prof. dr hab. Andrzej Dobek

@article{Sarbak2023,

title = {Expression of Concern: Direct observation of the THz Kerr effect (TKE) in deionized, distilled and buffered (PBS) water},

author = {Szymon Sarbak and Gargi Sharma and Cecil S. Joseph and Weronika E. Kucia and Krzysztof Dobek and Robert H. Giles and Andrzej Dobek},

url = {https://doi.org/10.1039/d2cp90241a},

doi = {10.1039/d2cp90241a},

year  = {2023},

date = {2023-01-01},

journal = {Physical Chemistry Chemical Physics},

volume = {25},

number = {4},

pages = {3547--3550},

publisher = {Royal Society of Chemistry (RSC)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sarbak2017,

title = {Direct observation of the THz Kerr effect (TKE) in deionized, distilled and buffered (PBS) water},

author = {Szymon Sarbak and Gargi Sharma and Cecil S Joseph and Weronika Kucia and Krzysztof Dobek and Robert H Giles and Andrzej Dobek},

doi = {10.1039/C7CP04061J},

year  = {2017},

date = {2017-09-08},

journal = {Physical Chemistry Chemical Physics},

volume = {19},

number = {39},

pages = {26749-26757},

abstract = {Nonlinear THz pump–optical probe (THz–OKE) measurements in deionized, distilled and buffered (PBS) water are reported. A laser system that produces pulses at 800 nm, 30 fs FWHM, at a repetition rate of 1 kHz and an energy of 6 μJ per pulse, was a source of the probe optical beam and of the pump beam of THz 2 ps pulses. The electric field strength inducing birefringence in water samples was ETHz = 1.35 × 106 V m−1. These samples were chosen in order to study the effect of ionic concentration on water behavior in the ultrafast time scale. Differentiation between ultrafast effects resulting from internal H2O properties and those resulting from H2O–ion interactions was analyzed. These two effects may be connected to a difference in the fluctuations of the network of intermolecular hydrogen bonds of water molecules in the presence and absence of ions in solution. The results indicate that such fluctuations significantly alter water birefringence amplitude and its dynamics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kucia2016,

title = {Optical Kerr effect of tRNA solution induced by femtosecond laser pulses},

author = {Weronika Kucia and Gargi Sharma and Cecil S Joseph and Szymon Sarbak and Cameron Oliver and Andrzej Dobek and Robert H Giles},

url = {https://www.sciencedirect.com/science/article/pii/S0009261416306996 http://linkinghub.elsevier.com/retrieve/pii/S0009261416306996},

doi = {10.1016/j.cplett.2016.09.027},

issn = {00092614},

year  = {2016},

date = {2016-10-01},

journal = {Chemical Physics Letters},

volume = {662},

pages = {132--136},

publisher = {North-Holland},

abstract = {The optical Kerr effect (OKE) in a transfer ribonucleic acid (tRNA) solution induced by femtosecond pulses of linearly polarized pump light ($łambda$i=800nm) and sounded by probe light ($łambda$p=800nm) was studied. The measurements were performed to find nonlinear optical parameters describing a single molecule (molecular Kerr constant K, mean nonlinear third order optical polarizability cpi) and to compare them with our previous OKE results obtained in ns and ps time range. The OKE experiment has proven to be an efficient method to obtain the nonlinear parameters of single molecules in solution, which reflects dynamic structure changes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sarbak2015,

title = {Sodium chloride-induced conformational change in tRNA as measured by circular dichroism},

author = {Szymon Sarbak and Melania Kujawa and Hanna Jurga-Nowak and Andrzej Dobek},

url = {https://www.degruyter.com/downloadpdf/j/ctb.2015.38.issue-1/ctb-2015-0001/ctb-2015-0001.pdf https://www.degruyter.com/view/j/ctb.2015.38.issue-1/ctb-2015-0001/ctb-2015-0001.xml},

doi = {10.1515/ctb-2015-0001},

issn = {1232-9630},

year  = {2015},

date = {2015-01-01},

journal = {Current Topics in Biophysics},

volume = {38},

number = {1},

pages = {1--5},

abstract = {The effect of 0.01-1 M sodium ions on the conformation of the folded brewer's yeast tRNA},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2013a,

title = {Analysis of the temperature-dependence of P+HA− charge recombination in the Rhodobacter sphaeroides reaction center suggests nanosecond temperature-independent protein relaxation},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and Andrzej Dobek and Jerzy Karolczak and Gotard Burdziński and Klaus Brettel and Michael R Jones},

url = {http://www.ncbi.nlm.nih.gov/pubmed/23999896 http://xlink.rsc.org/?DOI=c3cp44187c},

doi = {10.1039/c3cp44187c},

issn = {1463-9076},

year  = {2013},

date = {2013-10-01},

journal = {Physical Chemistry Chemical Physics},

volume = {15},

number = {38},

pages = {16321-16333},

abstract = {The temperature dependence of charge recombination of the pair P(+)HA(-) in isolated reaction centers from the purple bacterium Rhodobacter sphaeroides with prereduced quinone QA was studied by sub-nanosecond to microsecond time-scale transient absorption. Overall, the kinetics slowed down substantially upon cooling from room temperature to ∼200 K, and then remained virtually unchanged down to 77 K, indicating the coexistence of two competitive pathways of charge recombination, a thermally-activated pathway appearing only above ~200 K and a temperature-independent pathway. In our modelling, the thermally activated pathway includes an uphill electron transfer from HA(-) to BA(-) leading to transient formation of the state P(+)BA(-), whereas the temperature-independent pathway is due to direct downhill electron transfer from HA(-) to P(+). At all temperatures studied, the kinetics could be approximated by a four-component decay. Detailed analysis of the lifetimes and amplitudes of particular phases over the range of temperatures suggests that the kinetically resolved phases reveal the consecutive appearance of three conformational states characterized by an increasing free energy gap between the states P(+)BA(-) and P(+)HA(-). The initial gap between these states was estimated to be only ~8 meV, the intermediate gap being ~92 meV, and the final gap ~135 meV, with no dependence on temperature. It was also calculated through a very straightforward approach that the relaxation process from the initial to the intermediate state occurs within 0.6 ± 0.1 ns, whereas the second step of relaxation from the intermediate to the final state takes 11 ± 2 ns. Both phases of the protein relaxation process are essentially temperature-independent. Possible alternative models to describe the experimental data that cannot be definitely excluded are also discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2013b,

