Measurement of 2J(H,C)- and 3J(H,C)-coupling constants by α/β selective HC(C)H-TOCSY

A new heteronuclear NMR pulse sequence for the measurement of ⁿJ(C,H) coupling constants, the /selective HC(C)H-TOCSY, is described. It is shown that the S³E element (Meissner et al., 1997a,b) can be used to obtain spin state selective coherence transfer in molecules, in which adjacent CH moieties are labeled with ¹³C. Application of the / selective HC(C)H-TOCSY to a 10nt RNA tetraloop 5-CGCUUUUGCG-3, in which the four uridine residues are ¹³C labeled in the sugar moiety, allowed measurement of two bond and three bond J(C,H) coupling constants, which provide additional restraints to characterize the sugar ring conformation of RNA in cases of conformational averaging.     

Production of alkanes (C7–C29) from different part of poplar tree via direct deoxy-liquefaction

Poplar leaves, poplar bark and poplar wood were deoxy-liquefied directly in an air-proof stainless steel reactor at different temperatures. The oils from leaves at 350 °C, from bark at 400 °C and from wood at 450 °C, at which the liquid product yields were the maximum, were analyzed by GC–MS. The oils obtained from three parts of poplar tree were quite different from each other in the relative contents of their compositions. The oil from leaves was rich in hydrocarbons (alkanes: C₇–C₂₉; aromatics) and poor in phenolics, while oil from wood was rich in phenolics and poor in hydrocarbons. The oil from bark was moderate. Relative contents of hydrocarbons in the leaves oil were as high as 60.01% but decreased to 29.71% in bark oil and 11.43% in wood oil. GC analysis of gases and FT-IR, GC–MS and elemental analysis of oils were performed in this study.     

Does Bienertia cycloptera with the single-cell system of C(4) photosynthesis exhibit a seasonal pattern of delta (13)C values in nature similar to co-existing C (4) Chenopodiaceae having the dual-cell (Kranz) system?

Family Chenopodiaceae is an intriguing lineage, having the largest number of C₄ species among dicots, including a number of anatomical variants of Kranz anatomy and three single-cell C₄ functioning species. In some previous studies, during the culture of Bienertia cycloptera Bunge ex Boiss., carbon isotope values (δ¹³C values) of leaves deviated from C₄ to C₃−C₄ intermediate type, raising questions as to its mode of photosynthesis during growth in natural environments. This species usually co-occurs with several Kranz type C₄ annuals. The development of B. cycloptera morphologically and δ¹³C values derived from plant samples (cotyledons, leaves, bracts, shoots) were analyzed over a complete growing season in a salt flat in north central Iran, along with eight Kranz type C₄ species and one C₃ species. For a number of species, plants were greenhouse-grown from seeds collected from the site, in order to examine leaf anatomy and C₄ biochemical subtype. Among the nine C₄ species, the cotyledons of B. cycloptera, and of the Suaeda spp. have the same respective forms of C₄ anatomy occurring in leaves, while cotyledons of members of tribe Caroxyloneae lack Kranz anatomy, which is reflected in the δ¹³C values found in plants grown in the natural habitat. The nine C₄ species had average seasonal δ¹³C values of −13.9‰ (with a range between species from −11.3 to −15.9‰). The measurements of δ¹³C values over a complete growing season show that B. cycloptera performs C₄ photosynthesis during its life cycle in nature, similar to Kranz type species, with a seasonal average δ¹³C value of −15.2‰. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Structure and function of haemoglobin philly (Tyr C1 (35) β→Phe)

We have purified haemoglobin Philly by isoelectric focusing on polyacrylamide gel, and studied its oxygen equilibrium, proton nuclear magnetic resonance spectra, mechanical stability, and pH-dependent u.v. difference spectrum. Stripped haemoglobin Philly binds oxygen non-co-operatively with high affinity. Inorganic phosphate and 2,3-diphosphoglycerate have little effect on the equilibrium curve, but inositol hexaphosphate lowers the affinity and induces co-operativity. These properties are explained by the nuclear magnetic resonance spectra which show that stripped deoxyhaemoglobin Philly has the quaternary oxy structure and that inositol hexaphosphate converts it to the deoxy structure. An exchangeable proton resonance at ?8.3 p.p.m. from water, which is present in oxy- and deoxyhaemoglobin A, is absent in both these derivatives of haemoglobin Philly and can therefore be assigned to one of the hydrogen bonds made by tyrosine C1-(35)β, probably the one to aspartate H8(126)α at the α₁β₁ contact. Haemoglobin Philly shows the same pH-dependent u.v. difference spectrum as haemoglobin A, only weaker, so that a tyrosine other than 35β must be mainly responsible for this.     

