OPTICAL ABSORPTION AND ELECTRON SPIN RESONANCE SPECTRA OF CATION RADICALS OF DIMERIC CHLOROPHYLL a IN LOW-TEMPERATURE MATRICES

Abstract— A chlorophyll (Chl) a solution in 3-methylpentane at 77 K exhibits an absorption spectrum with a distinct peak at 706 nm in the red-band region. The formation of the 706 nm absorbing species (S706) was reversible with respect to temperature change; no chemical change was observed. γ-Irradiation of the rigid 3-methylpentane solution at 77 K yields an absorption spectrum which can be ascribed to S706⁺ and S706⁻. When carbon tetrachloride, an electron scavenger, was added to the solution, the absorption of S706⁺ survived, which has peaks at 850 and 956 nm. It is assumed that the S706 is hydrogen-bonded dimeric Chi a , which may be regarded as a model of P700 in photosynthesis. Cation radicals of monomeric Chi a were formed in a γ-irradiated sec -butyl chloride solution at 77 K, and an absorption spectrum with peaks at 730 and 813 nm was recorded. ESR spectra of the cation radicals of S706 and monomeric Chi a are of a similar shape but their linewidths are 7.5 and 11.0 Gauss, respectively. The linewidth narrowing observed for S706⁺ is clear evidence for the assumption that S706 is dimeric Chi a. Comparison was made of the absorption spectrum of S706⁺ with the light-induced spectrum of P700 reported earlier.     

TIME-RESOLVED RESONANCE RAMAN SPECTRA OF THE PHOTOCYCLE INTERMEDIATES OF ACID AND DEIONIZED BACTERIORHODOPSIN

Abstract— The photocycle of bacteriorhodopsin (bR) and its perturbed forms are investigated by a time-resolved resonance Raman study. These experiments were performed in the C=C stretching and in the fingerprint spectral regions for the acid blue, acid purple and deionized forms of bR.
The main observations are as follows: (1) isomerization of the retinal, from all- trans to 13- cis , occurs in native bR and in all of the acid and deionized perturbed bR species; (2) formation of the early intermediates (the K₆₁₀ and L₅₅₀ analogues) also occur in native bR and in all of the perturbed species; and (3) deprotonation of the protonated Schiff base (PSB), to give the M₄₁₂ type intermediate, occurs in native bR, but is inhibited in all of the perturbed bR species on the time-scale of the native bR photocycle.
The results show that isomerization alone is not a prerequisite for the PSB deprotonation process. The observed photocycle, initiated with retinal isomerization, is found to occur from all- trans to 13- cis in all of the perturbed forms of bR. In addition, the results imply that removal of the cations, of an increase in the hydrogen ion concentration, prevent only the PSB deprotonation process and not the formation of earlier cycle intermediates. Some attention is focused on the two blue forms of bR (acid and deionized) due to the fact that their ground-state absorption maximum, unphotolyzed Raman spectra, and Raman spectra changes during the photocycle are all very similar. The similarities between the acid blue and deionized blue forms in the fingerprint region support previous suggestions that both blue species have nearly the same retinal active site.     

FLUORESCENCE SPECTRA AND ZERO-FIELD MAGNETIC RESONANCE OF CHLOROPHYLL a-WATER COMPLEXES

Abstract. –Fluorescence detected magnetic resonance (FDMR) and fluorimetry have been used to study chlorophyll-water complexes at T = 4.2 K. By combining these methods, zero-field splitting (ZFS)-parameters can be assigned to the triplet state of the various species. It is found that these parameters decrease upon aggregation and/or complexation. These results can be rationalized by using a simple free-electron model for chlorophyll including excitonic interaction. Evidence is presented favouring a structure recently proposed by Shipman and Katz for a chlorophyll-dimer involving hydrogen-bonded water, present in non-polar solutions at low temperature with spectral properties similar to those of chlorophyll in vivo.     

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.     

吩噻嗪和吩噁嗪氧化中间体的共振喇曼光谱研究

本文对吩噻嗪和吩噁嗪的单电子氧化产生的两种氧化态的亚稳态正离子进行了共振喇曼光谱研究。随着吩噻嗪的p电子逐步失去,结构变形振动δ_(CNC)和δ_(CSC)的喇曼频移显著地增大,环C=C伸缩振动区域的喇曼峰数目明显变多。由此推断,随着吩噻嗪正离子氧化态的增高,正离子转变成平面共轭结构。     

二价铜、镍EDTA络合物晶体的电子吸收光谱

络合物晶体的电子吸收光谱作为研究晶体的电子结构的基础内容,很早以前就得到人们注意,虽然对Cu~(2+)、Ni~(2+)等络合物电子光谱的能级的经验指认已是一项较为成熟的工作,但对吸收光谱的系统的理论计算和定量解释在以前的文献中尚不多见.近年来,我们对多种晶体的电子吸收光谱进行了定量的解释,结果表明理论计算值总是能很好地符合于实验测定值。一般说来,吸收峰位的波数误差在8%以内. 早在本世纪四十年代就奠定了乙二胺四乙酸(EDTA)在分析化学中的应用基础。     

有机金属化合物的振动光谱(Ⅱ)——1,1′-二甲基环戊二烯铁夹心化合物振动光谱的简正坐标计算

测定了(CH_3Cp)_2Fe(Cp=C_5H_4~-)夹心化合物的Fourier变换红外光谱和激光Raman光谱, 并做了指认, 将G-F矩阵法计算得到的Cp_2M(M=Mn,Fe,Ru)夹心化合物的一套力常数, 完整地转移到该分子上, 计算得到的振动光谱频率与测得的基本一致。     

