Optimization of the mass spectrometric analysis of triacylglycerols using negative-ion chemical ionization with ammonia

Conditions for the mass spectrometric analysis of triacylglycerols,via direct exposure probe, with ammonia negative-ion chemical ionization were optimized. Triacylglycerols were most favorably ionized, using the reactant gas pressure of approximately 8500 mtorr at the ion source temperature of 200°C with the instrumentation used. Abundant [M-H]⁻ ions were produced under these conditions without the formation of [M+35]⁻ cluster ions, which would interfere with the molecular weight region of triacylglycerols in the spectra. A rapid desorption of the sample from the probe wire is recommended, using a relatively high heating rate (approximately 40 mA s⁻¹), to minimize thermal degradation of unsaturated molecules and the reducing effect of double bonds on the mass spectrometric response of triacylglycerols. Furthermore, the abundance of [M-H]⁻ ion was enhanced by rapid heating, which we found to be important to improve the sensitivity. The appropriate amount of sample applied to the rhenium wire was in the region of 50–300 ng for one determination, i.e., only a few nanograms of a single triacylglycerol is required for production of a reliable spectrum. The reproducibility of the method was good as demonstrated with standards and a raspberry seed oil sample. The described mass spectrometric method is a fast and potentially useful tool for semiquantitative determination of triacylglycerol mixtures of various fats and oils. The discrimination, caused by differences in molecular size and unsaturation of triacylglycerols with 50 to 56 acyl carbons, was negligible under our optimized ionization conditions, thus, no correction factors were needed. These findings have not yet been verified with instruments in other laboratories. However, the present study shows how the analysis of triacylglycerols can be improved, regardless of the instrument, by optimization of the analytical conditions.     

BRDF measurement of understory vegetation in pine forests: dwarf shrubs, lichen, and moss

The spectral and directional reflection properties of pine forest understory in Suonenjoki, Finland were measured using a newly developed transportable field goniospectrometer under direct sunlight or plant lamp. The samples represent the most typical types in Finnish forests. Large differences between species were found. Wax-leaved shrubs such as lingonberry and blueberry proved to be strong forward scatterers, whereas lichen and soft-leaved dwarf shrubs such as heather were strong backscatterers. The measured moss showed both forward and backscattering features. There were variations among the samples of the same species, but many typical features appeared consistent and reproducible. Both “pure” and mixed samples were measured, the latter showing smoother behavior than the former, that is, the strongest forward and backward features are downscaled. The results provide a starting point for an empirical understory model and a basis for development and validation of a theoretical model.     

Electrical sintering of nanoparticle structures

A method for sintering nanoparticles by applying voltage is presented. This electrical sintering method is demonstrated using silver nanoparticle structures ink-jet-printed onto temperature-sensitive photopaper. The conductivity of the printed nanoparticle layer increases by more than five orders of magnitude during the sintering process, with the final conductivity reaching 3.7 × 10(7)?S?m(-1) at best. Due to a strong positive feedback induced by the voltage boundary condition, the process is very rapid-the major transition occurs within 2?μs. The best obtained conductivity is two orders of magnitude better than for the equivalent structures oven-sintered at the maximum tolerable temperature of the substrate. Additional key advantages of the method include the feasibility for patterning, systematic control of the final conductivity and in situ process monitoring. The method offers a generic tool for electrical functionalization of nanoparticle structures.     

Mobility determination of lead isotopes in glass for retrospective radon measurements

In retrospective radon measurements, the 22-y half life of (210)Pb is used as an advantage. (210)Pb is often considered to be relatively immobile in glass after alpha recoil implanted by (222)Rn progenies. The diffusion of (210)Pb could, however, lead to uncertain wrong retrospective radon exposure estimations if (210)Pb is mobile and can escape from glass, or lost as a result of cleaning-induced surface modification. This diffusion was studied by a radiotracer technique, where (209)Pb was used as a tracer in a glass matrix for which the elemental composition is known. Using the ion guide isotope separator on-line technique, the (209)Pb atoms were implanted into the glass with an energy of 39 keV. The diffusion profiles and the diffusion coefficients were determined after annealing at 470-620 degrees C and serial sectioning by ion sputtering. In addition, the effect of surface cleaning on diffusion was tested. From the Arrhenius fit, the activation enthalpy (H) was determined, which is equal to 3.2 +/- 0.2 eV, and also the pre-exponential factor D(0), in the order of 20 m(2)s(-1). This result confirms the assumption that over a time period of 50 y (209)Pb (and (210)Pb) is effectively immobile in the glass. The boundary condition obtained from the measurements had the characteristic of a sink, implying loss of (209)Pb in the topmost surface at high temperatures.     