δ(13) C of leaf-respired CO(2) reflects intrinsic water-use efficiency in barley

Leaf intrinsic water-use efficiency (WUE), the ratio of photosynthetic rate to stomatal conductance (A/g(s) ), is a key plant trait linking terrestrial carbon and water cycles. A rapid, integrative proxy for A/g(s) is of benefit to crop breeding programmes aiming to improve WUE, but also for ecologists interested in plant carbon-water balance in natural systems. We hypothesize that the carbon isotope composition of leaf-respired CO(2) (δ(13) C(Rl) ), two hours after leaves are transferred to the dark, records photosynthetic carbon isotope discrimination and so provides a proxy for A/g(s) . To test this hypothesis, δ(13) C(Rl) was measured in four barley cultivars grown in the field at two levels of water availability and compared to leaf-level gas exchange (the ratio of leaf intercellular to ambient CO(2) partial pressure, C(i) /C(a) , and A/g(s) ). Leaf-respired CO(2) was more (13) C-depleted in plants grown at higher water availability, varied between days as environmental conditions changed, and was significantly different between cultivars. A strong relationship between δ(13) C(Rl) and δ(13) C of sucrose was observed. δ(13) C(Rl) was converted into apparent photosynthetic discrimination (Δ(13) C(Rl) ) revealing strong relationships between Δ(13) C(Rl) and C(i) /C(a) and A/g(s) during the vegetative stage of growth. We therefore conclude that δ(13) C(Rl) may provide a rapid, integrative proxy for A/g(s) in barley.     

Evolution of the C(4) photosynthetic mechanism: are there really three C(4) acid decarboxylation types?

Some of the most productive plants on the planet use a variant of photosynthesis known as the C(4) pathway. This photosynthetic mechanism uses a biochemical pump to concentrate CO(2) to levels up to 10-fold atmospheric in specialized cells of the leaf where Rubisco, the primary enzyme of C(3) photosynthesis, is located. The basic biochemical pathways underlying this process, discovered more than 40 years ago, have been extensively studied and, based on these pathways, C(4) plants have been subdivided into two broad groups according to the species of C(4) acid produced in the mesophyll cells and into three groups according to the enzyme used to decarboxylate C(4) acids in the bundle sheath to release CO(2). Recent molecular, biochemical, and physiological data indicate that these three decarboxylation types may not be rigidly genetically determined, that the possibility of flexibility between the pathways exists and that this may potentially be both developmentally and environmentally controlled. This evidence is synthesized here and the implications for C(4) engineering discussed.     

Estimation of canopy average mesophyll conductance using δ(13) C of phloem contents

Conductance to CO(2) inside leaves, known as mesophyll conductance (g(m)), imposes large limitations on photosynthesis. Because g(m) is difficult to quantify, it is often neglected in calculations of (13)C photosynthetic discrimination. The 'soluble sugar method' estimates g(m) via differences between observed photosynthetic discrimination, calculated from the δ(13)C of soluble sugars, and discrimination when g(m) is infinite. We expand upon this approach and calculate a photosynthesis-weighted average for canopy mesophyll conductance ((c) g(m)) using δ(13)C of stem phloem contents. We measured gas exchange at three canopy positions and collected stem phloem contents in mature trees of three conifer species (Pseudotsuga menziesii, Thuja plicata and Larix occidentalis). We generated species-specific and seasonally variable estimates of (c)g(m) . We found that (c)g(m) was significantly different among species (0.41, 0.22 and 0.09 mol m(-2) s(-1) for Larix, Pseudotsuga and Thuja, respectively), but was similar throughout the season. Ignoring respiratory and photorespiratory fractionations ((c)Δ(ef)) resulted in ≈30% underestimation of (c)g(m) in Larix and Pseudotsuga, but was innocuous in Thuja. Substantial errors (~1-4‰) in photosynthetic discrimination calculations were introduced by neglecting (c)g(m) and (c)Δ(ef) . Our method is easy to apply and cost-effective, captures species variation and would have captured seasonal variation had it existed. The method provides an average canopy value, which makes it suitable for parameterization of canopy-scale models of photosynthesis, even in tall trees.     

