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  • 1
    Electronic Resource
    Electronic Resource
    Reversible optical structuring of polymer waveguides doped with photochromic molecules (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 921-923 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that polymeric films doped with the photochromic molecule 1,8a-dihydro-2(4-iodophenyl)-1,1-azulenedicarbonitrile can be reversibly structured by light. We discuss the relevant material properties of the photochromic molecule in solution as well as in polymer films and demonstrate light-induced waveguides at the telecommunication wavelength of 1.313 μm. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288598
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  • 2
    Electronic Resource
    Electronic Resource
    Surface-enhanced raman spectroscopy investigation of fluoroquinolone/DNA/DNA gyrase/Mg2+ interactions: Part I. Adsorption of pefloxacin on colloidal silver - effect of drug concentration, electrolytes, and pH (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 423-436 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Surface-enhanced Raman spectra (SERS at Creighton colloidal silver) and UV/visible spectra have been recorded for an antimicrobial agent (pefloxacin) at a biologically active concentration (ca. 10-6 mol/L-1). The adsorption of pefloxacin on the silver surface occurs both via the carboxylate group and the carbonyl of the pyridinone ring. The conjugated part of the molecule is tilted and gives rise to a charge transfer between the drug and the plasmon surface. However the orientation of the drug on the colloid varies with the concentration of pefloxacin, salt addition, and pH. Adsorption via only the carboxylate is privileged in presence of strongly competitive anions such as C1-. Thus the carbonyl of the pyridinone ring is desorbed, and the charge transfer is not detected. In basic medium the competitive OH- ion leads to similar orientation changes. For acidic pHs few residual molecules having a carboxylate function, or few carboxylic species bonded via the pyridinone C=O group, remain adsorbed on the aggregated and unstable silver surface. The spectroscopic analyses and the measurements of the particle size of the colloid show that added salt increases the aggregation and enhances the pefloxacin SERS signals if the anion is not competitive. In the presence of NaNO3 an increase of the plasmon oscillations of the metal and a larger number of adsorption sites could explain the SERS amplitude. The competitive anions C1- and OH- to a lesser extent limit the colloid aggregation, pefloxacin adsorption, and SERS enhancement. The influence of the charge transfer on the Raman intensity appears to be weak. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bspy.350010607
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  • 3
    Electronic Resource
    Electronic Resource
    Surface-enhanced raman spectroscopy investigation of fluoroquinolones-DNA-DNA gyrase-Mg2+ interactions. II. Interaction of pefloxacin with Mg2+ and DNA (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 3 (1997), S. 31-45 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The interactions between pefloxacin (antimicrobial agent), magnesium, and DNA single or double strand are studied by UV/Vis and surface-enhanced Raman spectroscopies at biological active concentrations: pefloxacin 2 × 10-6, DNA 2 × 10-5, and Mg2+ 10-3M. Pefloxacin interacts with Mg2+ via its carboxylate and pyridinone C4=O groups. In presence of the colloid, with nitrate salts, Mg2+ is positioned near the C4=O and the drug is bound to the Ag surface via the carboxylate. The conjugated rings are tilted over the colloidal particles and a charge transfer from the plasmon of the surface to the pefloxacin occurs, as in absence of salts or in presence of sodium nitrate. With MgCl2, pefloxacin/Mg2+ species are also adsorbed onto the colloid but essentially via the C4=O of the pyridinone ring, the carboxylate being partly bound to Mg2+. The charge transfer is canceled as occurring with NaCl. Magnesium interacts with DNA single or double strand via the phosphodiester groups and amino bases are oriented toward the colloidal surface. Chlorides specifically favor the fixation of the adenine NH2 substituent. At low DNA concentration and in presence of Mg2+, the adsorbed bases are tilted over the Ag surface, more for double- than for single-strand DNA. Ternary pefloxacin-Mg2+-DNA complexes are adsorbed onto the silver surface, via the amino group of the DNA bases and via one carboxylate oxygen of the drug. The ternary complex formed with Mg2+ (nitrate) and DNA modifies the charge transfer from the plasmon of the surface to the drug. © 1997 John Wiley & Sons, Inc. Biospect 3: 31-45, 1997
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
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    Primary Human Cytomegalovirus Infection Induces the Expansion of Virus-Specific Activated and Atypical Memory B Cells (2014)
    Oxford University Press
    Details
    Publication Date: 2014-09-27
    Description: Background.  Although neutralizing antibodies play a central role in the control of cytomegalovirus (CMV) dissemination, little is known about the response of B lymphocytes to primary human CMV infection. Methods.  The proportion, phenotype, specificity, and functionality of B-cell subsets were studied in a cohort of pregnant women with primary CMV infection. CMV-seronegative pregnant women, as well as CMV-seronegative and CMV-seropositive healthy adults, were included as controls. Results.  Primary CMV infection was associated with a sustained expansion of activated (CD27 + CD20 + CD21 low ) and atypical (CD27 – CD20 + CD21 low ) memory B cells (MBCs). Both subsets expressed an effector phenotype, and their proportions were correlated with viremia . Activated MBCs expressed high levels of activation markers and included high frequencies of tumor necrosis α (TNF-α)–producing cells, whereas atypical MBCs expressed high levels of inhibitory receptors and had low TNF-α responses. Fluorescent-labeled antigen experiments indicated that activated and atypical MBCs were enriched in CMV-specific cells. Conclusions.  Primary CMV infection mobilizes a large pool of memory B cells that includes activated and atypical MBCs. The functional regulation of CMV-specific MBCs may limit the production of antibodies and the control of viral dissemination.
