Relaxation of green fluorescent protein chromophore anion observed by photodissociation in an electrostatic storage ring

The gas-phase absorption properties of the green fluorescent protein chromophore anion were studied using an electrostatic storage ring. The time sequence of neutral particles produced by photodissociation was detected following laser irradiation. The lifetimes of the photo-absorbed ions depended on their storage time in an ion trap before injection into the storage ring. The lifetime increased with the storage time and saturated, indicating a change in the population of rovibrationally excited states with respect to the storage time. Photodissociation neutral spectrum of the relaxed ions measured as a function of the laser wavelength was characterized by a narrow asymmetric shape, which was in good agreement with the photo fragment ion action spectrum reported recently.     

Vibrationally resolved photoabsorption spectroscopy of red fluorescent protein chromophore anions

Photoabsorption studies of red fluorescent protein chromophore anions have been performed at the ELISA electrostatic heavy-ion storage ring. The broad absorption band due to electronic excitation of the chromophores is tuned to a longer wavelength (redshifted) by extending the electronic conjugation of the molecule. A clear vibrational progression is resolved with E(vib) approximately 380 and 520 cm(-1) for two different forms of the chromophore. The vibrational modes correspond to collective motions of the entire molecular structure. It is argued that the excited electronic state has an equilibrium configuration far from that of the electronic ground state, i.e., poor Franck Condon overlap.     

The electronic structure and spectra of octacyanide complexes

The optical and electron spin resonance spectra of molybdenum and tungsten octacyanides have been measured and the results are interpreted by electrostatic crystal field theory using a point charge model of D _2d symmetry.     

Calculation of the electronic structure and spectra for bacteriochlorophyll analogs

Geometric structures and excited electronic states for free bases of bacteriochlorin (H₂BC) and tetraazabacteriochlorin (H₂TABC) as well as for their magnesium complexes (MgBC and MgTABC), analogs of bacteriopheophytin a (H₂BPhea) and bacteriochlorophyll a (MgBPhea), have been calculated by a DFT method and by an INDO/Sm method (the INDO/S method with parameterization modified by the authors), respectively. The factors responsible for the observed bathochromic shift of the long-wavelength Q _x (0–0) band of MgBPhea relative to H₂BPhea, \updelta E_Qx @ - 300  \textc\textm ^{- 1} {{\updelta }}{E_{{Q_x}}} \cong - 300\;{\text{c}}{{\text{m}}^{ - 1}} , have been clarified. Contributions of one- and two-electron interactions to the resulting shift of the Q _x (0–0) band have been analyzed in detail for the H₂BC/MgBC, H₂TABC/MgTABC, and porphine (H₂P)/Mg porphine (MgP) pairs. It is shown that the bathochromic shift under consideration for the tetrahydro derivatives is caused by a decrease of the orbital energy gap ε₁–ε₋₁ between the lowest unoccupied and highest occupied molecular orbitals. The variation of δ(ε₁–ε₋₁) is large and amounts to –1660 and –920 cm^–1 for the H₂BC/MgBC and H₂TABC/MgTABC pairs, respectively. The two-electron contributions, both into the energy of electronic configurations and due to the superposition of the configurations, produce a compensating hypsochromic effect such that the shifts \updelta E_Qx {{\updelta }}{E_{{Q_x}}} are –260 and –150 cm^–1 for the H₂BC/MgBC and H₂TABC/MgTABC pairs, respectively. It is also shown that the calculated electronic spectra for the considered molecules agree quantitatively with the experimental absorption spectra.     

Chromophores of the green fluorescent protein studied in the gas phase

Absorption of gas-phase biomolecules has been studied at the heavy-ion storage ring ELISA. Here we discuss the absorption characteristics of the chromophores of the Green Fluorescent Protein (GFP). The gas-phase absorption maximum of the deprotonated chromophore (anion form) is at 479 nm. This is almost identical to one of the two absorption maxima of the protein, being at 477 nm, which is ascribed to a deprotonated chromophore in the protein. The protonated chromophore (cation form) has a maximum at 406 nm in the gas phase. We compare the gas-phase results with absorption profiles of GFP and chromophores in liquids, and argue that the absorption characteristics of GFP are mainly ascribed to intrinsic chemical properties of the chromophore. Evidently, the special β-can structure of GFP provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains. Received 28 December 2001 Published online 13 September 2002     

Highly resolved electronic spectra and electronic structure of benzo[f]quinoxaline

Vibrational analysis of highly resolved phosphorescence (P), flourescence (F) and absorption spectra of benzo[f]quinoxaline (BQ) in Shpolskii matrices, at 77 K, was carried out. The spectra were dominated by phenanthrene-type fundamental vibrations. The appearance of several out-of-plane (op) modes in the P spectrum as well as the P lifetime, much shortened relative to that of the parent hydrocarbon, point to the proximity of the lowest n, π¹ and π, π¹ states of the BQ molecule. High activity of op modes in the F spectrum and complex structure of the absorption spectrum onset have been explained in terms of the pseudo-Jahn-Teller interaction between close-lying S₁ (π, π¹)and S₂(n, π¹) states.According to calculations of the BQ electronic structure, performed using a modified INDO CI method, the T₁(π, π¹)-T₂(n, π¹) and S₁(π, π¹-S₂(n, π¹) energy gaps are about 1200 and 700 cm^-1, respectively.     

Vibrational spectra and electronic structure of rhodanocomplexes of platinum metals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 2, pp. 221–224, August, 1991.     

Peculiarities of the electronic structure and optical spectra of Mott insulator nanoparticles

Changes in the electronic structure of Mott insulators upon transition from bulk crystals to nanoparticles have been considered. It is shown that an increase in the concentration of surface defects (in particular, oxygen vacancies for particles of transition metal oxides) leads to the formation of in-gap states of the spinpolaron origin inside the gap. As a result, the optical absorption spectrum of a nanoparticle undergoes a red shift with respect to a crystal.     

Wavelength modulation spectra of SbSI and its electronic band structure

The reflectivities of SbSI and their logarithmic derivatives between 1.8 and 4.5 eV have been measured at different temperatures. The structures in the reflectivities are compared with those calculated independently by the empirical pseudopotential method (EPM), using the pseudopotential form factors scaled from previous band structure calculations of other crystals. The large optical anisotropy of SbSI is explained. A preliminary band structure for SbSI is presented.     

X-ray appearance potential spectra and electronic structure of transition metals

The possibility of determining the density-of-states distribution function in the unoccupied part of the conduction bands of the transition metals Cr, Mo and W from experimental APS spectra is considered. Comparison of the results obtained with data from band-structure calculations for these metals is carried out.     

Characteristic electron loss spectra and electronic structure of thallium chloride

The bands, state densities N(E), and permittivity are theoretically found for TlCl crystals. On the basis of the experimental characteristic electron loss spectra, the spectra of the complete set of optical functions including permittivity and bulk electron loss spectra are calculated and decomposed into components. The obtained data are compared with the well-known theoretical results. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 8–11, June, 2008.