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  1. Article ; Online: 25-Hydroxycholesterol Effect on Membrane Structure and Mechanical Properties

    Marco M. Domingues / Bárbara Gomes / Axel Hollmann / Nuno C. Santos

    International Journal of Molecular Sciences, Vol 22, Iss 5, p

    2021  Volume 2574

    Abstract: Cholesterol is responsible for the plasticity of plasma membranes and is involved in physiological and pathophysiological responses. Cholesterol homeostasis is regulated by oxysterols, such as 25-hydroxycholesterol. The presence of 25-hydroxycholesterol ... ...

    Abstract Cholesterol is responsible for the plasticity of plasma membranes and is involved in physiological and pathophysiological responses. Cholesterol homeostasis is regulated by oxysterols, such as 25-hydroxycholesterol. The presence of 25-hydroxycholesterol at the membrane level has been shown to interfere with several viruses’ entry into their target cells. We used atomic force microscopy to assess the effect of 25-hydroxycholesterol on different properties of supported lipid bilayers with controlled lipid compositions. In particular, we showed that 25-hydroxycholesterol inhibits the lipid-condensing effects of cholesterol, rendering the bilayers less rigid. This study indicates that the inclusion of 25-hydroxycholesterol in plasma membranes or the conversion of part of their cholesterol content into 25-hydroxycholesterol leads to morphological alterations of the sphingomyelin (SM)-enriched domains and promotes lipid packing inhomogeneities. These changes culminate in membrane stiffness variations.
    Keywords cholesterol ; 25-hydroxycholesterol ; atomic force microscopy ; force spectroscopy ; supported lipid bilayers ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
    Language English
    Publishing date 2021-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Acyl-chain saturation regulates the order of phosphatidylinositol 4,5-bisphosphate nanodomains

    Luís Borges-Araújo / Marco M. Domingues / Alexander Fedorov / Nuno C. Santos / Manuel N. Melo / Fábio Fernandes

    Communications Chemistry, Vol 4, Iss 1, Pp 1-

    2021  Volume 13

    Abstract: Phosphatidylinositol-4,5-bisphosphates are involved in membrane regulation and signalling in eukaryotes, with the distribution of acyl chains changing in response to stimuli. Here, molecular dynamics simulations and fluorescence spectroscopy experiments ... ...

    Abstract Phosphatidylinositol-4,5-bisphosphates are involved in membrane regulation and signalling in eukaryotes, with the distribution of acyl chains changing in response to stimuli. Here, molecular dynamics simulations and fluorescence spectroscopy experiments show that increasing acyl chain saturation increases the ordering of lipid nanodomains in artificial membranes.
    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2021-11-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Epigenetic reprogramming by TET enzymes impacts co-transcriptional R-loops

    João C Sabino / Madalena R de Almeida / Patrícia L Abreu / Ana M Ferreira / Paulo Caldas / Marco M Domingues / Nuno C Santos / Claus M Azzalin / Ana Rita Grosso / Sérgio Fernandes de Almeida

    eLife, Vol

    2022  Volume 11

    Abstract: DNA oxidation by ten-eleven translocation (TET) family enzymes is essential for epigenetic reprogramming. The conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) initiates developmental and cell-type-specific transcriptional programs ...

    Abstract DNA oxidation by ten-eleven translocation (TET) family enzymes is essential for epigenetic reprogramming. The conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) initiates developmental and cell-type-specific transcriptional programs through mechanisms that include changes in the chromatin structure. Here, we show that the presence of 5hmC in the transcribed gene promotes the annealing of the nascent RNA to the template DNA strand, leading to the formation of an R-loop. Depletion of TET enzymes reduced global R-loops in the absence of gene expression changes, whereas CRISPR-mediated tethering of TET to an active gene promoted the formation of R-loops. The genome-wide distribution of 5hmC and R-loops shows a positive correlation in mouse and human stem cells and overlap in half of all active genes. Moreover, R-loop resolution leads to differential expression of a subset of genes that are involved in crucial events during stem cell proliferation. Altogether, our data reveal that epigenetic reprogramming via TET activity promotes co-transcriptional R-loop formation, disclosing new mechanisms of gene expression regulation.
    Keywords R-loops ; DNA hydroxymethylation ; TET enzymes ; gene expression ; stem cells ; Medicine ; R ; Science ; Q ; Biology (General) ; QH301-705.5
    Subject code 570
    Language English
    Publishing date 2022-02-01T00:00:00Z
    Publisher eLife Sciences Publications Ltd
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Application of Light Scattering Techniques to Nanoparticle Characterization and Development

    Patrícia M. Carvalho / Mário R. Felício / Nuno C. Santos / Sónia Gonçalves / Marco M. Domingues

    Frontiers in Chemistry, Vol

    2018  Volume 6

    Abstract: Over the years, the scientific importance of nanoparticles for biomedical applications has increased. The high stability and biocompatibility, together with the low toxicity of the nanoparticles developed lead to their use as targeted drug delivery ... ...

