Presence and significance of minor antenna components in the energy transfer sequence of the green photosynthetic bacterium Chloroflexus aurantiacus

Antenna components in the energy transfer processes of a green photosynthetic bacterium Chloroflexus aurantiacus were spectrally investigated by time-resolved fluorescence spectroscopy at −196°C on intact cells. Besides major antenna components so far reported, three minor components were resolved; those were Bchl c located at 785 nm, the baseplate Bchl a at 819 nm and Bchl a in the B808-866 complex at 910 nm. The last component was assigned to a longer wavelength antenna closely associated with a reaction center. An additional Bchl c fluorescence component was kinetically suggested to be present, which can be an energy donor to a major Bchl c. Presence of these minor components was signified in terms of (1) increase in the spectral overlap integral and (2) adjustment of the direction of dipole moments in the energy transfer sequence of intact cells.     

Microbial reductions of the sesquiterpene quadrone

One hundred microorganisms have been screened for their abilities to selectively modify the structure of the sesquiterpene lactone known as quadrone. The only products obtained were those formed when the 4-ketone functional group was reduced to the stereoisometric 4-quadronols. Quadrone alcohol isomers of (S) or (R) absolute configurations were identified by proton and carbon n.m.r., and high performance liquid chromatography (h.p.l.c.) was used to separate and quantitate these compounds in extracts of fermentations. Microorganisms were categorized according to their abilities to achieve Re- or Si-face carbonyl reduction to yield (S)- or (R)-alcohol isomers by h.p.l.c. Three groups of microorganisms were identified: those yielding only the (R)-alcohol isomer; those yielding only the (S)-alcohol isomer; and those providing mixtures of the two alcohol isomers. With quadrone as substrate, Mucor and Curvularia spp. may contain either Re- or Si-face reductases. The selection of microorganisms for their abilities to achieve enantiospecific reductions of ketones to alcohol products is discussed.     

Production of monoacylglycerol of conjugated linoleic acid by esterification followed by dehydration at low temperature using Penicillium camembertii lipase

Conjugated linoleic acid (CLA) has various physiological activities, and a commercial product is a mixture of free fatty acids (named FFA-CLA) which contains almost equal amounts of 9-cis, 11-trans (9c,11t) and 10t,12c isomers. We attempted to efficiently produce monoacylglycerol (MAG) of CLA by lipase-catalyzed esterification. Study on effect of reaction temperature clarified that synthesis of diacylglycerols (DAGs) from MAGs was repressed at low temperature. When FFA-CLA was esterified at 5 °C with 5 molar equivalents of glycerol using 200 U/g mixture of Penicillium camembertii lipase in the presence of 2% water, the degree of esterification reached 89.6% after 45 h and the contents of MAGs and DAGs were 87.0 and 4.5 wt.%, respectively. Triacylglycerols were not synthesized in this Penicillium lipase-catalyzed esterification. After the esterification was conducted for 20 h (the degree of esterification, 80.8%), dehydration was started by evaporation at 5 mmHg using a vacuum pump. The degree of esterification increased concomitantly with dehydration and reached 94.5% after 16 h (36 h in total). The contents of MAGs (main components, 1(3)-isomers) and DAGs were 92.7 and 2.9 wt.%, respectively. Fatty acid compositions in MAGs synthesized with and without dehydration were the same as that in FFA-CLA. These results showed that the esterification system with dehydration is effective for producing MAGs in a high yield.     

