Maria Elisabeth Michel-Beyerle

• Prof. Dr.
• Managing Director at Nanyang Technological University

Growing oriented and monocrystalline layers of lead halide perovskites over device substrates helps to harness their outstanding optoelectronic properties. Epitaxial growth of lead halide perovskites for device fabrication is limited by the lack of lattice‐matched substrates and the requirement of compact pinhole‐free films. Most optoelectronic dev...

The discovery of the GFP-type dye DFHBI that becomes fluorescent upon binding to an RNA aptamer, termed Spinach, led to the development of a variety of fluorogenic RNA systems that enable genetic encoding of living cells. In view of increasing interest in small RNA aptamers and the scarcity of their photophysical characterisation, this paper is a m...

As a light absorber in photovoltaic applications, hybrid organic-inorganic halide perovskites should have long and balanced diffusion lengths for both the separated electrons and holes before recombination, which necessitates high carrier mobility. In polar semiconductors, the room-temperature carrier mobility is often limited by the scattering bet...

We propose a simple scenario where the superimposed phonon modes on the photoconductive spectra are experimental artifacts due to the invalid formula used in data analysis. By use of experimental and simulated data of CH3NH3PbI3perovskites as a case study, we demonstrate that a correction term must be included in the approximated thin-film formula...

Excited state dynamics in two strong organic electron acceptor systems, TCNQ and F4TCNQ single crystals, was studied. After absorption of a single photon, dianions are formed in both crystals on ultrashort timescale: TCNQ τ < 50 fs, F4TCNQ τ = 4 ps. By use of transient absorption spectroscopy, we demonstrate that the dianion formation in F4TCNQ is...

Nature Communications 6: Article number: 8903 (2015); Published: 30 July 2015; Updated: 10 March 2016 This article contains errors in the units used for carrier mobility. In Fig. 2a–d, the units on the y axis should be ‘cm2V−1s−1’ not ‘V−1s−1cm−1’. Similarly, the second and third sentences of the second paragraph of the ‘Quantum yield calculation’...

Sodium-ion batteries may become an alternative to the widespread lithium-ion technology due to cost and kinetic advantages provided that cyclability is improved. For this purpose, the interplay between electrochemical and structural processes is key and is demonstrated in this work for Na2.46V6O16 (NVO) and Li2.55V6O16 employing operando synchrotro...

We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3: thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low...

Apart from broadband absorption of solar radiation, the performance of photovoltaic devices is governed by the density and mobility of photogenerated charge carriers. The latter parameters indicate how many free carriers move away from their origin, and how fast, before loss mechanisms such as carrier recombination occur. However, only lower bounds...

G-quadruplexes are four-stranded structures that are formed from the association of guanine nucleobases into cyclical arrangements known as tetrads. G-quadruplexes are involved in a host of biological processes and are of interest in nanomaterial applications. However, not much is known about their electronic properties. In the paper, we analyze el...

Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe–Salpeter equation augmented with the analysis of a conceptual hydrogen-like model...

The femtosecond transient absorption spectra of TCNQ neutral molecule, as well as its radical anion TCNQ(center dot-) have been reported for the first time. The excited electronic states of both species show ultrafast relaxation lifetimes due to the internal conversion. Our study offers a possibility for a clear assignment of the contribution from...

Analysis of the electrostatics of charge carrier injection into molecular crystals during nonequilibrium electron transfer reactions demonstrates the unique advantage of aqueous or similar electrodes in measuring limiting currents which yield the rate constant of the injection process. At the phase boundary molecular crystal/aqueous electrolyte ima...

A theoretical description for the magnetic field dependence of geminate recombination as observed in transient spectroscopy of electron transfer reactions, is given and applications of this novel magnetic field effect are discussed.

Recombination of the bacteriochlorophyll dimer cation and the bacteriopheophytin anion depends on the spin multiplicity of this radical ion pair and can be studied by optical spectroscopy in an external static magnetic field in the absence (MARY) and presence of microwaves (RYDMR). Model calculations of MARY- and RYDMR-spectra are discussed.

The light guide properties of planar lipid bilayers are discussed and experimentally verified. The interaction between the light and the constituents of the bilayer is substantially increased since the light path is as large as the diameter of the film, e.g. of the order of several millimeters. The influence of electric fields on the bilayer and on...

