灰色链霉菌YD3309菌丝体抗菌活性成分研究

采用生物活性跟踪法,从一株灰色链霉菌菌丝体中分离得到2个具有抑菌活性的化合物,通过核磁共振波谱和质谱等技术鉴定2个化合物的结构为新刺孢霉素A(1)和N-乙酰基色氨醇(2);化合物1首次从放线菌中分离得到。抑菌活性测定结果表明:化合物1和2对番茄灰霉病菌(Botrytis cinerea)、茄子黄萎病菌(Verticillium dahliae)和辣椒枯萎病菌(Fusarium oxysporum)等多种蔬菜病原真菌有抑制作用,其中化合物1对番茄灰霉病菌和番茄早疫病菌菌丝具有强烈的抑制作用,化合物2对茄子黄萎病菌的菌丝具有强烈的抑制作用;化合物1对番茄灰霉病菌和番茄早疫病菌菌丝生长的半抑菌浓度(IC_(50))分别为30.6和28.8 mg/L,化合物2对茄子黄萎病菌菌丝生长的半抑菌浓度(IC50)为34.3 mg/L。     

植物内生真菌Fusarium guttiforme次生代谢产物研究CSCD

采用多种色谱分离方法从植物内生真菌Fusarium guttiforme次生代谢产物中分离纯化得到7种化合物,并通过核磁共振和质谱等波谱学手段鉴定其结构,包括一个新型含过氧键的二聚苯衍生物:fucinum A(1)以及6个已知化合物:(Z)-1-hydroxy-4-(2-nitroethenyl)benzene(2)、对羟基苯甲醛(3)、stigmasta-4,6,8(14)-trien-3-one(4)、stigmast-4-ene-3,6-dione(5)、麦角甾醇(6)、5-羟甲基糠醛(7)均首次从该真菌次生代谢产物中分离。此外,对上述化合物进行NO生成抑制活性实验的研究,其结果表明化合物1、2对NO产生具有一定的抑制作用,IC_(50)值分别为48.1和46.6μmol/L。     

鹅不食草中具有抗菌活性的三萜类成分

从鹅不食草(Centipeda minima)全草的乙醇提取物中分离得到3个乌苏烷型三萜,其中一个新化合物用波谱学方法鉴定为ursane-20(30)-en-3β,16β,21α-triol(1),二个已知化合物的结构分别为taraxasterol acetate(2),taraxasterol(3)。抗菌试验表明化合物2和3具有较强的抗菌活性。     

源于植物内生无花果拟盘多毛孢真菌的新色原酮类次生代谢产物研究

从植物内生真菌无花果拟盘多毛孢菌株(Pestalotiopsis fici;AS3.9138=W106-1)的放大发酵粗提物中分离得到4个异戊二烯基取代的色原酮类新结构次生代谢产物pestaloficiolsM-P(1-4),并应用质谱和核磁共振技术确定了上述化合物的结构。生物活性测试结果表明化合物2能够抑制HIV-1病毒在C8166细胞中的复制;化合物3和4对宫颈癌细胞(HeLa)具有细胞毒活性;另外,化合物3对烟曲霉Aspergillus fumigatus也具有较强的抑制活性。     

1株白木香内生真菌中抗肿瘤活性成分的分离纯化和结构鉴定

采用活性追踪的方法对白木香内生真菌螺旋木霉Trichoderma spiraleA17的抗肿瘤活性代谢产物进行了分离纯化和结构鉴定。通过凝胶柱层析和反相硅胶柱层析,从其发酵液的活性组分中分离到2个无色针晶化合物,质谱和核磁共振的鉴定结果表明化合物1是一个八氢萘衍生物,命名为木霉酸(Trichodermic acid),化合物2是酪醇(Tyrosol)。活性实验显示化合物1对SF-268、MCF-7和NCI-H460 3种肿瘤细胞株都具有显著的增殖抑制活性,而化合物2对这3种肿瘤细胞株只有微弱的增殖抑制活性。     

异土木香内酯及土木香内酯的结构修饰研究

对土木香根中两个主要倍半萜内酯-异土木香内酯(1)和土木香内酯(2)进行结构修饰,研究结构修饰产物的体外抑制人肝癌细胞(HepG2)增殖的活性,并进行构效关系的研究.经结构修饰得到4,15β-环氧异土木香内酯(1b)、5α,6α-环氧土木香内酯(2b)、13α-甲氧基甲基土木香内酯(2d)等11个化合物,其中产物2d未见有文献报道.产物1b、2b对HepG2细胞的抑制作用均强于母体化合物,其他化合物的抑制活性均弱于母体化合物.推断11,13-去氢内酯基团是该类倍半萜内酯体外抑制HepG2肿瘤细胞增殖活性必需的活性基团,环氧基团的引入对化合物的抑制HepG2肿瘤细胞增殖活性具有促进作用.     

