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  1. Article ; Online: Algorithm to catalogue topologies of dynamic lipid hydrogen-bond networks.

    Karathanou, Konstantina / Bondar, Ana-Nicoleta

    Biochimica et biophysica acta. Biomembranes

    2022  Volume 1864, Issue 4, Page(s) 183859

    Abstract: Lipid membrane interfaces host reactions essential for the functioning of cells. The hydrogen-bonding environment at the membrane interface is particularly important for binding of proteins, drug molecules, and ions. We present here the implementation ... ...

    Abstract Lipid membrane interfaces host reactions essential for the functioning of cells. The hydrogen-bonding environment at the membrane interface is particularly important for binding of proteins, drug molecules, and ions. We present here the implementation and applications of a depth-first search algorithm that analyzes dynamic lipid interaction networks. Lipid hydrogen-bond networks sampled transiently during simulations of lipid bilayers are clustered according to main types of topologies that characterize three-dimensional arrangements of lipids connected to each other via short water bridges. We characterize the dynamics of hydrogen-bonded lipid clusters in simulations of model POPE and POPE:POPG membranes that are often used for bacterial membrane proteins, in a model of the Escherichia coli membrane with six different lipid types, and in POPS membranes. We find that all lipids sample dynamic hydrogen-bonded networks with linear, star, or circular arrangements of the lipid headgroups, and larger networks with combinations of these three types of topologies. Overall, linear lipid-water bridges tend to be short. Water-mediated lipid clusters in all membranes with PE lipids tend to be somewhat small, with about four lipids in all membranes studied here. POPS membranes allow circular arrangements of three POPS lipids to be sampled frequently, and complex arrangements of linear, star, and circular paths may also be sampled. These findings suggest a molecular picture of the membrane interface whereby lipid molecules transiently connect in clusters with somewhat small spatial extension.
    MeSH term(s) Algorithms ; Escherichia coli/metabolism ; Hydrogen Bonding ; Lipid Bilayers/chemistry ; Molecular Dynamics Simulation ; Phosphatidylethanolamines/chemistry ; Phosphatidylglycerols/chemistry
    Chemical Substances Lipid Bilayers ; Phosphatidylethanolamines ; Phosphatidylglycerols ; 1-palmitoyl-2-oleoylphosphatidylethanolamine (10015-88-0) ; 1-palmitoyl-2-oleoylglycero-3-phosphoglycerol (81490-05-3)
    Language English
    Publishing date 2022-01-07
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 60-7
    ISSN 1879-2642 ; 1879-2596 ; 1879-260X ; 1872-8006 ; 1879-2618 ; 1879-2650 ; 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    ISSN (online) 1879-2642 ; 1879-2596 ; 1879-260X ; 1872-8006 ; 1879-2618 ; 1879-2650
    ISSN 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    DOI 10.1016/j.bbamem.2022.183859
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Graph-Based Analyses of Dynamic Water-Mediated Hydrogen-Bond Networks in Phosphatidylserine: Cholesterol Membranes.

    Jain, Honey / Karathanou, Konstantina / Bondar, Ana-Nicoleta

    Biomolecules

    2023  Volume 13, Issue 8

    Abstract: Phosphatidylserine lipids are anionic molecules present in eukaryotic plasma membranes, where they have essential physiological roles. The altered distribution of phosphatidylserine in cells such as apoptotic cancer cells, which, unlike healthy cells, ... ...