    Print ISSN: 0022-1899
    Electronic ISSN: 1537-6613
    Topics: Medicine
    Published by Oxford University Press on behalf of The Infectious Diseases Society of America (IDSA).
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  • 5
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    Limited Effector Memory B-Cell Response to Envelope Glycoprotein B During Primary Human Cytomegalovirus Infection (2016)
    Oxford University Press
    Details
    Publication Date: 2016-04-21
    Description: Background.  Following primary human cytomegalovirus (HCMV) infection, the production of antibodies against envelope glycoprotein B (gB) is delayed, compared with production of antibodies against tegument proteins, and this likely reduces the control of HCMV dissemination. Methods.  The frequency and the phenotype of gB-specific and tegument protein–specific B cells were studied in a cohort of pregnant women with primary HCMV infection. Healthy adults who had chronic HCMV infection or were recently immunized with tetanus toxoid (TT) were included as controls. Results.  Primary HCMV infection was associated with high and similar frequencies of gB-specific and tegument protein–specific B cells following primary HCMV infection. During primary infection, tegument protein–specific B cells expressed an activated (CD21 low ) memory B-cell (MBC) phenotype. Activated MBCs were also induced by TT booster immunization, indicating that the expansion of this subset is part of the physiological B-cell response to protein antigens. In contrast, gB-specific B cells had a predominant classical (CD21 + ) MBC phenotype during both primary and chronic infections. Conclusions.  The delayed production of gB-specific immunoglobulin G (IgG) during primary HCMV infection is associated with a limited induction of MBCs with effector potential. This novel mechanism by which HCMV may interfere with the production of neutralizing antibodies could represent a target for therapeutic immunization.
    Print ISSN: 0022-1899
    Electronic ISSN: 1537-6613
    Topics: Medicine
    Published by Oxford University Press on behalf of The Infectious Diseases Society of America (IDSA).
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  • 6
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    Co-expression of RNA-protein complexes in Escherichia coli and applications to RNA biology (2013)
    Oxford University Press
    Details
    Publication Date: 2013-08-28
    Description: RNA has emerged as a major player in many cellular processes. Understanding these processes at the molecular level requires homogeneous RNA samples for structural, biochemical and pharmacological studies. We previously devised a generic approach that allows efficient in vivo expression of recombinant RNA in Escherichia coli . In this work, we have extended this method to RNA/protein co-expression. We have engineered several plasmids that allow overexpression of RNA–protein complexes in E. coli . We have investigated the potential of these tools in many applications, including the production of nuclease-sensitive RNAs encapsulated in viral protein pseudo-particles, the co-production of non-coding RNAs with chaperone proteins, the incorporation of a post-transcriptional RNA modification by co-production with the appropriate modifying enzyme and finally the production and purification of an RNA–His-tagged protein complex by nickel affinity chromatography. We show that this last application easily provides pure material for crystallographic studies. The new tools we report will pave the way to large-scale structural and molecular investigations of RNA function and interactions with proteins.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    S. aureus Toxic Peptide Structure from Toxin-Antitoxin Pair [Protein Structure and Folding] (2012)
    The American Society for Biochemistry and Molecular Biology (ASBMB)
    Details
    Publication Date: 2012-12-22
    Description: We report a functional type I toxin-antitoxin (TA) module expressed by a human pathogen, Staphylococcus aureus. TA systems consist of stable toxins and labile antitoxins encoded within small genetic modules widespread in eubacteria and archaea. TA genes provide stress adaptation and protection against DNA loss or invasion. The genes encoding the SprA1 toxic peptide (PepA1) and the SprA1AS RNA antitoxin are within a pathogenicity island on opposite strands and possess a 3′ overlap. To prevent peptide toxicity during S. aureus growth, PepA1 expression from stable (half-life 〉 3 h) SprA1 is repressed by elevated amounts of unstable (half-life = ∼10 mn) SprA1AS. In vivo, PepA1 localizes at the bacterial membrane and triggers S. aureus death. Based on NMR and CD data, its solution structure was solved and is a long bent, interrupted helix. Molecular dynamics simulations indicate that PepA1 compaction and helical content fluctuate in accordance with its cytoplasm or membrane location. When inserted into the S. aureus membrane, the PepA1 conformation switches to a ∼7-nm-long continuous helix, presumably forming pores to alter membrane integrity. PepA1 expression is induced upon acidic and oxidative stresses by reducing SprA1AS levels. As an altruistic behavior during infection, some cells may induce the expression of that toxin that would facilitate departure from the host immune cells for spreading.
