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Mass Values (mass + value)
Kinds of Mass Values Selected AbstractsPeptides of human gingival crevicular fluid determined by HPLC-ESI-MSEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2005Elisabetta Pisano The acidic-soluble protein content of human gingival crevicular fluid was analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC), and the eluent deriving from the chromatography separation was directly introduced into an ion-trap mass spectrometer through electrospray ionization (ESI-IT MS). By this technique the molecular weight of peptides/proteins was determined with a precision of ,,1/10,000 amu. On the basis of the chromatographic behavior and the knowledge of the molecular mass value, some peptides and proteins soluble in acidic solution were unambiguously recognized. Besides high quantities of human serum albumin, , -defensins 1,4 and minor amounts of cystatin A, statherin, basic PB salivary peptide and other unidentified components were detected. The presence of , -defensins in gingival crevicular fluid is in agreement with their relevant contribution to protein composition deriving from granulocyte secretions. Other peptides and proteins abundant in human saliva, such as proline-rich proteins (PRPs) and histatins, were not detected in gingival crevicular fluid. Further investigations will be necessary to establish the origin of statherin and PB salivary peptide in gingival crevicular fluid. [source] Exact mass measurement on an electrospray ionization time-of-flight mass spectrometer: error distribution and selective averagingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2003Jiejun Wu Abstract An automated, accurate and reliable way of acquiring and processing flow injection data for exact mass measurement using a bench-top electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Using Visual Basic programs, individual scans were selected objectively with restrictions on ion counts per second for both the compound of interest and the mass reference peaks. The selected ,good scans' were then subjected to two different data-processing schemes (,combine-then-center' and ,center-then-average'), and the results were compared at various ion count limit settings. It was found that, in general, the average of mass values from individual scans is more accurate than the centroid mass value of the combined (same) scans. In order to acquire a large number of good scans in one injection (to increase the sampling size for statistically valid averaging), an on-line dilution chamber was added to slow down the typically rapid mass chromatographic peak decay in flow-injection analysis. This simple addition worked well in automation without the need for manual sample dilution. In addition, by dissolving the reference compound directly into the mobile phase, manual syringe filling can be eliminated. Twenty-seven samples were analyzed with the new acquisition and process routines in positive electrospray ionization mode. For the best method found, the percentage of samples with RMS error less than 5 ppm was 100% with repetitive injection data (6 injections per sample), and 95% with single injection data. Afterwards, 31 other test samples were run (with MW ranging from 310 to 3493 Da, 21 samples in ESI+ and 10 in ESI, mode) and processed with similar parameters and 100% of them were mass-calculated to RMS error less than 5 ppm also. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of density homogeneity on the dynamic response of powder bedsAICHE JOURNAL, Issue 8 2003T. Yanagida Homogeneous and inhomogeneous powder beds subjected to low-magnitude vibration are compared in terms of the dynamic response. The inhomogeneous samples were segregated into two phases: loose and dense phases, layering the two phases horizontally or vertically. An apparent mass, defined as a ratio of the base force to base acceleration, was measured. Comparison of homogeneous and segregated data demonstrated a significant density gradient dependence on the apparent mass data. First, homogeneous systems showed a resonant peak, which gave the longitudinal elastic modulus of the bed via the velocity of longitudinal stress wave propagation. Second, vertically segregated systems exhibited two significant peaks at low frequencies, corresponding to the resonance of each phase. In addition, the apparent mass values at the two peaks were related to the quantity of each phase. Third, horizontally segregated systems exhibited a resonant peak, whose frequency was approximately equal to homogeneous data, but the apparent mass value at the peak differed from homogeneous data. A model based on the fourth-power scaling law, two-phase theory and Rayleigh's energy method gave an interpretation for the insensitivity of the peak frequency to the density gradient in the vertical direction. [source] Detection of four oxidation sites in viral prolyl-4-hydroxylase by top-down mass spectrometryPROTEIN SCIENCE, Issue 10 2003Ying Ge Abstract Oxidative inactivation is a common problem for enzymatic reactions that proceed via iron oxo intermediates. In an investigation of the inactivation of a viral prolyl-4-hydroxylase (26 kD), electrospray mass spectrometry (MS) directly shows the degree of oxidation under varying experimental conditions, but indicates the addition at most of three oxygen atoms per molecule. Thus, molecular ion masses (M + nO) of one sample indicate the oxygen atom adducts n = 0, 1, 2, 3, and 4 of 35, 41, 19, 5 ± 3, and <2%, respectively; "top-down" MS/MS of these ions show oxidation at the sites R28,V31, E95,F107, and K216 of 22%, 28%, and 34%, respectively, but with a possible (,4%) fourth site at V125,D150. However, for the doubly oxidized molecular ions (increasing the precursor oxygen content from 0.94 to 2), MS/MS showed an easily observable ,13% oxygen at the V125,D150 site. For the "bottom-up" approach, detection of the ,4% oxidation at the V125,D150 site by MS analysis of a proteolysis mixture would have been very difficult. The unmodified peptide containing this site would represent a few percent of the proteolysis mixture; the oxidized peptide not only would be just ,4% of this, but the uniqueness of its mass value (,1,2 kD) would be far less than the 11,933 Dalton value used here. Using different molecular ion precursors for top-down MS/MS also provides kinetic data from a single sample, that is, from molecular ions with 0.94 and 2 oxygens. Little oxidation occurs