Rhodium(I) complexes of the type [TpRh(LL)] (LL = 2 CO, NBD, COD) with trifluoromethyl substituted tris (pyrazolyl) borate ligands and their dynamic behaviour in solution. The X-ray crystal structure of TpRh(CO)2

Three seriesof Rh(I) complexes of the type Tp^3R,5RRh(LL), with LL = 2 CO (1), norbornadiene (NBD) (2) and 1,5-cyclooctadiene (COD) (3) and the tris (pyrazolyl)borate (Tp) ligands 3R=5R=Me (a), 3R=CF₃5R=Me (b); and 3R=5R=CF₃ (c) were synthesized and fully characterized by IR and multinuclear NMR spectroscopy. Three isomeric forms were identified in solutions of these complexes: two square-planar isomers with a κ²-Tp³R,5R ligand, the uncoordinated pyrazolyl ring occupying either an equatorial position (type A), or an axial position (type B), and a five-coordinate species with a κ³, Tp³R,5R ligand (type C). In the carbonyl complexes 1 the dynamic equilibria between these isomers are solvent dependent. Interestingly, solutions of complex 1c contained all three isomers simultaneously. ¹⁰³Rh and ¹³C NMR spectral studies indicate that the NBD compounds, 2, preferentially form square-planar complexes when Tp^CF₃,Me and Tp^CF₃,CF₃ are present, while for the COD complexes, 3, square-planar complexes are preferred for all three Tp-type ligands. The X-ray structure of Tp^CF₃,MeRh(CO)₂ (1b) was determined (spacce group C2/ c,a = 21.271(9), B = 11.004(3), C = 21.563(9) Å, β = 114.93(3)°, V=4577(3) ų, Z = 8, R = 3.41, R_w = 4.70). Its structure is of type B, with the third pyrazolyl ring axially placed, the N(4) being almost directly above the Rh atom but exerting only a weak Rh-N interaction.     

9种唇形科芳香植物挥发性萜类成分的比较分析

采用正己烷萃取法，结合GC-MS（气相色谱-质谱联用）技术，并通过谱库、保留指数和文献检索定性，内标法定量，分析9种唇形科芳香植物叶片的挥发性萜类成分并比较其差异，所得结果不仅为芳香植物的高效利用、合理开发提供参考，还为植物萜类的代谢研究提供依据。结果显示：从9种芳香植物中共检测到77种挥发性萜类物质，藿香中检测到的种类最多，为46种，迷迭香（35种）、百里香（33种）、药用鼠尾草（33种）和美国薄荷（31种）次之，石竹烯和蛇麻烯为9种植物共有成分。迷迭香中检测到的挥发性萜类的含量最高，其次是药用鼠尾草和藿香。单萜类成上分明显高于倍半萜类，因此迷迭香、药用鼠尾草、藿香、百里香和美国薄荷，较适宜作为提取挥发性萜类的材料；香蜂花只适宜柠檬醛的提取，牛至、凤梨鼠尾草和南欧丹参不适宜作为提取挥发性萜类的材料。上述芳香植物在正常环境中生成单萜类化合物的能力高于生成倍半萜类化合物的能力，可能与其含有的萜类合酶有关。     

Analysis of lycopene geometrical isomers in biological microsamples by liquid chromatography with coulometric array detection

Methods of analysis for determining low quantities of lycopene cis–trans isomers in biological tissues are needed. Development of two liquid chromatography (LC) methods based on the polymeric C₃₀ stationary phase equipped with coulometric electrochemical array detection (ED) is described. Separation of 13 lycopene isomers including prolycopene, (a novel tetra-cis-lycopene found in Tangerine tomatoes) was accomplished with both isocratic and gradient methods using different proportions of methanol, methyl tert.-butyl ether, water and 1 M ammonium acetate buffer. Carotenoids were detected at potential settings between 200 and 620 mV. Differences in generated current–voltage curves aided in tentative identification of trans carotenoid species and select cis isomers of lycopene. These methods were successfully applied in the analysis of small quantities of plasma, buccal mucosal cells, prostate and cervical tissues. Limits of detection for trans-lycopene by ED were found to be 50 fmol representing a 10- to 100-fold increase over conventional UV–Vis absorbance methods.     