title = {Analysis of the Kinetics of P + H A – Recombination in Membrane-Embedded Wild-Type and Mutant Rhodobacter sphaeroides Reaction Centers between 298 and 77 K Indicates That the Adjacent Negatively Charged Q A Ubiquinone Modulates the Free Energy of P + H A},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and Andrzej Dobek and Klaus Brettel and Michael R Jones},

url = {http://pubs.acs.org/doi/10.1021/jp4011235},

doi = {10.1021/jp4011235},

issn = {1520-6106},

year  = {2013},

date = {2013-09-01},

journal = {The Journal of Physical Chemistry B},

volume = {117},

number = {38},

pages = {11112--11123},

publisher = {American Chemical Society},

abstract = {Time-resolved spectroscopic studies of recombination of the P+HA– radical pair in photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides give an opportunity to study protein dynamics triggered by light and occurring over the lifetime of P+HA–. The state P+HA– is formed after the ultrafast light-induced electron transfer from the primary donor pair of bacteriochlorophylls (P) to the acceptor bacteriopheophytin (HA). In order to increase the lifetime of this state, and thus increase the temporal window for the examination of protein dynamics, it is possible to block forward electron transfer from HA– to the secondary electron acceptor QA. In this contribution, the dynamics of P+HA– recombination were compared at a range of temperatures from 77 K to room temperature, electron transfer from HA– to QA being blocked either by prereduction of QA or by genetic removal of QA. The observed P+HA– charge recombination was significantly slower in the QA-deficient RCs, and in both types of complexes, loweri...},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2012,

title = {Primary electron transfer reactions in membrane-bound open and closed reaction centers from purple bacterium Rhodobacter sphaeroides},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and Jerzy Karolczak and Gotard Burdziński and Andrzej Dobek and Michael R Jones},

doi = {10.12693/APhysPolA.122.263},

year  = {2012},

date = {2012-01-01},

journal = {Acta Physica Polonica A},

volume = {131},

number = {2},

pages = {263-268},

abstract = {Most ultrafast transient absorption studies of primary electron transfer in reaction centers from purple bacteria have been performed in complexes isolated from their natural lipid membrane environment using detergent. In this contribution we present near-UV-vis transient absorption studies of reaction centers embedded in their natural membrane environment. The evolution of absorption spectra recorded with subpicosecond resolution and reflecting primarily electron transfer reactions has been compared to data obtained previously for isolated reaction centers. We conclude that the overall spectral evolution in both types of samples is similar, and the environment of the reaction center protein has only a minor effect on the primary electron transfer reactions. The differences between the two samples are explained in terms of different energetic levels (and their different temporal evolution) of the two initial charge separated states P+BA- and P+HA-, with P being the primary electron donor and BA and HA the two consecutive electron acceptors. Additionally, in the electric field generated by P+HA-, BA in membrane-bound reaction centers undergoes a stronger electrochromic shift than in isolated reaction centers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2011,

title = {Mechanism of Recombination of the P + H A – Radical Pair in Mutant Rhodobacter sphaeroides Reaction Centers with Modified Free Energy Gaps Between P + B A – and P + H A –},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and Jane A Potter and Paul. K Fyfe and Andrzej Dobek and Klaus Brettel and Michael R Jones},

url = {http://pubs.acs.org/doi/abs/10.1021/jp206462g},

doi = {10.1021/jp206462g},

issn = {1520-6106},

year  = {2011},

date = {2011-11-01},

journal = {The Journal of Physical Chemistry B},

volume = {115},

number = {44},

pages = {13037--13050},

publisher = {American Chemical Society},

abstract = {The kinetics of recombination of the P+HA– radical pair were compared in wild-type reaction centers from Rhodobacter sphaeroides and in seven mutants in which the free energy gap, $Delta$G, between the charge separated states P+BA– and P+HA– was either increased or decreased. Five of the mutant RCs had been described previously, and X-ray crystal structures of two newly constructed complexes were determined by X-ray crystallography. The charge recombination reaction was accelerated in all mutants with a smaller $Delta$G than in the wild-type, and was slowed in a mutant having a larger $Delta$G. The free energy difference between the state P+HA– and the PHA ground state was unaffected by most of these mutations. These observations were consistent with a model in which the P+HA– → PHA charge recombination is thermally activated and occurs via the intermediate state P+BA–, with a mean rate related to the size of the $Delta$G between the states P+BA– and P+HA– and not the $Delta$G between P+HA– and the ground state. A more detailed analys...},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Graczykowski2011,

title = {Iron–dextran complex: Geometrical structure and magneto-optical features},

author = {Bartłomiej Graczykowski and Andrzej Dobek},

url = {http://www.ncbi.nlm.nih.gov/pubmed/21872262 http://linkinghub.elsevier.com/retrieve/pii/S0021979711009465},

doi = {10.1016/j.jcis.2011.07.080},

issn = {00219797},

year  = {2011},

date = {2011-11-01},

journal = {Journal of Colloid and Interface Science},

volume = {363},

number = {2},

pages = {551--556},

abstract = {Molecular mass of the iron-dextran complex (M(w)=1133 kDa), diameter of its particles (∼8.3 nm) and the content of iron ions in the complex core (N(Fe)=6360) were determined by static light scattering, measurements of refractive index increment and the Cotton-Mouton effect in solution. The known number of iron ions permitted the calculation of the permanent magnetic dipole moment value to be $mu$(Fe)=3.17×10(-18) erg Oe(-1) and the determination of anisotropy of linear magneto-optical polarizabilities components as $Delta$$chi$=9.2×10(-21) cm(3). Knowing both values and the value of the mean linear optical polarizability $alpha$=7.3×10(-20) cm(3), it was possible to show that the total measured CM effect was due to the reorientation of the permanent and the induced magnetic dipole moments of the complex. Analysis of the measured magneto-optical birefringence indicated very small optical anisotropy of linear optical polarizability components, $kappa$($alpha$), which suggested a homogeneous structure of particles of spherical symmetry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{graczykowski2011iron,

title = {Iron--dextran complex: Geometrical structure and magneto-optical features},

author = {Bartłomiej Graczykowski and Andrzej Dobek},

year  = {2011},

date = {2011-01-01},

journal = {Journal of colloid and interface science},

volume = {363},

number = {2},

pages = {551--556},

publisher = {Elsevier},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2009,

title = {Excitation and electron transfer in reaction centers from Rhodobacter sphaeroides probed and analyzed globally in the 1-nanosecond temporal window from 330 to 700 nm},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and J Karolczak and Andrzej Dobek},

