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Graham Hungerford - One of the best experts on this subject based on the ideXlab platform.

  • photophysics of Mesoporphyrin IX in solution and confined in sol gel derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of Mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control chemical additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the Mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrIX pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrIX environment, although differences were encountered between the various matrIX forms.

  • Photophysics of Mesoporphyrin IX in solution and confined in sol–gel-derived matrices
    Journal of Photochemistry and Photobiology A-chemistry, 2005
    Co-Authors: M Pereira, Joao A Ferreira, Graham Hungerford
    Abstract:

    Abstract In this work we investigate both the stationary and transient spectroscopic properties of Mesoporphyrin IX when incorporated into porous matrices produced using the sol–gel technique. These matrices were produced using both titanium and silicon containing precursors to form solid glassy monoliths, with the addition (in some samples) of DMF as a drying control chemical additive. Steady state and time-resolved fluorescence measurements were performed on the freshly gelled and finished matrices and comparison with solution studies made. The latter show a dependence of the Mesoporphyrin absorption and emission spectra with refractive index and also with the E T(30) solvent scale. Anomalies are encountered with both aprotic and protic solvents, respectively, when using these scales, indicating interaction with nitrogens in the pyrrole ring. The effect of pH is also clear and the presence of the cationic and dicationic forms of the porphyrin observed via steady state and time-resolved measurements, both in solution and with the porphyrin incorporated within the matrIX pore structure where an estimate of refractive index and E T(30) value were made. With time the porphyrin was found to aggregate and degrade within the matrIX environment, although differences were encountered between the various matrIX forms.

Liliya A Yatsunyk - One of the best experts on this subject based on the ideXlab platform.

  • n methyl Mesoporphyrin IX as a highly selective light up probe for g quadruplex dna
    Journal of Porphyrins and Phthalocyanines, 2019
    Co-Authors: Ariana Yett, Dana Beseiso, Joanne Miao, Liliya A Yatsunyk
    Abstract:

    N-methyl Mesoporphyrin IX (NMM) is a water-soluble, non-symmetric porphyrin with excellent optical properties and unparalleled selectivity for G-quadruplex (GQ) DNA. G-quadruplexes are non-canonica...

  • Optimized end-stacking provides specificity of N-methyl Mesoporphyrin IX for human telomeric G-quadruplex DNA.
    Journal of the American Chemical Society, 2012
    Co-Authors: John M Nicoludis, Steven P Barrett, Stephen T. Miller, Philip D. Jeffrey, Paul R. Rablen, Thomas J. Lawton, Liliya A Yatsunyk
    Abstract:

    N-Methyl Mesoporphyrin IX (NMM) is exceptionally selective for G-quadruplexes (GQ) relative to duplex DNA and, as such, has found a wide range of applications in biology and chemistry. In addition, NMM is selective for parallel versus antiparallel GQ folds, as was recently demonstrated in our laboratory. Here, we present the X-ray crystal structure of a complex between NMM and human telomeric DNA dAGGG(TTAGGG)3, Tel22, determined in two space groups, P21212 and P6, at 1.65 and 2.15 A resolution, respectively. The former is the highest resolution structure of the human telomeric GQ DNA reported to date. The biological unit contains a Tel22 dimer of 5′-5′ stacked parallel-stranded quadruplexes capped on both ends with NMM, supporting the spectroscopically determined 1:1 stoichiometry. NMM is capable of adjusting its macrocycle geometry to closely match that of the terminal G-tetrad required for efficient π–π stacking. The out-of-plane N-methyl group of NMM fits perfectly into the center of the parallel GQ c...

