Variability of aliphatic glucosinolates in Arabidopsis thaliana (L.) – Impact on glucosinolate profile and insect resistance

The glucosinolate(GS)-myrosinase system of Brassicaceae, including the model plant Arabidopsis thaliana (L.), comprises a defence which is effective especially against generalist herbivores. Based on their side chain structure GS are grouped into aliphatic, aromatic, and indolyl GS. Indolyl GS are widely distributed among A. thaliana ecotypes and the Brassicaceae family, but the presence of aliphatic GS is variable and under strong genetic control. We investigated the effect of AOP gene expression on the side chain modifications of GS and the impact on insect resistance. AOP2 and AOP3 genes from Mr-0 and Sap-0 ecotypes, respectively, were crossbred into the methylsulfinyl GS producing Gie-0. Successful crosses were heterozygote plants which produced allyl (AOP2) or 3-hydroxypropyl GS (AOP3). After self-pollination, the chemical profile of the F3 generation of plants was screened to identify homozygote lines. Homozygote lines producing 3-hydroxypropyl GS were compared to methylsulfinyl GS, which were used to study the impact of GS structure on insect performance in first experiments. Our experiments revealed that methylsulfinyl GS containing ecotype lines were more resistant to the generalist caterpillar Spodoptera exigua (Hübner) and to the specialist caterpillar Pieris brassicae (L.) than the lines containing hydroxypropyl GS as main compounds

Influence of the season on the salicylate and phenolic glycoside contents in the bark of Salix daphnoides, Salix pentandra, and Salix purpurea

Due to the benefits of herbal medicine and their wide range of application for human health, the usage of natural drug products, such as willow bark extract, has increased in the last few years. The principle active compounds of the drugs comprised primarily of willow bark are phenolic glycosides like salicylates. Phenolic glycoside profiles of bark vary among species and between the seasons. To identify and preserve willow clones with high salicylate content for possible commercial usage at a later stage, we have screened three Salix sp. in respect to their chemical profiles. The willow species analysed were: Salix daphnoides, Salix pentandra, and Salix purpurea. These species had distinct phenolic glycoside profiles. The major salicylate of S. daphnoides and S. purpurea clones was salicortin, whereas the main compound of S. pentandra was 2’- O-acetylsalicortin. According to the chemical profiles of 140 clones, seven independent clones of S. daphnoides and S. purpurea as well as four clones of S. pentandra with high phenolic glycoside contents were picked to study seasonal changes in bark chemistry. Overall, the clones of S. daphnoides showed the highest mean salicylate and phenolic glycoside contents, followed by S. pupurea and S. pentandra. The secondary metabolite content of willow bark clones decreased during the vegetative season from March to June 2007 and further from June to July 2007. Our study revealed that for optimum yield of phenolic glycosides the species, the clone, and the time of harvest during the season have to be taken in consideration

Impact of glucosinolate structure on the performance of the crucifer pest Phaedon cochleariae (F.)

Glucosinolates (GS) are sulfur-rich secondary metabolites found in the Brassicaceae and other related families of the order Brassicales. GS consist of structurally-related compounds with different side chains. To explore the possibility that various side chain confer divergent biological activities to individual GS, we have investigated the performance of the specialist pest beetle, Phaedon cochleariae (F.) on Arabidopsis thaliana L. mutants and Columbia wild-type (WT) which differ in the main group of GS. Plant lines of A. thaliana altered for the expression of MAM3, because of the introduction of an overexpression construct of MAM3 (mam3+) or containing double knockouts of CYP79B2 and CYP79B3 (cyp79B2-/cyp79B3-) were used for the study in comparison to the WT.A. thaliana genotypes differed in their GS profiles. The highest GS content was present in the WT followed by mam3+ and cyp79B2-/ cyp79B3-. A modified aliphatic GS content was detected for the mam3+ as compared to the WT lines. Furthermore, indolyl GS were completely absent in cyp79B2-/cyp79B3-. The percentage weight increase of larvae raised on each of the three plant genotypes was significant different. Larval performance was poorest on plants of cyp79B2-/cyp79B3- and best on WT, but there was no significant difference found in percentage weight increase on mam3+ and WT. There was no correlation between the weight increase of the larvae on genotypes and induced levels of aliphatic, indolyl, and total GS. However, the poor performance of beetle larvae on cyp79B2-/ cyp79B3-compared to WT and mam3+ might be explained by comparable high aliphatic GS levels of this mutant, a different induction of secondary metabolites, and the absence of indolyl GS. Basic knowledge about the relationship of GS structures and their insect pests may help in further resistance breeding of crucifer crops

Topological change of the Fermi surface in ternary iron-pnictides with reduced c/a ratio: A dHvA study of CaFe2P2