url = {http://xlink.rsc.org/?DOI=b912431d},

doi = {10.1039/b912431d},

issn = {1463-9076},

year  = {2009},

date = {2009-11-01},

journal = {Physical Chemistry Chemical Physics},

volume = {11},

number = {44},

pages = {10484},

publisher = {The Royal Society of Chemistry},

abstract = {Global analysis of a set of room temperature transient absorption spectra of Rhodobacter sphaeroidesreaction centers, recorded in wide temporal and spectral ranges and triggered by femtosecond excitation of accessory bacteriochlorophylls at 800 nm, is presented. The data give a comprehensive review of all spectral dynamics features in the visible and near UV, from 330 to 700 nm, related to the primary events in the Rb. sphaeroidesreaction center: excitation energy transfer from the accessory bacteriochlorophylls (B) to the primary donor (P), primary charge separation between the primary donor and primary acceptor (bacteriopheophytin, H), and electron transfer from the primary to the secondary electron acceptor (ubiquinone). In particular, engagement of the accessory bacteriochlorophyll in primary charge separation is shown as an intermediate electron acceptor, and the initial free energy gap of ∼40 meV, between the states P+BA− and P+HA− is estimated. The size of this gap is shown to be constant for the whole 230 ps lifetime of the P+HA− state. The ultrafast spectral dynamics features recorded in the visible range are presented against a background of results from similar studies performed for the last two decades.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kozak2009,

title = {Synchrotron radiation small angle scattering studies of d(TTAGGG)4 oligomer in solution},

author = {Maciej Kozak and Agnieszka Wlodarczyk and Andrzej Dobek},

url = {https://www.sciencedirect.com/science/article/pii/S0969806X09002333 http://linkinghub.elsevier.com/retrieve/pii/S0969806X09002333},

doi = {10.1016/j.radphyschem.2009.04.028},

issn = {0969806X},

year  = {2009},

date = {2009-10-01},

journal = {Radiation Physics and Chemistry},

volume = {78},

number = {10},

pages = {S134--S136},

publisher = {Pergamon},

abstract = {Telomeric DNA sequences play a crucial role in maintaining chromosome stability and integrity. In human chromosomes telomeres are composed of tandem (TTAGGG)n repeats. The structural parameters and low-resolution structure of a synthetic d(TTAGGG)4 oligomer in solution has been studied in the absence and in the presence of potassium cations, with the use of the small angle scattering of synchrotron radiation. The radii of gyration RG, calculated for d(TTAGGG)4 oligomer (in 10mM Tris/HCl pH 7.3) was 1.42nm, while RG, (in 10mM Tris/HCl pH 7.3; 0.1mM KCl) was 1.32nm. The pair distance distribution function, P(r), yielded a maximum dimension of 4.55and 4.35nm for solutions in the absence and the presence of potassium cations. On the basis of SAXS data, the low-resolution structure in solution has been reconstructed using ab inito methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2009b,

title = {Internal Electrostatic Control of the Primary Charge Separation and Recombination in Reaction Centers from Rhodobacter sphaeroides Revealed by Femtosecond Transient Absorption},

author = {Krzysztof Gibasiewicz and Maria Pajzderska and M Ziółek and J Karolczak and Andrzej Dobek},

url = {http://pubs.acs.org/doi/abs/10.1021/jp811234q},

doi = {10.1021/jp811234q},

issn = {1520-6106},

year  = {2009},

date = {2009-08-01},

journal = {The Journal of Physical Chemistry B},

volume = {113},

number = {31},

pages = {11023--11031},

publisher = {American Chemical Society},

abstract = {We report the observation of two conformational states of closed RCs from Rhodobacter sphaeroides characterized by different P+HA− → PHA charge recombination lifetimes, one of which is of subnanosecond value (700 ± 200 ps). These states are also characterized by different primary charge separation lifetimes. It is proposed that the distinct conformations are related to two protonation states either of reduced secondary electron acceptor, QA−, or of a titratable amino acid residue localized near QA. The reaction centers in the protonated state are characterized by faster charge separation and slower charge recombination when compared to those in the unprotonated state. Both effects are explained in terms of the model assuming modulation of the free energy level of the state P+HA− by the charges on or near QA and decay of the P+HA− state via the thermally activated P+BA− state.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pankowska2009,

title = {Linear and nonlinear magneto-optics of ferritin},

author = {M Pankowska and Andrzej Dobek},

doi = {10.1063/1.3159844},

year  = {2009},

date = {2009-01-01},

journal = {The Journal of Chemical Physics},

volume = {131},

pages = {01505-1-10},

abstract = {Measurements of Rayleigh light scattering and Cotton–Mouton (CM) effect are carried out at room temperature for 100 mM NaCl solutions of apoferritin/ferritin loaded with 0, 90, 100, 500, 700, and 1500 Fe atoms/molecule. Because of the spherical shape, ferritin macromolecule should not manifest magnetic anisotropy; however, in solution it shows the induced magnetic birefringence (CM effect) and changes in intensity of the scattered light components. The newly obtained data support the previously reported conclusions indicating that the deformation of linear optical polarizability induced in the ferritin by a magnetic field and the orientation of the induced magnetic dipole moment by this field are the main sources of the magneto-optical phenomena observed. Nevertheless, it is also found that the orientation of the permanent magnetic dipole moment contributes to both effects. The magnetic field induced changes in the light scattering and the CM effect theoretically depend on the linear magneto-optical polarizability, χχ, on the nonlinear magneto-optical polarizability, ηη, and square of the permanent magnetic dipole moment value of the macromolecule, μ2μ2. On the basis of the theory describing both effects as well as the experimental data, the values of the anisotropy of linear magneto-optical polarizabilities components, the values of the linear optical polarizability and its anisotropy, nonlinear magneto-optical polarizability and its anisotropy, are estimated. Also the magnetic dipole moment of the ferritin macromolecule is found. Interestingly, not all iron atoms in the ferritin are indicated to be in the superparamagnetic state, some of them occur in the diamagnetic form.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ziolek2005,

title = {Electron Transfer in the Reaction Center of the Rb. s phaeroides R-26 Studied by Transient Absorption},

author = {Marcin Ziolek and Natalia Pawlowicz and Ryszard Naskrecki and Andrzej Dobek},

url = {http://www.ncbi.nlm.nih.gov/pubmed/16853333 http://pubs.acs.org/doi/abs/10.1021/jp050682i},

