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1.
Janusz Dabrowski Michael Hauck Elzbieta Romanowska Andrzej Gamian 《Carbohydrate research》1988,180(2):163-174
The main features of the primary structure of the octasaccharide, -
-Glcp-(1→2)--
-Glcp-(1→2)-[-
-GalpNAc- (1→3)]--
-Galp-(1→3)--
-Glcp-(1→3)-[-
-Hepp-(1→7)]--
-Hepp-(1→3)--
-Hep, have been determined in the ab initio manner by 1H-n.m.r. spectroscopy without resorting to biochemical methods of analysis. Several nontypical interresidue n.O.e. values point to a preferred solution conformation of the molecule. 相似文献
2.
The structure of the K40 antigenic capsular polysaccharide (K40 antigen) of E. coli O8:K40:H9 was elucidated by determination of the composition, 1H- and 13C-n.m.r. spectroscopy, periodate oxidation and Smith degradation, and methylation analysis. The K40 polysaccharide consists of [(O-β-
-glucopyranosyluronic acid)-(1→4)-O-(2-acetamido-2-deoxy--
-glucopyranosyl)-(1→6)-O-(2-acetamido-2-deoxy--
-glucopyranosyl)-(1→4)] repeating units. All of the glucuronic acid residues are substituted amidically with
-serine. 相似文献
3.
Gaspare Barone Maria Michela Corsaro Cristina De Castro Rosa Lanzetta Lorenzo Mangoni Michelangelo Parrilli 《Carbohydrate research》1994,260(2):259-270
The polysaccharide fraction from Ceratozamia spinosa appears to be made up mainly by a chemically homogeneous polysaccharide but with a wide range of molecular weight. By NMR and chemical degradative methods, it is shown to consist essentially of a backbone of alternate → 4)-β-
-GlcpA-(1 → and → 2)--
-Manp-(1 → units. On the 4 position of the latter, β-
-GlcpA residues are linked. End units of -
-Ara f, β-
-Xylp, -
-Rhap, and -
-3-OMe-Rhap are linked to C-3 and/or C-4 positions of β-
-Glc pA residues. 相似文献
4.
Jeanny S. Maciel Luciano S. Chaves Bartolomeu W.S. Souza Drlio I.A. Teixeira Ana L.P. Freitas Judith P.A. Feitosa Regina C.M. de Paula 《Carbohydrate polymers》2008,71(4):559-565
Water soluble polysaccharide from Gracilaria birdiae cultivated along the northeast coast of Brazil was characterized by infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The composition of the polysaccharide in wt% was determined as: β-d-galp (50.3%), 3,6-anhydro--l-galp (40.5%) and --l-galp-6 sulfate (9.2%). The ratio of l/d units (β-d-galp units and 3,6-anhydro--l-galp + -l-galp-6 sulfate) is that of an ideal agarose. The sulfate content calculated by S% accounts for 6.4%. 1D and 2D NMR techniques were employed in order to assign the spin system of polysaccharide without partial degradation. The structure is composed of → 4-3,6-anhydro--l-galp (1 → 3)β-d-galp 1 → segments, with the possibility of a -l-galp unit substituted at the 6-position by sulfate ester. 相似文献
5.
Three main saponins were isolated from the seeds of Albizzia lucida. Their structures were established by spectral analyses and chemical and enzymatic transformations as 3-O-[β-
-xylopyranosyl(1→2)--
-arabinopyranosyl (1→6)] [β-
-glucopyranosyl (1→2)] β-
-glucopyranosyl echinocystic acid; 3-O-[-
-arabinopyranosyl (1→6)][β-
-glucopyranosyl (1→2)]-β-
-glucopyranosyl echinocystic acid and 3-O-[β-
-xylopyranosyl (1→2)-β-
-fucopyranosyl (1→6)-2-acetamido-2-deoxy-β-
-glucopyranosyl echinocystic acid, characterized as its methyl ester. 相似文献
6.
