共查询到8条相似文献,搜索用时 0 毫秒
1.
Moy FM 《Journal of photochemistry and photobiology. B, Biology》2011,104(3):444-448
Vitamin D status is influenced by sun exposure, geographic latitude, daily outdoor activities, body surface exposed to sunlight and dietary intakes. Malaysia, is sunny all year round. However, the vitamin D status of this population especially among the healthy and free living adults is not known. Therefore a study of vitamin D status and associated factors was initiated among an existing Malay cohort in Kuala Lumpur. A total of 380 subjects were sampled to have their vitamin D status assessed using 25-hydroxyvitamin D (25(OH)D). A short questionnaire enquiring socio-demographic characteristics, exposure to sunlight and clothing style was administered. Their mean age was 48.5±5.2years and the mean 25(OH)D for males and females were 56.2±18.9nmol/L and 36.2±13.4nmol/L respectively. There were significant positive correlation for sun exposure score (r=0.27, p<0.001) and negative correlation for sun protection score (r=-0.41, p<0.001) with 25(OH)D levels. In the logistic regression model, females (OR=2.93; 95% CI: 1.17, 7.31), BMI (1.1; 1.03, 1.20) and sun exposure score (0.998; 0.996, 0.999) were significantly associated with vitamin D status as represented by 25(OH)D levels. Our findings show that obesity, lifestyle behaviours and clothing style are directly associated with our participants especially females' low vitamin D status. 相似文献
2.
Renato Millioni Manuela Miuzzo Stefano Sbrignadello Ellen Murphy Lucia Puricelli Andrea Tura Elisa Bertacco Marcello Rattazzi Elisabetta Iori Paolo Tessari 《Electrophoresis》2010,31(8):1311-1317
2‐DE is a fundamental technology used in proteomics research. However, despite its high capacity to simultaneously separate several proteins for subsequent identification and quantitative comparison studies, a drawback for this technique is its limited reproducibility, especially when comparing data from different laboratories. 2‐DE‐related variability can be broadly divided into two categories: experimental and post‐experimental. Experimental variability depends on physical and chemical parameters, whereas post‐experimental variability arises when gels are analyzed by different software packages, particularly when different workflows are followed. In this paper, we compared the analysis performance of two software packages, Delta2D and Proteomweaver, using both standard and experimental gel images. Using standard gel images, the false negative spot count was 50% lower, the false positive count was 77% lower, the true positive count was 19% higher and spot matching was 4% higher in Delta2D when compared to Proteomeweaver. Using experimental gel images, we found that the total amount of time taken to complete the analysis with Delta2D was 30% that of the time needed with Proteomweaver and required fewer user interventions. The differences between ease of use and workflow strategy of these programs is discussed. 相似文献
3.
Focken U 《Rapid communications in mass spectrometry : RCM》2004,18(18):2087-2092
Back-calculation of the diet is one of the most frequent applications of stable isotope techniques in animal ecology. These calculations are often based on two assumptions: a constant trophic shift for all dietary items and a linear response of the isotopic ratios to different mixtures of two isotopically distinct feeds. In a laboratory experiment, fish (Nile tilapia, Oreochromis niloticus) were fed semi-synthetic diets prepared either from wheat or corn ingredients, or from three blended diets (25, 50, 75% wheat components). Isotopic analysis of the lipid-free and lipid fraction of the fish after the experiment revealed that the trophic shift was not constant for wheat- and corn-based diets. The isotopic response to the mixed diets was not linear, leading to a statistically significant over-estimation of the corn component in the back-calculation. Both effects are in agreement with published data on the isotopic effects of C3- and C4-plant materials in the diet. 相似文献
4.
Solid-phase microextraction (SPME) is a powerful technique, easy to implement for on-site static sampling of indoor VOCs emitted
by building materials. However, a major constraint lies in the establishment of calibration curves which requires complex
generation of standard atmospheres. Thus, the purpose of this paper is to propose a model to predict adsorption kinetics (i.e.,
calibration curves) of four model VOCs. The model is based on Fick’s laws for the gas phase and on the equilibrium or the
solid diffusion model for the adsorptive phase. Two samplers (the FLEC? and a home-made cylindrical emission cell), coupled
to SPME for static sampling of material emissions, were studied. A good agreement between modeling and experimental data is
observed and results show the influence of sampling rate on mass transfer mode in function of sample volume. The equilibrium
model is adapted to quite large volume sampler (cylindrical cell) while the solid diffusion model is dedicated to small volume
sampler (FLEC?). The limiting steps of mass transfer are the diffusion in gas phase for the cylindrical cell and the pore
surface diffusion for the FLEC?. In the future, this modeling approach could be a useful tool for time-saving development
of SPME to study building material emission in static mode sampling. 相似文献
5.
