Crystal Structure of Taxinine A

ＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆＴａｘｉｎｉｎｅＡＷＵＮａｎ；ＬＵＹａｎｇ；ＺＨＥＮＧＱｉ－Ｔａｉ；ＦＡＮＧＷｅｉ－Ｓｈｕｏ；ＴＯＮＧＸｉａｏ－Ｊｉｅ；ＦＡＮＧＱｉ－Ｃｈｅｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＭａｔｅｒｉａＭｅｄｉｃａ，ＣｈｉｎｅｓｅＡｃ...     

Studies on the Absorption Spectra of Aqueous L-Tyrosine and Its Application

ＳｔｕｄｉｅｓｏｎｔｈｅＡｂｓｏｒｐｔｉｏｎＳｐｅｃｔｒａｏｆＡｑｕｅｏｕｓＬ－ＴｙｒｏｓｉｎｅａｎｄＩｔｓＡｐｐｌｉｃａｔｉｏｎ￥ＪｉａＺｈｅｎＹＡＮＧ；ＺｉＦｕＺＨＡＮＧ；ＪｕｎＬＩＵ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｌｉａｏｎｉｎｇ...     

FT-Raman Spectra Studies on Open Ferrocene

ＦＴ－ＲａｍａｎＳｐｅｃｔｒａＳｔｕｄｉｅｓｏｎＯｐｅｎＦｅｒｒｏｃｅｎｅＷＡＮＧＹｕｅ;ＪＩＡＮＧＳｈｉ－ｍｅｉ;ＦＡＮＹｕ－ｇｕｏａｎｄＳＵＮＣｈｕｎ－ｔｉｎｇ（ＴｈｅＫｅｙＬａｂｏｒａｔｏｒｙｆｏｒＭｏｌｅｃｕｌａｒＳｐｅｃｔｒｕｍａｎｄＳｔｒ...     

TERMINAL-GROUP EFFECT ON COAGGREGATION

ＴＥＲＭＩＮＡＬ－ＧＲＯＵＰＥＦＦＥＣＴＯＮＣＯＡＧＧＲＥＧＡＴＩＯＮ￥ＧｕｏＺｈｅｎＪＩ；ＸｉＬｉｎＣＵＩ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆ－ＯｒｇａｎｉｃＣｈｅｍｉｓｔｒｙ．ＡｃａｄｅｍｉａＳｉｎｉｃａ，３５４ＦｅｎｇｌｉｎＬｕ．Ｓｈａｎｇ...     

INDO Studies on the Electronic Structure of(2,4-C_7H_(11))_2Yb(DME)

ＩＮＤＯＳｔｕｄｉｅｓｏｎｔｈｅＥｌｅｃｔｒｏｎｉｃｓＳｔｒｕｃｔｕｒｅｏｆ（２,４－Ｃ７Ｈ１１）２Ｙｂ（ＤＭＥ）ＦＥＮＧＪｉａｎ－ｎａｎ,ＷＡＮＧＺｈｉ－ｚｈｏｎｇ,ＺＨＡＮＧＳｏ－ｂｏ,ＬＩＵＪｕ－ｚｈｅｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＴｈｅｏｒｅｔ...     

MANNICH REACTION ON 1,2-DIHYDRO-1-PYRROLIZINONE

ＭＡＮＮＩＣＨＲＥＡＣＴＩＯＮＯＮ１，２－ＤＩＨＹＤＲＯ－１－ＰＹＲＲＯＬＩＺＩＮＯＮＥＳｈａｏＪｌｅ；ＷＡＮＧ，ＦｕＳｈｕａｎｇＬＩＵ，ＳｈｏｕＦａｎｇＺＨＡＮＧ（ＳｈｅｎｙａｎｇＰｈａｒｎａｃｅｕｔｌｃａｌＵｎｉｖｅｗｓｉｔｙ，Ｓｈｅｎｙａａｎｇ...     