    Abstract Over the years, the scientific importance of nanoparticles for biomedical applications has increased. The high stability and biocompatibility, together with the low toxicity of the nanoparticles developed lead to their use as targeted drug delivery systems, bioimaging systems, and biosensors. The wide range of nanoparticles size, from 10 nm to 1 μm, as well as their optical properties, allow them to be studied using microscopy and spectroscopy techniques. In order to be effectively used, the physicochemical properties of nanoparticle formulations need to be taken into account, namely, particle size, surface charge distribution, surface derivatization and/or loading capacity, and related interactions. These properties need to be optimized considering the final nanoparticle intended biodistribution and target. In this review, we cover light scattering based techniques, namely dynamic light scattering and zeta-potential, used for the physicochemical characterization of nanoparticles. Dynamic light scattering is used to measure nanoparticles size, but also to evaluate their stability over time in suspension, at different pH and temperature conditions. Zeta-potential is used to characterize nanoparticles surface charge, obtaining information about their stability and surface interaction with other molecules. In this review, we focus on nanoparticle characterization and application in infection, cancer and cardiovascular diseases.
    Keywords nanoparticles ; dynamic light scattering ; zeta-potential ; antimicrobial peptides ; anticancer peptides ; cardiovascular diseases ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2018-06-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Fibrinogen αC-subregions critically contribute blood clot fibre growth, mechanical stability, and resistance to fibrinolysis

    Helen R McPherson / Cedric Duval / Stephen R Baker / Matthew S Hindle / Lih T Cheah / Nathan L Asquith / Marco M Domingues / Victoria C Ridger / Simon DA Connell / Khalid M Naseem / Helen Philippou / Ramzi A Ajjan / Robert AS Ariëns

    eLife, Vol

    2021  Volume 10

    Abstract: Fibrinogen is essential for blood coagulation. The C-terminus of the fibrinogen α-chain (αC-region) is composed of an αC-domain and αC-connector. Two recombinant fibrinogen variants (α390 and α220) were produced to investigate the role of subregions in ... ...

    Abstract Fibrinogen is essential for blood coagulation. The C-terminus of the fibrinogen α-chain (αC-region) is composed of an αC-domain and αC-connector. Two recombinant fibrinogen variants (α390 and α220) were produced to investigate the role of subregions in modulating clot stability and resistance to lysis. The α390 variant, truncated before the αC-domain, produced clots with a denser structure and thinner fibres. In contrast, the α220 variant, truncated at the start of the αC-connector, produced clots that were porous with short, stunted fibres and visible fibre ends. These clots were mechanically weak and susceptible to lysis. Our data demonstrate differential effects for the αC-subregions in fibrin polymerisation, clot mechanical strength, and fibrinolytic susceptibility. Furthermore, we demonstrate that the αC-subregions are key for promoting longitudinal fibre growth. Together, these findings highlight critical functions of the αC-subregions in relation to clot structure and stability, with future implications for development of novel therapeutics for thrombosis.
    Keywords blood coagulation ; fibrinogen ; bleeding ; thrombosis ; vascular biology ; Medicine ; R ; Science ; Q ; Biology (General) ; QH301-705.5
    Subject code 621
    Language English
    Publishing date 2021-10-01T00:00:00Z
    Publisher eLife Sciences Publications Ltd
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: rBPI(21) promotes lipopolysaccharide aggregation and exerts its antimicrobial effects by (hemi)fusion of PG-containing membranes.

    Marco M Domingues / Miguel A R B Castanho / Nuno C Santos

    PLoS ONE, Vol 4, Iss 12, p e

    2009  Volume 8385

    Abstract: Antimicrobial peptides (AMPs) are important potential alternatives to conventional therapies against bacterial infections. rBPI(21) is a 21 kDa peptide based on the N-terminal region of the neutrophil bactericidal/permeability-increasing protein (BPI). ... ...

    Abstract Antimicrobial peptides (AMPs) are important potential alternatives to conventional therapies against bacterial infections. rBPI(21) is a 21 kDa peptide based on the N-terminal region of the neutrophil bactericidal/permeability-increasing protein (BPI). This AMP possesses highly selective bactericidal effects on Gram-negative bacteria and have affinity for lipopolysaccharide (LPS) which is believed to be at the origin of its neutralizing effect of the LPS segregated into the bloodstream. We aim at understanding the molecular bases of rBPI(21) bactericidal and LPS neutralization actions, using biomembrane model systems. Using dynamic light scattering spectroscopy we demonstrate that rBPI(21) promotes aggregation of negatively charged large unilamellar vesicles (LUV), even in the absence of LPS, and LPS aggregates, while for zwitterionic phosphatidylcholine (POPC) LUV the size remains unchanged. The peptide also promotes the fusion (or hemifusion) of membranes containing phosphatidylglycerol (POPG). The aggregation and fusion of negatively charged LUV are peptide concentration-dependent until massive aggregation is reached, followed by sample flocculation/precipitation. Concomitantly, there is a progressive change in the zeta-potential of the LUV systems and LPS aggregates. LUV systems composed of phosphatidylglycerol (POPG) and lipid mixtures with POPG have higher zeta-potential variations than in the absence of POPG. The interaction of rBPI(21) with lipid vesicles is followed by leakage, with higher effect in POPG-containing membranes. LPS aggregation can be related with a decreased toxicity, possibly by facilitating its clearance by macrophage phagocytosis and/or blocking of LPS specific receptor recognition. Our data indicate that rBPI(21) mechanism of action at the molecular level involves the interaction with the LPS of the outer membrane of Gram-negative bacteria, followed by internalization and leakage induction through the (hemi)fusion of the bacterial outer and inner membranes, both enriched in ...
    Keywords Medicine ; R ; Science ; Q
    Subject code 540
    Language English
    Publishing date 2009-12-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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