Isomers of conjugated linoleic acid decrease plasma lipids and stimulate adipose tissue lipogenesis without changing adipose weight in post-prandial adult sedentary or trained Wistar rat

The respective effects and interactions of supplementation with two conjugated linoleic acid (CLA) isomers and exercise on plasma metabolic profile, activity of lipogenic enzymes and cellularity in two adipose tissue sites, those of the liver and heart, were examined in adult Wistar rats. Rats that were either sedentary or exercise-trained by treadmill running were fed one of four diets: a diet without CLA; a diet with either 1% cis 9, trans 11 CLA or 1% trans 10, cis 12 CLA; or a mixture of both isomers (1% of each) for 6 weeks. We observed that the exercise decreased lipogenic enzyme activities in epididymal and perirenal adipose tissue. Plasma cholesterol, insulin, and leptin concentrations were lower in exercise-trained rats than in sedentary rats. The ingestion of either CLA mixture or the trans 10, cis 12 CLA increased lipogenic enzyme activities in epididymal tissue and more markedly in perirenal adipose tissue, especially in sedentary rats, and without affecting adipose tissue weight or cellularity. A similar effect of trans 10, cis 12 CLA was observed in regard to malic enzyme activity in the liver. In addition, this isomer decreased plasma lipid and urea concentrations and increased plasma 3-hydroxybutyrate levels. The ingestion of cis 9, trans 11 CLA increased fatty acid synthase activity in perirenal adipose tissue in sedentary rats and decreased plasma cholesterol and leptin concentrations. These results show that isomers of CLA decrease plasma lipids and stimulate adipose tissue lipogenesis without changing adipose weight in adult sedentary or exercise-trained rat, thus suggesting a stimulation of adipose tissue turnover.     

Properties of the cytochrome a-like material developed in the photosynthetic bacterium Rhodopseudomonas spheroides when grown aerobically

A photosynthetically-incompetent mutant Rhodopseudomonas spheroides that lacks bacteriochlorophyll was isolated. Spectroscopic evidence from CO difference spectra and cyanide difference spectra suggested that a cytochrome oxidase was present in this mutant that contained two components, corresponding to cytochromes a and a₃ of mitochondria. Potentiometric titration at 607 nm also showed the presence of two components with oxidation-reduction mid-point potentials of +375 mV and +200 mV. They were present in a ratio close to unity. No cytochrome of the the c-type corresponding to mitochondrial cytochrome c was detected, but a minor c component (near 10% of the total cytochrome c) with an oxidation-reduction mid-point potential of +120 mV was found

Growth of the mutant in medium with low aeration or lacking added copper diminished the concentration of the a-type cytochrome but not the concentrations of cytochromes of the b and c-type.     

Biocatalytic production of 2(E)-hexenal from hydrolysed linseed oil

Natural 2(E)-hexenal was produced in two steps from hydrolysed linseed oil, which contains the most linolenic acid among the available natural sources. In the first step 13-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid (13-HPOT) was formed from linolenic acid (100 mM) by soybean lipoxygenase-1 (Lox-1) isoenzyme with oxygen as co-substrate. The reaction resulted in 57 mM 13-HPOT with a yield of 62%. In the second step 13-HPOT (20 mM) was cleaved by green bell pepper hydroperoxide lyase resulting in 1.6 mM 2(E)-hexenal and 5.9 mM 3(Z)-hexenal (37% yield for the hexenal isomers together). Hexenals were isolated from the reaction mixture by repeated steam distillations. During distillations the 2(E)-hexenal:3(Z)-hexenal isomer ratio was changed from 0.27 to 7.86 as a consequence of heat.     

