by dynamic light scattering. We find three different regimes of the dependence of ξ as a function of φ. In the dilute regime (φ < 0.22), protein molecules are far apart from each other compared to their size. In this case, the dynamics mainly corresponds to Brownian motion. At an intermediate concentration (0.22 < φ < 0.47), inter-protein distances become comparable to the size of protein molecules, leading to a preferential orientation of the ellipsoidal protein molecules along with a possible deformation. In this regime, the dynamics shows two distinct relaxation times. At a very high concentration (φ > 0.47), the system reaches a jammed state. Subsequently, the secondary relaxation time in this state becomes extremely slow. In this state, the protein molecules have approximately one hydration layer. This study contributes to the understanding of protein molecular packing in crowded environments and the phenomenon of density-driven jamming for soft matter systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0sm00962hDOI Listing
August 2020

Structure-Transport Correlation Reveals Anisotropic Charge Transport in Coupled PbS Nanocrystal Superlattices.

Adv Mater 2020 Sep 28;32(36):e2002254. Epub 2020 Jul 28.

Institute of Physical and Theoretical Chemistry, University of Tuebingen, Auf der Morgenstelle 18, Tuebingen, 72076, Germany.

The assembly of colloidal semiconductive nanocrystals into highly ordered superlattices predicts novel structure-related properties by design. However, those structure-property relationships, such as charge transport depending on the structure or even directions of the superlattice, have remained unrevealed so far. Here, electric transport measurements and X-ray nanodiffraction are performed on self-assembled lead sulfide nanocrystal superlattices to investigate direction-dependent charge carrier transport in microscopic domains of these materials. By angular X-ray cross-correlation analysis, the structure and orientation of individual superlattices is determined, which are directly correlated with the electronic properties of the same microdomains. By that, strong evidence for the effect of superlattice crystallinity on the electric conductivity is found. Further, anisotropic charge transport in highly ordered monocrystalline domains is revealed, which is attributed to the dominant effect of shortest interparticle distance. This implies that transport anisotropy should be a general feature of weakly coupled nanocrystal superlattices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.202002254DOI Listing
September 2020

Enhanced protein adsorption upon bulk phase separation.

Sci Rep 2020 06 25;10(1):10349. Epub 2020 Jun 25.

Institute for Applied Physics, Auf der Morgenstelle 10, University of Tübingen, 72076, Tübingen, Germany.

In all areas related to protein adsorption, from medicine to biotechnology to heterogeneous nucleation, the question about its dominant forces and control arises. In this study, we used ellipsometry and quartz-crystal microbalance with dissipation (QCM-D), as well as density-functional theory (DFT) to obtain insight into the mechanism behind a wetting transition of a protein solution. We established that using multivalent ions in a net negatively charged globular protein solution (BSA) can either cause simple adsorption on a negatively charged interface, or a (diverging) wetting layer when approaching liquid-liquid phase separation (LLPS) by changing protein concentration (c) or temperature (T). We observed that the water to protein ratio in the wetting layer is substantially larger compared to simple adsorption. In the corresponding theoretical model, we treated the proteins as limited-valence (patchy) particles and identified a wetting transition for this complex system. This wetting is driven by a bulk instability introduced by metastable LLPS exposed to an ion-activated attractive substrate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-66562-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7316800PMC
June 2020

Multivalent ions and biomolecules: Attempting a comprehensive perspective.

Chemphyschem 2020 08 20;21(16):1742-1767. Epub 2020 Jul 20.

Institute of Applied Physics, University of Tübingen, Germany.

Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to folding, to self-organisation and assembly, to reaction equilibria, to signalling, to energy and material transport, to recognition etc. Going beyond monovalent ions to multivalent ions, the effects of the ions are frequently not only stronger (due to the obviously higher charge), but qualitatively different. A typical example is the process of binding of multivalent ions, such as Ca , to a macromolecule and the consequences of this ion binding such as compaction, collapse, potential charge inversion and precipitation of the macromolecule. Here we review these effects and phenomena induced by multivalent ions for biological (macro)molecules, from the "atomistic/molecular" local picture of (potentially specific) interactions to the more global picture of phase behaviour including, e. g., crystallisation, phase separation, oligomerisation etc. Rather than attempting an encyclopedic list of systems, we rather aim for an embracing discussion using typical case studies. We try to cover predominantly three main classes: proteins, nucleic acids, and amphiphilic molecules including interface effects. We do not cover in detail, but make some comparisons to, ion channels, colloidal systems, and synthetic polymers. While there are obvious differences in the behaviour of, and the relevance of multivalent ions for, the three main classes of systems, we also point out analogies. Our attempt of a comprehensive discussion is guided by the idea that there are not only important differences and specific phenomena with regard to the effects of multivalent ions on the main systems, but also important similarities. We hope to bridge physico-chemical mechanisms, concepts of soft matter, and biological observations and connect the different communities further.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cphc.202000162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496725PMC
August 2020

Stabilization of Highly Efficient and Stable Phase-Pure FAPbI Perovskite Solar Cells by Molecularly Tailored 2D-Overlayers.