Chemotactic behavior of Campylobacter spp. in function of different temperatures (37 °C and 42 °C)

The chemotactic behaviour of Campylobacter strains was determined in the presence of different amino acids at two temperatures (37 °C and 42 °C). Two strains of catalase positive (Campylobacter jejuni) and negative (Campylobacter sputurum) Campylobacter were isolated from river water in Tonekabon, Iran and identified by phenotyping and 16srRNA Gene sequencing methods. Chemotactic responses of the isolates were assessed toward a variety of amino acids viz., L-cystine, L-asparagine, L-histidine, L-aspartic acid, L-serine, L-phenylalanine, L-leucine and L-tryptophan by disc and capillary methods at two temperatures: 37 °C and 42 °C. C. jejuni showed positive chemotactic response towards L-cystine,L-tryptophan, L-phenylalanine, - L-leucine, L-asparagine and L-Serine at both, 37 °C and 42 °C however, it was greater at 37 °C. C. sputurum showed negative or weak response towards all of the amino acids. In addition, C. jejuni illustrated strong chemotactic response to L-asparagine follow by L-serine and weak chemotaxis response to L-phenylalanine and L-cysteine at 37 °C. Overall, C. jejuni showed relatively strong chemotactic response to some amino acids, likewise it was greater at 37 °C. Hence, the human body temperature (37 °C) in compared to avian body temperature (42 °C) probably promotes chemotactic response of C. jejuni, which it might be a reason for causing disease in human being compared to avian.     

DFT study of (17)O, (1)H and (13)C NMR chemical shifts in two forms of native cellulose, I(α) and I(β)

This computational study is intended to shed light on the crystalline and molecular structure, together with the hydrogen bonding (H-bonding) differences between two forms of native cellulose. DFT calculations were carried out to characterize the ¹⁷O, ¹H and ¹³C nuclear magnetic resonance (NMR) parameters in cellulose I_α and I_β with the B3LYP functional employing the 6–311++G7 and 6–31+G1 basis sets. Geometry optimization revealed that the average HB length is shortened by 0.01–0.08 Å when the chains are aligned, whereas the average bond angle increases by about 4–8° exhibiting the enhancement of HB strength. For the isolated cellotetramer chains, the isotropic ¹⁷O–H chemical shifts were plotted as a function of HB length. Our results indicated that as the HB length in cellotetramer I_α increases, the ¹⁷O–H chemical shift isotropy increases, but this parameter changes in the opposite direction for the other structure. Moreover, B3LYP/6–311++G7 calculations reveal that there is an acceptable correlation between the calculated ¹³C chemical shifts of the two structures and their experimental values.     

Synthesis of heterodinuclear FeRu(CO)6(R-DAB(6e))(R-DABRNC(H)C(H)NR) Part XV. Comparison of the reactivities of heterodinuclear FeRu(CO)6(R-DAB(6e)) and homodinuclear analogues M2(CO)6(R-DAB(6e)) (M = Fe,Ru). Single-crystal x-ray structures of FeRu(CO)6(i-Pr-DAB(6e)) and FeRu(CO)5(i-Pr-DAB(4e))(C3H4)