  • optimized end stacking provides specificity of n methyl Mesoporphyrin IX for human telomeric g quadruplex dna
    Journal of the American Chemical Society, 2012
    Co-Authors: John M Nicoludis, Steven P Barrett, Stephen T. Miller, Philip D. Jeffrey, Paul R. Rablen, Thomas J. Lawton, Liliya A Yatsunyk
    Abstract:

    N-methyl Mesoporphyrin IX (NMM) is exceptionally selective for G-quadruplexes (GQ) relative to duplex DNA and, as such, has found a wide range of applications in biology and chemistry. In addition, NMM is selective for parallel versus antiparallel GQ folds, as was recently demonstrated in our laboratory. Here, we present the X-ray crystal structure of a complex between NMM and human telomeric DNA dAGGG(TTAGGG)(3), Tel22, determined in two space groups, P2(1)2(1)2 and P6, at 1.65 and 2.15 A resolution, respectively. The former is the highest resolution structure of the human telomeric GQ DNA reported to date. The biological unit contains a Tel22 dimer of 5'-5' stacked parallel-stranded quadruplexes capped on both ends with NMM, supporting the spectroscopically determined 1:1 stoichiometry. NMM is capable of adjusting its macrocycle geometry to closely match that of the terminal G-tetrad required for efficient π-π stacking. The out-of-plane N-methyl group of NMM fits perfectly into the center of the parallel GQ core where it aligns with potassium ions. In contrast, the interaction of the N-methyl group with duplex DNA or antiparallel GQ would lead to steric clashes that prevent NMM from binding to these structures, thus explaining its unique selectivity. On the basis of the biochemical data, binding of NMM to Tel22 does not rely on relatively nonspecific electrostatic interactions, which characterize most canonical GQ ligands, but rather it is hydrophobic in nature. The structural features observed in the NMM-Tel22 complex described here will serve as guidelines for developing new quadruplex ligands that have excellent affinity and precisely defined selectivity.

  • interaction of human telomeric dna with n methyl Mesoporphyrin IX
    Nucleic Acids Research, 2012
    Co-Authors: John M Nicoludis, Steven P Barrett, Jeanlouis Mergny, Liliya A Yatsunyk
    Abstract:

    : The remarkable selectivity of N-methyl Mesoporphyrin IX (NMM) for G-quadruplexes (GQs) is long known, however its ability to stabilize and bind GQs has not been investigated in detail. Through the use of circular dichroism, UV-visible spectroscopy and fluorescence resonance energy transfer (FRET) melting assay we have shown that NMM stabilizes human telomeric DNA dAG(3)(TTAG(3))(3) (Tel22) and is selective for its parallel conformation to which it binds in 1:1 stoichiometry with a binding constant of ≈ 1.0 × 10(5)M(-1). NMM does not interact with an antiparallel conformation of Tel22 in sodium buffer and is the second example in the literature, after TOxaPy, of a ligand with an excellent selectivity for a specific GQ structure. NMM's stabilizing ability toward predominantly parallel GQ conformation is universal: it stabilizes a variety of biologically relevant G-rich sequences including telomeres and oncogene promoters. The N-methyl group is integral for selectivity and stabilization, as the unmethylated analogue, Mesoporphyrin IX, does not stabilize GQ DNA in FRET melting assays. Finally, NMM induces the isomerization of Tel22 into a structure with increased parallel component in K(+) but not in Na(+) buffer. The ability of NMM to cause structural rearrangement and efficient stabilization of Tel22 may bear biological significance.

Sebastian Schlucker - One of the best experts on this subject based on the ideXlab platform.

  • symmetry properties of vibrational modes in Mesoporphyrin IX dimethyl ester investigated by polarization sensitive resonance raman and cars spectroscopy
    Journal of Physical Chemistry A, 2006
    Co-Authors: J Koster, Jurgen Popp, W Kiefer, Sebastian Schlucker
    Abstract:

    The symmetry properties of selected vibrational modes of Mesoporphyrin IX dimethyl ester (MP-IX-DME) in solution are investigated under different electronic resonance conditions. The Raman band parameters of the macrocycle modes ν2, ν10, ν11, and ν19 are determined from a quantitative analysis of polarized spontaneous resonance Raman (RR) and polarization-sensitive (PS) multiplex coherent anti-Stokes Raman scattering (CARS) spectra obtained with pre-resonant B band and resonant Qx band excitation, respectively. Additionally, the molecular geometry and the vibrational modes of MP-IX-DME are calculated by employing density functional theory (DFT) on the B3LYP/6-31G(d) level. Both the DFT-derived structure and the Raman spectroscopic parameters of MP-IX-DME indicate minor deviations from an ideal D2h macrocycle symmetry. To assess the influence of the β substitution pattern on the in-plane symmetry, calculated normal-mode vectors and several experimentally detected parameters, such as peak positions, depolar...

