In this study, we discuss some relevant aspects concerning the determination of selenium in biological materials with special reference to fluorometry and hydride generation atomic absorption spectroscopy (HG-AAS) techniques. The two methods may be applied without modifications to the analysis of Se in a wide spectrum of specimen types, and we describe their reliability in serum and hair analyses. Thirty-six independent control serum samples, the concentrations of which were unknown to the analyst, were analyzed in duplicate using both techniques in the Italian External Quality Assessment Scheme (EQAS). Accuracy was assessed by comparing Se values with those previously assigned by the organizers of the scheme using graphite furnace atomic absorption spectrometry (GF-AAS), which is the most frequently used technique for selenium determination in serum among the participants in the Italian EQAS. The results confirmed that fluorometry has a higher degree of accuracy than HG-AAS: the mean differences between observed and expected values were 1.5 μg/liter (95% confidence interval, −1.06 to 3.97) for fluorometry and −1.1 μg/liter (95% confidence interval, −5.05 to 2.76) for Hg-AAS. We also report some results obtained for the determination of Se in hair. Since a critical step in hair preparation is the pretreatment for removal of external contamination, we compared six different washing procedures. In general, Se is poorly leached from hair, but the efficiency of removal differed with the substance used, ranging from 0 to 13% of the original content. A nonionic detergent like Triton X-100 offers the advantage of safe working conditions and a substantial reduction in costs compared with organic solvents. Lastly, in a consistent group (n= 131) of women, Se in hair was found to be strongly reduced by the use of dye (389.9 ng/g vs 498.7 ng/g,P< 0.001). We recommend recording information on cosmetic treatments when hair is collected to evaluate Se reference values in epidemiological studies. 相似文献
Summary. Simple isocratic HPLC systems without tedious purification steps are elaborated for analyses of fumaric acid, its dimethyl and monomethyl ester, useful for analyses in biological matrices. 相似文献
Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mass spectrometry imaging of biological tissue sections using a layer of deposited ice as an energy-absorbing matrix was investigated. Dynamics of plume ablation were first explored using a nanosecond exposure shadowgraphy system designed to simultaneously collect pictures of the plume with a camera and collect the Fourier transform ion cyclotron resonance FT-ICR mass spectrum corresponding to that same ablation event. Ablation of fresh tissue analyzed with and without using ice as a matrix were compared using this technique. Effect of spot-to-spot distance, number of laser shots per pixel, and tissue condition (matrix) on ion abundance were also investigated for 50 μm-thick tissue sections. Finally, the statistical method called design of experiments was used to compare source parameters and determine the optimal conditions for IR-MALDESI of tissue sections using deposited ice as a matrix. With a better understanding of the fundamentals of ablation dynamics and a systematic approach to explore the experimental space, it was possible to improve ion abundance by nearly one order of magnitude.
