Plasmon Resonance Analysis (plasmon + resonance_analysis)

Distribution by Scientific Domains

Kinds of Plasmon Resonance Analysis

  • surface plasmon resonance analysis


  • Selected Abstracts


    EthR, a repressor of the TetR/CamR family implicated in ethionamide resistance in mycobacteria, octamerizes cooperatively on its operator

    MOLECULAR MICROBIOLOGY, Issue 1 2004
    Jean Engohang-Ndong
    Summary Ethionamide (ETH) is an important second-line antitubercular drug used for the treatment of patients infected with multidrug-resistant Mycobacterium tuberculosis. Although ETH is a structural analogue of isoniazid, only little cross-resistance to these two drugs is observed among clinical isolates. Both isoniazid and ETH are pro-drugs that need to be activated by mycobacterial enzymes to exert their antimicrobial activity. We have recently identified two M. tuberculosis genes, Rv3854c (ethA) and Rv3855 (ethR), involved in resistance to ETH. ethA encodes a protein that belongs to the Flavin-containing monooxygenase family catalysing the activation of ETH. We show here that ethR, which encodes a repressor belonging to the TetR/CamR family of transcriptional regulators, negatively regulates the expression of ethA. By the insertion of the ethA promoter region upstream of the lacZ reporter gene, overexpression of ethR in trans was found to cause a strong inhibition of ethA expression, independently of the presence of ETH in the culture media. Electrophoretic mobility shift assays indicated that EthR interacts directly with the ethA promoter region. This interaction was confirmed by DNA footprinting analysis, which, in addition, identified the EthR-binding region. Unlike other TetR/CamR members, which typically bind 15 bp operators, EthR recognises an unusually long 55 bp region suggesting multimerization of the repressor on its operator. Identification by primer-extension of the ethA transcriptional start site indicated that it is located within the EthR-binding region. Taken together, bacterial two-hybrid experiments and gel filtration assays suggested a dimerization of EthR in the absence of its operator. In contrast, surface plasmon resonance analyses showed that eight EthR molecules bind cooperatively to the 55 bp operator, which represents a novel repression mechanism for a TetR/CamR member. [source]


    The stress response protein Gls24 is induced by copper and interacts with the CopZ copper chaperone of Enterococcus hirae

    FEMS MICROBIOLOGY LETTERS, Issue 1 2010
    Jivko V. Stoyanov
    Abstract Intracellular copper routing in Enterococcus hirae is accomplished by the CopZ copper chaperone. Under copper stress, CopZ donates Cu+ to the CopY repressor, thereby releasing its bound zinc and abolishing repressor,DNA interaction. This in turn induces the expression of the cop operon, which encodes CopY and CopZ, in addition to two copper ATPases, CopA and CopB. To gain further insight into the function of CopZ, the yeast two-hybrid system was used to screen for proteins interacting with the copper chaperone. This led to the identification of Gls24, a member of a family of stress response proteins. Gls24 is part of an operon containing eight genes. The operon was induced by a range of stress conditions, but most notably by copper. Gls24 was overexpressed and purified, and was shown by surface plasmon resonance analysis to also interact with CopZ in vitro. Circular dichroism measurements revealed that Gls24 is partially unstructured. The current findings establish a novel link between Gls24 and copper homeostasis. [source]


    Shed HER2 extracellular domain in HER2-mediated tumor growth and in trastuzumab susceptibility,

    JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2010
    Gaia C. Ghedini
    The question of the serum HER2 extracellular domain (HER2/ECD) measurement for prediction of response to the anti-HER2 antibody Trastuzumab is still an open and current matter of clinical debate. To elucidate the involvement of shed HER2/ECD in HER2-driven tumor progression and in guiding therapy of individual patients, we examined biological effects exerted by elevated HER2/ECD in cancer growth and in response to Trastuzumab. To this purpose SKOV3 tumor cells were stably transfected to release a recombinant HER2/ECD molecule (rECD). Transfectants releasing high levels of 110-kDa rECD, identical in size to native HER2/ECD (nECD), grew significantly slower than did controls, which constitutively released only basal levels of nECD. While transmembrane HER2 and HER1 were expressed at equal levels by both controls and transfected cells, activation of these molecules and of downstream ERK2 and Akt was significantly reduced only in rECD transfectants. Surface plasmon resonance analysis revealed heterodimerization of the rECD with HER1, -2, and -3. In cell growth bioassays in vitro, shed HER2 significantly blocked HER2-driven tumor cell proliferation. In mice, high levels of circulating rECD significantly impaired HER2-driven SKOV3 tumor growth but not that of HER2-negative tumor cells. In vitro and in mice, Trastuzumab significantly inhibited tumor growth due to the rECD-facilitated accumulation of the antibody on tumor cells. Globally our findings sustain the biological relevance of elevated HER2/ECD levels in the outcome of HER2-disease and in the susceptibility to Trastuzumab-based therapy. J. Cell. Physiol. 225: 256,265, 2010. © 2010 Wiley-Liss, Inc. [source]


    A simple method to discriminate between ,2 -glycoprotein I- and prothrombin-dependent lupus anticoagulants

    JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2003
    M. J. A. Simmelink
    Summary., Lupus anticoagulants (LAC) are a heterogeneous group of autoantibodies that prolong phospholipid-dependent clotting assays. The autoantibodies that cause LAC activity are predominantly directed against ,2 -glycoprotein I (,2GPI) or prothrombin. In the present study, we describe a method to differentiate between LAC caused by antibodies directed against ,2GPI or prothrombin. Monoclonal antibodies, affinity purified patient antibodies, and selected patient samples were used to show that in an aPTT-based clotting assay (PTT-LA; Diagnostica Stago), the use of cardiolipin vesicles in the neutralization procedure discriminates between ,2GPI- or prothrombin-dependent LAC activities. Addition of cardiolipin vesicles shortened the prolonged clotting time caused by anti-,2GPI antibodies with LAC activity, whereas this procedure further prolonged clotting times caused by antiprothrombin antibodies with LAC activity. In contrast, addition of phosphatidylcholine/phosphatidylserine vesicles corrected prolonged clotting times caused by either anti-,2GPI or antiprothrombin antibodies with LAC activity. The effects of cardiolipin (CL) on ,2GPI-induced LAC activity were specific for contact activation mediated clotting assays. Possible explanations for these findings are the relatively high affinity of ,2GPI for cardiolipin, as determined by surface plasmon resonance analysis, and inhibition by anti-,2GPI antibodies of the CL-induced prolongation of the PTT-LA. [source]


    Surface Plasmon-coupled Polarized Emission of N-Acetyl- l -Trytophanamide,

    PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2004
    Ignacy Gryczynski
    We report an observation of ultraviolet (UV) surface plasmon-coupled emission (SPCE) of N-acetyl- l -tryptophanamide (NATA). The sample was spin coated from poly(vinyl alcohol) (PVA) solution on 20 nmaluminium film deposited on a quartz substracte. The directional UV SPCE occurs within a well-defined narrow angle at 52dG from the normal to the coupling hemicylinder quartz prism. The NATA directional emission is highly p polarized as expected for surface plasmon-coupled radiation. The 10 nm protective SiO2 layer deposited on top of the aluminum film significantly neutralized the fluorophore quenching by the metal surface. SPCE of NATA demonstratees a remarkable intrinsic dispersive property,the maximum of the emission spectrum depends on the observation angle. The efficient spectral resolution of SPCE can be used in the construction of miniaturized spectrofluorometers. The observation of SPCE of tryptophan opens a new possibility for the study of many unlabeled proteins with the technique complementary to surface plasmon resonance analysis. [source]


    Crystal structures of the Arabidopsis thaliana proliferating cell nuclear antigen 1 and 2 proteins complexed with the human p21 C-terminal segment

    PROTEIN SCIENCE, Issue 5 2009
    Wojciech Strzalka
    Abstract The proliferating cell nuclear antigen (PCNA) is well recognized as one of the essential cellular components of the DNA replication machinery in all eukaryotic organisms. Despite their prominent importance, very little biochemical and structural information about plant PCNAs is available, in comparison with that obtained from other eukaryotic organisms. We have determined the atomic resolution crystal structures of the two distinct Arabidopsis thaliana PCNAs (AtPCNA), both complexed with the C-terminal segment of human p21. Both AtPCNAs form homotrimeric ring structures, which are essentially identical to each other, including the major contacts with the p21 peptide. The structure of the amino-terminal half of the p21 peptide, containing the typical PIP box sequence, is remarkably similar to those observed in the previously reported crystal structures of the human and archaeal PCNA-PIP box complexes. Meanwhile, the carboxy-terminal halves of the p21 peptide in the plant PCNA complexes are bound to the protein in a unique manner, most probably because of crystal packing effects. A surface plasmon resonance analysis revealed high affinity between each AtPCNA and the C-terminal fragment of human p21. This result strongly suggests that the interaction is functionally significant, although no plant homologs of p21 have been identified yet. We also discovered that AtPCNA1 and AtPCNA2 form heterotrimers, implying that hetero-PCNA rings may play critical roles in cellular signal transduction, particularly in DNA repair. [source]


    Templated assembly of the pH-sensitive membrane-lytic peptide GALA

    CHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2004
    D.H. Haas
    Abstract:, Delivery of protein or nucleic acid therapeutics into intracellular compartments may require facilitation to allow these macromolecules to cross otherwise impermeant cellular membranes. Peptides capable of forming membrane-spanning channels hold promise as just such facilitators, although the requirement for peptide oligomerization to form these channels may limit their effectiveness. Synthetic molecules containing multiple copies of membrane-active peptides attached to a template molecule in a pre-oligomerized form have attracted interest for drug-delivery applications. Using three template designs, we synthesized multimeric versions of the pH-sensitive lytic peptide GALA and compared their performance to monomeric GALA. Template assembly stabilized helix formation: templated GALA retained , -helical structure even at neutral pH, unlike monomeric GALA. In membrane leakage assays, templated GALA retained the pH sensitivity of the monomer, with improved leakage for dimeric GALA. Surprisingly, trimeric GALA was less effective, particularly when synthesized with a larger and more flexible spacer. Surface plasmon resonance analysis indicated that reversible binding of templated GALA to lipid surfaces at acidic conditions was greatly reduced compared with monomeric GALA, but that the amount of irreversibly bound material was similar. We interpreted these results to indicate that templated peptides may cyclize into ,self-satisfied' oligomeric structures, incapable of further aggregation and subsequent pore formation. Future design of templated peptides must be carefully performed to avoid this unwanted consequence. [source]