ULTRAVIOLET RESONANCE RAMAN SPECTROSCOPY OF BACTERIORHODOPSIN

Ultraviolet resonance Raman spectra of bacteriorhodopsin have been obtained using 229 nm excitation from a hydrogen-shifted neodymium yttrium aluminum garnet (Nd: YAG) laser. High signal-to-noise spectra are observed exhibiting vibrational bands at 762, 877, 1011, 1175, 1356, 1552 and 1617 cm-1 which are assigned to scattering from tryptophan and tyrosine side chains. This demonstrates the feasibility of using UV resonance Raman spectroscopy to monitor aromatic amino acid structural changes during the bacteriorhodopsin photocycle.     

PRIMARY PHOTOCHEMISTRY OF BACTERIORHODOPSIN: COMPARISON OF FOURIER TRANSFORM INFRARED DIFFERENCE SPECTRA WITH RESONANCE RAMAN SPECTRA

Abstract —Fourier transform infrared (FTIR) difference spectra of the BR→rK transition in bacteriorhodopsin at 77→K are compared with analogous resonance Raman difference spectra obtained using a spinning sample cell at 77→K. The vibrational frequencies observed in the FTIR spectra of native purple membrane and of purple membrane regenerated with 15-deuterioretinal are in good agreement with the frequencies observed in the Raman spectra, indicating that the lines in the FTIR difference spectra arise predominantly from retinal chromophore vibrations. This agreement confirms that the spinning cell method for obtaining resonance Raman spectra of K minimizes potential contributions from unwanted photoproducts. The unexpected similarity between the resonance Raman scattering intensities and the FTIR absorption intensities for BR and K is discussed in terms of the delocalized electronic structure of the chromophore. Finally, comparison of the Schiff base regions of the K Raman and FTIR spectra provide additional information on the assignment of its Schiff base vibration.     

RESONANCE RAMAN SPECTRA OF THE II-CATION RADICALS OF COPPER, COBALT, AND NICKEL METHYLOCTAETHYLCHLORINS: VIBRATIONAL CHARACTERISTICS OF CHLOROPHYLL MODELS

Abstract— By using excitation at 363.8 nm, resonance Raman (RR) spectra were obtained for Cu(II), Co(II), and Ni(II) complexes of methyloctaethylchlorin (MeOEC) and their ir-cation radicals. Additionally, the Raman spectra of the Cu(II) derivatives of (rarcs-octaethylchlorin (r-OEC) were included for comparison. The alkyl-substituted CuMeOEC exhibits a Raman spectrum that is nearly identical to that of the simpler (-CuOEC in both the neutral and oxidized states. Unlike the latter species, the cation radical of CuMeOEC is immune to oxidative dehydrogenation to porphyrin, and this has facilitated vibrational characterization of the ring-oxidized species. This study aims to compare the vibrational characteristics in the 1450 to 1700 cm^-t region of the metallochlorin ir-cation radicals to those of the corresponding oxidized metalloporphyrins. We focus on two modes in the1500–1520 cm^-1 and1620–1650 cm^-1 region that are analogous to the v₃ and v₁₀ vibrations, respectively, in the metalloporphyrin analogs. These vibrational modes are clearly defined in all species and exhibit a strong core-size dependency in the porphyrin complexes. The core-size study as well as the frequency changes upon oxidation support the conclusion that the v₃-like vibration in the chlorin species features substantial C_bC_b in addition to C_aC_m stretching character. The v,₀-like mode of the chlorin macrocycle, on the other hand, displays characteristics that closely resembles that of the porphyrin analog; consequently, these vibrations are of predominantly C_aC_m stretching character in both cases.     