黄白侧耳大米固体发酵次级代谢产物分析

从黄白侧耳Pleurotus cornucopiae大米固体发酵物中分离得到4个苯酞类化合物,2个为新结构化合物:2-(ethoxymethyl)-3,5-diethoxybenzyl acetate(1)、2-(acetoxymethyl)-4,6-dimethoxybenzyl tridecanoate(2),2个为已知化合物:5,7-dimethoxyisobenzofuran-1(3H)-one(3)、4,6-dimethoxyisobenzofuran-1(3H)-one(4)。对化合物进行生物活性评价发现,化合物3、4具有抑制肿瘤细胞HeLa生长活性,IC50值分别为66.2和65.7μmol/L;化合物3和4对LPS诱导的RAW264.7细胞释放NO有抑制作用,IC50值分别为17.2和67.9μmol/L。     

白黄小脆柄菇发酵液中的一个新的血苋烷型倍半萜（英文）北大核心CSCD

从白黄小脆柄菇(Psathyrellacandolleana)发酵液提取物的乙酸乙酯层中分离得到一个新的血苋烷型倍半萜(1)和一个已知的没药烷型倍半萜(2)。通过质谱、核磁等方法确定化合物1的结构为15-hydroxy-drimenol。通过文献对照核磁数据确定化合物2为1α-hydroxy-bisabola-2,10-dien-4-one。     

丽江乌头根中的二萜生物碱成分研究

为了寻找丽江乌头中结构新颖的化合物,丰富丽江乌头的化学成分多样性,本文对丽江乌头(Aconitum forrestii Stapf)根部的化学成分进行研究,采用硅胶柱层析从其乙醇提取物中分离得到14个化合物。通过HR-ESI-MS、1D和2D NMR等波谱技术鉴定了它们的结构,其中化合物1是一个新的乌头碱型二萜生物碱,命名为8-O-methyl-14-O-anisoylchasmanine(1)。其余13个化合物均为已知化合物:14-acetoxy-8-O-methylsachaconitine(2)、14-acetyltalatizamine(3)、talatisamine(4)、chasmanine(5)、ezochasmanine(6)、crassicautine(7)、geniculatine C(8)、cammaconine(9)、vilmoraconitine(10)、aconitramine A(11)、vilmorrianine G(12)、hemsleyaconitine G(13)和heterophylloidine(14)。测试了所有化合物对阿霉素诱导的H9c2心肌细胞损伤的保护活性,结果显示化合物3、10、11和12表现出一定的保护作用。     

粉防己根的化学成分及抗肝纤维化活性研究CSCD

研究粉防己根的化学成分和抗肝纤维化活性。采用硅胶、Sephadex LH-20、ODS和半制备HPLC对粉防己根的乙醇提取物进行分离纯化得到13个化合物。根据化合物的理化性质和波谱数据鉴定其结构,分别为cyclanoline(1)、coclaurine(2)、5-hydroxymethyl-1-[2-(4-hydroxyphenyl)-ethyl]-1H-pyrrole-2-carbaldehyde(3)、isosalsoline(4)、thalifoline(5)、northalifoline(6)、2-甲基-3-羟基吡啶(7)、(+)-lyoniresinol(8)、icariside B5(9)、丁香酸(10)、对羟基苯乙酸(11)、对羟基苯甲酸(12)、对羟基苯乙酸甲酯(13)。化合物1~13为首次从该植物中分离得到,在千金藤属植物中化合物3、4、6~9也未见报道。初步评价了化合物1~13的抗肝纤维化活性,化合物2、5、6、10~12对TGF-β1诱导的LX-2细胞增殖具有显著抑制作用。     

Spectral and thermodynamic properties of Ag(I), Au(III), Cd(II), Co(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(IV), and Zn(II) binding by methanobactin from Methylosinus trichosporium OB3b