Initiation Mechanism of Polymerization of Acryl－amide by Ceric Ion／2－Benzoyl Acetanilide System

ＩｎｉｔｉａｔｉｏｎＭｅｃｈａｎｉｓｍｏｆＰｏｌｙｍｅｒｉｚａｔｉｏｎｏｆＡｃｒｙｌ－ａｍｉｄｅｂｙＣｅｒｉｃＩｏｎ／２－ＢｅｎｚｏｙｌＡｃｅｔａｎｉｌｉｄｅＳｙｓｔｅｍＤＯＮＧＪｉａｎ－ｈｕａ，ＤＥＮＧＣｈａｏ，ＱＩＵＫｕｎ－ｙｕａｎａｎｄＦＥＮＧ...     

INDOStudiesonElectronicStructuresof（C＿8H＿8）Ln（2，4－C＿4H＿11）（THF）（Ln＝Nd，Sm，Er）

ＩＮＤＯＳｔｕｄｉｅｓｏｎＥｌｅｃｔｒｏｎｉｃＳｔｒｕｃｔｕｒｅｓｏｆ（Ｃ＿８Ｈ＿８）Ｌｎ（２,４－Ｃ＿４Ｈ＿１１）（ＴＨＦ）（Ｌｎ＝Ｎｄ,Ｓｍ,Ｅｒ）ＷＡＮＧＺｈｉ－ｚｈｏｎｇ＊,ＦＥＮＧＪｉａｎ－ｎａｎ,ＺＨＡＮＧＳｏ－ｂｏａｎｄＬＩＵＪｕ－ｚｈ...     

Study on a New Type of All-Solid-StateReference Electrode

ＳｔｕｄｙｏｎａＮｅｗＴｙｐｅｏｆＡｌｌ－Ｓｏｌｉｄ－ＳｔａｔｅＲｅｆｅｒｅｎｃｅＥｌｅｃｔｒｏｄｅＣｈａｏＬｕｎＨＵＡＮＧ；ＪｕＪｉｅＲＥＮ；ＤａＦｅｎｇＸＵ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈａｒｍａｃｙ，ＨｅｂｅｉＭｅｄｉｃａｌＵｎｉｖｅｒｓｉｔｙ，...     

The Responsivity of the Bacteriorhodopsin Langmuir－Blodgett Film Intermittent Light

ＴｈｅＲｅｓｐｏｎｓｉｖｉｔｙｏｆｔｈｅＢａｃｔｅｒｉｏｒｈｏｄｏｐｓｉｎＬａｎｇｍｕｉｒ－ＢｌｏｄｇｅｔｔＦｉｌｍＩｎｔｅｒｍｉｔｔｅｎｔＬｉｇｈｔ￥ＧｕａｎｇＹｕＷＡＮＧ；ＪｉａｎＨｕａＹＡＮＧ；ＺｈｉＧｕａｎｇＺＨＡＮＧ；ＳｈｕＨｕａｎｇＬＩＮ...     

Heme axial methionine fluxion in Pseudomonas aeruginosa Asn64Gln cytochrome c551

Heme axial methionine ligands in ferricytochromes c552 from Hydrogenobacter thermophilus (HT) and Nitrosomonas europaea, both members of the cyt c8 family, display fluxional behavior. The ligand motion, proposed to be inversion at sulfur, results in an unusually small range of hyperfine shifts for heme substituents in these proteins. Herein, heme axial Met fluxion is induced in a structurally homologous cytochrome c551 from Pseudomonas aeruginosa (PA) by substituting heme pocket residue Asn64 with Gln. The mutant, PA-N64Q, displays a highly compressed range of heme substituent hyperfine shifts, temperature-dependent heme methyl resonance line broadening, low rhombic magnetic anisotropy, and a magnetic axes orientation consistent with Met orientational averaging. Analysis of NMR properties of PA-N64Q demonstrates that the heme pocket of the mutant resembles that of HT. This result confirms the importance of peripheral interactions and, in particular, residue 64 in determining axial Met orientation and heme electronic structure in proteins in the cyt c8 family.     