Levente Herenyi - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of light-induced formation of reactive oxygen species and the membrane destruction of two Mesoporphyrin derivatives in liposomes
    Scientific Reports, 2019
    Co-Authors: Barnabás Bőcskei-antal, Ádám Zolcsák, Nikoletta Kósa, István Voszka, Gabriella Csík, Katalin Tóth, Levente Herenyi
    Abstract:

    The photodynamic effect requires the simultaneous presence of light, photosensitizer (PS) and molecular oxygen. In this process, the photoinduced damage of cells is caused by reactive oxygen species (ROS). Besides DNA, the other target of ROS is the membranes, separating internal compartments in living cells. Hence, the ability of ROS formation of porphyrins as PSs, in liposomes as simple models of cellular membranes is of outstanding interest. Earlier we compared the binding parameters and locations of Mesoporphyrin IX dihydrochloride (MPCl) and Mesoporphyrin IX dimethyl ester (MPE), in small unilamellar vesicles (SUV) made from various saturated phosphatidylcholines. In this study, we used the same kinds of samples for comparing the ROS forming ability. Triiodide production from potassium iodide because of light-induced ROS in the presence of molybdate catalyst was applied, and the amount of product was quantitatively followed by optical spectrometry. Furthermore, we demonstrated and carefully studied SUVs disruption as direct evidence of membrane destruction by the methods of dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS), applying unsaturated phosphatidylcholines as membrane components. Although the ROS forming ability is more pronounced in the case of MPCl, we found that the measured disruption was more effective in the samples containing MPE.

  • Comparison of Reactive Oxygen Species Production Activity and Binding Ability of Porphyrins in Cell Membrane Models
    Biophysical Journal, 2015
    Co-Authors: Barnabás Böcskei-antal, Nikoletta Kósa, István Voszka, Gabriella Csík, Bianka Nagy, Szilvia Anikó Tóth, Levente Herenyi
    Abstract:

    Photo dynamic therapy (PDT) is a widespread medical treatment based on the light-triggered generation of reactive oxygen species (ROS) by porphyrin derivatives. ROS may cause oxidative damage to membranes as well as to DNA and, in consequence, ultimately kill cells. Hence, the binding ability, the location within liposomes as simple cellular membrane models, and the ROS production ability of porphyrins are of outstanding interest. Earlier we determined the location of Mesoporphyrin IX dimethyl ester (MPE) and its non-esterified form, Mesoporphyrin IX dihydrochloride (MPCl) in small unilamellar vesicles (SUV) with fluorescence line narrowing spectroscopy (FLN). Here we investigated the production of ROS by the photosensitizers in the aqueous medium of the vesicles and in the lipid bilayer environment. The monocomponent vesicles were formed of various saturated phosphatidylcholines. The amount of generated oxygen radicals in the aqueous media was measured on the basis of the produced tri-iodide (I3-) from potassium iodide (KI) in the presence of molybdenum (MoO4) catalyst, which was followed by absorption spectrophotometry. The ROS in the lipophilic membranes and in near-membrane regions was measured with a dihydrorhodamine derivative by fluorescence spectroscopy. We observed in general that the binding ability of MPE is considerably higher than that of MPCl. In aqueous media (without liposomes) MPCl was highly effective in ROS formation whereas in case of MPE no similar effect was observed. Liposome-incorporated MPCl produced ROS in much higher amounts than the MPE in the aqueous medium of the liposomes. In near-membrane regions MPE produced ROS in the same amount as MPCl.