Methanobactin (mb) is a novel chromopeptide that appears to function as the extracellular component of a copper acquisition system in methanotrophic bacteria. To examine this potential physiological role, and to distinguish it from iron binding siderophores, the spectral (UV–visible absorption, circular dichroism, fluorescence, and X-ray photoelectron) and thermodynamic properties of metal binding by mb were examined. In the absence of Cu(II) or Cu(I), mb will bind Ag(I), Au(III), Co(II), Cd(II), Fe(III), Hg(II), Mn(II), Ni(II), Pb(II), U(VI), or Zn(II), but not Ba(II), Ca(II), La(II), Mg(II), and Sr(II). The results suggest metals such as Ag(I), Au(III), Hg(II), Pb(II) and possibly U(VI) are bound by a mechanism similar to Cu, whereas the coordination of Co(II), Cd(II), Fe(III), Mn(II), Ni(II) and Zn(II) by mb differs from Cu(II). Consistent with its role as a copper-binding compound or chalkophore, the binding constants of all the metals examined were less than those observed with Cu(II) and copper displaced other metals except Ag(I) and Au(III) bound to mb. However, the binding of different metals by mb suggests that methanotrophic activity also may play a role in either the solubilization or immobilization of many metals in situ.     

Circular dichroism spectra of DNA quadruplexes [d(G(5)T(5))](4) as formed with G(4) and T(4) tetrads and [d(G(5)T(5)). d(A(5)C(5))]2 as formed with Watson-Crick-like (G-C)(2) and (T-A)(2) tetrads

We utilize electrophoresis and find that a thermally treated equimolar mixture of the oligonucleotide d(G(5)T(5)) and its complementary oligonucleotide d(A(5)C(5)) exhibits either two bands or a single band in one lane, depending on the conditions of the incubation solutions. The thermally treated d(G(5)T(5)) solution loaded in a different lane exhibits a single band of the parallel quadruplex [d(G(5)T(5))](4), which is composed of homocyclic hydrogen-bonded G(4) and T(4) tetrads previously proposed. For the thermally treated equimolar mixture of d(G(5)T(5)) and d(A(5)C(5)), the fast band is assigned to a Watson-Crick d(G(5)T(5)). d(A(5)C(5)) duplex, so that the slow band with the same low mobility as that of [d(G(5)T(5))](4) may be assigned to either [d(G(5)T(5))](4) itself or a [d(G(5)T(5)). d(A(5)C(5))](2) quadruplex. If the latter compound is true, this may be the antiparallel quadruplex composed of the heterocyclic hydrogen-bonded G-C-G-C and T-A-T-A tetrads proposed previously. After removing these three bands for the duplex and two kinds of hypothetical quadruplexes, we electrophoretically elute the corresponding compounds in the same electrophoresis buffer using an electroeluter. The eluted compounds are ascertained to be stable by electrophoresis. The circular dichroism (CD) and UV absorption spectra measured for the three isolated compounds are found to be clearly different. For the electrophoretic elution of the hypothetical [d(G(5)T(5))](4) quadruplex, the result of the molecularity of n = 4 obtained from the CD melting curve analysis provides further support for the formation of the parallel [d(G(5)T(5))](4) quadruplex already proposed. For the thermally treated equimolar mixture of d(G(5)T(5)) and d(C(5)A(5)), the fast band with a molecularity of n = 2 corresponds to the Watson-Crick duplex, d(G(5)T(5)). d(A(5)C(5)). The slow band with a molecularity of n = 4 indicates the antiparallel quadruplex [d(G(5)T(5)). d(A(5)C(5))](2), whose observed CD and UV spectra are different from those of [d(G(5)T(5))](4). By electrophoresis, after reannealing the eluted compound [d(G(5)T(5)). d(A(5)C(5))](2), a distinct photograph showing the band splitting of this quadruplex band into the lower duplex and upper quadruplex bands is not possible; but by a transilluminator, we occasionally observe this band splitting with the naked eye. The linear response polarizability tensor calculations for the thus determined structures of the [d(G(5)T(5))](4) quadruplex, the McGavin-like [d(G(5)T(5)). d(A(5)C(5))](2) quadruplex, and the Watson-Crick d(G(5)T(5)). d(A(5)C(5)) duplex are found to qualitatively predict the observed CD and UV spectra.     