The dependence of the sensitized injection current and of the crystal's sensitized delayed fluorescence on the electric and magnetic field is utilized to examine the process of charge separa-tion at the phase boundary crystal/water electrode. Hole currents, sensitized by electron transfer interaction between rhodamine B molecules in their lowest ex...

The light guide properties of planar lipid bilayers offer a novel approach to bilayer spectroscopy. Potential applications are outlined.

Significance In contrast to other chromophore/protein systems in photobiology, the UV-B photoreceptor UV resistance locus 8 (UVR8) utilizes tryptophan residues as light absorbers. The initial step of a signaling pathway that ultimately leads to UV-B protection and damage repair in plants is the breaking of salt bridges that stabilize the UVR8 prote...

A special stack: In the presence of K(+) ions, a specific guanine-rich DNA sequence forms a stacked G-quadruplex dimer giving rise to excimer emission in the 400 nm region. This emission with nanosecond lifetime occurs only for a particular base overlap pattern between two stacked G-quadruplex blocks and can be manipulated by changing DNA sequence...

G-quadruplex nucleic acids represent a unique avenue for the building of electrically conductive wires. These four-stranded structures are formed through the stacking of multiple planar guanine assemblies termed G-tetrads. The diverse folding patterns of G-quadruplexes allow for several geometries to be adopted by stacked guanine bases within the c...

The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet...

We have studied fluorescence in rubrene single crystals by use of fluorescence up-conversion, fluorescence anisotropy, and temperature-dependent time-resolved fluorescence techniques. Thermally activated singlet fission was demonstrated to play an important role in the quenching of two intrinsic fluorescence bands, 565 and 610 nm. At low temperatur...

The excited state dynamics of rubrene in solution and in the single crystal were studied by femtosecond pump-probe spectroscopy under various excitation conditions. Singlet fission was demonstrated to play a predominant role in the excited state relaxation of the rubrene crystal in contrast to rubrene in solution. Upon 500 nm excitation, triplet ex...

We characterized and compared the fluorescence properties of various well-defined G-quadruplex structures. The increase of intrinsic fluorescence of G-rich DNA sequences when they form G-quadruplexes can be used to monitor the folding and unfolding of G-quadruplexes as a function of cations and temperature. The temperature-dependent fluorescence sp...

We present a survey of the current ‘state of the art’ of our understanding of the primary electron transfer dynamics in bacterial photosynthesis.

Der aus potentiometrischen Untersuchungen hergeleitete Schluß auf Protonenleitung in mit wäßrigen Elektrolyten kontaktierten Anthracenkristallen konnte nicht bestätigt werden. Es ergab sich jedoch ein sehr wirkungsvoller Effekt der Protonen auf die Injektion von Defektelektronen in Anthracenkristallen. Für diese Injektionswirkung werden zwei versch...

Für Generationen war Frühstück die wichtigste Mahlzeit des Tages. Inzwischen wird jedoch weltweit ein Trend zum Verzicht auf das Frühstück festgestellt. Die Auswirkungen dieses Verzichts und die Bedeutung der ersten Mahlzeit des Tages werden hier untersucht. Berücksichtigt wurden rund 120 wissenschaftliche Arbeiten aus dem Zeitraum 1998–2008. Ein A...

Abstract— Dye-sensitized hole currents have been investigated in aromatic single crystals of increasing ionisation energies. The influence of various parameters on these sensitized currents have been studied: voltage, intensity and wavelength of the incident light, concentration of the sensitizer and of an additional oxidant. Direct transfer of an...

The mechanism of photoinduced hole injection into DNA has been studied using an integrated approach that combines NMR structural analysis, time-resolved spectroscopy, and quantum-chemical calculations. A covalently linked acridinium derivative, the protonated 9-amino-6-chloro-2-methoxyacridine (X+), is replacing a thymine and separated from either...

Femtosecond time-resolved spectroscopy is applied to study the mechanism of the light-induced increase of fluorescence quantum yield of the initially non-fluorescent (dark) chromoprotein asFP595. Spectroscopic and kinetic characteristics of this unique fluorescence “kindling” phenomenon are: (i) the small Stokes shift of the dark chromophore consis...

The radical pair recombination of an intramolecular electron-transfer system containing a transition metal moiety has been addressed by femtosecond spectroscopy. The radical pair is formed by ultrafast electron transfer (90 fs) from a ferrocene residue to a photoexcited Nile blue moiety. Its recombination proceeds on the picosecond time scale in a...