    Abstract Phosphatidylserine lipids are anionic molecules present in eukaryotic plasma membranes, where they have essential physiological roles. The altered distribution of phosphatidylserine in cells such as apoptotic cancer cells, which, unlike healthy cells, expose phosphatidylserine, is of direct interest for the development of biomarkers. We present here applications of a recently implemented Depth-First-Search graph algorithm to dissect the dynamics of transient water-mediated lipid clusters at the interface of a model bilayer composed of 1-palmytoyl-2-oleoyl-sn-glycero-2-phosphatidylserine (POPS) and cholesterol. Relative to a reference POPS bilayer without cholesterol, in the POPS:cholesterol bilayer there is a somewhat less frequent sampling of relatively complex and extended water-mediated hydrogen-bond networks of POPS headgroups. The analysis protocol used here is more generally applicable to other lipid:cholesterol bilayers.
    MeSH term(s) Phosphatidylserines ; Membranes ; Cholesterol ; Water ; Hydrogen
    Chemical Substances Phosphatidylserines ; Cholesterol (97C5T2UQ7J) ; Water (059QF0KO0R) ; Hydrogen (7YNJ3PO35Z)
    Language English
    Publishing date 2023-08-11
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2701262-1
    ISSN 2218-273X ; 2218-273X
    ISSN (online) 2218-273X
    ISSN 2218-273X
    DOI 10.3390/biom13081238
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Using Graphs of Dynamic Hydrogen-Bond Networks To Dissect Conformational Coupling in a Protein Motor.

    Karathanou, Konstantina / Bondar, Ana-Nicoleta

    Journal of chemical information and modeling

    2019  Volume 59, Issue 5, Page(s) 1882–1896

    Abstract: DExD/H-box proteins are soluble enzymes that couple binding and hydrolysis of adenosine triphosphate (ATP) with reactions involving RNA metabolism or bind and push newly synthesized proteins across bacterial cell membranes. Knowledge of the reaction ... ...

    Abstract DExD/H-box proteins are soluble enzymes that couple binding and hydrolysis of adenosine triphosphate (ATP) with reactions involving RNA metabolism or bind and push newly synthesized proteins across bacterial cell membranes. Knowledge of the reaction mechanism of these enzymes could help the development of new therapeutics. In order to explore the mechanism of long-distance conformational coupling in SecA, the DEAD-box motor of the Sec protein secretion in bacteria, we implemented algorithms that provide simplified graph representations of the protein's dynamic hydrogen-bond networks. We find that mutations near the nucleotide-binding site or changes of the nucleotide-binding state of SecA associate with altered dynamics at the preprotein binding domain and identify extended networks of hydrogen bonds that connect the active site of SecA to the region where SecA binds newly synthesized secretory proteins. Water molecules participate in hydrogen-bonded water chains that bridge functional domains of SecA and could contribute to long-distance conformational coupling.
    MeSH term(s) Adenosine Triphosphate/chemistry ; Adenosine Triphosphate/metabolism ; Bacillus subtilis/chemistry ; Bacillus subtilis/metabolism ; Bacterial Proteins/chemistry ; Bacterial Proteins/metabolism ; Binding Sites ; Hydrogen Bonding ; Models, Molecular ; Protein Conformation ; Protein Domains ; SecA Proteins/chemistry ; SecA Proteins/metabolism ; Water/chemistry ; Water/metabolism
    Chemical Substances Bacterial Proteins ; Water (059QF0KO0R) ; Adenosine Triphosphate (8L70Q75FXE) ; SecA Proteins (EC 7.4.2.4)
    Language English
    Publishing date 2019-04-30
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 190019-5
    ISSN 1549-960X ; 0095-2338
    ISSN (online) 1549-960X
    ISSN 0095-2338
    DOI 10.1021/acs.jcim.8b00979
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Dynamic hydrogen-bond networks in bacterial protein secretion.

    Karathanou, Konstantina / Bondar, Ana-Nicoleta

    FEMS microbiology letters

    2018  Volume 365, Issue 13

    Abstract: The Sec protein secretion machinery includes proteins whose reaction coordinates involve large-scale conformational changes. Dynamic hydrogen-bond networks can provide structural plasticity required by the SecA protein motor and the SecY protein ... ...