Angew Chem Int Ed Engl 2020 Sep 22;59(36):15688-15694. Epub 2020 Jun 22.

Laboratory of Photonics and Interfaces, Department of Chemistry and Chemical Engineering, École Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.

As a result of their attractive optoelectronic properties, metal halide APbI perovskites employing formamidinium (FA ) as the A cation are the focus of research. The superior chemical and thermal stability of FA cations makes α-FAPbI more suitable for solar-cell applications than methylammonium lead iodide (MAPbI ). However, its spontaneous conversion into the yellow non-perovskite phase (δ-FAPbI ) under ambient conditions poses a serious challenge for practical applications. Herein, we report on the stabilization of the desired α-FAPbI perovskite phase by protecting it with a two-dimensional (2D) IBA FAPb I (IBA=iso-butylammonium overlayer, formed via stepwise annealing. The α-FAPbI /IBA FAPb I based perovskite solar cell (PSC) reached a high power conversion efficiency (PCE) of close to 23 %. In addition, it showed excellent operational stability, retaining around 85 % of its initial efficiency under severe combined heat and light stress, that is, simultaneous exposure with maximum power tracking to full simulated sunlight at 80 °C over 500 h.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202005211DOI Listing
September 2020

Peripheral nerve imaging in amyotrophic lateral sclerosis.

Clin Neurophysiol 2020 Sep 13;131(9):2315-2326. Epub 2020 Apr 13.

Department of Neurology, Wake Forest School of Medicine, NC, USA.

We systematically identified and reviewed 29 studies of peripheral nerve ultrasound or magnetic resonance imaging (MRN) in amyotrophic lateral sclerosis (ALS). The majority of the ultrasound studies reported smaller nerves and nerve roots in ALS compared to healthy controls, but there was a large overlap of the cross-sectional nerve area between ALS and controls. Most of the MRN studies confirmed nerve abnormalities demonstrating slight T2 hyperintensities and, sometimes, mild enlargement of more proximal nerve segments (plexus, roots) in ALS. The size of the proximal nerve segments, i.e. nerve roots, is thus somewhat incongruent between nerve ultrasound and MRN in ALS. Peripheral nerve ultrasound has the potential to differentiate between ALS and multifocal motor neuropathy (MMN) in that patients with MMN have significantly larger nerves. Conversely, there is an overlap of MRN abnormalities in ALS and MMN, restricting the techniques' utility in the clinical setting. A subgroup of patients with ALS seems to reveal a sonographic nerve pattern suggesting peripheral nerve inflammation. In the future, combined imaging with nerve ultrasound and MRN assessing parameters such as blood flow or textural markers may aid in the understanding of the deep nerve microstructure down to the fascicle level, and thus, in the classification of the nerve state as more degenerative or more inflammatory in ALS. This systematic review provides evidence that nerve imaging abnormalities are common in ALS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clinph.2020.03.026DOI Listing
September 2020

Sonographic and 3T-MRI-based evaluation of the tongue in ALS.

Neuroimage Clin 2020 2;26:102233. Epub 2020 Mar 2.

Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany; German Center for Neurodegenerative Diseases (DZNE) within the Helmholtz Association, Magdeburg, Germany; Center for behavioral brain sciences (CBBS), Magdeburg, Germany. Electronic address:

A few systematic imaging studies employing ultrasound (HRUS) and magnetic resonance imaging (MRI) have suggested tongue measures to aid in diagnosis of amyotrophic lateral sclerosis (ALS). The relationship between structural tongue alterations and the ALS patients' bulbar and overall motor function has not yet been elucidated. We here thus aimed to understand how in-vivo tongue alterations relate to motor function and motor function evolution over time in ALS. Our study included 206 ALS patients and 104 age- and sex-matched controls that underwent HRUS and 3T MRI of the tongue at baseline. Sonographic measures comprised coronal tongue echointensity, area, height, width and height/width ratio, while MRI measures comprised sagittal T1 intensity, tongue area, position and shape. Imaging-derived markers were related to baseline and longitudinal bulbar and overall motor function. Baseline T1 intensity was lower in ALS patients with more severe bulbar involvement at baseline. Smaller baseline coronal (HRUS) and sagittal (MRI) tongue area, smaller coronal height (HRUS) and width (HRUS) as well as more rounded sagittal tongue shape predicated more rapid functional impairment - not only of bulbar, but also of overall motor function - in ALS. Our results suggest that in-vivo sonography und MRI tongue measures could aid as biomarkers to reflect bulbar and motor function impairment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.nicl.2020.102233DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7068685PMC
February 2021

Heteromolecular Bilayers on a Weakly Interacting Substrate: Physisorptive Bonding and Molecular Distortions of Copper-Hexadecafluorophthalocyanine.