A new steroidal glycoside, agaveside D, isolated from the fruits of Agave cantata was characterized as 3β-{-
-rhamnopyranosyl-(1→2), β-
-glycopyranosyl-(1→3)-β-
-glucopyranosyl[β-
-xylopyransoyl-(1→4)--
-rhamnopyranosyl-(1→2)]-β-
-glucopyranosyl}-25R-5- spirostane on the basis of chemical degradation and spectrometry. 相似文献
7.
Umberto Belluco Roberta Bertani Rino A. Michelin Mirto Mozzon Franco Benetollo Gabriella Bombieri Robert J. Angelici 《Inorganica chimica acta》1995,240(1-2):567-574
The chloro complexes trans-[Pt(Me)(Cl)(PPh3)2], after treatment with AgBF4, react with 1-alkynes HC---C---R in the presence of NEt3 to afford the corresponding acetylide derivatives trans-[Pt(Me) (C---C---R) (PPh3)2] (R = p-tolyl (1), Ph (2), C(CH3)3 (3)). These complexes, with the exception of the t-butylacetylide complex, react with the chloroalcohols HO(CH2)nCl (n = 2, 3) in the presence of 1 equiv. of HBF4 to afford the alkyl(chloroalkoxy)carbene complexes trans-[Pt(Me) {C[O(CH2)nCl](CH2R) } (PPh3)2][BF4] (R = p-tolyl, N = 2 (4), N = 3 (5); R=Ph, N = 2 (6)). A similar reaction of the bis(acetylide) complex trans-[Pt(C---C---Ph)2(PMe2Ph)2] with 2 equiv. HBF4 and 3-chloro-1-propanol affords trans-[Pt(C---CPh) {C(OCH2CH2CH2Cl)(CH2Ph) } (PMe2Ph)2][BF4] (7). T alkyl(chloroalkoxy)-carbene complex trans-[Pt(Me) {C(OCH2CH2Cl)(CH2Ph) } (PPh3)2][BF4] (8) is formed by reaction of trans-[Pt(Me)(Cl)(PPh3)2], after treatment with AgBF4 in HOCH2CH2Cl, with phenylacetylene in the presence of 1 equiv. of n-BuLi. The reaction of the dimer [Pt(Cl)(μ-Cl)(PMe2Ph)]2 with p-tolylacetylene and 3-chloro-1-propanol yields cis-[PtCl2{C(OCH2CH2CH2Cl)(CH2C6H4-p-Me}(PMe2Ph)] (9). The X-ray molecular structure of (8) has been determined. It crystallizes in the orthorhombic system, space group Pna21, with a = 11.785(2), B = 29.418(4), C = 15.409(3) Å, V = 4889(1) Å3 and Z = 4. The carbene ligand is perpendicular to the Pt(II) coordination plane; the PtC(carbene) bond distance is 2.01(1) Å and the short C(carbene)-O bond distance of 1.30(1) Å suggests extensive electronic delocalization within the Pt---C(carbene)---O moietry. 相似文献
8.
The structure of pullullan-like polysaccharides produced as exocellular material by different strains of Cryphonectria parasitica, the fungus responsible for chestnut tree cankers, was investigated with nuclear magnetic resonance (NMR) techniques. 13C, mono- and bidimensional 1H, and 1H–13C heteronuclear correlated NMR spectra (HSQC and HMBC) were recorded. Advanced analysis of the NMR spectra allowed the main resonance of the atoms in the maltotriose and in the maltotetraose repeat units of pullulan-like polysaccharides from C. parasitica to be recognised with confidence. In all cases investigated, the presence of large amounts of -(1→6) maltotetraose subunits was evidenced, in addition to the -(1→6) maltotriose subunits, corresponding to the repeating unit of pullulan produced by Aureobasidium pullulans and other fungi. The results were in agreement with other data from this laboratory, obtained with independent techniques. The belief that in ‘pullulans’ the maximum amount of -(1→6) maltotetraose subunits is about 7% can thus be considered as definitely outdated. 相似文献
9.