呫吨类染料的表面增强共振喇曼散射光谱

本文研究了呫吨类染料分子(R110, RB, SRB, R_6G, R101和SF)吸附于化学沉积银岛膜上的表面增强共振喇曼散射(SERRS)光谱。文中详细的介绍了获得SERRS的实验条件, 对谱线的归属作了指认, 并讨论了共振、表面增强、吸附状态和衬底制备条件等因素对SERRS的特征和对喇曼散射截面的增强的影响。结果表明, SERRS是研究强荧光染料分子以及它们与金属表面相互作用的一种新的有效手段。     

RESONANCE RAMAN SPECTRA AND MOLECULAR ORIENTATION DISTRIBUTION OF INTERFACIAL MONOLAYERS

An orientation distribution model has been suggested for interfacial monomolecular lay-ers by taking account of the orientational uniaxiality of long-chain amphiphilic molecules inmonolayers. The resonance Raman spectra of azo-containing monolayers are the oreticallytreated on the basis of the model. Order parameters and (P_4> are obtained from polar-ized Raman measurements, giving rise to distribution graphs. These analyses indicate thatthe orientation distribution alters upon the increase of adsorption amount and displays inter-esting variation among different interfacial monolayers. The aggregate aspects of the 2-dimensional condensed states are also discussed from the viewpoint of molecular orientation.     

LOW TEMPERATURE RESONANCE RAMAN STUDY OF THE L INTERMEDIATE OF BACTERIORHODOPSIN

Abstract— Resonance Raman spectra of photostationary state mixtures at — 80°C of bR568, L, L', and M for light-adapted bacteriorhodopsin were obtained. The approximate Raman spectrum of L + L' was obtained by computer, subtracting the known Raman spectra of bR568 and M from the photostationary state spectra. Several new species not previously observed with the bacteriorhodopsin photocycle have been proposed recently. We compare our results to these studies in order to investigate the photoreaction scheme of bacteriorhodopsin.     

RESONANCE RAMAN SPECTRA AND NORMAL MODE DESCRIPTIONS OF A BACTERIOCHLOROPHYLL a MODEL COMPLEX

Abstract— Resonance Raman (RR) spectra are reported for the bacteriochlorophyll a (BChl a) model complex, copper methylbacteriopheophorbide a (CuBPheo a). The spectra are acquired at a number of excitation wavelengths in the Q_y+ Q_x and B regions of the absorption spectrum. The RR data obtained for CuBPheo a are correlated to those previously reported for BChl a. The normal modes of the BChl structure are calculated by using the semiempirical quantum chemistry force field (QCFF/ PI) method of Warshel and Karplus [J. Am. Chem. Soc. 94 ,5612–5625 (1972)]. The vibrational data are used in conjunction with the calculations to obtain a cohesive assignment for the normal modes of BChl a with frequencies between 1100 and 1700 cm^-1. The forms of the normal modes of BChl a are predicted to be different both from those of chlorophyll a and from those of porphyrins.     

RESONANCE RAMAN STUDIES OF BACTERIORHODOPSIN ANALOGUES

Abstract— We present the results of resonance Raman measurements on a series of bacteriorhodopsin (bR) analogues formed from synthetic retinals which have replaced the native chromophore in the active site. Specifically, 5,6-dihydro-bR, 13-desmethyl-bR, 10-methyl-bR, 14-methyl-bR, and 10.14-dimethyl-bR have been studied. All five analogues bind and form Schiff base retinal-apoprotein linkages. While the Schiff base linkages of 5,6-dihydro-bR, 13-desmethyl-bR, and 10-methyl-bR are protonated, like the native chromophore, the 14-methyl-bR, and 10,14-dimethyl-bR Schiff bases are unprotonated. These results suggest that the binding site of bacteriorhodopsin near the Schiff base moiety is different from that of rhodopsin. The protonated Schiff base -C=NH- stretching frequency of 5.6-dihydro-bR lies at 1660 cm^-1 which is unusually high for a bacteriorhodopsin based pigment. The downward shift upon deuteration is 16 cm^-1, essentially identical to that measured for bacteriorhodopsin. This and the other analogue results strongly reinforce our previous arguments that the Schiff base stretching frequency is determined in large part by two factors, the C=N force constant and the stretch interaction with C=N-H bend. On the other hand, the deuterium isotope effect is determined primarily by the stretch-bend interaction.     