We report a de Haas-van Alphen effect study of the Fermi surface of CaFe2P2 using low temperature torque magnetometry up to 45 T. This system is a close structural analogue of the collapsed tetragonal non-magnetic phase of CaFe2As2. We find the Fermi surface of CaFe2P2 to differ from other related ternary phosphides in that its topology is highly dispersive in the c-axis, being three-dimensional in character and with identical mass enhancement on both electron and hole pockets (~1.5). The dramatic change in topology of the Fermi surface suggests that in a state with reduced (c/a) ratio, when bonding between pnictogen layers becomes important, the Fermi surface sheets are unlikely to be nested

Athermal analogue of sheared dense Brownian suspensions

The rheology of dense Brownian suspensions of hard spheres is investigated numerically beyond the low shear rate Newtonian regime. We analyze an athermal analogue of these suspensions, with an effective logarithmic repulsive potential representing the vibrational entropic forces. We show that both systems present the same rheology without adjustable parameters. Moreover, all rheological responses display similar Herschel-Bulkley relations once the shear stress and the shear rate are respectively rescaled by a characteristic stress scale and by a microscopic reorganization time-scale, both related to the normal confining pressure. This pressure-controlled approach, originally developed for granular flows, reveals a striking physical analogy between the colloidal glass transition and granular jamming.Comment: 6 figures, 6 page

Benchtop NMR analysis of piperazine-based drugs hyperpolarised by SABRE

Piperazine-based drugs, such as N-benzylpiperazine (BZP), became attractive in the 2000s due to possessing effects similar to amphetamines. Herein, BZP, in addition to its pyridyl analogues, 2-, 3- and 4-pyridylmethylpiperidine (2-PMP, 3-PMP and 4-PMP respectively) were subjected to the hyperpolarisation technique SABRE (Signal Amplification By Reversible Exchange) in order to demonstrate the use of this technique to detect these piperazine-based drugs. Although BZP was not hyperpolarised via SABRE, 2-PMP, 3-PMP and 4-PMP were, with the ortho- and meta-pyridyl protons of 4-PMP showing the largest enhancement of 313-fold and 267-fold respectively in a 1.4 T detection field, following polarisation transfer at earth's magnetic field. In addition to the freebase, 4-PMP.3HCl was also appraised by SABRE and was found not to polarise, however, the addition of increasing equivalents of triethylamine (TEA) produced the freebase, with a maximum enhancement observed upon the addition of three equivalents of TEA. Further addition of TEA led to a reduction in the observed enhancement. SABRE was also employed to polarise 4-PMP.3HCl (ca. 20% w/w) in a simulated tablet to demonstrate the forensic application of the technique (138-fold enhancement for the ortho-pyridyl protons). The amount of 4-PMP.3HCl present in the simulated tablet was quantified via NMR using D2 O as a solvent and compared well to complimentary GC-MS data. Exchanging D2 O for CD3 OD as the solvent utilised for analysis resulted in a significantly lower amount of 4-PMP.3HCl being determined, thus highlighting safeguarding issues linked to drug abuse in relation to determining the amount of active pharmaceutical ingredient present

Fermi surface of SrFe2_2P2_2 determined by de Haas-van Alphen effect

We report measurements of the Fermi surface (FS) of the ternary phosphide SrFe$_2$P$_2$ using the de Haas-van Alphen effect. The calculated FS of this compound is very similar to SrFe$_2$As$_2$, the parent compound of the high temperature superconductors. Our data show that the Fermi surface is composed of two electron and two hole sheets in agreement with bandstructure calculations. Several of the sheets show strong c-axis warping emphasizing the importance of three-dimensionality in the non-magnetic state of the ternary pnictides. We find that the electron and hole pockets have a different topology, implying that this material does not satisfy a nesting condition.Comment: 5 pages, 4 Figures, 1 Tabl

Utilisation of the static Evans method to measure magnetic susceptibilities of transition metal acetylacetonate complexes as part of an undergraduate inorganic laboratory class

The Evans method is routinely utilised to collect paramagnetic susceptibility data via the employment of relevant Nuclear Magnetic Resonance (NMR) methods. As the sample is normally spun, the lack of such a function on benchtop NMR instrumentation required a “static” approach to be employed. We have utilised the static Evan’s method approach to measure the magnetic susceptibilities, and subsequently the effective magnetic moment, of a series of synthesised transition metal acetylacetonate complexes in order to appraise the d-electron configuration. The obtained values were compared to those obtained using a Guoy balance and theoretical calculations. The collection of T1 relaxation data further exemplifies the effect of the paramagnetic centre in terms of aiding relaxation, and therefore links to Magnetic Resonance Imaging (MRI) contrast agents, thus providing students with real-world perspective of the experiment conducted