doi = {10.1021/jp050682i},

issn = {1520-6106},

year  = {2005},

date = {2005-09-01},

journal = {The Journal of Physical Chemistry B},

volume = {109},

number = {38},

pages = {18171--18176},

abstract = {Electron transfer at the reaction center of the purple photosynthetic bacterium Rb. sphaeroides R-26 was measured at room temperature by the time-resolved transient absorption spectroscopy technique with 200 fs temporal resolution. The absorbance changes characteristic of the excited state of the primary donor and extending over the whole spectral range investigated from 350 nm up to 720 nm appeared after excitation with a laser pulse of about 100 fs duration at 800 nm. The time evolution of the spectra reflected the excitation of bacteriochlorophylls (BChl) M and L and the subsequent transfer of this excitation to the primary electron donor (P), with the time constant shorter than 1 ps. The decay time constant of the excited primary donor P was determined as about 3 ps, and it was faster than the rise of the reduced intermediary acceptor bacteriopheophytin (BPhe(L)). Photoreduction of BPhe(L) and its further reoxidation was clearly observed as an increase in its bleaching band intensity at around 540 nm in about 4 ps and its decrease in about 200 ps. Our findings support the theoretical model assuming the involvement of the intermediate state P(+)BChl- in the so-called "two-step" model. In this model an electron is transferred in a sequence from the excited special pair P* to bacteriochlorophyll, BChl(L), then to bacteriopheophytin, BPhe(L), and further on to quinone, Q(A). The branched charge separation, partially via P and partially via BChl(L), was also observed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wodarczyk2005,

title = {Effect of Ions on the Polymorphism, Effective Charge, and Stability of Human Telomeric DNA. Photon Correlation Spectroscopy and Circular Dichroism Studies},

author = {Agnieszka Włodarczyk and Przemysław Grzybowski and Adam Patkowski and Andrzej Dobek},

url = {http://www.ncbi.nlm.nih.gov/pubmed/16851398 http://pubs.acs.org/doi/abs/10.1021/jp045274d},

doi = {10.1021/jp045274d},

issn = {1520-6106},

year  = {2005},

date = {2005-03-01},

journal = {The Journal of Physical Chemistry B},

volume = {109},

number = {8},

pages = {3594--3605},

abstract = {The effect of different ions on the formation and behavior of quadruplex structures of the human telomere sequence d(TTAGGG)(4) has been studied by photon correlation spectroscopy (PCS) and circular dichroism (CD). The saturation and melting curves obtained in the presence of K(+), Na(+), Rb(+), Li(+), Cs(+), and Sr(2+) ions were recorded by CD spectroscopy and indicated the formation of monomeric quadruplexes. Analysis of the saturation curves obtained at 2 degrees C has shown that the presence of a single Sr(2+) ion per oligomer is sufficient for the formation of a monomeric quadruplex of the DNA sequence studied. In the presence of SrCl(2) at a concentration of 50 mM, the formation of tetrameric quadruplexes has been detected. The effect of Sr(2+) ions on the formation of quadruplex structures by the human telomere sequence d(TTAGGG)(4) is stronger and different from that of the other ions tested. The paper also presents results of a study of electrostatic interactions in solution. The translation diffusion coefficients D(T) of the structures present in solution have been determined by photon correlation spectroscopy and the effective charges on the structures have been calculated by combining the experimental data with the results based on the coupled mode theory. Analysis of the melting points monitored by the CD method has permitted a determination of Deltan, the number of ions released in the process of thermal denaturation. All the results are in good agreement with the predictions based on the theory of polyelectrolytes. The effect of ions on the formation and behavior of quadruplex structures of the human telomere sequence d(TTAGGG)(4) has been studied by photon correlation spectroscopy and circular dichroism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wodarczyk2004,

title = {The effect of mono- and divalent cations on Tetrahymena thermophila telomeric repeat fragment. A photon correlation spectroscopy study.},

author = {Agnieszka Włodarczyk and Adam Patkowski and Przemysław Grzybowski and Andrzej Dobek},

url = {http://www.actabp.pl/pdf/4_2004/971.pdf http://www.ncbi.nlm.nih.gov/pubmed/15625569},

doi = {045104971},

issn = {0001-527X},

year  = {2004},

date = {2004-01-01},

journal = {Acta Biochimica Polonica},

volume = {51},

number = {4},

pages = {971-981},

abstract = {The structure of the Tetrahymena thermophila telomeric sequence d(TGGGGT)(4) was studied by photon correlation spectroscopy (PCS) in aqueous solution in the presence of NaCl, KCl and SrCl(2). The sample studied was polydisperse in all conditions studied. Translational diffusion coefficients D(T) describing the diffusion modes observed were determined. On the basis of a comparison between the experimental D(T) values with those calculated assuming the bead model, two forms were identified as telomeric quadruplex structures: monomer and tetramer. In the presence of SrCl(2) formation of aggregates was observed, with a size that reached several micrometres. The relative weighted concentrations of the structures observed for different concentrations of a salt and DNA were determined. The results obtained in the presence of monovalent ions were qualitatively similar and could be presented in a coherent plot in which the concentration of salt was expressed by the number of ions per DNA molecule. A large number of ions per DNA molecule favoured tetramer formation while a small number favoured the monomer form. A structural phase transition from the monomer to the tetramer induced by a change in the number of ions per DNA molecule was observed. The main difference between the results for Na(+) and K(+) was a greater effectiveness of the K(+) ions in formation of tetramers. The effect of Sr(2+) ions on the structures formed was different than that of the monovalent ions. The results obtained in the presence of Sr(2+) could not be described as a function of the number of ions per DNA molecule.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jurga-Nowak2004,

title = {Supramolecular Guanosine 5 ′-Monophosphate Structures in Solution. Light Scattering Study},

author = {Hanna Jurga-Nowak and Ewa Banachowicz and Andrzej Dobek and Adam Patkowski},

url = {http://pubs.acs.org/doi/abs/10.1021/jp030905%2B},

doi = {10.1021/jp030905},

issn = {1520-6106},

year  = {2004},

date = {2004-01-01},

journal = {Journal of Physical Chemistry B},

volume = {108},

pages = {2744--2750},

publisher = {American Chemical Society},

abstract = {During the past decade, from the vast evidence it became clear that DNA oligomers rich in guanine stretches can form in solution highly ordered forms called G-quadruplexes and G-wires. G-quadruplexes are present in many sites of the human genome, can inhibit telomerase, and can be used as drug delivery supramolecules. G-wires and related structures seem to be an excellent material of biological origin for nanostructures. Therefore, in this paper we have studied the structures formed by specific association of guanosine 5‘-monophosphate (GMP) nucleotide molecules in water solutions by photon correlation spectroscopy and depolarized Rayleigh light scattering. One relaxation process with distinct amplitude was observed, as a function of temperature and sample concentration. It was attributed to the translational diffusion coefficient of the stacks of G-quartets in a range of high concentration and to the stacks of GMP monomer associates for low concentration (less than 40 mg/mL). From the measurements the hy...},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek2002,