RESONANCE RAMAN SPECTRA OF BACTERIORHODOPSIN MUTANTS WITH SUBSTITUTIONS AT ASP-85, ASP-96, AND ARG-82

Detergent solubilized bacteriorhodopsin (BR) proteins which contain alterations made by site-directed mutagenesis (Asp-96----Asn, D96N; Asp-85----Asn, D85N; and Arg-82----Gln, R82Q) have been studied with resonance Raman spectroscopy. Raman spectra of the light-adapted (BRLA) and M species in D96N are identical to those of native BR, indicating that this residue is not located near the chromophore. The BRLA states of D85N and especially R82Q contain more of the 13-cis, C = N syn (BR555) species under ambient illumination compared to solubilized native BR. Replacement of Asp-85 with Asn causes a 25 nm red-shift of the absorption maximum and a frequency decrease in both the ethylenic (-7 cm-1) and the Schiff base C = NH+ (-3 cm-1) stretching modes of BRLA. These changes indicate that Asp-85 is located close to the protonated retinal Schiff base. The BRLA spectrum of R82Q exhibits a slight perturbation of the C = NH+ band, but its M spectrum is unperturbed. The Raman spectra and the absorption properties of D85N and R82Q suggest that the protein counterion environment involves the residues Asp-85-, Arg-82+ and presumably Asp-212-. These data are consistent with a model where the strength of the protein-chromophore interaction and hence the absorption maximum depends on the overall charge of the Schiff base counterion environment.     

二溴三烯丙基硫脲合镉单晶的拉曼光谱

将有一定极性或非极性的有机分子与金属离子进行络合形成非线性光学材料,是探索具有高倍频效率新晶体的有效途径.二溴三烯丙基硫脲合镉Cd(CH_2=CHCH_2NHCSNH_2)_3Br_2(简称ATCB)晶体就是基于无机畸变多面体与不对称共轭有机分子基团相结合的双重基元结构物理模型指导下的又一具有高倍频效率的新晶体.其粉末倍频效应为脲素的1.5倍,为KDP晶体的12.5倍.它具有较宽的透光波段和较高的非线性系数、较好的化学稳定性和     

RESONANCE RAMAN SPECTRA OF THE "BLUE" and THE REGENERATED "PURPLE" MEMBRANES OF Halobacterium halobium

Abstract— We have obtained the resonance Raman spectra of the deionized form of the purple membrane, the so called blue membrane, as well as the purple membrane regenerated by titrating the blue membrane with either Na+, Ca²+ or La³+. All types of regenerated purple membrane have identical Raman spectra which are virtually indistinguishable from the native light-adapted bacteriorhodopsin spectrum. On the other hand, Raman data for the blue membrane suggest that it consists of essentially two pigment forms with absorption maxima around 605 and 570 nm and containing 13-cis and all-trans isomeric configurations of the chromophore. This is consistent with our chromophore extraction results which reveal that the blue membrane consists of 30% 13-cir and 70% all-trans chromophore.     

荧光素钠互变异构体的表面增强共振喇曼散射光谱

本文报导了不同pH值下荧光素钠吸附于银岛膜的表面增强共振喇曼散射(SERRS)光谱。由于在不同pH值的溶液中荧光素钠具有不同的离子构型, 其SERRS光谱也有所不同, 其差异主要表现在谱线强度的变化而不是频率变化。谱线强度随pH值的变化形式可分为两种类型, 这与其相对应的振动模的性质有关。利用“四级能模型”和共振喇曼理论对实验结果进行了分析。     

Fe vibrational spectroscopy of myoglobin and cytochrome f

The Fe vibrational density of states (VDOS) has been determined for the heme proteins deoxymyoglobin, metmyoglobin, and cytochrome f in the oxidized and reduced states, using nuclear resonance vibrational spectroscopy (NRVS). For cytochrome f in particular, the NRVS spectrum is compared with multiwavelength resonance Raman spectra to identify those Raman modes with significant Fe displacement. Modes not seen by Raman due to optical selection rules appear in the NRVS spectrum. The mean Fe force constant extracted from the VDOS illustrates how Fe dynamics varies among these four monoheme proteins, and is correlated with oxidation and spin state trends seen in model heme compounds. The protein's contribution to Fe motion is dominant at low frequencies, where coupling to the backbone tightly constrains Fe displacements in cytochrome f, in contrast to enhanced heme flexibility in myoglobin.     