A central requirement for DNA biochips is the coupling of the DNA duplex to surfaces made of glass, metal, metal oxide or semi-conductor-like materials. The simplest method of surface coupling is immobilization of a molecule by electrostatic interactions that often suffer from the weak binding strength. This paper discusses the objectives, goals, a...

Colored proteins are widely used as gene markers in biotechnology. Chromophores result from autocatalytic posttranslational reactions involving several amino acids. The protein asCP595 was isolated for the first time from the coral as a weakly fluorescent chromoprotein with a fluorescence maximum at 595 nm. Strong illumination in the blue wing of t...

Alanyl peptide nucleic acids have been designed to generate linear and rigid pairing complexes. Femtosecond time resolved electron transfer dynamics studies of alanyl-PNA double strands where both strands contain an intercalated 9-amino-6-chloro-2-methoxy-acridine in its protonated state reveal a strong similarity to nearest neighbor interstrand/in...

When electron transfer to the primary quinone is blocked, the radical pair P⁺H⁻ (P: primary donor, H: bacteriopheophytin at the A-branch) recombines on the 10 ns time scale either to the ground state P or, after hyperfine-induced singlet-triplet-mixing, to the triplet state ³P*. An external magnetic field hinders singlettriplet-mixing, thus reducin...

The temporal evolution of the initially excited singlet state of flavine mononucleotide, which is the cofactor in the LOV2 domain of the blue photoreceptor phototropin, has been studied in picosecond time-resolved fluorescence and femtosecond time-resolved absorption experiments. In the LOV2-WT protein of Avena sativa singlet–triplet intersystem cr...

We describe the syntheses of Boc-protected amino acids bearing the chromophores pyromellitic diimide, naphthalene diimide, and pyrene in their side chains, as well as nucleo amino acids with the artificial purines 7-carbaguanine, 7-carbaadenine, isoadenine, and 7-carbaisoadenine covalently linked to the alanyl side chain. These amino acids incorpor...

This is the report of a DOE-sponsored workshop organized to discuss the status of our understanding of charge-transfer processes on the nanoscale and to identify research and other needs for progress in nanoscience and nanotechnology. The current status of basic electron-transfer research, both theoretical and experimental, is addressed, with empha...

Time-resolved fluorescence measurements at 275 K show that the excited-state lifetime of a model chromophore of the green fluorescent protein (GFP) substantially increases from subpicoseconds in low-viscosity solvents such as ethanol (η = 1.7 cP) to 30 ps in glycerol (η = 9.9 × 103 cP) and reaches 2.1 ns in glycerol glass at 150 K. At high temperat...

The origin of the low steady-state fluorescence quantum yield of some blue-emitting variants of the green fluorescent protein (GFP) is investigated in single-site mutants in which the tyrosine residue at position 66 has been replaced by phenylalanine or by histidine. Time-resolved fluorescence measurements reveal excited-state lifetimes of 74 ps (Y...

Faster than 200 fs is the time scale of dynamic solvation of an acridine derivative (ACMA) intercalated into an abasic site of the DNA duplex. This observation implies that the Strokes shift of).41 eV is due to ultrafast repolarization od the nuclear degrees of freedom of the DNA pocket. in this system, the environmental reorganization induced by t...

The cover picture shows an acridine derivative (ACMA) intercalated at an abasic site between nucleobases in B-DNA. Unlike the Stokes shift on the nanosecond time scale reported for this chromophore in polar solvents, dynamic solvation of 1(ACMA)* in DNA occurs within 200 fs. The absence of slow relaxation components has been shown to be important f...

Anticalins are a novel class of engineered ligand-binding proteins with tailored specificities derived from the lipocalin scaffold. The anticalin FluA complexes fluorescein as ligand with high affinity, and it effects almost complete quenching of its steady-state fluorescence. To study the underlying mechanism, we have applied femtosecond absorptio...

The recent investigation of the apparently anomalous attenuation factor (beta > 1.5 A(-1)) for photoinduced hole injection into DNA duplexes modified by protonated 9-amino-6-chloro-2-methoxyacridine (X+) led to the conclusion that in addition to the electronic couplings, the activation energy must also be distance-dependent. In this communication w...