Occurrence of singlet oxygen oxygenation of oleic acid and linoleic acid in the skin of live mice

To assess the contribution of singlet molecular oxygen [O₂ (¹Δ_g)] to lipid peroxidation in vivo, this study combined gas chromatography-mass spectrometry with thin layer chromatography to analyse peroxidized lipids in the skin of hairless mice. Hydroxyoctadecenoate isomers and unconjugated hydroxyoctadecadienoate isomers derived from peroxidized oleic acid and linoleic acid, respectively, which are specific to O₂ (¹Δ_g)-dependent oxygenation, were detected in the skin of live mice under ordinary feeding conditions. Short-term ultraviolet A (UVA)-irradiation of the skin in vivo elevated levels of the unconjugated hydroxyoctadecadienoate isomers significantly, whereas the irradiation of skin homogenate in vitro increased levels of all isomers derived from both O₂ (¹Δ_g) and free radical-dependent oxygenation to a much greater extent. This is the first report to demonstrate the occurrence of O₂ (¹Δ_g)-specific oxygenation of unsaturated fatty acids in living animals.     

High-performance liquid chromatographic determination of amitriptyline and its main metabolites using a silica column with reversed-phase eluent : Application in mice

A method was developed for the assay of amitriptyline, amitriptyline-N-oxide, nortriptyline, desmethylnortriptyline and E (trans) and Z (cis) isomers of 10-hydroxyamitriptyline and of 10-hydroxynortriptyline in plasma and brain of animals, using high-performance liquid chromatography with ultraviolet detection (254 nm). Single extraction was performed at pH 10.5 from 0.25 ml of plasma or 1 ml of brain mixture. Chromatographic separations were achieved with a silica column and an aqueous methanol mobile phase containing ammonia. This procedure offers high sensitivity (8–10 ng/ml), high linearity (r > 0.99) and acceptable precision (coefficient of variation ≤ 13.3%). The method was used to determine levels of amitriptyline and its major metabolites in mice 30 min after a single intraperitoneal administration of amitriptyline (20 mg/kg).     

The synthesis and reactions of A-ring aromatic steroid complexes of manganese tricarbonyl

Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO)₅⁺BF₄⁻ in CH₂Cl₂ yields the corresponding [(steroid)Mn(CO)₃]BF₄ salts 1 and 2 as mixtures of and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO)₃]BF₄ · CH₂Cl₂ (1) having the Mn(CO)₃ moiety on the side of the steroid is reported: space group P2₁ with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) ų, _calc=.481 cm⁻³, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear Mn---C---O linkages. The nucleophiles NaBH₄ and LiCH₂C(O)CMe₃ add to [(β-estradiol 3,17-dimethyl ether)Mn(CO)₃]BF₄ (2) in high yield to give the corresponding - and β-cyclohexadienyl manganese tricarbonyl complexes (3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH₂C(O)CMe₃ substituent is reported (complex 4): space group P2₁2₁2₁ with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) ų, _calc=1.244 g cm⁻³, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.     

Differential inhibition of fungal oxidosqualene cyclase by 6E and 6Z isomers of 2,3-epoxy-10-aza-10,11-dihydrosqualene

Inhibitory properties of 6E (compound 1) and 6Z (compound 2) isomers of 2,3-epoxy-10-aza-10,11-dihydrosqualene against oxidosqualene-lanosterol cyclase were assayed on microsomes and whole cells of Saccharomyces cerevisiae and Candida albicans. Only the 6E isomer (compound 1), bearing a correct substrate-like configuration, strongly inhibited the enzyme both in microsomes and cell cultures. The difference between compounds 1 and 2 (which had an unfavorable geometry) was especially evident when measuring [¹⁴C]acetate incorporation into non-saponifiable lipids extracted from treated cells. While isomer Z was totally ineffective at up to 30 μM, in cells treated with 5 μM isomer E, labelled oxidosqualene, the level of which was negligible in the control, rose to over 60% of the non-saponifiable lipids.     

Diversity in cyclic sesquiterpene production by Gossypium hirsutum

Major sesquiterpene components of oil of Texas Race Stock 810 of Gossypium hirsutum were - and β-selinene. This is the seventh cyclic terpene type found to date in this genus. Both - and β-selinene, along with aromadendrene, were found but only as minor components of extracts of several domestic cultivars of G. hirsutum.     