The reactions of Fe(CO)₃(R-DAB; R¹, H(4e)) (1a: R = i-Pr, R¹ = H; 1b: R = t-Bu, R¹ = H; 1c: R = c-Hex, R¹ = H; 1e: R = p-Tol, R¹ = H; 1f: R = i-Pr, R¹ = Me) with Ru₃(CO)₁₂ and of Ru(CO)₃(R-DAB; R¹, H(4e)) (2a: R = i-Pr, R¹ = H; 2d: R = CH(i-Pr)₂, R¹ = H) with Fe₂(CO)₉ in refluxing heptane both afforded FeRu(CO)₆(R-DAB; R¹, H(6e)) (3) in yields between 50 and 65%.The coordination mode of the ligand has been studied by a single crystal X-ray structure determination of FeRu(CO)₆(i-Pr-DAB(6e)) (3a). Crystals of 3a are monoclinic, space group P2₁/a, with four molecules in a unit cell of dimensions: a = 22.436(3), b = 8.136(3), c = 10.266(1) Å and β = 99.57(1)°. The structure was refined to R = 0.049 and R_w = 0.052 using 3045 reflections above the 2.5σ(I) level. The molecule contains an FeRu bond of 2.6602(9) Å, three terminally bonded carbonyls to Fe, three terminally bonded carbonyls to Ru and bridging 6e donating i-Pr-DAB ligand. The i-Pr-DAB ligand is coordinated to Ru via N(1) and N(2) occupying an apical and equatorial site respectively (RuN(1) = 2.138(4) RuN(2) = 2.102(3) Å). The C(2)N(2) moiety of the ligand is η²-coordinated to Fe with C(2) in an apical and N(2) in an equatorial site (FeC(2) = 2.070(5) and FeN(2) = 1.942(3) Å).The ¹H and ¹³C NMR data indicate that in all FeRu(CO)₆(R-DAB(6e)) complexes (3a to 3f) exclusively η²-CN coordination to the Fe atom and not to the Ru atom is present irrespective of whether 3 was prepared by reaction of Fe(CO)₃(R-DAB(4e)) (1) with Ru₃(CO)₁₂ or by reaction of Ru(CO)₃(R-DAB(4e)) (2) with Fe₂(CO)₉. In the case of FeRu(CO)₆(i-Pr-DAB; Me, H(6e)) (3f) the NMR data show that only the complex with the C(Me)N moiety of the ligand σ-N coordinated to the Ru atom and the C(H)N moiety η²-coordinated to the Fe atom was formed. Variable temperature NMR experiments up to 140 °C showed that the α-diimine ligand in 3a is stereochemically rigid bonded.FeRu(CO)₆(R-DAB(6e)) (3a and 3e) reacted with allene to give FeRu(CO)₅(R-DAB(4e))(C₃H₄) (4a and 4e). A single crystal X-ray structure determination of FeRu(CO)₅(i-Pr-DAB(4e))(C₃H₄) (4a) was performed. Crystals of 4a are triclinic, space group P1, with two molecules in a unit cell of dimensions: a = 9.7882(7), b = 12.2609(9), c = 8.3343(7) Å, α = 99.77(1)°, β = 91.47(1)° and γ = 86.00(1)°. The structure was refined to R = 0.028 and R_w = 0.043 using 4598 reflections above the 2σ(I) level. The molecule contains an FeRu bond of 2.7405(7) Å and three terminally bonded carbonyls to iron. Two carbonyls are terminally bonded to the Ru atom together with a chelating 4e donating i-Pr-DAB ligand [RuN = 2.110(1) (mean)]. The allene ligand is coordinated in an η³-allylic fashion to the Fe atom while the central carbon of the allene moiety is σ-bonded to the Ru atom (FeC(14) = 2.166(3), FeC(15) = 1.970(2), FeC(16) = 2.127(3) and RuC(15) = 2.075(2) Å). The ¹H and ¹³C NMR data show that in solution the coordination modes of the R-DAB and the allene ligands are the same as in the solid state.Thermolysis reactions of 3a with R-DAB or carbodiimides gave decomposition and did not afford C(imine)C(reactant) coupling products. Thermolysis reactions of 3a with M₃(CO)₁₂ (M = Ru, Os) and Me₃NO gave decomposition. When the reaction of 3a with Me₃NO was performed in the presence of dimethylacetylenedicarboxylate (DMADC) the known complex FeRu(CO)₄(i-Pr-DAB(8e))(DMADC) (5a) was formed in low yield. In 5a the R-DAB ligand is in the 8e coordination mode with both the imine bonds η²-coordinated to iron. The acetylene ligand is coordinated in a bridging fashion, parallel with the FeRu bond.     