FOURIER-TRANSFORM RAMAN AND INFRARED SPECTRA AND VIBRATIONAL ASSIGNMENT FOR SOLID GLUTARIMIDE

Abstract

The FT-Raman and FT-IR spectra of crystalline glutarimide and its N-deuterated derivative have been recorded in the range 4000-100 cm^?1. A complete vibrational assignment is given for all internal modes and is supported by normal coordinate analysis based on a general valence force field. The calculated frequencies are in very good agreement with experiment. A close similarity is found for frequencies of the corresponding vibrations of glutarimide and uracils in the solid state. It is concluded that the strength of hydrogen bonding in glutarimide is very similar to that in crystalline pyrimidine nucleic bases.     

RESONANCE RAMAN SPECTRA OF THE Pr-FORM OF PHYTOCHROME

Abstract— Resonance Raman spectra of the P_r-form of oat phytochrome have been obtained at 77 K. Interference from phytochrome fluorescence is avoided by employing far-red 752 nm excitation. Vibrational assignments are suggested for the tetrapyrrole chromophore in phytochrome by comparison with previously published model compound spectra and by examining the characteristic shifts induced by deuteration of the pyrrole nitrogens. The lack of carbonyl intensity, the frequencies of the 1626 and 1644 cm^-1 C=C stretching modes, and the presence of an intense mode at 1326 cm^-1 are all consistent with a protonated structure for the tetrapyrrole chromophore in P_r. This suggests that the -50 nm red-shift of the protein-bound chromophore absorption compared to the chromophore in vitro is caused by protonation of the pyrrole nitrogen.     

RESONANCE RAMAN AND SURFACE-ENHANCED RESONANCE RAMAN SPECTROSCOPY OF HYPERICIN

Hypericin has been found to exhibit a variety of photodynamic effects. To correlate biological activity with molecular structure, complete physical characterization of hypericin is required. The vibrational spectrum has been determined and resonance Raman and surface enhanced resonance Raman scattering spectra are reported. In addition, the Raman spectrum of a model compound has been studied to facilitate assignment of the vibrational modes of hypericin.     

对苯二胺和N-取代衍生物正离子自由基的共振喇曼光谱研究

本文中报道了对苯二胺和四种N-烷基取代衍生物正离子自由基的共振喇曼光谱, 揭示了自由基是具有明显C=C和C=N双键性质的半醌式结构, N原子上给电子基团的取代引起上述化学键振动峰低频移动, 反映出结构一端N上有烷基的自由基中与取代基直接相连的N原子失去一个p电子带正电荷, 并吸引环上的π电子形成一定程度C=N双键. 共振喇曼光谱随激发光波长的变化表明, 自由基的两个可见电子吸收带分别主要产生于环结构的π→π*和包含N原子结构的n→π*电子跃迁。     

2—乙基己基膦酸单2—乙基己基酯与钴,镍,铜,锌固体萃合物的研究

酸性磷(瞵)酸酯是一类重要的萃取剂,它们对金属离子的萃取性能和机理研究巳有报导,但大多限于溶液体系。酸性磷酸酯金属萃合物的研究也有报导,但对固态烷基膦酸单烷基酯金属萃合物方面的报导较少。本文报导2-乙基已基膦酸2-乙基已基酯(简称HEH(EH)P或HA)金属(M=Co、Ni、Cu、Zn)固体萃合物的磁性,电子光谱和红外光谱,结合热分析结果对萃合物的成键特性和可能构型进行了讨论。     

晶体中铜锌铁钙镁镍钴测定

讨论了火焰原子吸收法测定晶体中铜、锌、铁、钙、镁和催化极谱法测定镍、钴的方法以及样品的采集、保存与消化处理。方法灵敏度高,操作简便、样品用量少,适合晶体中微量元素的测定。     

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.     

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.     

两次双波长分光光度法同时测定钴、镍、铜

本文用两次双波长分光光度法实现了三组分混合体系的同时测定。结果表明,两次双波长测量信号△A_1和△A_2的线性组合与混合体系中各组分浓度呈线性关系。该法用于钻、镍、铜三组分同时测定,定量结果令人满意。     

6-取代苯并噻唑偶氮苯甲酸型试剂与铁钴镍铜钯显色的反应

在显色剂BTAMB的苯并噻唑环的6-位引入不同的取代基,合成-类新显色剂2-[2’-(6’=取代苯并噻唑)-偶氮]-5-二甲氨基苯甲酸(6-R-BTAMB,R=CH_3,OCH_3,Cl,Br,NO_2,CH_3SO_2).研究了在表面活性剂或有机溶剂存在下,新试剂6-R-BTAMB与Fe(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)和Pd(Ⅱ)离子的络合显色反应及其光度分析特性.试验结果表明,引入的R基因明显地影响试剂的络合能力.并从R基因的电子效应等方面讨论了试剂结构与性能之间的关系.     

流动注射pH梯度技术－卡尔曼滤波分光光度法同时测定铜钴镍多元混合物

流动注射ｐＨ梯度技术－卡尔曼滤波分光光度法同时测定铜钴镍多元混合物毛东森，张国莹，陈同岳（上海工业大学化学化工系，上海，２０００７２）关键词：流动注射分析，梯度技术，卡尔曼滤波，分光光度法，同时测定探索不经任何分离而同时测定多个相互干扰组分混合物的分...