Feiler U, Albouy D, Robert B, Mattioli T A
Section de Biophysique des Protéines et des Membranes, DBCM, CEA and URA 1290 CNRS, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
Biochemistry. 1995 Sep 5;34(35):11099-105. doi: 10.1021/bi00035a015.
The protein binding interactions of the constituent bacteriochlorophyll a molecules of the primary electron donor, P840, in isolated reaction centers from Chlorobium limicola f thiosulphatophilum and the electronic symmetry of the radical cation P840+. were determined using near-infrared Fourier transform (FT) Raman spectroscopy excited at 1064 nm. The FT Raman vibrational spectrum of P840 indicates that it is constituted of a single population of BChl a molecules which are spectrally indistinguishable. The BChl a molecules of P840 are pentacoordinated with only one axial ligand on the central Mg atom, and the pi-conjugated C2 acetyl and C9 keto carbonyls are free of hydrogen-bonding interactions. The FT Raman spectrum of P840+. exhibits a 1707 cm-1 band attributable to a BChl a C9 keto carbonyl group vibrational frequency that has upshifted 16 cm-1 upon oxidation of P840; this upshift is exactly one-half of that expected for the one-electron oxidation of monomeric BChl a in vitro. The 16 cm-1 upshift, thus, indicates that the resulting +1 charge is equally shared between two BChl a molecules. This situation is markedly different from that of the oxidized primary donor of the purple bacterial reaction center of Rhodobacter sphaeroides, (i) which exhibits a 1717 cm-1 band that has upshifted 26 cm-1, indicating an asymmetric distribution of the resulting +1 charge over the two constituent BChl a molecules, and (ii) whose H-bonding pattern with respect to the pi-conjugated carbonyl groups is asymmetric.(ABSTRACT TRUNCATED AT 250 WORDS)
利用在1064nm激发的近红外傅里叶变换（FT）拉曼光谱，测定了嗜硫代硫酸盐绿弯菌分离反应中心中初级电子供体P840的组成成分细菌叶绿素a分子的蛋白质结合相互作用以及自由基阳离子P840⁺的电子对称性。P840的FT拉曼振动光谱表明，它由单一群体的光谱无法区分的细菌叶绿素a分子组成。P840的细菌叶绿素a分子在中心镁原子上只有一个轴向配体，呈五配位，且π共轭的C2乙酰基和C9酮羰基没有氢键相互作用。P840⁺的FT拉曼光谱显示出一条1707cm⁻¹的谱带，归因于细菌叶绿素a C9酮羰基的振动频率，该频率在P840氧化后上移了16cm⁻¹；这种上移恰好是体外单体细菌叶绿素a单电子氧化预期值的一半。因此，16cm⁻¹的上移表明所产生的+1电荷在两个细菌叶绿素a分子之间平均分配。这种情况与球形红细菌紫色细菌反应中心的氧化初级供体明显不同，（i）后者显示出一条1717cm⁻¹的谱带，上移了26cm⁻¹，表明所产生的+1电荷在两个组成细菌叶绿素a分子上的分布不对称，（ii）其相对于π共轭羰基的氢键模式也是不对称的。（摘要截短于250字）