The recent investigation of the apparently anomalous attenuation factor (β > 1.5 Å-1) for photoinduced hole injection into DNA duplexes modified by protonated 9-amino-6-chloro-2-methoxyacridine (X+) led to the conclusion that in addition to the electronic couplings, the activation energy must also be distance-dependent. In this communication we rep...

The fastest electron transfer processes between molecular donor/acceptor systems have been observed for solvent to solute type reactions, where the number of solvent molecules participating could be high. This might explain the very short electron transfer times of observed. Here the photo-induced electron transfer in a bridged donor/acceptor syste...

The photophysics of intercalated chromophores is an important tool in studies of DNA structure and dynamics. detection of DNA hybridization, the fluorescent imaging of DNA in gels, and fluorescent staining of chromosomal DNA.1,2 The transfer of a conjugated chromophore from aqueous solution to an intercalation site in the duplex often significantly...

Comparison of the ultrafast electron transfer kinetics of a solute-solvent, system and its intramolecular analogue shows that the large solvent to solute rates are intrinsic and not due to accumulation of reaction probabilities.

From previous thermal and photoinduced charge-transfer reactions in duplex DNA there is accumulative evidence for an attenuation parameter beta of the distance dependence in the range 0.6-0.8 A(-1), with the exception of one specific system exhibiting beta = 1.5 A(-1) which is reinvestigated in this paper. Femtosecond to nanosecond time-resolved pu...

The energetics of electron transfer in DNA has been estimated via differences of electron affinities (EAs) of nucleobases B in trimers of Watson–Crick pairs 5′-XBY-3′ calculated with the semi-empirical method AM1. The EA values of the nucleobases were found to decrease in the order . The destabilizing effect of the subsequent base Y is more pronoun...

Spectroscopic characteristics of the green fluorescent protein (GFP) and its mutants are controlled through protonation states of the chromophore and the polarity of its environment. Using the semiempirical method NDDO-G, absorption spectra of all possible protonation states of a model chromophore in the gas phase and in polar solution (ethanol) we...

Ultrafast, intra-oligomer fluorescence resonance energy transfer (FRET) between an immature green-emitting GFP-like chromophore to the mature red-emitting chromophore is found in the novel red fluorescent protein wt-DsRed (the picture shows the steady-state absorption (solid line) and emission (dotted) spectra). Since FRET is by its very nature a s...

Hole transfer from an excited, DNA-intercalated injector (1), to either G or to the “traps” GG or GGG occurs with similar rates, and always results in oxidation of the proximate guanine residue. These results indicate that charge trapping in GG or GGG must occur by a relaxation mechanism (structural and/or energetic) which is inherent in these sequ...

The magnetic field effects on the picosecond photo-dynamics of two different nickel(II) centered tetrapyrroles dissolved in coordinating solvents are compared. These compounds exhibit fast intersystem crossing processes with multi-exponential kinetics which are altered by external magnetic fields of some teslas. The influence of molecular symmetry...

The feasibility of using the vibrational Stark effect for the observation of charge transfer reactions on a short time scale is demonstrated. The photoinduced oxidation of ferrocenophanone induces a fast shift of the carbonyl stretching frequency which is observable by femtosecond time-resolved IR spectroscopy. The observed shift is in good agreeme...

We report a comparative study of wild-type green fluorescent protein (GFP) and single-site mutants in which threonine at position 203 has been replaced by aliphatic and aromatic residues, i.e., by valine (V), isoleucine (I), phenylalanine (F), tyrosine (Y), and histidine (H). Steady-state absorption spectra reveal changes that reflect different cha...

The fundamental mechanisms of charge migration in DNA are pertinent for current developments in molecular electronics and electrochemistry-based chip technology. The energetic control of hole (positive ion) multistep hopping transport in DNA proceeds via the guanine, the nucleobase with the lowest oxidation potential. Chemical yield data for the re...

The influence of strong magnetic fields up to 9 T on the decay kinetics of Ni2+−bacteriochlorophyll a was studied by femtosecond pump−probe spectroscopy. The appearance of a magnetic field effect depends on the initial electron spin state of the molecule, which can be switched by using suitable solvents. In toluene, where the central Ni2+ is tetrac...