Reconstitution of vacuolar-type rotary H+-ATPase/synthase from Thermus thermophilus

Vacuolar-type rotary H(+)-ATPase/synthase (V(o)V(1)) from Thermus thermophilus, composed of nine subunits, A, B, D, F, C, E, G, I, and L, has been reconstituted from individually isolated V(1) (A(3)B(3)D(1)F(1)) and V(o) (C(1)E(2)G(2)I(1)L(12)) subcomplexes in vitro. A(3)B(3)D and A(3)B(3) also reconstituted with V(o), resulting in a holoenzyme-like complexes. However, A(3)B(3)D-V(o) and A(3)B(3)-V(o) did not show ATP synthesis and dicyclohexylcarbodiimide-sensitive ATPase activity. The reconstitution process was monitored in real time by fluorescence resonance energy transfer (FRET) between an acceptor dye attached to subunit F or D in V(1) or A(3)B(3)D and a donor dye attached to subunit C in V(o). The estimated dissociation constants K(d) for V(o)V(1) and A(3)B(3)D-V(o) were ～0.3 and ～1 nm at 25 °C, respectively. These results suggest that the A(3)B(3) domain tightly associated with the two EG peripheral stalks of V(o), even in the absence of the central shaft subunits. In addition, F subunit is essential for coupling of ATP hydrolysis and proton translocation and has a key role in the stability of whole complex. However, the contribution of the F subunit to the association of A(3)B(3) with V(o) is much lower than that of the EG peripheral stalks.     

Two interconverting pentaiodide forms in the cyclomaltohexaose (alpha-cyclodextrin) polyiodide inclusion complex with sodium ion: dielectric and Raman spectroscopy studies

The polycrystalline inclusion complex of cyclomaltohexaose, (alpha-CD)(2) x NaI(5) x 8H(2)O, has been investigated via dielectric spectroscopy over a frequency range of 0-100 kHz and the temperature range of 125-450 K. Additionally, a Raman spectroscopy study was accomplished in the temperature ranges of (i) 153-298 K and (ii) 303-413 K. The ln sigma versus 1/T variation revealed the order-disorder transition of some normal hydrogen bonds to those of a flip-flop type at 200.9 K. From 278.3 up to 357.1K, the progressive transformation (H(2)O)(tightly bound)-->(H(2)O)(easily movable) takes place resulting in an Arrhenius linear increment of the ac-conductivity with activation energy E(a)=0.32 eV. In the range of 357.1-386.1K a second linear part with E(a)=0.55 eV is observed, indicating the contribution of sodium ions via the water-net.The rapid decrease of the ac-conductivity at T>386.1K is due to the removal of the water molecules from the crystal lattice, whereas the abrupt increase at T>414.9 K is caused by the sublimation of iodine.The Raman bands at 160 and 169 cm(-1) indicate the coexistence of (I(2) x I(-) x I(2)) and (I3(-) x I(2)<-->I(2) x I3(-)) units, respectively.The (I3(-) x I(2)<-->I(2) x I3(-)) units are presented as form (I), and their central I(-) ion is disordered in occupancy ratio different from 50/50 (e.g., ...60/40...70/30...).The(I(2) x I(-) x I(2)) units are displayed by the 2 equiv forms (IIa) and (IIb). In (IIa) the central I(-) ion is twofold disordered in an occupancy ratio of 50:50, whereas in (IIb) the central I(-) ion is well-ordered and equidistant from the two I(2) molecules. At low temperatures the transformation (I)-->(IIa) takes place, whereas at high temperatures the inverse one (IIa)-->(I) happens. X-ray powder diffraction and Rietveld analysis revealed a triclinic crystal form with space group P1 and lattice parameters that are in good agreement with the theoretical values.     

Electronic ground states of low-spin iron(III) porphyrinoids

Six-coordinate low-spin iron(III) porphyrinates adopt either common (d(xy))(2)(d(xz),d(yz))(3) or less common (d(xz),d(yz))(4)(d(xy))(1) ground state. In this review article, three major factors that affect the electronic ground state have been examined. They are (i) nature of the axial ligand, (ii) electronic effect of peripheral substituents, and (iii) deformation of porphyrin ring. On the basis of the (1)H NMR, (13)C NMR, and EPR data, it is now clear that (i) the axial ligands with low-lying pi* orbitals such as tert-butylisocyanide and 4-cyanopyridine, (ii) the electron donating groups at the meso-carbon atoms, and (iii) the ruffled deformation of porphyrin ring stabilize the (d(xz),d(yz))(4)(d(xy))(1) ground state. By manipulating these factors, we are able to prepare various low-spin iron(III) porphyrinates with unusual electronic structures such as bis(imidazole) complexes with the (d(xz),d(yz))(4)(d(xy))(1) ground state or bis(tert-butylisocyanide) complexes with the (d(xy))(2)(d(xz),d(yz))(3) ground state; bis(imidazole) and bis(tert-butylisocyanide) complexes usually adopt the (d(xy))(2)(d(xz),d(yz))(3) and (d(xz),d(yz))(4)(d(xy))(1) ground state, respectively.     