The behaviour of different hardwood glucuronoxylans during the kraft pulping process was investigated. Woods and pulps xylans were isolated and characterized by size exclusion chromatography, methylation (linkage) analysis and 1H NMR. Eucalyptus globulus and Eucalyptus urograndis showed xylan retention significantly higher than that of Betula pendula. The higher retention of Eucalyptus xylans was assigned to (i) their higher average molecular weight (31 against 24 KDa in B. pendula) and to (ii) the presence of O-2 substituted 4-O-methyl--d-glucuronic acid groups ([→2)-GlcpA-(1→]) with galactopyranosyl/glucopyranosyl residues belonging to fragments of galactan/glucan chains that were absent in B. pendula xylans. A significant part of uronic acids, particularly [→2)-GlcpA-(1→] units, remain in fibres until the end of pulping. The acetylation degree and distribution of acetyl groups between Xylp units, in general terms, was similar in the three types of xylans. Unexpectedly, about 20% of the acetyl groups persisted in pulps xylans till the end of pulping. 相似文献
10.
P.Muir Wood 《BBA》1974,357(3):370-379
The rate of electron transfer between reduced cytochrome ƒ and plastocyanin (both purified from parsley) has been measured as k = 3.6 · 107 M−1 · s−1, at 298 °K and pH 7.0, with activation parameters ΔH‡ = 44 kJ · mole−1 and ΔS‡ = +46 J · mole−1 · °K−1. Replacement of cytochrome ƒ with red algal cytochrome c-553, Pseudomonas cytochrome c-551 and mammalian cytochrome c gave rates at least 30 times slower: k = 5 · 105, 7.5 · 105 and 1.0 · 106 M−1 · s−1, respectively.
Similar measurements made with azurin instead of plastocyanin gave k = 6 · 106 and approx. 2 · 107 M−1 · s−1 for reaction of reduced azurin with cytochrome ƒ and algal cytochrome respectively.
Rate constants of 115 and 80 M−1 · s−1 were found for reduction of plastocyanin by ascorbate and hydroquinone at 298 °K and pH 7.0. The rate constants for the oxidation of plastocyanin, cytochrome ƒ, Pseudomonas cytochrome c-551 and red algal cytochrome c-553 by ferricyanide were found to be between 3 · 104 and 8 · 104 M−1 · s−1.
The results are discussed in relation to photosynthetic electron transport. 相似文献
11.
A. S. Peregudov D. N. Kravtsov G. I. Drogunova I. A. Godovikov 《Inorganica chimica acta》1998,280(1-2):238-242
The triazenide complex of Pt(II) trans-(o-Tol)Pt(PEt3)2N3Ar2(1) (Ar = p-FC6H4) was synthesized by reaction of (o-Tol)Pt(PEt3)2BF4 with Ar2N3Na. The 1H, 19F and 31P NMR spectra of this complex in toluene-d8 were studied at different temperatures. Two kinds of dynamic processes were observed. The first one is the intramolecular N,N′ migration of the (o-Tol)Pt(PEt3)2 group, detected by 19F NMR. The second process, revealed by 1H, 19P NMR, is the rotation around the partially double N(2)–N(3) bond. Thermodynamic parameters for these processes were calculated from dynamic NMR spectra. 相似文献
12.
Otilia D. L. Pessoa Telma L. G. De Lemos M rio G. De Carvalho Raimundo Braz-Filho 《Phytochemistry》1995,40(6):1777-1786
Further cordiachromes, rel-10,11β-epoxy-11-ethoxy-8-hydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10aβ-octahydro-1,4-anthracendione, 6-formyl-2-methoxy-9-methyl-7,8-dihydro-1,4-phenanthrendione, rel-8,11;9,11-diepoxy-1,4-dihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-9,11-epoxy-1,4,8-trihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-2″-methoxy-7″-methyl-1″,4″-naphtalendione-(6″→5)-tetrahydropyran-(2-eq→O→2ax)-tetrahydropyran-(5′→6)- 2-methoxy-7-methyl-1,4-naphthalendione, together with the known, allantoin, sitosterol and 3β-O-d-glucopyranosylsitosterol, have been isolated from Auxemma oncocalyx. Their structures were determined from spectral data, including 2D NMR experiments. 相似文献
13.