  • Comparison of binding ability and location of two Mesoporphyrin derivatives in liposomes explored with conventional and site-selective fluorescence spectroscopy.
    Biophysical Journal, 2012
    Co-Authors: Daniel V. Veres, Judit Fidy, István Voszka, Gabriella Csík, Barnabás Böcskei-antal, Károly Módos, Andras D. Kaposi, Levente Herenyi
    Abstract:

    Application of porphyrins as photosensitizers is based on their light-triggered generation of reactive oxygen species (ROS) that may cause oxidative tissue damage and ultimately kill cells. Cellular membranes are the action grounds of many sensitizers due to their hydrophobic or amphiphilic character as well as the location of many of the targets attacked by ROS. Hence, the binding ability and location of porphyrins in liposomes as simple models of cellular membranes are of outstanding interest. Here we compare Mesoporphyrin IX dimethyl ester (MPE) and its nonesterified form, Mesoporphyrin IX dihydrochloride (MPCl). Monocomponent small unilamellar vesicles formed of various saturated phosphatidylcholines with incorporated Mesoporphyrins were investigated. We determined the binding parameters and the inhomogeneous distribution functions (IDFs) by different fluorescence techniques. We found in general that the binding ability of MPE is considerably greater than that of MPCl. In the case of MPCl, the IDFs suggest that only one of the two binding site types identified earlier for MPE ("site II") exists; the other one ("site I") vanishes while a new one appears ("site III"). We can confirm that "site I" is located between the two lipid layers, "site II" is situated between the hydrocarbon chains, while the location of the novel "site III" is along the outer part of the hydrocarbon chains partially inserted between the lipid head groups.

  • Deuteration effects on the conformational dynamics of proteins in a trehalose glass
    Journal of Physical Chemistry B, 2002
    Co-Authors: J. Schlichter, Levente Herenyi, Josef Friedrich, Judit Fidy
    Abstract:

    We present results of a hole-burning spectral diffusion experiment on a deuterated sample of horseradish peroxidase (substituted with free-base Mesoporphyrin-IX) in a trehalose/glycerol glass. Like in earlier experiments,the spectral diffusion dynamics is well-described by a diffusion picture; the most noticeable observation is a power-law dependence of the hole-broadening on time. In addition, the comparison of the present data with our earlier experiments allows for a microscopic interpretation of the influence of trehalose on protein dynamics. Here, internal water molecules in the proteins seem to be of great importance.

  • Protein dynamics at low temperatures
    Journal of Chemical Physics, 2000
    Co-Authors: J. Schlichter, Levente Herenyi, Josef Friedrich, Judit Fidy
    Abstract:

    The low temperature conformational dynamics of the heme type protein Mesoporphyrin-IX-substituted horseradish peroxidase is investigated by spectral diffusion waiting time/aging experiments. Spectral diffusion broadening is governed by a power law in time. There is a small but significant aging effect. It is assumed that the conformational dynamics of the protein which leads to the spectral broadening of the burnt-in holes is governed by a diffusion type equation. In this case the shape of the spectral diffusion kernel is Gaussian. This model is contrasted with spectral diffusion phenomena as described by the TLS-model (TLS, two level system).

J Manriquez - One of the best experts on this subject based on the ideXlab platform.

  • electrophoretically assisted deposition of Mesoporphyrin IX on nanoparticulate tio2 films for constructing efficient dye sensitized solar cells
    Journal of The Electrochemical Society, 2011
    Co-Authors: U Lopezgarcia, Oscar A Castellanos, Luis A Godinez, J Manriquez
    Abstract:

    The successful fabrication of efficient dye-sensitized solar cells containing electrophoretically-deposited Mesoporphyrin IX in semiconductor films based on sintered TiO 2 nanoparticles is presented in this work. For comparison purposes, photocells utilizing Mesoporphyrin IX-sensitized TiO 2 electrodes were also constructed following the traditional dip-coating deposition technique. Electrochemical responses obtained from these modified surfaces revealed that the electrophoretic methodology generated perpendicularly-arranged porphyrin layers on the sintered oxide nanoparticles, while the dip-coating deposition technique resulted in parallel layers of porphyrin. It was demonstrated that the photovoltaic performance of cells containing electrophoretically-dyed TiO 2 films was three times higher than that of devices having photoelectrodes constructed according to the dip-coating protocol. To better understand this behavior, both types of solar cells were further investigated by means of photoelectrochemical impedance spectroscopy.