title = {Magneto-optics of Ferritin},

author = {Andrzej Dobek and M Pankowska and Jacek Gapiński},

url = {http://www.ncbi.nlm.nih.gov/pubmed/16290858 http://linkinghub.elsevier.com/retrieve/pii/S0021979702985632},

doi = {10.1006/jcis.2002.8563},

issn = {00219797},

year  = {2002},

date = {2002-09-01},

journal = {Journal of Colloid and Interface Science},

volume = {253},

number = {2},

pages = {265--272},

abstract = {Measurements of Rayleigh light scattering, nonlinear light scattering in DC magnetic fields, and the Cotton-Mouton effect were carried out for 15 mM NaCl and water solutions of ferritin at room temperature. The spherical geometry of the molecule implies that it is optically isotropic. Such a macromolecule should not manifest magnetic anisotropy; however, in solution it shows induced magnetic birefringence (Cotton-Mouton effect) and changes in the intensity of the scattered light components. The analysis of the obtained results indicates the deformation of linear optical polarizability induced in the ferritin by a magnetic field as the main source of the magneto-optical phenomena observed. Light scattering and the CM effects theoretically depend on the linear magneto-optical polarizability, chi, and the nonlinear magneto-optical polarizability, eta. Using the theory describing the phenomena as well as the experimental data, the values of the anisotropy of linear magneto-optical polarizability components, chi(parallel) - chi(perpendicular) = -(1.3 +/- 0.7) x 10(-22) [cm3] (in SI units chi(parallel) - chi(perpendicular) = -(2.0 +/- 1.2) x 10(-33) [m3]), the linear optical polarizability},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2001b,

title = {Modulation of Primary Radical Pair Kinetics and Energetics in Photosystem II by the Redox State of the Quinone Electron Acceptor QA},

author = {Krzysztof Gibasiewicz and Andrzej Dobek and Jacques Breton and Winfried Leibl},

url = {https://www.sciencedirect.com/science/article/pii/S0006349501761346 http://linkinghub.elsevier.com/retrieve/pii/S0006349501761346},

doi = {10.1016/S0006-3495(01)76134-6},

issn = {00063495},

year  = {2001},

date = {2001-04-01},

journal = {Biophysical Journal},

volume = {80},

number = {4},

pages = {1617--1630},

publisher = {Cell Press},

abstract = {Time-resolved photovoltage measurements on destacked photosystem II membranes from spinach with the primary quinone electron acceptor QA either singly or doubly reduced have been performed to monitor the time evolution of the primary radical pair P680+Pheo−. The maximum transient concentration of the primary radical pair is about five times larger and its decay is about seven times slower with doubly reduced compared with singly reduced QA. The possible biological significance of these differences is discussed. On the basis of a simple reversible reaction scheme, the measured apparent rate constants and relative amplitudes allow determination of sets of molecular rate constants and energetic parameters for primary reactions in the reaction centers with doubly reduced QA as well as with oxidized or singly reduced QA. The standard free energy difference $Delta$G° between the charge-separated state P680+Pheo− and the equilibrated excited state (ChlNP680)* was found to be similar when QA was oxidized or doubly reduced before the flash (∼−50 meV). In contrast, single reduction of QA led to a large change in $Delta$G° (∼+40 meV), demonstrating the importance of electrostatic interaction between the charge on QA and the primary radical pair, and providing direct evidence that the doubly reduced QA is an electrically neutral species, i.e., is doubly protonated. A comparison of the molecular rate constants shows that the rate of charge recombination is much more sensitive to the change in $Delta$G° than the rate of primary charge separation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dubiel2001,

title = {Comparison of power Doppler and velocimetry in predicting outcome of high-risk pregnancy.},

author = {M Dubiel and Andrzej Dobek and G Breborowicz and K Marsal and S Gudmundsson},

url = {http://www.ncbi.nlm.nih.gov/pubmed/11423243},

issn = {0929-8266},

year  = {2001},

date = {2001-03-01},

journal = {European Journal of Ultrasound},

volume = {12},

number = {3},

pages = {197--202},

abstract = {OBJECTIVE Prospectively evaluate semi-quantitative computer analysis of power Doppler (PD) signals in the placenta, tetal brain, lung, liver, kidney and spleen in high-risk pregnancies in relationship to perinatal outcome and also to compare tissue blood flow in the fetal brain and placenta with Doppler velocimetry. METHODS PD signals were recorded in 180 high-risk pregnancies between 27 and 41 weeks of gestation. Images from PD angiographic scans were transmitted for computer analysis of pixel intensity. Mean flow signal intensity was recorded for each organ. The PD brain/lung ratio was calculated. The PD results were plotted on reference values and related to perinatal outcome. Middle cerebral (MCA), umbilical (UA) and uterine artery (Ut. A) velocimetry was also performed. RESULTS High-risk pregnancies displayed lower PD signal intensity from the placenta, fetal lung, liver and kidney as compared to normals. However, the brain and spleen signals showed higher intensities suggesting increased tissue perfusion. PD signals from the fetal brain, lung, placenta and PD brain/lung ratio were correlated with perinatal outcome. The PD signal intensity from the fetal liver, kidney and spleen showed poor correlation with perinatal outcome. Fetal brain tissue blood flow showed better correlation with the outcome than MCA velocimetry. Placental tissue blood flow results were similar in predicting outcome to those obtained by means of UA and Ut. A velocimetry. CONCLUSION In comparison with conventional Doppler velocimetry, computer analysis of PD signals, give similar results in the prediction of adverse perinatal outcome.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Porzucek2001,

title = {Brain power Doppler in healthy and hypoxic neonates},

author = {Iwona Porzucek and Mariusz Dubiel and Grzegorz H Bręborowicz and Andrzej Dobek and Janusz Gadzinowski and Saemundur Gudmundsson},