Absorption changes induced in chlorophyll protein (CP 1) particles by short laser flashes have been analyzed in order to decide whether a state lasting for a few microseconds at 21°C or 800 μs at 10 K corresponds to the biradical P-700+ ... A−1 (A1 being a chlorophyll a) or to a triplet state produced in a submicrosecond recombination of the preceding state. At 21°C the spectrum of the flash-induced ΔA (720–870 nm) presents a flat-topped band from 740 to 820 nm, clearly different from that of P-700+. A saturation curve (ΔA vs. laser energy), obtained with a 2 or 10 ns laser pulse, indicates that ΔA saturates at a value 2- or 3-times smaller than that expected on the basis of the chemical oxidation of P-700. At 21°C the size of flash-induced ΔA is slightly decreased (5–15%) when the sample is subjected to a 400 G magnetic field. The kinetics of decay are not affected; they are not affected either by the oxygen concentration. At 10 K the spectrum of the flash-induced ΔA has been measured between 650 and 1700 nm. Between 650 and 720 nm, the spectrum presents only one major negative peak at 702 nm; it is quite different from that due to the chemical oxidation of P-700 (which has additional peaks at 688 and 677 nm). Between 720 and 870 nm, the spectrum is identical to that obtained at 21°C. Above 870 nm, the spectrum includes a broad band around 1250 nm, which is absent in P-700+. A saturation curve leads to a maximum ΔA greater than that at 21°C and which is also greater with a 1 μs dye laser flash than with a 10 ns ruby laser flash. An analysis of the spectral data indicates that these do not fit correctly with the hypothesis of a contribution of P-700+ and of a chlorophyll a anion radical. They fit more closely with the hypothesis of a triplet state of P-700, a hypothesis which is discussed in relation to other experimental data. 相似文献
14.
A pterocarpan and two isoflavans from alfalfa 总被引:4,自引:0,他引:4
Gayland F. Spencer Barry E. Jones Ronald D. Plattner David E. Barnekow Linda S. Brinen Jon Clardy 《Phytochemistry》1991,30(12):4147-4149
(−)6aR,11aR-Dihydro-3-hydroxy-9,10-dimethoxy-6H-benzofuro[3,2c] [1]-benzopyran (10-methoxymedicarpin), (+)-(2,3,4,-trimethoxyphenyl)-2,3-dihydro-7-hydroxy-4H-1-benzopyran (7-hydroxy-2′,3′,4′-trimethoxyisoflavan) and (+)-(2,3,4-trimethoxy-5-hydroxyphenyl)-2,3-dihydro-7-hydroxy-4H-1-benzopyran (7,5′-dihydroxy-2′,3′,4′-trimethoxyisoflavan) were isolated for the first time from dried Medicago sativa hay. Structural assignments were based on 1H NMR and mass spectra, X-ray crystallography, and optical rotations. 相似文献
15.
Guilherme L. Sassaki Julio C. Ferreira Chirlei Glienke-Blanco Giangiacomo Torri Fabiana De Toni Philip A. J. Gorin Marcello Iacomini 《Carbohydrate polymers》2002,48(4):177-389
Guignardia citricarpa is a phytopathogenic fungus and the causal agent of citrus black spot. Incubation in a semi-defined media resulted in formation of exopolysaccharides [EPS(s)]. A medium containing glucose gave rise to a (1→6)-linked β-glucan (200 kD), pustulan, which was characterized by NMR and methylation analysis. A sucrose-containing medium provided a homogalactan (376 kD) and methylation analysis showed nonreducing end- (20%), 6-O- (53%) and 5,6-di-O-substituted Galf units (27%). An HMQC spectrum of the homogalactan showed C-1/H-1 signals at δ 108.2/4.820, 108.3/4.820 and 107.1/5.079, corresponding to three types of β-
-Galf units. A DEPT analysis showed inverted signals (CH2) at δ 67.8 and 67.2, corresponding to 6-O-substituted β-
-Galf units, whereas a C-5 signal at δ 77.0 suggests 5-O-substitution, confirming a novel structure for a β-galactofuranan. 相似文献
16.