Inhibitors of human 20α-hydroxysteroid dehydrogenase (AKR1C1)

Human 20α-hydroxysteroid dehydrogenase (AKR1C1), a member of the aldo-keto reductase (AKR) superfamily, is one of four isoforms (with >84% amino acid sequence identity) existing in human tissues. AKR1C1 most efficiently reduces biologically active progesterone and 5α-pregnan-3α-ol-20-one into their corresponding 20α-hydroxysteroids among the isoforms. The enzyme also accepts endogenous and xenobiotic non-steroidal carbonyl compounds as the substrates. In addition to the up-regulation of the AKR1C1 gene in cancer cells, the enzyme's over-expression in the cells of lung, ovary, uterine cervix, skin and colon carcinomas was reported to be associated with resistance against several anticancer agents. Thus, AKR1C1 may be a marker of the above cancers and a target of poor prognosis in cancer therapy. The recently determined X-ray crystal structures of AKR1C1/NADP(+)/20α-hydroxyprogesterone and AKR1C1/NADP(+)/3,5-dichlorosalicylic acid ternary complexes have provided a strong foundation for structure-based design methods to improve inhibitor selectivity and potency. In this review we provide an overview of the different types of AKR1C1 inhibitors and an update on the design of potent and selective inhibitors based on the crystal structure of the enzyme-inhibitor complex. Article from the Special issue on Targeted Inhibitors.     

Preparation of the β-cyclodextrin-vitamin C (β-CD-Vc) inclusion complex under high hydrostatic pressure (HHP)

In this study, a novel high hydrostatic pressure (HHP) technique was used to prepare the β-cyclodextrin-vitamin C (β-CD-Vc) inclusion complex. The inclusion ratio was positively correlated with the pressure under 300MPa and remained at above 50.0% when the pressure was more than 300MPa. Fourier-transform infrared spectroscopy (FI-IR) and UV-visible spectroscopy (UV-vis) analysis showed that characteristic absorption bands and the absorption peak of Vc disappeared in the spectra of the β-CD-Vc inclusion complex. Furthermore, differential scanning calorimetry (DSC) data revealed that only one endothermic peak appeared at about 138°C in the DSC curve of the β-CD-Vc inclusion complex. These results indicate that the HHP treatment effectively induces the formation of β-CD-Vc inclusion complex.     

Kinetic models for the dynamical behavior of polyacrylamide (PAAm)–κ-carrageenan (κC) composite gels

A fluorescence method was employed for studying the drying and swelling of PAAm–κC composite gels, which were formed from acrylamide (AAm) and N, N’- methylenebisacrylamide (BIS) with various κ–carrageenan (κC) contents by free radical crosslinking copolymerization in water. Composite gels were prepared at 80 °C with pyranine (Py) as a fluorescence probe. Scattered light, I_sc, and fluorescence emission intensities, I_em, were monitored during drying and swelling of these gels. The fluorescence intensity of pyranine increased and decreased as drying and swelling time are increased, respectively, for all gel samples. The Stern–Volmer equation combined with moving boundary and Li-Tanaka models were used to explain the behavior of I_em during drying and swelling processes respectively. It is found that the desorption coefficient D_d decreased as κC contents were increased for a given temperature during drying. However, the cooperative diffusion coefficient, D_s presented exactly the opposite case. Conventional gravimetrical and volumetric experiments were also carried out during drying and swelling of PAAm–κC composite gels. It was observed that D_d and D_s values measured with the fluorescence method were found to be much larger than they were measured with the conventional methods.     

Evaluation of n-alkanes and their carbon isotope enrichments (δ(13)C) as diet composition markers