url = {http://www.ptmp.com.pl/archives/apm/7-2/apm72_9.htm},

year  = {2001},

date = {2001-01-01},

journal = {Archives of Perinatal Medicine},

volume = {7},

number = {2},

pages = {44--46},

abstract = {The aim: was to investigate cerebral tissue blood flow in healthy term-born neonates and in neonates born with signs of asphyxia by means of power Doppler (PD) technique in early stage of life. 38 healthy neonates were enrolled, born between 38 and 42 week of gestation (median 39 week). Examinations were also performed in 22 neonates born with signs of intra-uterine asphyxia. The median gestational age at delivery was 35 weeks (range 34-38). During longitudinal study each patient was examined 5 times: one hour after delivery and than after 12, 24, 48, 72 hours during stable periods without vigorous movements. Each ultrasound examination included PD recordings and Doppler velocimetry. PD recordings were performed in 6 planes. The PD signal in hypoxic neonates shown significantly higher signal values as compared to control group. The PD signal in hypoxic neonates shown significantly higher signal values as compared to control group. This indicates the brain-sparing effect, which lasts at least 72 hours after birth and might be the continuation of the brain-sparing effect in utero.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz2001bb,

title = {Electron Transfer in the Reaction Center of the Photosynthetic Bacterium Rb. sphaeroides R-26 Measured by Transient Absorption in the Blue Spectral Range},

author = {Krzysztof Gibasiewicz and R Naskrecki and M Ziółek and M Lorenc and J Karolczak and J Kubicki and J Goc and J Miyake and Andrzej Dobek},

url = {http://link.springer.com/10.1023/A:1016695515341},

doi = {10.1023/A:1016695515341},

issn = {10530509},

year  = {2001},

date = {2001-01-01},

journal = {Journal of Fluorescence},

volume = {11},

number = {1},

pages = {33--40},

publisher = {Kluwer Academic Publishers-Plenum Publishers},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dubiel2000,

title = {Placental power Doppler imaging and velocimetry in high-risk pregnancy - a prospective study},

author = {Mariusz Dubiel and Grzegorz H Bręborowicz and Andrzej Dobek and Karel Marsal and Saemundur Gudmundsson},

year  = {2000},

date = {2000-01-01},

journal = {Archives of Perinatal Medicine},

volume = {6},

number = {1},

abstract = {Objective: The aim of the study was to prospectively evaluate semiquantitative computer analysis of power Doppler (PD) signals in placenta in high-risk pregnancies in relationship with perinatal outcome and also to compare placental tissue blood flow with umbilical and uterine arteries velocimetry. Study design: PD signals were recorded in 107 high-risk pregnancies between 27 and 41 weeks of gestation. Images from PD scans were transmitted for computer analysis. Mean flow signal intensity was recorded for placental flow. The PD results were plotted on reference values and related to perinatal outcome. Umbilical (UA) and uterine artery (Ut. A) velocimetry were also performed. Results: High-risk pregnancies had less placental PD signal intensity as compared to normals. Placental PD had similar prediction for adverse perinatal outcome as did conventional Doppler velocimetry findings. Conclusion: The results from the present study indicate a decreased placental perfusion in high-risk pregnancies, which is concordant with conventional Doppler velocimetry findings.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gibasiewicz1999,

title = {Re-examination of primary radical pair recombination in Rp. viridis with QA reduced},

author = {Krzysztof Gibasiewicz and K Brettel and Andrzej Dobek and W Leibl},

url = {https://www.sciencedirect.com/science/article/pii/S0009261499011586 http://linkinghub.elsevier.com/retrieve/pii/S0009261499011586},

doi = {10.1016/S0009-2614(99)01158-6},

issn = {00092614},

year  = {1999},

date = {1999-12-01},

journal = {Chemical Physics Letters},

volume = {315},

number = {1-2},

pages = {95--102},

publisher = {North-Holland},

abstract = {Charge recombination in the primary radical pair P+H− of the purple photosynthetic bacterium Rp. viridis with pre-reduced secondary acceptor QA, has been studied by time-resolved photovoltage measurements and transient absorption spectroscopy with a time resolution of 1 ns. The lifetime of P+H− was found to be 2.4–3 ns in intact membranes and ∼5 ns in isolated reaction centers, in contrast to a lifetime of ∼15 ns which has been widely accepted in the literature for reaction centers. The origin of the difference between lifetimes of P+H− in membranes and isolated reaction centers is discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wodarczyk1999,

title = {Structural polymorphism of telomeres studied by photon correlation spectroscopy.},

author = {Agnieszka Włodarczyk and Jacek Gapiński and Adam Patkowski and Andrzej Dobek},

url = {http://www.ncbi.nlm.nih.gov/pubmed/10698269},

issn = {0001-527X},

year  = {1999},

date = {1999-01-01},

journal = {Acta Biochimica Polonica},

volume = {46},

number = {3},

pages = {609-613},

abstract = {Photon Correlation Spectroscopy (PCS) was used to study the dynamics and structure of Tetrahymena telomeric sequence d(5'-TGGGGT-3')4. Two different modes were observed, corresponding to the following structures: intermolecular (tetramolecular) G-quadruplex and intramolecular (monomeric) G-quartet. Experimental values of translational diffusion coefficients DT were obtained for each structural form. The value of DT for the monomer equals to 1.4 x 10(6) (cm2/s), while for the tetramolecular structure, to 0.8 x 10(6) (cm2/s). The relative weight concentrations of these two forms were analyzed versus the concentration of NaCl varied from 10 mM to 500 mM. The values of experimentally determined diffusion coefficients were compared with those calculated assuming the "bead model" and with the atomic coordinates from the NMR and X-ray crystallographic data. For both structures the experimental and calculated values of DT were in reasonable agreement. In the entire NaCl concentration range studied, the contribution of the relative weight concentration of the monomeric telomere form changed from 85% for 10 mM NaCl to 60% for 500 mM NaCl.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Paillotin1998,

title = {Light Gradients in Spherical Photosynthetic Vesicles},

author = {G Paillotin and W Leibl and Jacek Gapiński and J Breton and Andrzej Dobek},

url = {https://www.sciencedirect.com/science/article/pii/S0006349598775009 http://linkinghub.elsevier.com/retrieve/pii/S0006349598775009},

doi = {10.1016/S0006-3495(98)77500-9},

issn = {00063495},

year  = {1998},

date = {1998-07-01},

journal = {Biophysical Journal},

volume = {75},

number = {1},

pages = {124--133},

publisher = {Cell Press},

abstract = {Light-gradient photovoltage measurements were performed on EDTA-treated thylakoids and on osmotically swollen thylakoids (blebs), both of spherical symmetry but of different sizes. In the case of EDTA vesicles, a negative polarity (due to the normal light gradient) was observed in the blue range of the absorption spectrum, and a positive polarity, corresponding to an inverse light gradient, was observed at $łambda$=530 and $łambda$=682nm. The sign of the photovoltage polarity measured in large blebs (swollen thylakoids) is the same as that obtained for whole chloroplasts, although differences in the amplitudes are observed. An approach based on the use of polar coordinates was adapted for a theoretical description of these membrane systems of spherical symmetry. The light intensity distribution and the photovoltage in such systems were calculated. Fits to the photovoltage amplitudes, measured as a function of light wavelength, made it possible to derive the values of the dielectric constant of the protein, ϵs=3, and the refractive index of the photosynthetic membrane for light propagating perpendicular and parallel to the membrane surface},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek1998a,