High-rate ferric sulfate generation by a Leptospirillum ferriphilum-dominated biofilm and the role of jarosite in biomass retention in a fluidized-bed reactor

The aims of this work were to develop a high-rate fluidized-bed bioprocess for ferric sulfate production, to characterize biomass retention, and to determine the phylogeny of the enrichment culture. After 7 months of continuous enrichment and air aeration at 37 degrees C, the iron oxidation rate of 8.2 g Fe(2+) L(-1)h(-1) (4.5.10(-12) g Fe(2+) cell(-1) h(-1)) was obtained at a hydraulic retention time (HRT) of 0.6 h. However, oxygen supply became the rate-limiting factor. With gas mixture (99.5% O(2)/0.5% CO(2) (vol/vol)) aeration and HRT of 0.2 h, the iron oxidation rate was 26.4 g Fe(2+) L(-1)h(-1) (1.0.10(-11) g Fe(2+) cell(-1) h(-1)). Leptospirillum sp. was predominant in the mesophilic fluidized-bed reactor (FBR) enrichment culture as determined by fluorescent in situ hybridization, while Acidithiobacillus ferrooxidans was not detected. Denaturing gradient gel electrophoresis (DGGE) of the amplified partial 16S rDNA showed only three bands, indicating a simple microbial community. DGGE fragment excision and sequencing showed that the populations were related to L. ferriphilum (100% similarity in sequence) and possibly to the genus Ferroplasma (96% similarity to F. acidiphilum). Jarosite precipitates accumulated on the top of the activated carbon biomass carrier material, increasing the rate of iron oxidation. The activated carbon carrier material, jarosite precipitates, and reactor liquid contained 59% (or 3.71.10(9) cells g(-1)), 31% (or 3.12.10(10) cells g(-1)) and 10% (or 1.24.10(8) cells mL(-1)) of the total FBR microbes, respectively, demonstrating that the jarosite precipitates played an important role in the FBR biomass retention.     

Physicochemical and biological properties of 6(1),6(3),6(5)-tri-O-alpha-maltosyl-cyclomaltoheptaose (6(1),6(3),6(5)-tri-O-alpha-maltosyl-beta-cyclodextrin)

A unique multibranched cyclomaltooligosaccharide (cyclodextrin, CD) of 6(1),6(3),6(5)-tri-O-alpha-maltosyl-cyclomaltoheptaose [6(1),6(3),6(5)-tri-O-alpha-maltosyl-beta-cyclodextrin, (G(2))(3)-betaCD] was prepared. The physicochemical and biological properties of (G(2))(3)-betaCD were determined together with those of monobranched CDs (6-O-alpha-D-glucopyranosyl-alpha-cyclodextrin (G(1)-alphaCD), 6-O-alpha-D-glucopyranosyl-beta-cyclodextrin (G(1)-betaCD), and 6-O-alpha-maltosyl-beta-cyclodextrin (G(2)-betaCD)). NMR spectra of (G(2))(3)-betaCD were measured using various 2D NMR techniques. The solubility of (G(2))(3)-betaCD in water and MeOH-water solutions was extremely high in comparison with nonbranched betaCD and was about the same as that of the other monobranched betaCDs. The formation of an inclusion complex of (G(2))(3)-betaCD with stereoisomers (estradiol, retinoic acid, quinine, citral, and glycyrrhetinic acid) depends on the cis-trans isomers of guest compounds. The cis isomers of estradiol, retinoic acid, and glycyrrhetinic acid were included more than their trans isomers, while the trans isomers of citral and quinine fit more tightly than their cis isomers. (G(2))(3)-betaCD was the most effective host compound in the cis-trans resolution of glycyrrhetinic acid. Among the branched betaCDs, (G(2))(3)-betaCD exhibited the weakest hemolytic activity in human erythrocytes and showed negligible cytotoxicity in Caco-2 cells up to 200 microM. These results indicate unique characteristics of (G(2))(3)-betaCD in some biological responses of cultured cells.     