Andr s Lipt k Lajos Szab J nos Ker kgy rt J nos Harangi P l N n si
Helmut Duddeck
《Carbohydrate research》1986,150(1):187-197The title tetrasacharide having the structure 3-O-Me-β-
-Xylp-(1→4)--
-Rhap-(1→4)--
-Rhap-(1→2)-
-Rhap was obtained by reaction of the -acetobromo derivative of 4-O-(3-O-methyl-β-
-xylopyranosyl)-
-rhamnopyranose and benzyl 3,4-di-O-benzyl-2-O-(2,3-O-isopropylidene--
-rhamnopyranosyl)--
-rhamnopyranoside, followed by removal of the protecting groups. The synthesised compounds were characterised on the basis of n.m.r. data. 相似文献
17.
S. R. T. Prado P. A. J. Gorin P. M. Stuelp N. K. Honda M. Iacomini 《Carbohydrate polymers》1999,40(4):271-276
The lichenised ascomycete, Collema leptosporum Malme, was extracted with aqueous methanol to give traces of mannitol and 3-O-β-
-glucopyranosyl-
-mannitol (2.7% yield). The residue was consecutively extracted with hot water to give a complex uronic acid-containing polysaccharide, and then with hot aqueous alkali which provided a mixture of polysaccharides. This was fractionated with Cetavlon to give a branched galactomannan, which had the lowest content of galactose yet reported for such a lichen polysaccharide. It has a main chain of (1→6)-linked -Manp units partly substituted at O-2,4 by non-reducing end-units of Manp and Galp, shown by NMR spectroscopy to have - and β-configurations, respectively. The other polysaccharide component was unexpectedly a branched (1→3), (1→6)-linked β-glucan, which is typical of a basidiomycete, whereas those of ascomycetes contain similar linkages but in linear glucans. 相似文献
18.
Toshiaki Yonemura Kimi Shibuya Ken-ichi Okamoto Tomoharu Ama Hiroshi Kawaguchi Takaji Yasui 《Inorganica chimica acta》1997,260(2):m1127-128
Cobalt(III) complexes with a thiolate or thioether ligand, t-[Co(mp)(tren)]+ (2), t-[Co(mtp)(tren)]2+ (1Me) and t-[Co(mta)(tren)]2+ (2Me), (mp = 3-mercaptopropionate, MA = 3-(methylthio)propionate and MTA = 2-(methylthio)acetate) have been prepared in aqueous solutions. The crystal structures of 1, 2, 1Me and 2Me were determined by X-ray diffraction methods. The crystal data are as follows, t-[Co(mp)(tren)]ClO4 (1CIO4): monoclinic, P21/n, A = 10.877(8), B = 11.570(4), c = 12.173(7) Å, β = 92.20(5)°, V = 1531(1) Å3, Z = 4 and R = 0.060; t-[Co(ma)(tren)]Cl·3H2O (2Cl·3H2O): monoclinic, P21/n, a = 7.7688(8), B = 27.128(2), C = 7.858(1) Å, β = 100.63(1)°, V = 1627.7(3) Å3, Z = 4 and R = 0.066; (+)465CD-t-[Co(mtp)(tren)](ClO4)2 ((+)465CD-1Me(ClO4)2): orthorhombic, P212121, A = 10.6610(7), B = 11.746(1), C = 15.555(1) Å, V = 1947.9(3) Å3, Z = 4 and R = 0.068; (+)465CD-t-[Co(mta)(tren)](ClO4)2 ((+)465CD-2Me(ClO4)2): orthorhombic, P212121, a = 10.564(1), B = 11.375(1), C = 15.434(2) Å, V = 1854.7(4) Å3, Z = 4 and R = 0.047. All central Co(III) atoms have approximately octahedral geometry, coordinated by four N, one O, and one S atoms. All of the complexes are only isomer, of which the sulfur atom in the didentate-O,S ligands are located at the trans position to the tertiary amine nitrogen atom of tren. 1 and 1Me contain six-membered chelate ring, and 2 and 2Me do five-membered chelate ring in the didentate ligand. The chirality of the asymmetric sulfur donor atom in (+)465CD-1Me is the S configuration and that in (+)465CD-2Me is the R one. The 1H NMR, 13C NMR and electronic absorption spectral behaviors and electrochemical properties of the present complexes are discussed in relation to their stereochemistries. 相似文献
19.