title = {Light Gradients in Photosynthetic Systems of Spherical Symmetry: Theory and Experiment},

author = {Andrzej Dobek and G Paillotin and Jacques Breton and Winfried Leibl},

year  = {1998},

date = {1998-01-01},

journal = {Current Topics in Biophysics},

volume = {22},

number = {1},

pages = {3--20},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek1998bb,

title = {Pierwotne zjawiska fotosyntezy w świetle ultraszybkich badań fotonapięciowych},

author = {Andrzej Dobek},

year  = {1998},

date = {1998-01-01},

journal = {Current Topics in Biophysics},

volume = {22},

number = {Suplement},

pages = {8--17},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek1994,

title = {Amplitude and Polarity of the Light Gradient Photovoltage from Chloroplasts},

author = {Andrzej Dobek and G Paillotin and Jacek Gapiński and J Breton and W Leibl and H -W Trissl},

url = {https://www.sciencedirect.com/science/article/pii/S0022519384711738 http://linkinghub.elsevier.com/retrieve/pii/S0022519384711738},

doi = {10.1006/jtbi.1994.1173},

issn = {00225193},

year  = {1994},

date = {1994-09-01},

journal = {Journal of Theoretical Biology},

volume = {170},

number = {2},

pages = {129--143},

publisher = {Academic Press},

abstract = {The primary charge separation in reaction centers embedded in the photosynthetic membranes induces an electric polarization in chloroplast suspensions. Photovoltages elicited by short non-saturating flashes, were observed almost 20 years ago by Witt & Zickler (1973, FEBS Lett,37, 307-310) and Fowler & Kok (1974, Progress in Photobiology, Frankfurt: Deutsche Gesellschaft). The photovoltage was interpreted as the result of the so-called "light-gradient" effect, in which the stronger excitation of the membrane facing the light source compared to the shadowed one creates a difference of dipole density in these two membranes. Owing to the anti-parallel orientation of reaction centers in opposite thylakoid membranes, a small potential difference results. It was thought that the polarity of this potential difference could be deduced from the known position of electron carriers in the photosynthetic reaction center. However, the observed polarity was often opposite to that predicted by this model. Also, the measured photovoltage amplitudes could not be quantitatively related to experimental parameters. In the present paper, we show that the "classical" explanation of the light-gradient effect does not hold true and we give an alternative explanation that is based on light propagation and interference in pigmented multilayers. A model calculation is carried out for a pair of membranes simulating stroma lamellae of chloroplasts. It predicts a wavelength-dependent light distribution as well as the polarity of the photovoltage. For low intensities, the amplitude is found to be proportional to the intensity of the incoming light, to the optical density, and to the reciprocal of the dielectric constant of the sample. When the membranes contain no chromophores or when the absorption coefficient is low, the predicted polarity is opposite to that expected from the classical picture. The model is tested with a set of experimental photovoltage data obtained at different wavelengths.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gapinski1994,

title = {Light Gradient in Photosynthetic Systems: Theory and Experiment},

author = {Jacek Gapiński and Andrzej Dobek and G Paillotin and J Breton and W Leibl and H -W Trissl},

year  = {1994},

date = {1994-01-01},

journal = {Laser Physics},

volume = {4},

number = {1},

pages = {191-198},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Paillotin1993,

title = {Why does the light-gradient photovoltage from photosynthetic organelles show a wavelength-dependent polarity?},

author = {G Paillotin and Andrzej Dobek and J Breton and W Leibl and H W Trissl},

url = {http://www.ncbi.nlm.nih.gov/pubmed/8369444 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC1225732 http://linkinghub.elsevier.com/retrieve/pii/S000634959381066X},

doi = {10.1016/S0006-3495(93)81066-X},

issn = {00063495},

year  = {1993},

date = {1993-07-01},

journal = {Biophysical Journal},

volume = {65},

number = {1},

pages = {379--385},

publisher = {The Biophysical Society},

abstract = {The light-gradient photovoltage from photosynthetic organisms and organelles is thought to arise from the primary charge separation in the reaction centers. The current explanation of the effect is the stronger excitation of the membrane side of a vesicle facing the light source than the one on the opposite side. Together with the known orientation of reaction centers, this explanation predicts unequivocally the polarity of the photovoltage. However, a polarity opposite to the one expected has often been reported. A dependence of the polarity on the wavelength has been published but no explanation was given (Graeber, P., and H.-W. Trissl. 1981. FEBS Lett. 123:95-99). Here we report on a theoretical treatment of light propagation and interference in pigmented and nonpigmented multilayers. A model calculation is carried out for a pair of membranes, demonstrating the wavelength-dependent light distribution as well as the relative photovoltage and its polarity. When the membranes contain no chromophores or when the absorption coefficient is low, the predicted polarity to that expected from a simple macroscopic absorption behavior. The model is tested by comparing new photovoltage data obtained at 532 nm as well as in the blue and red absorption bands of chlorophyll in chloroplasts. It is concluded that outside the main absorption bands the amplitude and polarity of the photovoltage is determined by the ratio of the refractive indices of the membrane and the medium.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Depres1991,

title = {Excitation trapping and annihilations in the photosynthetic membrane in the picosecond time scale},

author = {Jean Deprez and Andrzej Dobek and Guy Paillotin and Hans-W. Trissl and Jacques Breton},

year  = {1991},

date = {1991-01-01},

journal = {Zagadnienia Biofizyki Współczesnej},

volume = {15},

number = {1},

pages = {60-70},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek1990,

title = {Excitation trapping efficiency and kinetics in Rb. sphaeroides R26.1 whole cells probed by photovoltage measurements on the picosecond time-scale},

author = {Andrzej Dobek and J Deprez and Guy Paillotin and W Leibl and H -W Trissl and J Breton},

url = {https://www.sciencedirect.com/science/article/pii/0005272890900364 http://linkinghub.elsevier.com/retrieve/pii/0005272890900364},