Maintenance and growth requirements in the metabolism of Debaryomyces hansenii performing xylose-to-xylitol bioconversion in corncob hemicellulose hydrolyzate

In order to improve the biotechnological production of xylitol, the metabolism of Debaryomyces hansenii NRRL Y-7426 in corncob hemicellulose hydrolyzate has been investigated under different conditions, where either maintenance or growth requirements predominated. For this purpose, the experimental results of two sets of batch bioconversions carried out alternatively varying the starting xylose concentration in the hydrolyzate (65.6 < or = S(0) < or = 154.7 g L(-1)) or the initial biomass level (3.0 < or = X(0) < or = 54.6 g(DM) L(-1)) were used to fit a metabolic model consisting of carbon material and ATP balances based on five main activities, namely fermentative assimilation of pentoses, semi-aerobic pentose-to-pentitol bioconversion, biomass growth on pentoses, catabolic oxidation of pentoses, and acetic acid and NADH regeneration by the electron transport system. Such an approach allowed separately evaluating the main bioenergetic constants of this microbial system, that is, the specific rates of ATP and xylose consumption due to maintenance (m(ATP) = 21.0 mmol(ATP) C-mol(DM) (-1)h(-1); m(Xyl) = 6.5 C-mmol(Xyl) C-mol(DM) (-1)h(-1)) and the true yields of biomass on ATP (Y(ATP) (max) = 0.83 C-mol(DM) mol(ATP) (-1)) and on xylose (Y(Xyl) (max) = 0.93 C-mol(DM) C-mol(Xyl) (-1)). The results of this study highlighted that the system, at very high S(0) and X(0) values, dramatically increased its energy requirements for cell maintenance, owing to the occurrence of stressing conditions. In particular, for S(0) > 130 g L(-1), these activities required an ATP consumption of about 2.1 mol(ATP) L(-1), that is, a value about seven- to eightfold that observed at low substrate concentration. Such a condition led to an increase in the fraction of ATP addressed to cell maintenance from 47% to 81%. On the other hand, the very high percentage of ATP addressed to maintenance (> 96%) at very high cell concentration (X(0) > or = 25 g(DM) L(-1)) was likely due to the insufficient substrate to sustain the growth.     

Mass spectrometry identification of covalent attachment sites of two related estrogenic ligands on human estrogen receptor alpha

A purified preparation of human estrogen receptor alpha (hERalpha) ligand-binding domain (LBD) involving mainly the Ser(309)Ala(569) (approximately 30%) and Ser(309)Ala(571) (approximately 63%) ER portions was used to identify the covalent attachment sites of two closely related estrogenic ER affinity labels 17alpha-bromoacetamidopropylestradiol (17BAPE(2)) and 17alpha-bromoacetamidomethylestradiol (17BAME(2)). To identify and quantify the electrophile covalent attachment sites, [(14)C]17BAPE(2)- and [(14)C]17BAME(2)-alkylated hLBD preparations were trypsinized and submitted to HPLC. In each case, two radioactive fractions were obtained. Mass spectrometry analyses of the two fractions showed signals, which closely matched the molecular masses of alkylated Cys(530)Lys(531) and Cys(417)Arg(434) hLBD tryptic peptides. The covalent attachment of the two electrophiles on hLBD was assigned to the S atoms of Cys(530) and Cys(417). However, the balance between Cys(530) and Cys(417) labeling markedly differed according to the affinity label used, with the Cys(530)/Cys(417) ratio being 2.1 for 17BAPE(2), and 20 for 17BAME(2). We attempted to interpret the covalent attachment of electrophiles by molecular modeling using the crystallographic structure of LBD bound to E(2). In agreement with the different levels of Cys(417) alkylation, the LBD model with unchanged helices could not easily account for Cys(417) labeling by 17BAME(2), whereas favorable results were obtained through 17BAPE(2) docking. Moreover, labeling at Cys(530) by the two electrophiles could not be interpreted using the LBD model. This indicates that some states of solute LBD bound to the estrogenic E(2) 17alpha-derivatives differ from the structure of crystallized LBD bound to E(2).