    Abstract The Sec protein secretion machinery includes proteins whose reaction coordinates involve large-scale conformational changes. Dynamic hydrogen-bond networks can provide structural plasticity required by the SecA protein motor and the SecY protein translocon. Here we discuss hydrogen-bond networks of these two Sec proteins from crystal structures and molecular simulations, and the usefulness of molecular simulations approaches to studying dynamic hydrogen bonds and their role in bacterial protein secretion.
    MeSH term(s) Bacteria/chemistry ; Bacteria/genetics ; Bacteria/metabolism ; Bacterial Proteins/chemistry ; Bacterial Proteins/genetics ; Bacterial Proteins/metabolism ; Bacterial Secretion Systems/chemistry ; Bacterial Secretion Systems/genetics ; Bacterial Secretion Systems/metabolism ; Hydrogen Bonding ; Protein Transport
    Chemical Substances Bacterial Proteins ; Bacterial Secretion Systems
    Language English
    Publishing date 2018-06-14
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 752343-9
    ISSN 1574-6968 ; 0378-1097
    ISSN (online) 1574-6968
    ISSN 0378-1097
    DOI 10.1093/femsle/fny124
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Correction to "NanoCrystal: A Web-Based Crystallographic Tool for the Construction of Nanoparticles Based on Their Crystal Habit".

    Chatzigoulas, Alexios / Karathanou, Konstantina / Dellis, Dimitris / Cournia, Zoe

    Journal of chemical information and modeling

    2019  Volume 59, Issue 4, Page(s) 1681

    Language English
    Publishing date 2019-04-01
    Publishing country United States
    Document type Journal Article ; Published Erratum
    ZDB-ID 190019-5
    ISSN 1549-960X ; 0095-2338
    ISSN (online) 1549-960X
    ISSN 0095-2338
    DOI 10.1021/acs.jcim.9b00251
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Dynamic Water Hydrogen-Bond Networks at the Interface of a Lipid Membrane Containing Palmitoyl-Oleoyl Phosphatidylglycerol.

    Karathanou, Konstantina / Bondar, Ana-Nicoleta

    The Journal of membrane biology

    2018  Volume 251, Issue 3, Page(s) 461–473

    Abstract: Lipid membrane interfaces are complex environments that host essential cellular processes such as binding of proteins or drug molecules. A key open question is how water molecules at the interface of membranes with anionic lipids participate in protein ... ...

    Abstract Lipid membrane interfaces are complex environments that host essential cellular processes such as binding of proteins or drug molecules. A key open question is how water molecules at the interface of membranes with anionic lipids participate in protein binding. To address this question, we studied the dynamics of water hydrogen bonding at the interface of membranes composed of phosphatidylcholine and phosphatidylglycerol, and implemented an algorithm to identify hydrogen-bonded networks at the interface of a lipid membrane, and to characterize their dynamics and linear connections. We find that the membrane interface is characterized by a rich network of hydrogen-bonded water chains that bridge lipid headgroups, some of which form transient lipid clusters. Water-mediated bridges between with lipid phosphate groups are dynamic, with residence lifetimes on the order of picoseconds. These clusters of water/lipid headgroup hydrogen bonds could provide a platform for the binding of proteins or of drug molecules with cationic groups.
    MeSH term(s) Hydrogen Bonding ; Lipid Bilayers/chemistry ; Membrane Lipids/chemistry ; Molecular Dynamics Simulation ; Phosphatidylglycerols/chemistry ; Water/chemistry
    Chemical Substances Lipid Bilayers ; Membrane Lipids ; Phosphatidylglycerols ; Water (059QF0KO0R)
    Language English
    Publishing date 2018-03-09
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 3082-x
    ISSN 1432-1424 ; 0022-2631
    ISSN (online) 1432-1424
    ISSN 0022-2631
    DOI 10.1007/s00232-018-0023-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Graphs of dynamic H-bond networks: from model proteins to protein complexes in cell signaling.

    Lazaratos, Michalis / Karathanou, Konstantina / Bondar, Ana-Nicoleta

    Current opinion in structural biology

    2020  Volume 64, Page(s) 79–87

    Abstract: Proton transfer reactions are ubiquitous in biology, as they are involved in the functioning of numerous proteins. Studies of model proteins have revealed mechanisms by which proteins use hydrogen-bond networks for proton transfers, and couple proton ... ...