    Print ISSN: 0021-9258
    Electronic ISSN: 1083-351X
    Topics: Biology , Chemistry and Pharmacology
    Published by The American Society for Biochemistry and Molecular Biology (ASBMB)
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  • 8
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    Functional Exhaustion Limits CD4+ and CD8+ T-Cell Responses to Congenital Cytomegalovirus Infection (2015)
    Oxford University Press
    Details
    Publication Date: 2015-07-11
    Description: Background.  Cytomegalovirus (CMV) infection during fetal life causes severe symptoms and is associated with prolonged viral excretion. Previous studies reported low CD4 + T-cell responses to CMV infection in early life, contrasting with large responses of effector CD8 + T cells. The mechanisms underlying the defective CD4 + T-cell responses and the possible dissociation with CD8 + T-cell responses have not been clarified. Methods.  The magnitude and the quality of the fetal CD8 + and CD4 + T-cell responses to CMV infection were compared to those of adults with primary or chronic infection. Results.  In utero CMV infection induced oligoclonal expansions of fetal CD4 + and CD8 + T lymphocytes expressing a T-helper type 1 or Tc1 effector phenotype similar to that of adult CMV-specific cells. However, the effector cytokine responses and the polyfunctionality of newborn CD4 + and CD8 + T cells were markedly lower than those of adult cells. This reduced functionality was associated with a higher expression of the programmed death 1 inhibitory receptor, and blockade of this receptor increased newborn T-cell responses. Conclusions.  Functional exhaustion limits effector CD4 + and CD8 + T-lymphocyte responses to CMV during fetal life.
    Print ISSN: 0022-1899
    Electronic ISSN: 1537-6613
    Topics: Medicine
    Published by Oxford University Press on behalf of The Infectious Diseases Society of America (IDSA).
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  • 9
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    Functional Exhaustion of CD4+ T Lymphocytes during Primary Cytomegalovirus Infection [CLINICAL IMMUNOLOGY] (2012)
    The American Association of Immunologists (AAI)
    Details
    Publication Date: 2012-08-21
    Description: Human CMV establishes lifelong persistence after primary infection. Chronic CMV infection is associated with intermittent viral reactivation inducing high frequencies of CD4 + T lymphocytes with potent antiviral and helper properties. Primary CMV infection is characterized by an intense viral replication lasting for several months. The impact of this prolonged exposure to high Ag loads on the functionality of CD4 + T cells remains incompletely understood. In pregnant women with primary CMV infection, we observed that CMV-specific CD4 + T lymphocytes had a decreased capacity to proliferate and to produce IL-2. A very large proportion of CMV-specific CD4 + T cells had downregulated the expression of CD28, a costimulatory molecule centrally involved in the production of IL-2. Unexpectedly, both CD28 – and CD28 + CD4 + T cells produced low levels of IL-2. This defective production of IL-2 was part of a larger downregulation of cytokine production. Indeed, CMV-specific CD4 + T cells produced lower amounts of IFN- and TNF-α and showed lower functional avidity during primary as compared with chronic infection. Increased programmed death-1 expression was observed in CD28 + CMV-specific CD4 + T cells, and programmed death-1 inhibition increased proliferative responses. These results indicate that primary CMV infection is associated with the exhaustion of CMV-specific CD4 + T cells displaying low functional avidity for viral Ags.
    Print ISSN: 0022-1767
    Electronic ISSN: 1550-6606
    Topics: Medicine
    Published by The American Association of Immunologists (AAI)
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