Vera Thoss

A novel optically based chemosensor for the detection of blood Na

Abstract The azo dye based chemosensor 2 displays extremely good sensitivity and selectivity for Na+ over other physiologically important alkali and alkali earth metal ions in the 0.3–1.0×10−4 M concentration range as well as being pH independent above pH 3.9. This sensitivity coincides with the Na+ concentration range found in blood. The sensor exhibits almost 110 nm hypsochromic shift in the absorption spectrum upon Na+ detection, with a strong colour change from red to yellow in aqueous solution which is clearly visible to the naked eye even at low concentrations.

Novel sodium-selective fluorescent PET and optically based chemosensors: towards Na + determination in serum

The anthracene based fluorescent PET chemosensor 1 and the azo-dye based chemosensor 2 show high selectivity for Na+ over other alkali and alkaline-earth metal cations in the 12–300 mM concentration range in 50 ∶ 50 MeOH–H2O at pH 7.4. Chemosensor 1 shows fluorescence ‘off-on’ switching upon Na+ complexation with λFmax of 440 nm and a log βNa of 2.5 (±0.05) and a pKa of 5.3 with no concomitant changes in the absorption spectra. Conversely, 2 displays only a weak fluorescent emission at around 520–640 nm, and large changes in its absorption spectra upon addition of Na+, with a log βNa of 1.25 (±0.05) and a pKa of 3.9. In 100% water the sensitivity of 2 for Na+ was somewhat lower with a log βNa of 0.8 (±0.05). The crystal structure of 2, and its corresponding protonated form (2·H+) were obtained, showing 2 in its trans conformation with the crown ether moiety at a 75° angle to the plane of the chromophore. These results, in conjunction with 1H NMR measurements of 2, and UV–VIS measurements of the ion receptor 3, suggest that upon complexation of Na+, the 2′-methoxy group of the crown receptor participates in the Na+ complexation through chelation to the Na+ ion. We propose that this interaction forces the amine moiety of the crown ether to twist out of the plane of the chromophore, inducing loss of conjugation which gives rise to large Na+-induced spectral changes in the absorption spectra, which are most noticeable for 2.

Spectroscopic Characterization of Asphaltene Fraction of Nigerian Bitumen

This research article offers data on the spectroscopic elucidation of the asphaltene fraction of Nigerian bitumen in order to establish its features that might aid the developmental processes of the fossil fuel. Bitumen was extracted from the oil sands obtained from six locations where there were oil sand out-crops in Southwestern Nigeria using toluene via Soxhlet extraction and then deasphalted using n-pentane. The organic components of the precipitated asphaltenes were investigated using Fourier transform infrared spectrometry, while the elemental contents were determined using Inductively coupled plasma atomic emission spectroscopy and carbon/nitrogen analyzer. The results revealed that the average content (29.15 wt%) of Nigerian bitumen asphaltenes was less than that of Athabasca (40.10 wt%) but slightly higher than that of Cold Lake bitumen (24.40 wt%). The IR spectra of the asphaltenes indicated the presence of various organics and heteroatoms corroborating that asphaltenes composed of high molecular weight polycyclic constituents comprising of nitrogen, sulfur, and oxygen heteroatoms. The results indicated that the values of Cr, Cu, Fe, Mn, Ni, S, V, and Zn were comparatively higher in the asphaltenes than the parent bitumen due to the presence of comparatively high levels of porphyrins in the asphaltenes than the bitumen, while the concentrations of all the elements were higher in the Nigerian bitumen asphaltene than Nigerian crude oil asphaltene (except S and C). Cross plot analysis result between the asphaltenes and bitumen using their elemental mean concentrations as variables indicates that significant and positive correlation (R2 = 0.975) exists between them, indicating very strong interelement and geochemical relationships between them. The elements showed close clustering, indicating similar sources because the elements were known to associate with petroleum hydrocarbon formation. Also, apart from N, S, and C, other elements are transition metals with similar chemical affinity.