We have been able to determine the occupancy of the quinone site at the A-branch (Q(A)) of a reaction center preparation with an accuracy of 2%. This is achieved by accumulating the P(+)Q(-)(A) state after multiple actinic excitation and monitoring the extent of the 30 ms ground state bleaching. This bleaching is corrected for deviations from compl...

The ultrafast photodynamics of bacteriochlorophyll with the central Mg2+-ion replaced by Ni2+ ([Ni]-BChl) in toluene and pyridine have been studied by femtosecond time-resolved fluorescence and absorption spectroscopy with a time resolution of 100 fs in the spectral range of 470−900 nm. Excitation of tetracoordinated [Ni]-BChl in toluene in its red...

The decay of the excited state of the primary donor () of reaction centers (RC) of Rb. sphaeroides R26 has been monitored via its spontaneous emission. Although there is general agreement that (i) a prominent drop of prompt emission within a few picoseconds results from fast charge separation of the majority of RCs and that (ii) a ∼15 ns delayed em...

We describe a method for the quantum yield determination of transmembrane charge separation in bacterial reaction centers (RC) that is independent of the content of quinone at the QA site and of loss channels in any time domain. We applied the method to RCs, where the energy of the radical pair P+BA− is lowered by replacing BA site bacteriochloroph...

Proton exchange between pyrimidine photodimers and their environment may have a profound impact on DNA photorepair. On the basis of B3LYP/6-31G* and AM1 calculations, we present the first computational study of the influence of protonation and deprotonation on the splitting reactions of pyrimidine dimer ion radicals. While proton transfer from a co...

Hopping between bases of similar redox potentials is the mechanism by which charge transport occurs through DNA. This was shown by rate measurements performed with double strands 1–3. This mechanism explains why hole transfer displays a strong sequence dependence, and postulates that electron transfer in unperturbed DNA should not be dependent on t...

In Hopping-Schritten zwischen Basen ähnlichen Redoxpotentials erfolgt der Ladungstransport durch DNA, wie Geschwindigkeitsmessungen an den Doppelsträngen 1–3 ergeben. Dieser Mechanismus erklärt, warum Lochtransfer stark sequenzabhängig ist, und postuliert, daß Elektronentransfer in ungestörter DNA nicht von der Sequenz abhängen sollte.

Hopping between bases of similar redox potentials is the mechanism by which charge transport occurs through DNA. This was shown by rate measurements performed with double strands 1–3. This mechanism explains why hole transfer displays a strong sequence dependence, and postulates that electron transfer in unperturbed DNA should not be dependent on t...

Molecular dynamics simulations have been carried out to study structural aspects of the photo repair mechanism of DNA photolyase. In particular, we investigated the docking and binding of bare and dressed model pyrimidine dimers, UT and dUpdT, respectively, in the enzyme pocket. These dimers, which split after photoinduced electron transfer, are es...

A guanine radical cation (G+•) was site-selectively generated in double stranded DNA and the charge transfer in different oligonucleotide sequences was investigated. The method is based on the competition between a charge transfer from G+• through the DNA and its trapping reaction with H2O. We analyzed the hole transfer from this G+• to a GGG unit...

Semiempirical CISD calculations were carried out on models of differently protonated forms of the isolated chromophore active in the green fluorescent protein (GFP). Electronic excitation (S0→S1) is found to considerably alter the equilibrium conformation of the chromophore. Low activation barriers to rotation about the exocyclic bond Cγ–Cβ adjacen...

We explore charge migration in DNA, advancing two distinct mechanisms of charge separation in a donor (d)–bridge ({Bj})–acceptor (a) system, where {Bj} = B1,B2, … , BN are the N-specific adjacent bases of B-DNA: (i) two-center unistep superexchange induced charge transfer, d*{Bj}a → d∓{Bj}a±, and (ii) multistep charge transport involves charge inje...

Steady-state absorption and fluorescence excitation spectra together with ps-fluorescence and fs-absorption measurements have identified an important relaxation channel of excited states in Green Fluorescent Protein (GFP). GFP derivatives with (1) shortened lifetimes of the protonated chromophore RH* state and deprotonated chromophore R−* state, an...

The lowest excited singlet (S1) and triplet (T1) states of bacteriochlorophyll a (BChl) and its central metal derivatives [Zn]- and [Pd]- BChl were investigated by femtosecond time-resolved absorption and fluorescence spectroscopy. In contrast to previously reported dynamic solvation effects on the picosecond time scale for BChl, no short kinetic c...