    Abstract Proton transfer reactions are ubiquitous in biology, as they are involved in the functioning of numerous proteins. Studies of model proteins have revealed mechanisms by which proteins use hydrogen-bond networks for proton transfers, and couple proton transfers with protein and water dynamics. In this review we focus on graph-based analyses of dynamic hydrogen-bond networks at membrane interfaces, protein H-bond networks for allosteric conformational coupling and pH sensitivity, and challenges in extrapolating from knowledge acquired from studies of model membrane proteins to computational studies of macro-molecular protein complexes that are part of cell signaling networks directly relevant to the development of new therapeutics.
    MeSH term(s) Hydrogen Bonding ; Membrane Proteins ; Protons ; Signal Transduction ; Water
    Chemical Substances Membrane Proteins ; Protons ; Water (059QF0KO0R)
    Language English
    Publishing date 2020-07-16
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 1068353-7
    ISSN 1879-033X ; 0959-440X
    ISSN (online) 1879-033X
    ISSN 0959-440X
    DOI 10.1016/j.sbi.2020.06.006
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: Dynamic hydrogen-bond networks in bacterial protein secretion

    Karathanou, Konstantina / Bondar, Ana-Nicoleta

    FEMS microbiology letters. 2018 May 15, v. 365, no. 13

    2018  

    Abstract: The Sec protein secretion machinery includes proteins whose reaction coordinates involve large-scale conformational changes. Dynamic hydrogen-bond networks can provide structural plasticity required by the SecA protein motor and the SecY protein ... ...

    Abstract The Sec protein secretion machinery includes proteins whose reaction coordinates involve large-scale conformational changes. Dynamic hydrogen-bond networks can provide structural plasticity required by the SecA protein motor and the SecY protein translocon. Here we discuss hydrogen-bond networks of these two Sec proteins from crystal structures and molecular simulations, and the usefulness of molecular simulations approaches to studying dynamic hydrogen bonds and their role in bacterial protein secretion.
    Keywords bacterial proteins ; crystal structure ; hydrogen bonding ; membrane proteins ; molecular dynamics ; plasticity ; protein secretion
    Language English
    Dates of publication 2018-0515
    Publishing place Oxford University Press
    Document type Article
    ZDB-ID 752343-9
    ISSN 1574-6968 ; 0378-1097
    ISSN (online) 1574-6968
    ISSN 0378-1097
    DOI 10.1093/femsle/fny124
    Database NAL-Catalogue (AGRICOLA)

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  9. Article ; Online: NanoCrystal: A Web-Based Crystallographic Tool for the Construction of Nanoparticles Based on Their Crystal Habit.

    Chatzigoulas, Alexios / Karathanou, Konstantina / Dellis, Dimitris / Cournia, Zoe

    Journal of chemical information and modeling

    2018  Volume 58, Issue 12, Page(s) 2380–2386

    Abstract: Modeling of nanoparticles is an essential first step to assess their capacities for different uses such as energy storage and drug delivery. However, creating an initial starting conformation for modeling and simulation is tedious because every ... ...

    Abstract Modeling of nanoparticles is an essential first step to assess their capacities for different uses such as energy storage and drug delivery. However, creating an initial starting conformation for modeling and simulation is tedious because every crystalline material grows with a different crystal habit. In this application note, we describe NanoCrystal, a novel web-based crystallographic tool that creates nanoparticle models from any crystal structure guided by their preferred equilibrium shape under standard conditions according to the Wulff morphology (crystal habit). Users can upload a cif file, define the Miller indices and their corresponding minimum surface energies according to the Wulff construction of a particular crystal, and specify the size of the nanocrystal. As a result, the nanoparticle is constructed and visualized, and the coordinates of the atoms are output to the user. NanoCrystal can be accessed at http://nanocrystal.vi-seem.edu/ .
    MeSH term(s) Crystallization ; Crystallography/methods ; Internet ; Molecular Conformation ; Nanoparticles/chemistry ; Software ; Surface Properties
    Language English
    Publishing date 2018-12-13
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 190019-5
    ISSN 1549-960X ; 0095-2338
    ISSN (online) 1549-960X
    ISSN 0095-2338
    DOI 10.1021/acs.jcim.8b00269
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Coating of magnetic nanoparticles affects their interactions with model cell membranes.