Electron paramagnetic resonance (EPR) power saturation and saturation recovery methods have been used to determine the spin lattice, T1, and spin-spin, T2, relaxation times of P-700+ reaction-center chlorophyll in Photosystem I of plant chloroplasts for 10 K T 100 K. T1 was 200 μs at 100 K and increased to 900 μs at 10 K. T2 was 40 ns at 40 K and increased to 100 ns at 10 K. T1 for 40 K T 100 K is inversely proportional to temperature, which is evidence of a direct-lattice relaxation process. At T = 20 K, T1 deviates from the 1/T dependence, indicating a cross relaxation process with an unidentified paramagnetic species. The individual effects of ascorbate and ferricyanide on T1 of P-700+ were examined: T1 of P-700+ was not affected by adding 10 mM ascorbate to digitonin-treated chloroplast fragments (D144 fragments). The P-700+ relaxation time in broken chloroplasts treated with 10 mM ferricyanide was 4-times shorter than in the untreated control at 40 K. Ferricyanide appears to be relaxing the P-700+ indirectly to the lattice by a cross-relaxation process. The possibility of dipolar-spin broadening of P-700+ due to either the iron-sulfur center A or plastocyanin was examined by determining the spin-packet linewidth for P-700+ when center A and plastocyanin were in either the reduced or oxidized states. Neither reduced center A nor oxidized plastocyanin was capable of broadening the spin-packet linewidth of the P-700+ signal. The absence of diplolar broadening indicates that both center A and plastocyanin are located at a distance at least 3.0 nm from the P-700+ reaction center chlorophyll. This evidence supports previous hypotheses that the electron donor and acceptor to P-700 are situated on opposite sides of the chloroplast membrane. It is also shown that the ratio of photo-oxidized P-700 to photoreduced centers A and B at low temperature is 2 : 1 if P-700 is monitored at a nonsaturating microwave power. 相似文献
20.
Patrick W. Blosser Mario Calligaris David G. Schimpff Andrew Wojcicki 《Inorganica chimica acta》2001,320(1-2):110-116
Reactions of [(PPh3)2Pt(η3-CH2CCPh)]OTf with each of PMe3, CO and Br− result in the addition of these species to the metal and a change in hapticity of the η3-CH2CCPh to η1-CH2CCPh or η1-C(Ph)=C=CH2. Thus, PMe3 affords [(PMe3)3Pt(η1-C(Ph)=C=CH2)]+, CO gives both [trans-(PPh3)2Pt(CO)(η1-CH2CCPh)]+ and [trans-(PPh3)2Pt(CO)(η1-C(Ph)=C=CH2)]+, and LiBr yields cis-(PPh3)2PtBr(η1-CH2CCPh), which undergoes isomerization to trans-(PPh3)2PtBr(η1-CH2CCPh). Substitution reactions of cis- and trans-(PPh3)2PtBr(η1-CH2CCPh) each lead to tautomerization of η1-CH2CCPh to η1-C(Ph)=C=CH2, with trans-(PPh3)2PtBr(η1-CH2CCPh) affording [(PMe3)3Pt(η1-C(Ph)=C=CH2)]+ at ambient temperature and the slower reacting cis isomer giving [trans-(PPh3)(PMe3)2Pt(η1-C(Ph)=C=CH2)]+ at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR (1H, 13C{1H} and 31P{1H}) spectroscopy. The structure of [(PMe3)3Pt(η1-C(Ph)=C=CH2)]BPh4·0.5MeOH was determined by single-crystal X-ray diffraction analysis. 相似文献