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  1. Article ; Online: Influence of Surface Flows on the Shape of Fractal Domains.

    Gellert, Florian / Ahrens, Heiko / Helm, Christiane A

    Langmuir : the ACS journal of surfaces and colloids

    2023  Volume 39, Issue 26, Page(s) 9078–9084

    Abstract: Tidal breathing is associated with a 30% change of the surfactant-covered alveolar surface occurring about 16 times per minute. To model this highly dynamic process, erucic acid monolayers at the air-water interface were compressed fast. Brewster angle ... ...

    Abstract Tidal breathing is associated with a 30% change of the surfactant-covered alveolar surface occurring about 16 times per minute. To model this highly dynamic process, erucic acid monolayers at the air-water interface were compressed fast. Brewster angle microscopy imaged the fractal liquid-condensed (LC) domains and quantified the surface flow in size, direction, and duration. Radial branch distribution of the domains has a minimum in the flow direction, as was shown with directionality histograms. The fast Fourier transform of the domains shows a preferential growth perpendicular to the flow direction. Additionally, at the beginning of the flow, the downstream side of the domain grows faster than the upstream side. Surface flows act on the mm to cm scale, cause an anisotropic flow in the liquid expanded phase surrounding the LC domain, and affect the overall domain shape. On the μm-scale, the dendritic or seaweed domains' branches were only slightly disturbed. These results may help to understand pulmonary surfactant layers.
    Language English
    Publishing date 2023-06-26
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.3c00815
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Book ; Online ; Thesis: Construction of biocompatible and electrically conductive coatings consisting of carbon nanotubes and polyelectrolytes

    Neuber, Sven [Verfasser] / Helm, Christiane A. [Gutachter] / Sukhishvili, Svetlana [Gutachter]

    2024  

    Author's details Sven Neuber ; Gutachter: Christiane A. Helm, Svetlana Sukhishvili
    Keywords Naturwissenschaften ; Science
    Subject code sg500
    Language English
    Publisher Universität Greifswald
    Publishing place Greifswald
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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    Inter-library loan at ZB MED

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  3. Article: First report of infection with metacestode stages of

    Delling, Cora / Helm, Christiane / Heinze, Peggy / Friedman, Miroslava / Böttcher, Denny

    International journal for parasitology. Parasites and wildlife

    2023  Volume 22, Page(s) 80–83

    Abstract: While the principle definitive host of the zoonotic ... ...

    Abstract While the principle definitive host of the zoonotic cestode
    Language English
    Publishing date 2023-09-09
    Publishing country England
    Document type Case Reports
    ZDB-ID 2715239-X
    ISSN 2213-2244
    ISSN 2213-2244
    DOI 10.1016/j.ijppaw.2023.09.003
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Seaweed and Dendritic Growth in Unsaturated Fatty Acid Monolayers.

    Gellert, Florian / Ahrens, Heiko / Wulff, Harm / Helm, Christiane A

    Membranes

    2022  Volume 12, Issue 7

    Abstract: The lateral movement in lipid membranes depends on their diffusion constant within the membrane. However, when the flux of the subphase is high, the convective flow beneath the membrane also influences lipid movement. Lipid monolayers of an unsaturated ... ...

    Abstract The lateral movement in lipid membranes depends on their diffusion constant within the membrane. However, when the flux of the subphase is high, the convective flow beneath the membrane also influences lipid movement. Lipid monolayers of an unsaturated fatty acid at the water-air interface serve as model membranes. The formation of domains in the liquid/condensed coexistence region is investigated. The dimension of the domains is fractal, and they grow with a constant growth velocity. Increasing the compression speed of the monolayer induces a transition from seaweed growth to dendritic growth. Seaweed domains have broad tips and wide and variable side branch spacing. In contrast, dendritic domains have a higher fractal dimension, narrower tips, and small, well-defined side branch spacing. Additionally, the growth velocity is markedly larger for dendritic than seaweed growth. The domains' growth velocity increases and the tip radius decreases with increasing supersaturation in the liquid/condensed coexistence region. Implications for membranes are discussed.
    Language English
    Publishing date 2022-07-08
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2614641-1
    ISSN 2077-0375
    ISSN 2077-0375
    DOI 10.3390/membranes12070698
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  5. Article ; Online: X-ray and Neutron Reflectometry of Thin Films at Liquid Interfaces.

    Delcea, Mihaela / Helm, Christiane A

    Langmuir : the ACS journal of surfaces and colloids

    2019  Volume 35, Issue 26, Page(s) 8519–8530

    Abstract: In the 1980s, Helmuth Möhwald studied lipid monolayers at the air/water interface to understand the thermodynamically characterized phases at the molecular level. In collaboration with Jens Als-Nielsen, X-ray reflectometry was used and further developed ... ...