The oxidation products of crude mesobilirubinogen

Bile pigment esters were separated by ascending t.l.c. Apparently pure pigments, obtained by ferric chloride oxidation of crude mesobilirubinogen, derived from commercial bilirubin by reduction with sodium amalgam, were shown to be complex mixtures. Successive chromatography of their dimethyl esters on silica gel in methyl acetate-methyl propionate-dichloromethane-carbon tetrachloride (1:1:1:1, by vol.), ethyl methyl ketone-1,2-dichloroethane (1:2, v/v) and benzene-ethanol (100:3, v/v) revealed two major blue pigments (verdins), six major violet pigments (violins) and a red pigment (rhodin) together with numerous minor components. i-Urobilin dimethyl ester, prepared from mesobilirubinogen by dehydrogenation with aqueous iodine, was resolved into three major and at least four minor components on silica gel-kieselguhr (3:1, w/w) in benzene-ethanol (25:2, v/v). The chemical nature of these pigments was investigated by oxidation, by visible and u.v. spectroscopy, by mass spectrometry and by n.m.r. spectrometry. The evidence suggests unusual rearrangement of bilirubin during reduction leading to the formation of IIIalpha and XIIIalpha isomers. Isomeric forms of mesobiliviolin IXalpha and of i-urobilin IXalpha may also be formed.     

Isolation and characterization of soluble sulfated polysaccharide from the red seaweed Gracilaria cornea

The composition, structure and rheological properties of a soluble sulfated polysaccharide from Gracilaria cornea (Brazilian red marine alga) were investigated. Agarocolloid yield, intrinsic viscosity, monosaccharide composition, sulfate and cation content as well as molecular weight were determined. The main polysaccharide components were 3,6-anhydrogalactose (24.7%) and galactose (64.6%). In addition, minor components such as 6-O-methyl-galactose (8.5%), glucose (1.5%), xylose (0.7%) and sulfated groups (4.8%) were detected. Comparison between sulfate contents determined by Fourier transform IR (FT-IR) spectroscopy and microelemental analysis was made. Data from ¹³C NMR and FT-IR provided evidence of sulfation in C-4 and C-6 of galactose. Sodium, calcium, magnesium and potassium cations were detected in the agarocolloid. The intrinsic viscosities were lower than typical values for agar in the same experimental conditions. No gelation in 1.5, 2.0 and 3.0% (w/v) aqueous solution was observed, even by cooling up to 4 °C. Gel permeation chromatography indicated two major polysaccharide fractions of M_pk 7.4×10⁴ and 1.8×10⁴ g/mol and a minor fraction of M_pk 2.1×10⁶ g/mol, probably a protein–polysaccharide complex.     

Geometrical configuration of monomethyl–platinum(II) complexes driven by the size of entering nitrogen ligands

The reaction of the monoalkyl complex trans-[Pt(DMSO)₂Cl(CH₃)] with a large variety of heterocyclic nitrogen bases L, in chloroform solution, leads to the formation of uncharged complexes of the type [Pt(DMSO)(L)Cl(CH₃)], containing four different groups coordinated to the metal center. Only two out of the three different possible isomers were detected in solution. These two trans(C,N) and cis(C,N) species can be unambiguously identified through ¹H NMR spectroscopy. For the trans(C,N) isomers, average values of ²J_PtH=75±4 Hz and ³J_PtH=36±4 Hz have been observed for the coordinated methyl and DMSO ligands, respectively. In the case of the cis(C,N) isomers, these values increase to ²J_PtH=83±2 Hz, and decrease to ³J_PtH=26±3 Hz due to the mutual exchange of ligands in trans position to CH₃ and DMSO. In the case of bulky asymmetric ligands, such as quinoline, 2-quinolinecarboxaldehyde, 2-methylquinoline, 5-aminoquinoline, 2-phenylpyridine and 2-chloropyridine, slow rotation of the hindered group around the Pt---N bond makes the coordinated DMSO ligand prochiral. NMR experiments have shown that the first reaction product is the trans(C,N) isomer as a consequence of the very fast removal of one DMSO ligand by the nitrogen bases from the starting complex trans-[Pt(DMSO)₂Cl(CH₃)]. This trans kinetic product undergoes a geometrical conversion into the more stable cis(C,N) isomer through the intermediacy of fast exchanging aqua-species. The rate of isomerization and the relative stability of the two isomers depends essentially on the rate of aquation and on the steric congestion imposed by the new L ligand on the metal.     