Plant cuticular n-alkanes have been successfully used as markers to estimate diet composition and intake of grazing herbivores. However, additional markers may be required under grazing conditions in botanically diverse vegetation. This study was conducted to describe the n-alkane profiles and the carbon isotope enrichment of n-alkanes of common plant species from the Mid Rift Valley rangelands of Ethiopia, and evaluate their potential use as nutritional markers. A total of 23 plant species were collected and analysed for long-chain n-alkanes ranging from heptacosane to hexatriacontane (C(27) to C(36)), as well as their carbon isotopic ratio ((13)C/(12)C). The analysis was conducted by gas chromatography/combustion isotope ratio mass spectrometry following saponification, extraction and purification. The isotopic composition of the n-alkanes is reported in the delta notation (δ(13)C) relative to the Vienna Pee Dee Belemnite standard. The dominant n-alkanes in the species were C(31) (mean ± s.d., 283 ± 246 mg/kg dry matter) and C(33) (149 ± 98 mg/kg dry matter). The carbon isotopic enrichment of the n-alkanes ranged from -19.37‰ to -37.40‰. Principal component analysis was used to examine interspecies differences based on n-alkane profiles and the carbon isotopic enrichments of individual n-alkanes. Large variability among the pasture species was observed. The first three principal components explained most of the interspecies variances. Comparison of the principal component scores using orthogonal procrustes rotation indicated that about 0.84 of the interspecies variances explained by the two types of data sets were independent of each other, suggesting that the use of a combination of the two markers can improve diet composition estimations. It was concluded that, while the n-alkane profile of the pasture species remains a useful marker for use in the study region, the δ(13)C values of n-alkanes can provide additional information in discriminating diet components of grazing animals.     

Effect of hypoxia (6,060 m) and cold (−5°C) on sexual organs of male rabbits

Studies have been carried out on 18 adult male rabbits divided into three groups. One group (hypoxic) was exposed to a simulated altitude (6,060 m for 6 h daily for 21 days), the second group was exposed to the same altitude plus cold (–5°C) for the same duration, and the third acted as control. The results showed no difference in the body weight of the three groups, but the weights of the sex organs in the exposed groups were significantly reduced. In both these groups the number, motility and survival time of spermatozoa decreased significantly; the sex organs showed atrophy on histological examination; and there was an increase in the alkaline and acid phosphatase activity and cholesterol concentration, and a fall in GPC level. These changes were more marked in the cold plus altitude group than in the group exposed to altitude alone. It has been concluded that hypoxia affects not only the testis but also the epididymis and the vas deferens. The spermatozoal quality of rabbits deteriorates. When cold and hypoxia are combined, their effects are additive.     

Synthesis of N′-propylhydrazide analogs of hydroxamic inhibitors of histone deacetylases (HDACs) and evaluation of their impact on activities of HDACs and replication of hepatitis C virus (HCV)

N′-Propylhydrazide analogs of hydroxamic inhibitors of histone deacetylases (HDACs), including tubastatin A, vorinostat and belinostat, were synthesized. All prepared compounds inhibited HDAC1/2/3, but not HDAC6, except for one hydrazide analog of HDAC4/5/7 inhibitor that was completely inactive. A novel 4-substituted derivative of N′-propylbenzohydrazide with extremely high anti-HCV activity was discovered.     

Effect of high levels of dietary vitamin C on the blood responses of matrinxã (Brycon amazonicus)

Juvenile matrinx? (Brycon amazonicus) were fed with different dietary vitamin C (ascorbic acid or AA) concentrations for 2 months in order to evaluate its effect on the physiological condition of this species. Five treatments were tested: Reference diet-RD (350 mg AA kg(-1) and 45% crude protein commercial feed); C400, C500, C600 and C800 with supplementation of 400, 500, 600 and 800 mg AA kg(-1). Fish fed 800 mg AA kg(-1) supplemented diets presented greater weight gain and survival. Hematocrit, hemoglobin concentrations and erythrocytes showed significant increase (p<0.05) in C600 and C800 relatively to the others. Total leukocyte values were significantly higher in fish fed vitamin C supplemented diets relatively to those fed RD and leukocytes count of C600 and C800 were the highest among the treatments. Monocytes were the only cells of fish defense mechanism that presented variation, and C600 and C800 presented the lowest values (P<0.05). Glucose level was significantly different relatively to RD only in C400 and the plasmatic total protein values for fish fed vitamin C supplemented diets were higher than for fish fed the RD. Fish plasmatic ions (Na(+) and Cl(-)) were significantly lower for C500, C600 and C800 relatively to C400 and RD. The physiological profile and the growth performance of matrinx? suggest that diet supplemented with 800 mg AA kg(-1) can improve its performance and increase the survival rate.