    Abstract In the 1980s, Helmuth Möhwald studied lipid monolayers at the air/water interface to understand the thermodynamically characterized phases at the molecular level. In collaboration with Jens Als-Nielsen, X-ray reflectometry was used and further developed to determine the electron density profile perpendicular to the water surface. Using a slab model, parameters such as thickness and density of the individual molecular regions, as well as the roughness of the individual interfaces, were determined. Later, X-ray and neutron reflectometry helped to understand the coverage and conformation of anchored and adsorbed polymers. Nowadays, they resolve molecular properties in emerging topics such as liquid metals and ionic liquids. Much is still to be learned about buried interfaces (e.g., liquid/liquid interfaces). In this Article, a historical and theoretical background of X-ray reflectivity is given, recent developments of X-ray and neutron reflectometry for polymers at interfaces and thin layers are highlighted, and emerging research topics involving these techniques are emphasized.
    Language English
    Publishing date 2019-03-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.8b04315
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Cryptosporidium parvum

    Veshkini, Arash / Dengler, Franziska / Bachmann, Lisa / Liermann, Wendy / Helm, Christiane / Ulrich, Reiner / Delling, Cora / Kühn, Christa / Hammon, Harald M

    Frontiers in immunology

    2024  Volume 15, Page(s) 1351427

    Abstract: One of the leading causes of infectious diarrhea in newborn calves is the apicomplexan ... ...

    Abstract One of the leading causes of infectious diarrhea in newborn calves is the apicomplexan protozoan
    MeSH term(s) Animals ; Cattle ; Male ; Humans ; Cryptosporidiosis ; Cryptosporidium parvum/genetics ; Cryptosporidium/genetics ; Transcriptome ; Cattle Diseases/genetics ; Intestinal Mucosa ; Tumor Necrosis Factor-alpha/genetics ; Adaptive Immunity ; Immune System Phenomena
    Chemical Substances Tumor Necrosis Factor-alpha
    Language English
    Publishing date 2024-01-22
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Comment
    ZDB-ID 2606827-8
    ISSN 1664-3224 ; 1664-3224
    ISSN (online) 1664-3224
    ISSN 1664-3224
    DOI 10.3389/fimmu.2024.1351427
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  7. Article: X-ray and Neutron Reflectometry of Thin Films at Liquid Interfaces

    Delcea, Mihaela / Helm, Christiane A

    Langmuir. 2019 Mar. 22, v. 35, no. 26

    2019  

    Abstract: In the 1980s, Helmuth Möhwald studied lipid monolayers at the air/water interface to understand the thermodynamically characterized phases at the molecular level. In collaboration with Jens Als-Nielsen, X-ray reflectometry was used and further developed ... ...

    Abstract In the 1980s, Helmuth Möhwald studied lipid monolayers at the air/water interface to understand the thermodynamically characterized phases at the molecular level. In collaboration with Jens Als-Nielsen, X-ray reflectometry was used and further developed to determine the electron density profile perpendicular to the water surface. Using a slab model, parameters such as thickness and density of the individual molecular regions, as well as the roughness of the individual interfaces, were determined. Later, X-ray and neutron reflectometry helped to understand the coverage and conformation of anchored and adsorbed polymers. Nowadays, they resolve molecular properties in emerging topics such as liquid metals and ionic liquids. Much is still to be learned about buried interfaces (e.g., liquid/liquid interfaces). In this Article, a historical and theoretical background of X-ray reflectivity is given, recent developments of X-ray and neutron reflectometry for polymers at interfaces and thin layers are highlighted, and emerging research topics involving these techniques are emphasized.
    Keywords air ; ionic liquids ; lipids ; liquids ; metals ; models ; polymers ; reflectometry ; roughness ; thermodynamics ; X-radiation ; X-ray reflectivity
    Language English
    Dates of publication 2019-0322
    Size p. 8519-8530.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.8b04315
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  8. Article ; Online: Oxidation of Unsaturated Phospholipids: A Monolayer Study.

    Gellert, Florian / Ahrens, Heiko / Helm, Christiane A

    Langmuir : the ACS journal of surfaces and colloids

    2020  Volume 36, Issue 41, Page(s) 12213–12220

    Abstract: Lipid oxidation does strongly influence the self-organization of plasma membranes; the detailed influence is not yet clear. In this work, phospholipid monolayers at the air/water interface were used as model membranes. Oxidation was induced by the ... ...