ACS Appl Mater Interfaces 2020 Mar 11;12(12):14542-14551. Epub 2020 Mar 11.

Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany.

Heteromolecular bilayers of π-conjugated organic molecules on metals, considered as model systems for more complex thin film heterostructures, are investigated with respect to their structural and electronic properties. By exploring the influence of the organic-metal interaction strength in bilayer systems, we determine the molecular arrangement in the physisorptive regime for copper-hexadecafluorophthalocyanine (FCuPc) on Au(111) with intermediate layers of 5,7,12,14-pentacenetetrone and perylene-3,4,9,10-tetracarboxylic diimide. Using the X-ray standing wave technique to distinguish the different molecular layers, we show that these two bilayers are ordered following their deposition sequence. Surprisingly, FCuPc as the second layer within the heterostructures exhibits an inverted intramolecular distortion compared to its monolayer structure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.9b22812DOI Listing
March 2020

Binding and electronic level alignment of π-conjugated systems on metals.

Rep Prog Phys 2020 Jun 26;83(6):066501. Epub 2020 Feb 26.

Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.

We review the binding and energy level alignment of π-conjugated systems on metals, a field which during the last two decades has seen tremendous progress both in terms of experimental characterization as well as in the depth of theoretical understanding. Precise measurements of vertical adsorption distances and the electronic structure together with ab initio calculations have shown that most of the molecular systems have to be considered as intermediate cases between weak physisorption and strong chemisorption. In this regime, the subtle interplay of different effects such as covalent bonding, charge transfer, electrostatic and van der Waals interactions yields a complex situation with different adsorption mechanisms. In order to establish a better understanding of the binding and the electronic level alignment of π-conjugated molecules on metals, we provide an up-to-date overview of the literature, explain the fundamental concepts as well as the experimental techniques and discuss typical case studies. Thereby, we relate the geometric with the electronic structure in a consistent picture and cover the entire range from weak to strong coupling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6633/ab7a42DOI Listing
June 2020

Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply.

J Biol Chem 2020 04 24;295(14):4383-4397. Epub 2020 Feb 24.

Department of Neurology, Otto-von-Guericke-University, D-39120 Magdeburg, Germany

Mitochondrial oxidative phosphorylation (OXPHOS) and cellular workload are tightly balanced by the key cellular regulator, calcium (Ca). Current models assume that cytosolic Ca regulates workload and that mitochondrial Ca uptake precedes activation of matrix dehydrogenases, thereby matching OXPHOS substrate supply to ATP demand. Surprisingly, knockout (KO) of the mitochondrial Ca uniporter (MCU) in mice results in only minimal phenotypic changes and does not alter OXPHOS. This implies that adaptive activation of mitochondrial dehydrogenases by intramitochondrial Ca cannot be the exclusive mechanism for OXPHOS control. We hypothesized that cytosolic Ca, but not mitochondrial matrix Ca, may adapt OXPHOS to workload by adjusting the rate of pyruvate supply from the cytosol to the mitochondria. Here, we studied the role of malate-aspartate shuttle (MAS)-dependent substrate supply in OXPHOS responses to changing Ca concentrations in isolated brain and heart mitochondria, synaptosomes, fibroblasts, and thymocytes from WT and MCU KO mice and the isolated working rat heart. Our results indicate that extramitochondrial Ca controls up to 85% of maximal pyruvate-driven OXPHOS rates, mediated by the activity of the complete MAS, and that intramitochondrial Ca accounts for the remaining 15%. Of note, the complete MAS, as applied here, included besides its classical NADH oxidation reaction the generation of cytosolic pyruvate. Part of this largely neglected mechanism has previously been described as the "mitochondrial gas pedal." Its implementation into OXPHOS control models integrates seemingly contradictory results and warrants a critical reappraisal of metabolic control mechanisms in health and disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.RA119.011902DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7135991PMC
April 2020

Surface-Controlled Crystal Alignment of Naphthyl End-Capped Oligothiophene on Graphene: Thin-Film Growth Studied by in Situ X-ray Diffraction.

Langmuir 2020 Mar 21;36(8):1898-1906. Epub 2020 Feb 21.

Department of Physics, Technical University of Denmark, Kgs. Lyngby 2800, Denmark.