doi = {10.1016/0005-2728(90)90036-4},

issn = {00052728},

year  = {1990},

date = {1990-02-01},

journal = {Biochimica et Biophysica Acta (BBA) - Bioenergetics},

volume = {1015},

number = {2},

pages = {313--321},

publisher = {Elsevier},

abstract = {Light-gradient photovoltage measurements in whole cells of the purple bacterium Rb. sphaeroides R26.1 were used to probe the trapping kinetics and the trapping efficiency resulting from 30 ps excitation at 532 nm. The time-course of the photovoltage is described by two distinct phases. The slower phase is characterized by a time constant of 190 ± 10 ps, contributing to about 60% of the total amplitude. It is independent of the excitation energy and of the initial fraction of reaction centers (RC) in the open state (primary donor reduced). This phase is assigned to the forward electron transfer from the bacteriopheophytin intermediary acceptor to the quinone. The fast phase is assigned to the appearance of the primary charge separated state (i.e., trapping). If all the RCs were in the open state before excitation, the time constant of the fast phase decreased from 55 ± 10 ps to less than 40 ps upon increasing the energy of the flash from less than 0.5 to more than 3 photons absorbed per RC. At the latter energy, 90 ± 5% of the RCs are closed by the flash. If the initial concentration of RCs in the closed state was increased from 0 to about 100%, either by background illumination or by preexcitation with another picosecond flash delivered 20 ns before the measuring flash, the mean trapping time increased from 55 ± 10 to 90 ± 15 ps for a probe flash energy corresponding to 0.5 photon absorbed per RC. The data are analyzed and described in terms of the competition between trapping and exciton-exciton annihilation in the lake model of the photosynthetic membrane of purple bacteria (Deprez, J., Paillotin, G., Dobek, A., Leibl, W., Trissl, H.-W. and Breton, J. (1990) Biochim. Biophys. Acta 1015, 295-303). textcopyright 1990.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Deprez1990,

title = {Competition between energy trapping and exciton annihilation in the lake model of the photosynthetic membrane of purple bacteria},

author = {J Deprez and G Paillotin and Andrzej Dobek and W Leibl and H -W Trissl and J Breton},

url = {https://www.sciencedirect.com/science/article/pii/0005272890900342 http://linkinghub.elsevier.com/retrieve/pii/0005272890900342},

doi = {10.1016/0005-2728(90)90034-2},

issn = {00052728},

year  = {1990},

date = {1990-02-01},

journal = {Biochimica et Biophysica Acta (BBA) - Bioenergetics},

volume = {1015},

number = {2},

pages = {295--303},

publisher = {Elsevier},

abstract = {General equations are formulated to describe the competition between primary photochemistry (trapping) by photosynthetic reaction centers (RCs) and bimolecular singlet-singlet annihilation which occur upon excitation with picosecond laser flashes. These equations are solved under the assumption of fast equilibration and free energy migration between photosynthetic units (lake model) with homogeneous antenna and of irreversible trapping (the initial charge separation does not repopulate an excited state). The yield and the kinetics of fluorescence and of trapping are calculated as a function of the energy of the picosecond flash and of the fraction of RCs closed before excitation. Theoretical curves are adjusted to fluorescence yield measurements in the purple bacterium Rhodospirillum rubrum (Bakker, J.C.G., Van Grondelle, R. and Den Hollander, W.T.F. (1983) Biochim. Biophys. Acta 725, 508–518) and are used to analyse time-resolved photovoltage measured on Rhodobacter sphaeroides R26.1 whole cells. From these analyses, a parameter that relates the competition between trapping and annihilation as well as the ratio of the quenching efficiency for open and closed RCs are determined.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Trissl1990a,

title = {Trapping kinetics, annihilation, and quantum yield in the photosynthetic purple bacterium Rps. viridis as revealed by electric measurement of the primary charge separation},

author = {H -W Trissl and J Breton and J Deprez and Andrzej Dobek and W Leibl},

url = {https://www.sciencedirect.com/science/article/pii/0005272890900375 http://linkinghub.elsevier.com/retrieve/pii/0005272890900375},

doi = {10.1016/0005-2728(90)90037-5},

issn = {00052728},

year  = {1990},

date = {1990-02-01},

journal = {Biochimica et Biophysica Acta (BBA) - Bioenergetics},

volume = {1015},

number = {2},

pages = {322--333},

publisher = {Elsevier},

abstract = {The kinetics and the yield of the primary charge separation in whole cells of Rps. viridis was studied with the light-gradient technique using 30 ps and 12 ns flashes at 532 nm and 1064 nm. When the menaquinone acceptor, QA, of the reaction centers (RCs) is oxidized the primary charge separation occurs with two electrogenic phases. The faster phase with a time constant of 45 ± 20 ps contributed with 40% and the slower phase with a time constant of 140 ± 15 ps contributed with 60% to the total electrogenicity. We interpret the fast phase as the trapping time, monitored by the charge separation between the primary donor P-965 and the intermediary pheophytin acceptor, H. The second phase is ascribed to the electron transfer from H to QA. The reduction of QA, either chemically or photochemically, prior to the flash leaves only the fast rising phase. This signal decays with a time constant of 2.3–2.8 ns. At the excitation wavelength of 1064 nm the quantum yield of primary photochemistry is 0.97 ± 0.07. The reduction of QA does not change the quantum yield. The recombination of the state P+H− when QA is reduced can repopulate the excited state (ant.textperiodcenteredP)∗ as demonstrated by a fluorescence phase with the same time constant. The fast phase of fluorescence was not affected by the reduction of QA, indicating an unaffected primary photochemistry. Fluorescence measurements with double flashes delayed by nanoseconds showed that the quenching power of P+ is approx. 1.4-times smaller than that of P. A comparison of the photovoltage amplitude evoked by 12 ns flashes and 30 ps flashes at 1064 nm revealed marked competition between annihilation and trapping. At 532 nm the competition was less pronounced. The influence of the fraction of closed RCs (as defined by the state P+Q−A on the trapping efficiency was studied by excitation with trains of 30 ps flashes. These data and the data resulting from the nanosecond versus picosecond measurements are analyzed with a theory for the light-gradient photovoltage (Leibl and Trissl (1990) Biochim. Biophys. Acta 1015, 304–312) and a theory of exciton dynamics in the lake model (Deprez et al. (1990) Biochim. Biophys. Acta 1015, 295–303).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dobek1988,

title = {Pierwotne reakcje fizyczne w procesie widzenia},

author = {Andrzej Dobek},

year  = {1988},

date = {1988-01-01},

journal = {Zeszyty Naukowe Uniwersytetu Jagiellońskiego, DCCCLXXV, prace z biol. mol.},

volume = {17},

pages = {97--106},

keywords = {},

pubstate = {published},

tppubtype = {article}

}