Browse Selection in Response to Simulated Seasonal Changes in Diet Quality through Postingestive Effects

Browse species undergo seasonal changes in nutritional value and secondary plant compound concentrations. The capacity of herbivores to monitor such change through postingestive effects and to modify their food choice appropriately was investigated. Twenty-four goats were offered a different conifer species on four successive learning days per 7-d period for six periods. During conifer consumption on learning days, animals received either a positive or a negative digestive stimulus to simulate the nutritional rewards and toxic consequences of browse consumption. For each animal, a different postingestive stimulus treatment was associated with each conifer species. The treatments consisted of an increasing positive stimulus, a decreasing positive stimulus, an increasing negative stimulus, or a decreasing negative stimulus. The levels of the stimuli were adjusted in 20% increments in successive periods (from 0 to 100% for the increasing treatments and from 100 to 0% in the decreasing treatments) to simulate seasonal changes in browse characteristics. Diet preference was measured on d 5 of each period. Animals adjusted their diet choice in response to the changing intensity of the negative stimulus, but not the positive stimulus. Animals avoided foods associated with the negative stimulus to a greater extent when the stimulus was increasing each period compared to when it was decreasing. The results suggest that herbivores are adept at monitoring and responding to temporal change in secondary compound concentrations through assessing their changing postingestive effects and adjusting their food choice accordingly.

Phosphorus speciation by (31)P NMR spectroscopy in bracken (Pteridium aquilinum (L.) Kuhn) and bluebell (Hyacinthoides non-scripta (L.) Chouard ex Rothm.) dominated semi-natural upland soil.

Access to P species is a driver for plant community composition based on nutrient acquisition. Here we investigated the distribution and accumulation of soil inorganic P (Pi) and organic P (Po) forms in a bracken and bluebell dominated upland soil for the period between bluebell above ground dominance until biomass is formed from half bluebells and half bracken. Chemical characterisation and (31)P Nuclear Magnetic Resonance spectroscopy was used to determine the organic and inorganic P species. Total P concentration in soils was 0.87gkg(-1), while in plants (above- and below-ground parts) total P ranged between 0.84-4.0gkg(-1) and 0.14-2.0gkg(-1) for bluebell and bracken, respectively. The P speciation in the plant samples was reflected in the surrounding soil. The main forms of inorganic P detected in the NaOH-EDTA soil extracts were orthophosphate (20.0-31.5%), pyrophosphate (0.6-2.5%) and polyphosphate (0.4-7.0%). Phytate (myo-IP6) was the most dominant organic P form (23.6-40.0%). Other major peaks were scyllo-IP6 and α- and β- glycerophosphate (glyP). In bluebells and bracken the main P form detected was orthophosphate ranging from (21.7-80.4%) and 68.5-81.1%, in above-ground and below-ground biomass, respectively. Other detected forms include α-glyP (4.5-14.4%) and β-glyP (0.9-7.7%) in bluebell, while in bracken they were detected only in stripe and blade in ranges of 2.5-5.5% and 4.4-9.6%, respectively. Pyrophosphate, polyphosphate, scyllo-IP6, phosphonates, found in soil samples, were not detected in any plant parts. In particular, the high abundance of phytate in the soil and in bluebell bulbs, may be related to a mechanism through which bluebells create a recalcitrant phosphorus store which form a key part of their adaptation to nutrient poor conditions.

Assessing rare earth elements in quartz rich geological samples

Sodium peroxide (Na2O2) fusion coupled to Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS) measurements was used to rapidly screen quartz-rich geological samples for rare earth element (REE) content. The method accuracy was checked with a geological reference material and Instrumental Neutron Activation Analysis (INAA) measurements. The used mass-mode combinations presented accurate results (only exception being (157)Gd in He gas mode) with recovery of the geological reference material QLO-1 between 80% and 98% (lower values for Lu, Nd and Sm) and in general comparable to INAA measurements. Low limits of detection for all elements were achieved, generally below 10 pg g(-1), as well as measurement repeatability below 15%. Overall, the Na2O2/ICP-MS/MS method proved to be a suitable lab-based method to quickly and accurately screen rock samples originating from quartz-rich geological areas for rare earth element content; particularly useful if checking commercial viability.