    Lazaratos, Michalis / Karathanou, Konstantina / Mainas, Eleftherios / Chatzigoulas, Alexios / Pippa, Natassa / Demetzos, Costas / Cournia, Zoe

    Biochimica et biophysica acta. General subjects

    2020  Volume 1864, Issue 11, Page(s) 129671

    Abstract: Background: The use of functionalized iron oxide nanoparticles of various chemical properties and architectures offers a new promising direction in theranostic applications. The increasing applications of nanoparticles in medicine require that these ... ...

    Abstract Background: The use of functionalized iron oxide nanoparticles of various chemical properties and architectures offers a new promising direction in theranostic applications. The increasing applications of nanoparticles in medicine require that these engineered nanomaterials will contact human cells without damaging essential tissues. Thus, efficient delivery must be achieved, while minimizing cytotoxicity during passage through cell membranes to reach intracellular target compartments.
    Methods: Differential Scanning Calorimetry (DSC), molecular modeling, and atomistic Molecular Dynamics (MD) simulations were performed for two magnetite nanoparticles coated with polyvinyl alcohol (PVA) and polyarabic acid (ARA) in order to assess their interactions with model DPPC membranes.
    Results: DSC experiments showed that both nanoparticles interact strongly with DPPC lipid head groups, albeit to a different degree, which was further confirmed and quantified by MD simulations. The two systems were simulated, and dynamical and structural properties were monitored. A bimodal diffusion was observed for both nanoparticles, representing the diffusion in the water phase and in the proximity of the lipid bilayer. Nanoparticles did not enter the bilayer, but caused ordering of the head groups and reduced the area per lipid compared to the pure bilayer, with MAG-PVA interacting more strongly and being closer to the lipid bilayer.
    Conclusions: Results of DSC experiments and MD simulations were in excellent agreement. Our findings demonstrate that the external coating is a key factor that affects nanoparticle-membrane interactions. Magnetite nanoparticles coated with PVA and ARA did not destabilize the model membrane and can be considered promising platforms for biomedical applications.
    General significance: Understanding the physico-chemical interactions of different nanoparticle coatings in contact with model cell membranes is the first step for assessing toxic response and could lead to predictive models for estimating toxicity. DSC in combination with MD simulations is an effective strategy to assess physico-chemical interactions of coated nanoparticles with lipid bilayers.
    MeSH term(s) Cell Membrane/chemistry ; Diffusion ; Gum Arabic/chemistry ; Lipid Bilayers/chemistry ; Magnetite Nanoparticles/chemistry ; Membranes, Artificial ; Molecular Dynamics Simulation ; Polyvinyl Alcohol/chemistry
    Chemical Substances Lipid Bilayers ; Magnetite Nanoparticles ; Membranes, Artificial ; arabic acid (32609-14-6) ; Gum Arabic (9000-01-5) ; Polyvinyl Alcohol (9002-89-5)
    Language English
    Publishing date 2020-06-19
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 60-7
    ISSN 1872-8006 ; 1879-2596 ; 1879-260X ; 1879-2642 ; 1879-2618 ; 1879-2650 ; 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    ISSN (online) 1872-8006 ; 1879-2596 ; 1879-260X ; 1879-2642 ; 1879-2618 ; 1879-2650
    ISSN 0006-3002 ; 0005-2728 ; 0005-2736 ; 0304-4165 ; 0167-4838 ; 1388-1981 ; 0167-4889 ; 0167-4781 ; 0304-419X ; 1570-9639 ; 0925-4439 ; 1874-9399
    DOI 10.1016/j.bbagen.2020.129671
    Database MEDical Literature Analysis and Retrieval System OnLINE

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