We report on the microstructure, morphology, and growth of 5,5'-bis(naphth-2-yl)-2,2'-bithiophene (NaT2) thin films deposited on graphene, characterized by grazing incidence X-ray diffraction (GIXRD) and complemented by atomic force microscopy (AFM) measurements. NaT2 is deposited on two types of graphene surfaces: custom-made samples where chemical vapor deposition (CVD)-grown graphene layers are transferred onto a Si/SiO substrate by us and common commercially transferred CVD graphene on Si/SiO. Pristine Si/SiO substrates are used as a reference. The NaT2 crystal structure and orientation depend strongly on the underlying surface, with the molecules predominantly lying down on the graphene surface (face-on orientation) and standing nearly out-of-plane (edge-on orientation) on the Si/SiO reference surface. Post growth GIXRD and AFM measurements reveal that the crystalline structure and grain morphology differ depending on whether there is polymer residue left on the graphene surface. In situ GIXRD measurements show that the thickness dependence of the intensity of the (111) reflection from the crystalline edge-on phase does not intersect zero at the beginning of the deposition process, suggesting that an initial wetting layer, corresponding to 1-2 molecular layers, is formed at the surface-film interface. By contrast, the (111) reflection intensity from the crystalline face-on phase grows at a constant rate as a function of film thickness during the entire deposition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.langmuir.9b03467DOI Listing
March 2020

The upper cervical spinal cord in ALS assessed by cross-sectional and longitudinal 3T MRI.

Sci Rep 2020 02 4;10(1):1783. Epub 2020 Feb 4.

Department of Neurology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany.

The upper cervical spinal cord is measured in a large longitudinal amyotrophic lateral sclerosis (ALS) cohort to evaluate its role as a biomarker. Specifically, the cervical spinal cord´s cross-sectional area (CSA) in plane of the segments C1-C3 was measured semi-automatically with T1-weighted 3T MRI sequences in 158 ALS patients and 86 controls. Six-month longitudinal follow-up MRI scans were analyzed in 103 patients. Compared to controls, in ALS there was a significant mean spinal cord atrophy (63.8 mm² vs. 60.8 mm², p = 0.001) which showed a trend towards worsening over time (mean spinal cord CSA decrease from 61.4 mm² to 60.6 mm² after 6 months, p = 0.06). Findings were most pronounced in the caudal segments of the upper cervical spinal cord and in limb-onset ALS. Baseline CSA was related to the revised ALS functional rating scale, disease duration, precentral gyrus thickness and total brain gray matter volume. In conclusion, spinal cord atrophy as assessed in brain MRIs in ALS patients mirrors the extent of overall neurodegeneration and parallels disease severity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-58687-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000761PMC
February 2020

Unification of lower and upper critical solution temperature phase behavior of globular protein solutions in the presence of multivalent cations.

Soft Matter 2020 Feb;16(8):2128-2134

Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany.

In globular protein systems, upper critical solution temperature (UCST) behavior is common, but lower critical solution temperature (LCST) phase transitions are rare. In addition, the temperature sensitivity of such systems is usually difficult to tune. Here we demonstrate that the charge state of globular proteins in aqueous solutions can alter their temperature-dependent phase behavior. We show a universal way to tune the effective protein interactions and induce both UCST and LCST-type transitions in the system using trivalent salts. We provide a phase diagram identifying LCST and UCST regimes as a function of protein and salt concentrations. We further propose a model based on an entropy-driven cation binding mechanism to explain the experimental observations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9sm02329aDOI Listing
February 2020

Reorientation of π-conjugated molecules on few-layer MoS films.

Phys Chem Chem Phys 2020 Feb 22;22(5):3097-3104. Epub 2020 Jan 22.

Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany.

Small π-conjugated organic molecules have attracted substantial attention in the past decade as they are considered as candidates for future organic-based (opto-)electronic applications. The molecular arrangement in the organic layer is one of the crucial parameters that determine the efficiency of a given device. The desired orientation of the molecules is achieved by a proper choice of the underlying substrate and growth conditions. Typically, one underlying material supports only one inherent molecular orientation at its interface. Here, we report on two different orientations of diindenoperylene (DIP) molecules on the same underlayer, i.e. on a few-layer MoS substrate. We show that DIP molecules adopt a lying-down orientation when deposited on few-layer MoS with horizontally oriented layers. In contrast, for vertically aligned MoS layers, DIP molecules are arranged in a standing-up manner. Employing in situ and real-time grazing-incidence wide-angle X-ray scattering (GIWAXS), we monitored the stress evolution within the thin DIP layer from the early stages of the growth, revealing different substrate-induced phases for the two molecular orientations. Our study opens up new possibilities for the next-generation of flexible electronics, which might benefit from the combination of MoS layers with unique optical and electronic properties and an extensive reservoir of small organic molecules.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9cp05728eDOI Listing
February 2020