Diran Herebian Marc Lamshöft Ertan Mayatepek Ute Spiekerkoetter 《Rapid communications in mass spectrometry : RCM》2010,24(6):791-800
The objective of our work was to identify known and unknown metabolites of the drug NTBC (2‐(2‐nitro‐4‐trifluoromethylbenzoyl)‐1,3‐cyclohexanedione) in urine from patients during the treatment of hereditary tyrosinemia type 1 (HT‐1) disease, a severe inborn error of tyrosine metabolism. Two different mass spectrometric techniques, a triple stage quadrupole and an LTQ‐Orbitrap (Fourier transform mass spectrometry (FTMS)), were used for the identification and the structural elucidation of the detected metabolites. Initially, the mass spectrometric (MS) approach consisted of the precursor ion scan detection of the selected product ions, followed by the corresponding collision‐induced dissociation (CID) fragmentation analysis (MS2) for the targeted selected reaction monitoring (SRM) mode. Subsequently, accurate and high‐resolution full scan and MS/MS measurements were performed on the possible metabolites using the LTQ‐Orbitrap. Final confirmation of the identified metabolites was achieved by measuring commercially supplied or laboratory‐synthesized standards. Altogether six metabolites, including NTBC itself, were extracted, detected and identified. In addition, two new NTBC metabolites were unambiguously identified as amino acid conjugates, namely glycine‐NTBC and β‐alanine‐NTBC. These identifications were based on their characteristics of chromatographic retention times, protonated molecular ions, elemental compositions, product ions (using CID and higher‐energy C‐trap dissociation (HCD) techniques) and synthesized references. The applied MS strategy, based on two different MS platforms (LC/MS/MS and FTMS), allowed the rapid identification analysis of the drug metabolites from human extracts and could be used for pharmaceutical research and drug development. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
6.
Stanton CL Kuo IF Mundy CJ Laino T Houk KN 《The journal of physical chemistry. B》2007,111(43):12573-12581
Despite decades of study, the mechanism by which orotidine-5'-monophosphate decarboxylase (ODCase) catalyzes the decarboxylation of orotidine monophosphate remains unresolved. A computational investigation of the direct decarboxylation mechanism has been performed using mixed quantum mechanical/molecular mechanical (QM/MM) dynamics simulations. The study was performed with the program CP2K that integrates classical dynamics and ab initio dynamics based on the Born-Oppenheimer approach. Two different QM regions were explored. The free energy barriers for direct decarboxylation of orotidine-5'-monophosphate (OMP) in solution and in the enzyme (using the larger QM region) were determined with the metadynamics method to be 40 and 33 kcal/mol, respectively. The calculated change in activation free energy (DeltaDeltaG++) on going from solution to the enzyme is therefore -7 kcal/mol, far less than the experimental change of -23 kcal/ mol (for k(cat.)/k(uncat.): Radzicka, A.; Wolfenden, R., Science 1995, 267, 90-92). These results do not support the direct decarboxylation mechanism that has been proposed for the enzyme. However, in the context of QM/MM calculations, it was found that the size of the QM region has a dramatic effect on the calculated reaction barrier. 相似文献
7.
Pól J Varadová Ostrá E Karásek P Roth M Benesová K Kotlaríková P Cáslavský J 《Analytical and bioanalytical chemistry》2007,388(8):1847-1857
Pressurised fluid extraction using water or methanol was employed for the extraction of stevioside from Stevia rebaudiana Bertoni. The extraction method was optimised in terms of temperature and duration of the static or the dynamic step. Extracts
were analysed by liquid chromatography followed by UV and mass-spectrometric (MS) detections. Thermal degradation of stevioside
was the same in both solvents within the range 70–160 °C. Methanol showed better extraction ability for isolation of stevioside
from Stevia rebaudiana leaves than water within the range 110–160 °C. However, water represents the green alternative to methanol. The limit of
detection of stevioside in the extract analysed was 30 ng for UV detection and 2 ng for MS detection. 相似文献
8.
In ESI‐source H/D exchange under atmospheric pressure for peptides and proteins of different molecular weights from 1 to 66 kDa: the role of the temperature of the desolvating capillary on H/D exchange 下载免费PDF全文
Yury Kostyukevich Alexey Kononikhin Igor Popov Alexander Spasskiy Eugene Nikolaev 《Journal of mass spectrometry : JMS》2015,50(1):49-55
Transition of proteins from the solution to the gas phase during electrospray ionization remains a challenging problem despite the large amount of attention it has received during the past few decades. One of the major questions relates to the extent to which proteins in the gas phase retain their condensed phase structures. We have used in‐electrospray source hydrogen/deuterium exchange to determine the number of deuterium incorporations as a function of protein mass, charge state and temperature of the desolvating capillary where the reaction occurs. All experiments were performed on a Thermo LTQ FT Ultra equipped with a 7‐T superconducting magnet. Ions were generated by an IonMax Electrospray ion source operated in the positive ESI mode. Deuterium exchange was performed by introducing a droplet of D2O beneath the ESI capillary. We systematically investigated gas phase hydrogen/deuterium (H/D) exchange under atmospheric pressure for peptides and proteins of different molecular weights from 1 to 66 kDa. We observed that almost all proteins demonstrate similar exchange rates for all charge states and that these rates increase exponentially with the temperature of the desolvating capillary. We did not observe any clear correlation of the number of H/D exchanges with the value of the cross section for a corresponding charge state. We have demonstrated the possibility of performing in‐ESI source H/D exchange of large proteins under atmospheric pressure. The simplicity of the experimental setup makes it a useful experimental technique that can be applied for the investigation of gas phase conformations of proteins. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献