Based on consecutive extractions using bismuth diethyldithiocarbamate and thallium diethyldithiocarbamate as reagents, molybdenum was selectively and highly enriched from biological matrices, and then subjected to neutron activation analysis. Most of interfering elements, e.g., Na, K, Br, P, Fe, U, etc. were simultaneouly removed and the preconcentrated samples always showed only the r rays from molybdenum after neutron bombardment. Thus, molybdenum in the biological matrices could be accurately determined. 相似文献
Biological applications of mass spectrometry have grown exponentially since the discovery of MALDI and electrospray ionization
techniques. This growth has been further fueled by the massive volume of DNA sequence information that is now available. An
ambitious goal of some of this research is to monitor the level and modification of all proteins and metabolites in a biological
sample such as plasma. A major research effort in mass spectrometry and related disciplines has been expended over the past
several years toward reaching this and other less ambitious goals, and considerable progress has been made; but the presently
available tools are clearly not sufficient for these very difficult tasks. In this “critical insight” discussion we suggest
that recent advances in time-of-flight (TOF) technology with MALDI ionization may provide some important new tools for achieving
the goals of biological research. 相似文献
Abstract An isocratic reversed-phase liquid chromatographic method for the determination of chloramphenicol 1- and 3-succinate and chloramphenicol in serum within 5 minutes following precipitation with perchloric acid is described. An ion-pair chromatographic method gives the additional option of co-determination of chloramphenicol 3-glucuronide in urine and serum. An extraction method for the determination of chloramphenicol in biological tissues is presented. 相似文献
Direct analysis of plant and animal tissue samples by laser electrospray mass spectrometry (LEMS) was investigated using low-energy, femtosecond duration laser vaporization at wavelengths of 800 and 1042 nm followed by nanospray postionization. Low-energy (<50 μJ), fiber-based 1042 nm LEMS (F-LEMS) allowed interrogation of the molecular species in fresh flower petal and leaf samples using 435 fs, 10 Hz bursts of 20 pulses from a Ytterbium-doped fiber laser and revealed comparable results to high energy (75–1120 μJ), 45 fs, 800 nm Ti:Sapphire-based LEMS (Ti:Sapphire-LEMS) measurements. Anthocyanins, sugars, and other metabolites were successfully detected and revealed the anticipated metabolite profile for the petal and leaf samples. Phospholipids, especially phosphatidylcholine, were identified from a fresh mouse brain section sample using Ti:Sapphire-LEMS without the application of matrix. These lipid features were suppressed in both the fiber-based and Ti:Sapphire-based LEMS measurements when the brain sample was prepared using the optimal cutting temperature compounds that are commonly used in animal tissue cryosections.
Mutations at codons 248 and 249 of p53 gene showed a relatively high incidence in gastric cancer patients. Development of novel methods for the detection of codon mutations is of great importance for gastric cancer research. Studies have showed that the separation matrix can significantly influence the separation efficiency and resolution of small DNA fragments in CE. In order to achieve baseline separation of PCR-amplified products of small DNA fragments from gastric cancer tissue, linear polyacrylamides (LPA I and LPAII) were designed and synthesized in the current study. LPAI and LPAII were used as separation matrixes to separate small size fragments (less than 70 bp) of pBR322/BsuRI DNA Marker and the separation conditions were optimized. Optimum separations were performed at 25 kV in reversed-polarity mode with capillary temperature set at 15 °C. The signal of DNA fragments was detected using laser-induced fluorescence detector, with an argon ion laser as the excitation source that emits at 488 nm. A 520 nm bandpass filter was used as an emission cut-off filter. The resolution of small DNA fragments was higher when LPAI was used as separation matrix compared to LPAII, accompanied with longer migration time. The results indicated that LPAI as separation matrix was more efficient for the separation of small DNA fragments (less than 70 bp) than other LPAs. A rapid and sensitive analysis method for the separation and detection of small DNA fragments (less than 70 bp) was established in this study. The method was successfully applied to detect the mutations at codons 248 and 249 in p53 gene from gastric cancer tissues. 相似文献
This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca2+ on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology.
Amyloid fibrils are self‐assembled protein structures with important roles in biology (either pathogenic or physiological), and are attracting increasing interest in nanotechnology. However, because of their high aspect ratio and the presence of some polymorphism, that is, the possibility to adopt various structures, their characterization is challenging and basic information such as their mass is unknown. Here we show that charge‐detection mass spectrometry, recently developed for large self‐assembled systems such as viruses, provides such information in a straightforward manner. 相似文献
Abstract Triple quadrupole mass spectrometers are generally not considered a choice of instrument for determination of peptide molecules, for the reason that a collision cascade or a multiple fragmentation in the triple quadrupoles tends to decrease the sensitivity of peptide detection. Vasopressin, a peptide drug with an intra-chain disulfide bond, however, was found to generate a different fragmentation pattern. Its 20 member intra-loop went through an abrupt bond cleavage and structurally distinctive immonium ions produced in the secondary fragmentation were observed in abundance. With these immonium ions, an effective methodology for analyzing the peptides with intra-loops in biological matrices was developed in this report. 相似文献