    Abstract Lipid oxidation does strongly influence the self-organization of plasma membranes; the detailed influence is not yet clear. In this work, phospholipid monolayers at the air/water interface were used as model membranes. Oxidation was induced by the reactive oxygen species formed in a H
    Language English
    Publishing date 2020-10-08
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2005937-1
    ISSN 1520-5827 ; 0743-7463
    ISSN (online) 1520-5827
    ISSN 0743-7463
    DOI 10.1021/acs.langmuir.0c01950
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Identification of a critical lipid ratio in raft-like phases exposed to nitric oxide: An AFM study.

    Karanth, Sanjai / Azinfar, Amir / Helm, Christiane A / Delcea, Mihaela

    Biophysical journal

    2021  Volume 120, Issue 15, Page(s) 3103–3111

    Abstract: Lipid rafts are discrete, heterogeneous domains of phospholipids, sphingolipids, and sterols that are present in the cell membrane. They are responsible for conducting cell signaling and maintaining lipid-protein functionality. Redox-stress-induced ... ...

    Abstract Lipid rafts are discrete, heterogeneous domains of phospholipids, sphingolipids, and sterols that are present in the cell membrane. They are responsible for conducting cell signaling and maintaining lipid-protein functionality. Redox-stress-induced modifications to any of their components can severely alter the mechanics and dynamics of the membrane causing impairment to the lipid-protein functionality. Here, we report on the effect of sphingomyelin (SM) in controlling membrane permeability and its role as a regulatory lipid in the presence of nitric oxide (NO). Force spectroscopy and atomic force microscopy imaging of raft-like phases (referring here to the coexistence of "liquid-ordered" and "liquid-disordered" phases in model bilayer membranes) prepared from lipids: 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC):SM:cholesterol (CH) (at three ratios) showed that the adhesion forces to pull the tip out of the membrane increased with increasing SM concentration, indicating decreased membrane permeability. However, in the presence of NO radical (1 and 5 μM), the adhesion forces decreased depending on SM concentration. The membrane was found to be stable at the ratio POPC:SM:CH (2:1:1) even when exposed to 1 μM NO. We believe that this is a critical ratio needed by the raft-like phases to maintain homeostasis under stress conditions. The stability could be due to an interplay existing between SM and CH. However, at 5 μM NO, membrane deteriorations were detected. For POPC:SM:CH (2:2:1) ratio, NO displayed a pro-oxidant behavior and damaged the membrane at both radical concentrations. These changes were reflected by the differences in the height profiles of the raft-like phases observed by atomic force microscopy imaging. Malondialdehyde (a peroxidation product) detection suggests that lipids may have undergone lipid nitroxidation. The changes were instantaneous and independent of radical concentration and incubation time. Our study underlines the need for identifying appropriate ratios in the lipid rafts of the cell membranes to withstand redox imbalances caused by radicals such as NO.
    MeSH term(s) Cell Membrane ; Cholesterol ; Lipid Bilayers ; Membrane Microdomains ; Nitric Oxide ; Phosphatidylcholines ; Sphingomyelins
    Chemical Substances Lipid Bilayers ; Phosphatidylcholines ; Sphingomyelins ; Nitric Oxide (31C4KY9ESH) ; Cholesterol (97C5T2UQ7J)
    Language English
    Publishing date 2021-06-29
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 218078-9
    ISSN 1542-0086 ; 0006-3495
    ISSN (online) 1542-0086
    ISSN 0006-3495
    DOI 10.1016/j.bpj.2021.06.009
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    In stock of ZB MED Cologne/Königswinter

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  10. Article ; Online: Determination of refractive index and layer thickness of nm-thin films via ellipsometry.

    Nestler, Peter / Helm, Christiane A

    Optics express

    2017  Volume 25, Issue 22, Page(s) 27077–27085

    Abstract: Ellipsometric measurements give information on two film properties with high precision, thickness and refractive index. In the simplest case, the substrate is covered with a single homogenous, transparent film. Yet, with ellipsometry, it is only possible ...

    Abstract Ellipsometric measurements give information on two film properties with high precision, thickness and refractive index. In the simplest case, the substrate is covered with a single homogenous, transparent film. Yet, with ellipsometry, it is only possible to determine the two film properties thickness and refractive simultaneously if the layer thickness exceeds 15 nm - a restriction well known for a century. Here we present a technique to cross this limitation: A series expansion of the ellipsometric ratio ρ to the second order of the layer thickness relative to the wavelength reveals the first and second ellipsometric moment. These moments are properties of the thin film and independent of incident angle. Using both moments and one additional reference measurement enables to determine simultaneously both thickness and refractive index of ultra-thin films down to 5 nm thickness.
    Language English
    Publishing date 2017-10-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.25.027077
    Database MEDical Literature Analysis and Retrieval System OnLINE

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