Formation of 6,13-dihydroxyoctadecatrienoic acid isomers from gamma-linolenic acid

Incubation of gamma-linolenic acid with soybean lipoxygenase initially at pH 9.3 and subsequently at pH 7.9 gave rise to the conjugated triene dioxygenation product (lambda max = 267 nm, greater than 50% yield), which was reduced to form 9-cis isomer of 6,13-dihydroxyoctadecatrienoic acid (6,13-diHOT) accompanied by minor isomers. Meanwhile, hemoglobin converted 13-hydroperoxyoctadecatrienoic acid into two major 9-trans isomers of 6,13-diHOT and two 9-cis isomers as minor products. The four isomers of 6,13-diHOT methyl ester were separated from each other on SP-HPLC, and characterized by chromatographic, spectrometric and cis----trans isomerization analyses.     

Determination of fatty acid and triacylglycerol composition of human very-low-density lipoproteins

The fatty acid composition of human very-low-density lipoproteins (VLDL) was studied in a population from western Andalusia with a diet in which the fat content came mainly from olive oil. The lipid composition of VLDL, including the fatty acid composition of the phospholipids and triacylglycerols, was examined by capillary gas chromatography. Twenty-five peaks were resolved, ranging in chain length from 14 to 24 carbon atoms, including geometric and positional isomers. The major fatty acids present in phospholipids were 16:0, 18:0, 18:1(n − 9) and 18:2(n − 6), and in triacylglycerols were 18:1(n − 9), 16:0 and 18:2(n − 6). The major triacylglycerol was POO, followed by PLO and OOO. MLP, PPS and LLL were absent. The presence of a large amount of OOO in this fraction demonstrates that the triacylglycerol composition of the VLDL depends on the type of diet consumed.     

Biophysical characterization of double-stranded oligonucleotides using ETBR and isothermal fluorescence spectroscopy: implication for SNP genotyping

The UV-absorption, fluorescence and CD spectra of aps 23 bp oligoduplexes were performed for potential diagnostic purpose. These oligonucleotide sequences were mimicked from natural mutations (mitochondrial genome) of human population (unpublished). This work was designed on the basis of hybridization of non-self complementary oligoduplexes (aps) containing no mismatch, one-mismatch and two-mismatches. Since melting temperature™ is dependent on concentration of the oligoduplex, various concentrations were used in this study protocol. The thermal spectra profiles (UV absorbance and fluorescence) of these oligoduplexes (aps) are different for a particular concentration, and can be implicated for mutations. − dF/dT (or dA/dT) vs T, lnK (or RlnK) vs T_M, ΔG vs T_M, ΔS vs T_M and ΔH vs T_M are also variable for those sequences. All these thermodynamic data were calculated from absorbance (at 260 nm) data. On the contrary to the 23 bp oligoduplexes (aps), the PCR products of 97 bp and 256 bp length were genotyped with ETBR (excitation 530 nm, emission 600 nm) fluorimetrically. But our attempts to genotype these PCR sequences with isothermal UV absorbance spectroscopy were unsuccessful. Isothermal UV absorbance spectra has a limitation of sequence length. However, the structural conformation (all B-type) of the oligoduplexes (aps) was determined using CD. The minor discrepancy in CD spectra of these oligoduplexes are not significant for mutational analysis. 97 bp nested PCR product was an amplicon having either GcT or AcC mutation of mitochondria of normal human population, whereas 256 bp PCR product was an amplicon of human BRCA2 gene (NCBI Accession No. AY151039) of chromosome 13 having either A or G mutation at position − 26.