PHOTOOXIDATION AND ELECTRON-TRANSFER PROCESSES IN FREE-BASE TETRAPHENYLPORPHIN PROBED BY RESONANCE RAMAN SPECTROSCOPY

Abstract
We report here the resonance Raman studies of photooxidation of free base tetraphenylporphin (H₂TPP) in the presence of external electron acceptors such as CCl₄ and chloranil under selective laser irradiation. From the dependence of photooxidation on the concentration of electron acceptors, polarity of solvents, excitation lines and temperatures, we have inferred that a weak triplet exciplex formed between the excited H₂TPP and electron acceptor in non-polar solvents serves as transient species and the light-induced intermolecular charge transfer from H₂TPP to the electron acceptor is the primary process involved in photooxidation. Observation of partial photooxidation in the rigid matrix at low temperatures has been interpreted to be due to long-range quantum mechanical electron tunneling process. Almost complete photooxidation is observed in a soft matrix as the donor and acceptor molecules can attain favorable relative orientation and separation for electron transfer during the excited state lifetime of the exciplex.     

RESONANCE RAMAN and ABSORPTION SPECTRA OF ISOMERIC RETINALS IN THEIR LOWEST EXCITED TRIPLET STATES

Abstract— The triplet-triplet absorption spectra of 9-cis-, 13-cis- and all-fraw-retinal as well as the time-resolved resonance Raman spectra of the lowest electronically excited triplet states of 9-cis-, 11-cis, 13-ciy and all-trans-retinal in aromatic solvents at room temperature have been obtained under conditions ensuring the isomeric purity of the starting materials. The triplet states were produced by triplet energy transfer from a sensitizer in pulse-radiolysis experiments. The overall results suggest that the isomeric retinals form either different relaxed triplet species or different mixtures of relaxed triplet species. The possible implications about the size of the energy barriers separating the various triplet species are discussed. The resonance Raman spectra obtained by using either anthracene (E_T= 177.7 kJ mol^-1) or naphthalene (E_T= 254.8 kJ mol^-1) as sensitizers were virtually identical for the corresponding triplet states from each of the isomers 11-cis-, 13-a's- and all-tams-retinal, suggesting that the relaxed triplet species or the mixture of relaxed triplet species formed from each isomer is independent of the energy of the sensitizer.     

TRIPLET STATES OF CAROTENOIDS BOUND TO REACTION CENTERS OF PHOTOSYNTHETIC BACTERIA: TIME-RESOLVED RESONANCE RAMAN SPECTROSCOPY

Time-resolved, low-temperature resonance Raman spectra of triplet states of the carotenoids specifically present in bacterial reaction centers in a strained cis conformation have been obtained, thus demonstrating the possibility of studying intermediate transient states of these structures using resonance Raman spectroscopy. Resonance Raman spectra of triplet cis spheroidene and cis methoxyneurosporene present in reaction centers of Rhodopseudomonas spheroides, (strains 2.4.1. and Ga, respectively) exhibit marked differences with those of triplet, all- trans carotenoids previously studied in vitro. These differences, together with the frequency shifts measured for the v ₁ modes, indicate that triplet carotenoids bound to reaction centers retain a cis conformation, and that probably no isomerization occurs to all- trans carotenoids upon T ← S₀ excitation. P_i electron distributions along the polyene backbone are probably less regular in the triplet state than in the singlet ground state, although probably not to the extent suggested by previous theoretical calculations. The apparently anomalous behaviour of the v ₂ bands of all- trans carotenoids upon T ← S₀ excitation is shown to result largely from the actual complexity of this region of the Raman spectra, together with a weak participation of the v _c—–c internal coordinate in the corresponding modes. Finally, the Raman scattering efficiency of triplet spheroidene bound to reaction centers is lower than that of the singlet, ground state form, under equivalent excitation conditions.     