Photodissociation of heme distal methionine in ferrous cytochrome C revealed by subpicosecond time-resolved resonance Raman spectroscopy

Cytochrome c (cyt c) is an electron-transfer heme protein that also binds nitric oxide (NO). In resting cyt c, two endogenous ligands of the heme iron are histidine-18 (His) and methionine-80 (Met) side chains, and NO binding requires the cleavage of one of the axial bonds. Previous femtosecond transient absorption studies suggested the photolysis of either Fe-His or Fe-Met bonds. We aimed at unequivocally identifying the internal side chain that is photodissociated in ferrous cyt c and at monitoring heme structural dynamics, by means of time-resolved resonance Raman (TR3) spectroscopy with approximately 0.6 ps time resolution. The Fe-His stretching mode at 216 cm-1 has been observed in photoproduct TR3 spectra for the first time for a c-type heme. The same transient mode was observed for a model ferrous cyt c N-fragment (residues 1-56) ligated with two His in the resting state. Our TR3 data reveal that upon ferrous cyt c photoexcitation, (i) distal Met side chain is instantly released, producing a five-coordinated domed heme structure, (ii) proximal His side chain, coupled to the heme, exhibits distortion due to strain exerted by the protein, and (iii) alteration in heme-cysteine coupling takes place along with the relaxation of the protein-induced deformations of the heme macrocycle.     

Comparison of thioethers and sulfoxides as axial ligands for N-acetylmicroperoxidase-8: implications for oxidation of methionine-80 in cytochrome c

Methionine-80 (Met-80) in mitochondrial cytochrome c (cyt c) can be oxidized to the corresponding sulfoxide by reactive oxygen species, a reaction of potential biological significance. As an approach to investigating how oxidation of Met-80 would influence its interactions with heme iron, we have examined binding of 2-(methylthio)ethanol (MTE) and dimethyl sulfoxide (DMSO), models for the side chains of Met and Met(SO), respectively, to ferrous and ferric N-acetylmicroperoxidase-8 (AcMP8). We find that DMSO coordinates 1.2 kcal/mol less strongly to Fe(III)-AcMP8 than does MTE, although both ligands form low-spin complexes. Comparison of spectroscopic data for the DMSO complex of Fe(III)-AcMP8 with published data for the Met(SO)-80 form of ferric cyt c allows us to conclude that Met(SO)-80 does not coordinate to iron in the latter. DMSO coordinates to Fe(II)-AcMP8 1.3 kcal/mol more strongly than does MTE, whereas Met-80 and Met(SO)-80 are reported to have approximately equal affinity for Fe(II) in cyt c. This result suggests that the steric environment near the heme iron in cyt c discriminates against coordination of Met(SO)-80. Vacuum quantum chemical density functional theory calculations confirm the greater affinity of the sulfoxide and show that coordination via oxygen is strongly favored. Resonance Raman spectroscopic data indicate that the preference for coordination via oxygen is maintained in solution. The computational data further indicate that the DMSO complex derives significant enthalpic stabilization from pi back-bonding but that iron to sulfur pi back-bonding does not make a significant contribution to bonding in the thioether complex.     

Interaction Between Cytochrome c and the Hapten 2,4-Dinitro-fluorobenzene by Electrospray Ionization Mass Spectrometry

Allergic contact dermatitis is a delayed hypersensitivity reaction, which results from skin exposure to low molecular weight chemicals such as haptens. To clarify the pathogenic mechanism, electrospray ionization mass spectrometry (ESI-MS) and hydrogen/deuterium (H/D) exchange, as well as UV spectroscopy, were applied to determine the interaction between the model protein cytochrome c (cyt c) and the hapten 2,4-dinitro-fluorobenzene (DNFB). The ESI-MS results demonstrate that the conformation of cyt c can change from native folded state into partially unfolded state with the increase of DNFB. The equilibrium state H/D exchange followed by ESI-MS further confirms the above results. UV spectroscopy indicates that the strongfield coordination between iron of heme (prosthetic group) and His18 or Met80 of cyt c is not obviously affected by the hapten.     