The recombination dynamics of a transition metal redox system monitored by femtosecond pump-probe spectroscopy are shown to be sensitive to high magnetic fields at times shorter than 10 picoseconds. The effect, based on coherent population beats of different spin states, is quantitatively accounted for and allows direct access to spin relaxation ra...

As a first step towards modeling the green fluorescent protein (GFP), we have carried out absorption spectra calculations on chromophores of both native and mutant proteins using the semiempirical method INDO/S. A number of protonated and deprotonated states of the GFP fluorophore were considered. We find predicted and observed absorbance energies...

The nonexponetial fluorescence decay pattern of the primary donor state 1P* in the reaction center (RC) of Rhodobacter sphaeroides R26 has been investigated in order to identify the origin of such dispersive kinetics. Of particular interest was the open question, whether “intermediate” fluorescence components (≈40 ps to 1 ns) reflect (i) the decay...

In order to gain insight into the light-driven repair of DNA by the enzyme DNA photolyase, the conformation of the photoactive cofactor FAD, a flavin adenine dinucleotide, has been studied by molecular dynamic simulations. In contrast to FAD in the gas phase and in water where the MD procedure yields various "open" I-shaped as well as "closed" U-sh...

The high efficiency of charge separation in photosynthetic reaction centers arises from the interplay of energetics, electronic couplings, and reorganization energies relevant for the fast charge separation and slow recombination processes. All these parameters can be determined unambiguously only from magnetic-field-dependent measurements of the r...

Steady-state absorption and fluorescence excitation spectra together with ps-fluorescence and fs-absorption measurements have identified an important relaxation channel of excited states in Green Fluorescent Protein (GFP). GFP derivatives with (1) shortened lifetimes of the protonated chromophore RH* state and deprotonated chromophore R−* state, an...

The kinetics and energetics of the electron transfer reactions occurring in the enzyme·substrate complex of DNA photolyase have been studied by transient absorption spectroscopy with picosecond time resolution in the temperature range 275−90 K. The results can be summarized as follows:  (i) The lifetime of 1(FADH-)* depends not only on the presence...

The quenching of excited singlet methylene blue (1MB+*) by N,N-dimethylaminomethylferrocene (FcN) in acetonitrile at room temperature has been studied using femtosecond pump-probe absorption spectroscopy. At high FcN concentration static quenching via an intermolecular electron transfer mechanism constitutes the predominating decay channel for 1MB+...

The absorption spectrum of the chromophore of the green fluorescent protein (GFP) was investigated by INDO/S-CI model calculations. Geometrical variations of the hydrogen bonds between the chromophore and its environment were studied in detail. Based on the good agreement between experimental and calculated data, the spectrum of GFP is assigned. Th...

Recently steady-state and picosecond time-resolved absorption and fluorescence spectroscopy on the Green Fluorescent Protein (GFP) have been interpreted by a mechanism where the key process is an excited state deprotonation of the chromophore (M. Chattoraij, B.A. King, G.U. Bublitz and S.G. Boxer, Proc. Natl. Acad. Sci. USA, 93 (1996) 8362–8367). S...

Photoinduced charge separation and recombination in a series of cyclophane-bridged porphyrin-quinone systems (PQ) in toluene solution have been investigated by means of sub-ps time-resolved absorption spectroscopy. Temporal profiles and transient spectra of the porphyrin cation (P+) show the photoinduced formation and decay of the charge-separated...

The most prominent cornerstone of reaction center function is the high quantum yield of transmembrane charge separation approaching unity in the systems studied so far. This feature necessarily implies that the deactivation rate of the excited primary donor 1P* not involving electron transfer is not accessible in native systems. Therefore, reaction...

The rate of charge separation in a series of cyclophane-bridged Zn−porphyrin−quinone systems has been investigated in nonpolar and polar solvents by means of fluorescence upconversion. In all systems with driving forces in the range 0.3−1.3 eV, ultrafast charge separation occurs with a rate constant of (2−5) × 1012 s-1. In combination with previous...

As a first step toward modeling the photoinduced repair of DNA, electronic structure calculations on the cleavage reaction of various pyrimidine dimers (uracil, thymine, and cytosine) as well as of their anion and cation radicals have been carried out using the AM1 UHF method. Two different paths of the splitting reaction have been studied by locat...