Triacylglycerol composition of British bluebell ( Hyacinthoides non-scripta ) seed oil

Bluebell seeds were collected from the same location for five different growth periods (2006–2010). The composition of fatty acids in the triacylglycerols present in bluebell seeds was determined using 1H- and 13C NMR and GC-MS of fatty acid methyl esters with good agreement between the different methods of analysis for the proportion of individual fatty acids. The seed oil comprised 80% ω-9 monounsaturated (C18:1, C20:1, C22:1), 10% ω-6,9 biunsaturated (C18:2) and 10% saturated fatty acids (C16:0, C18:0, C20:0, C22:0). The oil contained 25% of fatty acids with 20 or 22 carbon chain length. Gondoic acid (C20:1) was present at 20% and there was a consistency in the composition of the seed oil for the different harvest years. Based on the composition of bluebell seed oil, possible future uses are suggested and the combination of bio refining bluebell seeds in tandem with conservation efforts is proposed.

Role of monoterpenes in Hylobius abietis damage levels between cuttings and seedlings of Picea sitchensis

Abstract This study investigated the role of monoterpenes, a group of chemicals known to be involved in plant defence, in the susceptibility of Sitka spruce [Picea sitchensis (Bong.) Carr.] plants derived from both cuttings and seedlings to attack by the large pine weevil Hylobius abietis (L.). Results showed that, given the choice, weevils prefer to feed on the shoots of seedlings than of cuttings and that this preference continued over a period of 6 days, although the overall level of feeding declined. This observation was associated with a higher level of monoterpenes in the shoots from cuttings than in those from seedlings. When the weevils were restricted to the stems and given no choice, levels of damage to the bark were similar in both plant types.

Characterization of Plant Seeds by Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy

ABSTRACT Plant seeds accumulate and store phosphorus for the initial growth of seedlings. Phosphorus speciation by 31P nuclear magnetic resonance spectroscopy of NaOH–EDTA seed extracts showed that P was mainly present in organic forms such as phytate and α- and β-glycerophosphate in poppy, sesame, mustard, fennel, and cumin seeds. The inorganic P forms present included orthophosphate and pyrophosphate. The highest concentration of orthophosphate was found in NaOH–EDTA extracts of fennel seeds (41.7%) and the lowest in mustard (9.3%) and sesame seeds (6.9%). For the organic P forms, the highest concentration of phytate was found in mustard seeds (85.2%) and the lowest in fennel seeds (43.3%). Other organic P forms detected were α- and β-glycerophosphate ranging from 1.2 to 5.1% and 0.7 to 2.1%, respectively. Pyrophosphate was detected in trace amounts only in fennel (0.7%) and poppy seeds (0.5%). The only orthophosphate diester observed was in sesame seeds at a low concentration (0.7%), while phosphonates and polyphosphates were not present in any seeds. Phytate was the most dominant P form in all seeds except for fennel and cumin, which contained the lowest phytate concentration but the highest orthophosphate and glycerophosphate concentrations. These results suggest that P transferred from the plant vegetative parts to the developing seeds during maturation is converted to phytate (organic P) in addition to being stored as orthophosphate (inorganic P).

An unusual example of stereoelectronic control in the ring opening of 3,3-disubstituted 1,2-dichlorocyclopropenes

Quantitative SCF-MO calculations at the PM3 and ab initio level reveal that the origin of the stereoselective ring opening of 1,2-dichloro-3,3-disubstituted cyclopropenes (1, R2= CH2Cl, CH2OMe or CH2Ph) to give vinylcarbenes 2via transition state 5 arises from stereoelectronic control, in contrast to that of cyclopropenes having bulky non-polar substituents such as R2= Pri which favours a less hindered transition state 6.