Redox reactivity and reorganization energy of zinc cytochrome c cation radical

Little is known about transient intermediates in photoinduced electron-transfer reactions of metalloproteins. Oxidative quenching of the triplet state of zinc cytochrome c, 3Zncyt, is done at 20 degrees C, pH 7.00, and ionic strength of 1.00 M, conditions that suppress the thermal back-reaction and prolong the lifetime of the cation radical, Zncyt+. This species is reduced by [Fe(CN)6]4-, [W(CN)8]4-, [Os(CN)6]4-, [Mo(CN)8]4-, and [Ru(CN)6]4- complexes of similar structures and the same charge. The rate constants and thermodynamic driving forces for these five similar electron-transfer reactions were fitted to Marcus theory. The reorganization energy of Zncyt+ is lambda = 0.38(5) eV, lower than that of native cytochrome c, because the redox orbital of the porphyrin cation radical is delocalized and possibly because Met80 is not an axial ligand to the zinc(II) ion in the reconstituted cytochrome c. The rate constant for electron self-exchange between Zncyt+ and Zncyt, k11 = 1.0(5) x 10(7) M(-1) s(-1), is large owing to the extended electron delocalization and relatively low reorganization energy. These results may be relevant to zinc(II) derivatives of other heme proteins, which are often used in studies of photoinduced electron-transfer reactions.     

Control of cytochrome C redox potential: axial ligation and protein environment effects

Axial iron ligation and protein encapsulation of the heme cofactor have been investigated as effectors of the reduction potential (E degrees ') of cytochrome c through direct electrochemistry experiments. Our approach was that of partitioning the E degrees ' changes resulting from binding of imidazole, 2-methyl-imidazole, ammonia, and azide to both cytochrome c and microperoxidase-11 (MP11), into the enthalpic and entropic contributions. N-Acetylmethionine binding to MP11 was also investigated. These ligands replace Met80 and a water molecule axially coordinated to the heme iron in cytochrome c and MP11, respectively. This factorization was achieved through variable temperature E degrees ' measurements. In this way, we have found that (i) the decrease in E degrees ' of cytochrome c due to Met80 substitution by a nitrogen-donor ligand is almost totally enthalpic in origin, as a result of the stronger electron donor properties of the exogenous ligand which selectively stabilize the ferric state; (ii) on the contrary, the binding of the same ligands and N-acetylmethionine to MP11 results in an enthalpic stabilization of the reduced state, whereas the entropic effect invariably decreases E degrees ' (the former effect prevails for the methionine ligand and the latter for the nitrogenous ligands). A comparison of the reduction thermodynamics of cytochrome c and the MP11 adducts offers insight on the effect of changing axial heme ligation and heme insertion into the folded polypeptide chain. Principally, we have found that the overall E degrees ' increase of approximately 400 mV, comparing MP11 and native cytochrome c, consists of two opposite enthalpic and entropic terms of approximately +680 and -280 mV, respectively. The enthalpic term includes contributions from both axial methionine binding (+300 mV) and protein encapsulation of the heme (+380 mV), whereas the entropic term is almost entirely manifest at the stage of axial ligand binding. Both terms are dominated by the effects of water exclusion from the heme environment.     

新型环状金属Pt(Ⅱ)配合物:合成、晶体结构及光谱性质

合成了一种新的环状金属配体4-甲氧甲酰基-6-(4-甲基苯基)-2,2’-联吡啶(HL)及它的单核与双核Pt(Ⅱ)配合物[Pt(L)PPh₃](ClO₄)(1)与[Pt₂L₂(μ-dppm)](ClO₄)₂(2)(dppm=二(二苯基磷)-甲烷),并研究了它们的结构及光物理性质.配合物2的晶体结构分析表明,中心金属离子Pt(Ⅱ)呈扭曲平面正方形构型,桥配体dppm连接两个金属中心,0.3375 nm的Pt——Pt距离表明双核配合物中存在金属-金属相互作用.两配合物在～450 nm处的肩峰归属于金属到配体的电荷转移(MLCT)吸收,在固体及溶液中均观测到强烈的光致磷光发射.配合物1在固态时620 nm的低能发射归属为³(π-π)跃迁,并暗示配合物1晶体结构中存在分子间配体-配体相互作用,然而在溶液中仅观察到³MLCT发射光谱,但配合物2在固态及溶液中都观察到明显的金属和金属相互作用到配体的电荷转移(³MMLCT)发射.     