POWER- AND TIME-RESOLVED RESONANCE RAMAN STUDIES AND CONFORMATIONAL CHANGES IN BACTERIORHODOPSIN

Abstract— By comparing the resonance Raman spectra of the retinal of the intermediates of bacteriorho-dopsin (obtained by using fixed flow with residence of time of 10 ps. variable laser power and frequency as well as computer subtraction techniques) with those of model compounds and with each other, the following possible conclusions can be obtained: (1) There exists stronger interaction between the retinal and the opsin in bacteriorhodopsin than that present in rhodopsin. (2) Conformational changes seem to take place during the dark light adaptation process as well as during the photosynthetic cycle. (3) The appearance of the spectrum of the retinal in the fingerprint region for the bL₅₅₀ and bM₄₁₂ intermediates is similar despite large shifts in their optical absorption maxima. This might argue against the theory that proposes ground state retinal conformational changes to explain the observed red shift in the optical spectra of retinal upon combining with the opsin. (4) Contrary to bM ₄₁₂ , the bL₅₅₀ species seems to be protonated. The fact that loss of proton does not seem to change the retinal conformation greatly might suggest that the protein and its ionic environment might carry the larger share of the load in the deprotonation process.     

RESONANCE RAMAN SPECTRUM OF THE EXCITED 21Ag STATE OF ß-CAROTENE

Abstract— Resonance Raman (RR) bands assignable to the 2¹A_g excited state of ß-carotene are recorded using picosecond time-resolved resonance Raman (PTR³) spectroscopy. The RR spectrum contains bands in both the C-C (1204 cm^?1, 1243 cm^?1, and 1282 cm^?1) and C=C (1777 cm^?1) stretching regions. The time-dependent intensities of these RR features, measured with ? 30 ps. resolution, are found (i) to closely correlate with picosecond transient absorption (PTA) data recorded at 575 nm on the same sample and (ii) inversely correlate with the time-dependent intensities of RR bands assigned to the 1¹A_g ground state. Both of these observations support the assignment of these four RR features to the 2¹A_g excited state. These results remove uncertainties associated with earlier experiments in which excited-state RR scattering from (3-carotene was not observed in spite of predicted trends emanating from studies of shorter polyene compounds. The observed C=C band position also agrees with a recent report of this feature.     

PHOTOOXIDATION AND ELECTRON-TRANSFER PROCESSES IN FREE-BASE TETRAPHENYLPORPHIN PROBED BY RESONANCE RAMAN SPECTROSCOPY

Abstract —We report here the resonance Raman studies of photooxidation of free base tetraphenylporphin (H₂TPP) in the presence of external electron acceptors such as CCl₄ and chloranil under selective laser irradiation. From the dependence of photooxidation on the concentration of electron acceptors, polarity of solvents, excitation lines and temperatures, we have inferred that a weak triplet exciplex formed between the excited H₂TPP and electron acceptor in non-polar solvents serves as transient species and the light-induced intermolecular charge transfer from H₂TPP to the electron acceptor is the primary process involved in photooxidation. Observation of partial photooxidation in the rigid matrix at low temperatures has been interpreted to be due to long-range quantum mechanical electron tunneling process. Almost complete photooxidation is observed in a soft matrix as the donor and acceptor molecules can attain favorable relative orientation and separation for electron transfer during the excited state lifetime of the exciplex.     

稀土催化聚乙炔的拉曼光谱研究

比较了用稀土和白川催化体系,制备的70％顺式含量及全反式聚乙炔的拉曼光谱及其随激发光源波长的变化。报道了用稀土催化体系制备的可溶性聚乙炔的拉曼光谱。这些实验结果支持导致反式聚乙炔拉吏异常的主要原因是反式聚乙炔链段共轭长度分散的解释。