Fish Oil Finishing Diet Maintains Optimal n-3 Long-Chain Fatty Acid Content in European Whitefish (<Emphasis Type="Italic">Coregonus lavaretus</Emphasis>)

This study examined the effect of substituting vegetable oil for fish oil in feed, with subsequent re-introduction of fish oil-rich feed (finishing feeding) in late stages of growth, on the fatty acids of cultivated European whitefish (Coregonus lavaretus). Restorative finishing feeding with fish oil-rich feed for 15 and 25 weeks was sufficient to change the total content of nutritionally valuable long-chain n-3 fatty acids, eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3), to correspond to that of fish fed the fish oil-rich feed throughout their lifespan. Under natural conditions, 15 and 25 weeks correspond to weight gains of 75% and 100% (i.e. doubling), respectively. Also, the fatty acid profile of the fish was restored after finishing periods of 15 and 25 weeks. Limiting the use of fish oil by lowering the overall fat content of the feed (no vegetable oil added) resulted in a decrease in the long-chain n-3 fatty acids. Based on the results, after receiving a vegetable oil-rich diet, restorative fish oil-rich feeding in the last stages of growth in European whitefish is nutritionally justified in order to balance nutritional gain for consumers with sustainable use of finite marine oils. The results encourage commercial efforts to further utilize and optimize finishing feeding practices.     

New approach to the analysis of oxidized triacylglycerols in lipoproteins

The oxidation of human LDL lipids and the structures of oxidized TAG molecules found in LDL were investigated. Pooled samples of 10 normolipidemic and 10 hyperlipidemic subjects were analyzed. For determination of the oxidation levels, the LDL baseline diene conjugation (LDL-BDC) method was used. A method based on HPLC and electrospray ionization-MS was optimized and applied to the analysis of molecular structures of oxidized TAG in LDL. Differences were found between the oxidation levels of the samples. The LDL-BDC value was 22.2 μmol/L serum in the normolipidemic group, and 88.1 μmol/L serum in the hyperlipidemic group. The amounts of oxidized TAG molecules were small. However, several species of oxidized TAG were identified. These included TAG molecules with a keto or an epoxy group attached to a FA, and TAG molecules with a FA core aldehyde. In some TAG, the keto/epoxy ratio was greater in the hyperlipidemic group compared to the normolipidemic group. The results show that our approach is applicable to research on lipid oxidation in lipoproteins.     

The association of noise sensitivity with coronary heart and cardiovascular mortality among Finnish adults

The association of coronary heart and cardiovascular mortality with noise sensitivity was studied. We also investigated how this association is affected by self-reported lifetime noise exposure. In 1988 a case-control study, based on the Finnish Twin Cohort, was carried out to investigate the relationship between noise and hypertension (n=1495). Potential confounders were obtained from questionnaire in 1981 for the same individuals. Data on deaths and causes of death were obtained from record linkage to the nationwide register of death certificates. All deaths that occurred among the study population during the 15 years of follow-up were classified as being due to all causes (n=382), to cardiovascular diseases (n=193), including the number of deaths due to coronary heart diseases (n=111) and to other causes than cardiovascular diseases (n=189). Cardiovascular mortality (Hazard ratio 1.80, 95% CI 1.07-3.04) was significantly increased among noise-sensitive women. Among men, there were no statistically significant effects. Noise sensitivity may be a risk factor for cardiovascular mortality in women.     

Alarm Pheromones Do Not Mediate Rapid Shifts in Honey Bee Guard Acceptance Threshold

Honey bee (Apis mellifera) guards discriminate nestmates from non-nestmates at the hive entrance. The acceptance threshold of guards is known to change adaptively, for example becoming less permissive when the number of intruder bees from other colonies increases. These adaptive shifts can occur within minutes. What is unknown is the mechanism behind this rapid shift. It was hypothesized that alarm pheromones released by guards may cause the adoption of a less permissive acceptance threshold. Here, we tested this hypothesis on five discriminator hives by using a behavioral assay. We used three amounts each of iso-pentyl acetate (IPA) and 2-heptanone (2H), which are the major components of the pheromones from the sting and the mandibular glands, respectively. Biologically relevant levels of chemicals were delivered to the hive entrance platform via an air pump. We found no effect of either IPA or 2H: there was no change in guard acceptance of either nestmate (on average, 91% accepted) or non-nestmate (on average, 30% accepted) under any of the pheromone treatments compared to the pentane control (98% nestmates accepted and 32% non-nestmates accepted). Therefore, we reject the hypothesis that the presence of IPA or 2H causes a rapid shift of guard acceptance threshold.