Intermolecular interaction of photoexcited Cu(TMpy-P4) with water studied by transient resonance Raman and picosecond absorption spectroscopies

photoinduced complex between Cu(TMpy-P4) and water molecules, reversibly axially coordinated to the central metal, was observed in picosecond transient absorption and nanosecond resonance Raman experiments. This complex is rapidly created (τ1 = 15 ± 5 ps) in the excited triplet (π, π*) state of Cu-porphyrin, and the subsequent relaxation is proposed to proceed via two parallel pathways. One is fast and efficient (≥90% of molecules), and presumably involves a (π, d) charge-transfer state. The second pathway is slow (τ2 >> 1 ns), has a low quantum yield (≤10%) and involves the excited (d, d) state which is responsible for transient Raman features at ≈ 1553 cm−1 (ν2*) and ≈ 1347 cm−1 (ν4*), and for low-intensity long-lived transient absorption features

ДИНАМИЧЕСКИЕ ХАРАКТЕРИСТИКИ КОЛЬЦЕВЫХ ЛАЗЕРОВ

The results of the theoretical analysis of dynamics of correlation determination between the contradirectional waves in ring lasers for low frequencies are given. This dynamics ensures a differential mode of an operation of the ring lasers as a sensor of the angle displacements. Presence of two modes of stabilization of a correlation is determined: a fast and a slow.Приведены результаты теоретического анализа динамики установления связи между встречными волнами в кольцевых лазерах, обеспечивающей корреляцию низкочастотных флуктуаций и дифференциальный режим работы кольцевых лазеров, как датчика угловых перемещений. Показано наличие двух времен становления связи: быстрого и медленного

DYNAMIC PARAMETERS OF THE RING LASERS

The results of the theoretical analysis of dynamics of correlation determination between the contradirectional waves in ring lasers for low frequencies are given. This dynamics ensures a differential mode of an operation of the ring lasers as a sensor of the angle displacements. Presence of two modes of stabilization of a correlation is determined: a fast and a slow

Resonance CARS study of the structure of "green" and "red" chromophores within the red fluorescent protein DsRed

Vibrational spectra of red fluorescent protein DsRed have been studied for the first time by polarization-sensitive multiplex coherent anti-Stokes Raman scattering at two excitation wavelengths, 545 nm and 583 nm, in resonance with the absorption bands of the immature "green" and mature "red" protein chromophores. Overall vibrational patterns of both DsRed chromophores were found to be similar to each other and to differ substantially from that of S65T-GFP at pH8. Our data suggest that both "green" and "red" DsRed forms possess an extended chromophore structure, and, consequently, that maturation of red fluorescence is governed bz the interactions with the protein environment after isomerization around a cis peptide bond between Phe 65 and Gin 66. Besides, a coexistence of the major anoinic and minor neutral DsRed species can be suggested from virbational features in 1600-1700 cm-1 range; the hypothesis awaits verification after the detailed assignment of vibrational modes for the DsRed chromophore

Role of heme iron coordination and protein structure in the dynamics and geminate rebinding of nitric oxide to the H93G myoglobin mutant: Implications for nitric oxide sensors

International audienceThe influence of the heme iron coordination on nitric oxide binding dynamics was investigated for the myoglobin mutant H93G (H93G-Mb) by picosecond absorption and resonance Raman time-resolved spectroscopies. In the H93G-Mb, the glycine replacing the proximal histidine does not interact with the heme iron so that exogenous substituents like imidazole may coordinate to the iron at the proximal position. Nitrosylation of H93G-Mb leads to either 6- or 5-coordinate species depending on the imidazole concentration. At high concentrations, (imidazole)-(NO)-6-coordinate heme is formed, and the photoinduced rebinding kinetics reveal two exponential picosecond phases (~10 and ~100 ps) similar to those of wild type myoglobin. At low concentrations, imidazole is displaced by the trans effect leading to a (NO)-5-coordinate heme, becoming 4-coordinate immediately after photolysis as revealed from the transient Raman spectrum. In this case, NO rebinding kinetics remain bi-exponential with no change in time constant of the fast component whose amplitude increases with respect to the 6-coordinate species. Bi-exponential NO geminate rebinding in 5-coordinate H93G-Mb is in contrast with the single-exponential process reported for nitrosylated soluble guanylate cyclase (Negrerie, M., Bouzhir, L., Martin, J. L., and Liebl, U. (2001) J. Biol. Chem. 276, 46815-46821). Thus, our data show that the iron coordination state or the heme iron out-of-plane motion are not at the origin of the bi-exponential kinetics, which depends upon the protein structure, and that the 4-coordinate state favors the fast phase of NO geminate rebinding. Consequently, the heme coordination state together with the energy barriers provided by the protein structure control the dynamics and affinity for NO-binding enzymes. Cop. 2006 by The American Society for Biochemistry and Molecular Biology, Inc

Excited States of Water-Soluble Metal Porphyrins as Microenvironmental Probes for DNA and DNA-Model Compounds: Time-Resolved Transient Absorption and Resonance Raman Studies of Ni(TMpy-P4) in [Poly(dG-dC)]2 and [Poly(dA-dT)]2

The dynamics and mechanisms of photoexcitation relaxation of the water-soluble cationic metalloporphyrin nickel(II) 5,10,15,20-tetrakis[4-(N-methylpyridyl)]porphyrin (Ni(TMpy-P4)) bound to DNA-model polynucleotides, i.e. poly(dG-dC)2 and poly(dA-dT)2, and free in a mere phosphate buffer, have been studied in detail by using time-resolved picosecond transient absorption (TA) and nanosecond resonance Raman (RR) spectroscopies. For the Ni(TMpy-P4)−poly(dG-dC)2 complex, double-exponential kinetics of relaxation has been found, with time constants of ≤10 and 350 ± 20 ps, and absolute absorption spectra have been reconstructed from experimentally measured difference spectra. The long-lived transient species has been assigned to the excited intramolecular metal-centered (d,d) state 3B1g of the 4-coordinate Ni porphyrin intercalated between G-C base pairs. Transient RR spectra originating from this state have also been obtained and discussed. A much more complicated process of excitation relaxation has been found for the Ni(TMpy-P4)−poly(dA-dT)2 complex, where at least four relaxation components can be separated with time constants of ≤10, ∼100, ∼450 ps, and ≫1 ns. Our studies support the existence of at least two types of Ni(TMpy-P4) interaction with poly(dA-dT)2, each having its own kinetics of TA decay and transient RR spectra. Both TA and RR sets of data show that a major part of Ni porphyrin molecules yields a photophysical behavior typical for a 4-coordinate species, the excited (d,d) state 3B1g playing the key role in relaxation processes, while a minor part of Ni(TMpy-P4) also participates in axial ligand binding/release photoprocesses. Comparative analysis of transient RR spectra of Ni(TMpy-P4) bound to the A-T sequence and free in a phosphate buffer shows that no 6-coordinate 3B1g(L)2 transient species is photogenerated in the complex with poly(dA-dT)2, and therefore, axial coordination of only one extra-ligand molecule (most probably from the surrounding water solution) to the porphyrin central Ni ion is proposed to explain the experimental results. Possible processes of Ni(TMpy-P4) binding to poly(dA-dT)2 are discussed on the basis of the current photophysical data