Synthesis and characterization of bioorganometallic conjugates composed of NCN-pincer platinum(II) complexes and uracil derivatives

The conjugation of the NCN-pincer platinum(II) complexes as an oraganometallic compound and the uracil derivatives as a nucleobase was demonstrated to give the corresponding bioorganometallics. The NCN-pincer ligands bearing the 6-ethynyl-1-octyluracil, 5-ethynyl-1-octyluracil, and the furanopyrimidine moiety were synthesized. In a crystal state, the NCN-pincer ligand bearing the 6-ethynyl-1-octyluracil moiety was found to form a hydrogen-bonded dimer through intermolecular hydrogen bonds between the uracil moieties, which was connected through π-π interaction between the uracil and benzene moieties of the NCN-pincer ligand. The reaction of the NCN-pincer ligand bearing the 6-ethynyl-1-octyluracil moiety with [Pt(tolyl-4)₂(SEt₂)]₂ led to the formation of the NCN-pincer platinum(II) complex bearing the 6-ethynyl-1-octyluracil moiety. The NCN-pincer platinum(II) complex bearing the furanopyrimidine moiety was obtained by the reaction of the NCN-pincer ligand bearing the furanopyrimidine moiety with [Pt(tolyl-4)₂(SEt₂)]₂. The single-crystal X-ray structure determination of the NCN-pincer platinum(II) complex bearing the furanopyrimidine moiety revealed the formation of the furanopyrimidine ring and the π stack dimer between the furanopyrimidine and benzene moieties of the NCN-pincer ligand in the crystal packing. The NCN-pincer platinum(II) complexes bearing the 6-ethynyl-1-octyluracil moiety or the furanopyrimidine moiety exhibited emission in both solution and solid states.     

吡啶、2-甲基吡啶存在下细胞色素c碱式异构化和配体细胞色素c配合物的电化学研究

用半胱氨酸修饰的金电极研究了吡啶、2 甲基吡啶存在下细胞色素c碱式异构化和配体结合细胞色素c的电化学。在此电极上 ,细胞色素c可发生准可逆的电极反应而吡啶结合细胞色素c和 2 甲基吡啶结合细胞色素c在循环伏安图上只给出还原峰。高浓度 (1.2 7mol·L- 1)的吡啶和 2 甲基吡啶可诱导碱式细胞色素c在中性条件下生成。进一步的研究表明 ,这种诱导作用与配体和细胞色素c的键合无关     

Protein-ligand docking against non-native protein conformers

In the validation of protein-ligand docking protocols, performance is mostly measured against native protein conformers, i.e. each ligand is docked into the protein conformation from the structure that contained that ligand. In real-life applications, however, ligands are docked against non-native conformations of the protein, i.e. the apo structure or a structure of a different protein-ligand complex. Here, we have constructed an extensive test set for assessing docking performance against non-native protein conformations. This new test set is built on the Astex Diverse Set (which we recently constructed for assessing native docking performance) and contains 1112 non-native structures for 65 drug targets. Using the protein-ligand docking program GOLD, the Astex Diverse Set and the new Astex Non-native Set, we established that, whereas docking performance (top-ranked solution within 2 A rmsd of the experimental binding mode) is approximately 80% for native docking, this drops to 61% for non-native docking. A similar drop-off is observed for sampling performance (any solution within 2 A): 91% for native docking vs 72% for non-native docking. No significant differences were observed between docking performance against apo and nonapo structures. We found that, whereas small variations in protein conformation are generally tolerated by our rigid docking protocol, larger protein movements result in a catastrophic drop-off in performance. Some docking performance and nearly all sampling performance can be recovered by considering dockings produced against a small number of non-native structures simultaneously. Docking against non-native structures of complexes containing ligands that are similar to the docked ligand also significantly improves both docking performance and sampling performance.