at V125,D150 until K216 is oxidized, suggesting that these are competitively catalyzed by the iron center; among several prolyl-4-hydroxylases the K216, H137, and D139 are conserved residues. [source] Stable Nickel Catalysts for Fast Norbornene Polymerization: Tuning ReactivityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2005Juan A. Casares Abstract The air-stable complexes trans -[Ni(C6Cl2F3)2L2] (L = SbPh3, 1; AsPh3, 2; AsCyPh2, 3; AsMePh2, 4; PPh3, 5) have been synthesized by arylation of [NiBr2(dme)] (dme = 1,2-dimethoxyethane) in the presence of the corresponding ligand L (for compounds 1,4) or by ligand substitution starting from 1 (for compound 5). The structures of 1, 2, and 5 have been determined by X-ray diffraction and show an almost perfect square-planar geometry in all cases. Their catalytic activity in insertion polymerization of norbornene have been tested showing a strong dependence of the yield and molecular mass of the polymer on the ligand used and the solvent. High yield and high molecular mass values are obtained using complexes with ligands easy to displace from NiII (SbPh3 is the best) and noncoordinating solvents. Complexes 1,3 are suggested as convenient bench-catalysts to have available in the lab. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Low Leptin Levels in Migraine: A Case Control StudyHEADACHE, Issue 7 2008Baburhan Guldiken MD Background., Obesity has been shown to be a risk factor for transformation of episodic migraine to chronic form, and adipocytokines have been implicated to modulate some of the cytokins such as interleukin-6 and tumor necrosis factor, which also act in the neurogenic inflammation in migraine. The aim of the study was to assess leptin levels, one of the adipocytokines, in headache-free period of migraine patients and investigate its relation to vascular risk factors. Material and Methods., Sixty-one patients with episodic migraine headaches and 64 control subjects were enrolled in the study. Demographic data and anthropometric measurements were obtained from all participants; body mass index and fat mass values were calculated. Glucose and lipid parameters were measured by oxidase technique and cholesterol esterase enzymatic assays, and leptin levels were measured by ELISA in serum samples obtained after an overnight fasting. Results., Leptin levels were found significantly lower in migraineurs than controls (40.1 ± 21.2 ng/mL, 48.5 ± 24.5 ng/mL; P < .05). Although body mass index did not differ between 2 groups, fat mass, and fat percentages were significantly lower in migraine patients (19.4 ± 8.8 kg, 26.0 ± 8.7 kg; P < .001 and 28 ± 9%, 34 ± 5%; P < .001, respectively). Conclusion., Migraine patients have low leptin levels and fat mass which may be related to the pathogenesis of migraine. The importance and impact of our findings on the prevalence, characteristics, and treatment of migraine needs to be investigated in further detailed studies. [source] Pubertal Maturation Characteristics and the Rate of Bone Mass Development Longitudinally Toward MenarcheJOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2001Silvia C. C. M. Van Coeverden Abstract To assess risks for osteoporosis and to compare bone mass in different groups of healthy children or children with diseases, it is important to have knowledge of their sexual maturation status during puberty. The aim of our study was to evaluate bone mass formation longitudinally in relation to pubertal maturation characteristics in healthy white girls. We investigated the bone mineral content (BMC) and the bone mineral density (BMD) at different skeletal sites in 151 girls with increasing pubertal stages in relation with their chronological age and with an early or late onset of puberty or menarche and with a slow or fast maturation. Bone mass was measured at the onset of puberty, during puberty, and at menarche. We conclude the following: (1) from midpuberty to menarche, the increase in bone mass formation is highest at all skeletal sites in white girls; (2) early mature girls at the onset of puberty have slightly but definitely lower bone masses at all skeletal sites and at all pubertal stages than late mature girls, whereas the average bone mass formation from the onset of puberty to menarche is similar in both groups; (3) girls with a slow rate of pubertal maturation have lower bone mass values 2 years after the onset of puberty, but at menarche bone mass is similar compared with fast maturers; and (4) it cannot be confirmed that there is an effect of menarcheal age on bone mass values at menarche. [source] Exact mass measurement on an electrospray ionization time-of-flight mass spectrometer: error distribution and selective averagingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2003Jiejun Wu Abstract An automated, accurate and reliable way of acquiring and processing flow injection data for exact mass measurement using a bench-top electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Using Visual Basic programs, individual scans were selected objectively with restrictions on ion counts per second for both the compound of interest and the mass reference peaks. The selected ,good scans' were then subjected to two different data-processing schemes (,combine-then-center' and ,center-then-average'), and the results were compared at various ion count limit settings. It was found that, in general, the average of mass values from individual scans is more accurate than the centroid mass value of the combined (same) scans. In order to acquire a large number of good scans in one injection (to increase the sampling size for statistically valid averaging), an on-line dilution chamber was added to slow down the typically rapid mass chromatographic peak decay in flow-injection analysis. This simple addition worked well in automation without the need for manual sample dilution. In addition, by dissolving the reference compound directly into the mobile phase, manual syringe filling can be eliminated. Twenty-seven samples were analyzed with the new acquisition and process routines in positive electrospray ionization mode. For the best method found, the percentage of samples with RMS error less than 5 ppm was 100% with repetitive injection data (6 injections per sample), and 95% with single injection data. Afterwards, 31 other test samples were run (with MW ranging from 310 to 3493 Da, 21 samples in ESI+ and 10 in ESI, mode) and processed with similar parameters and 100% of them were mass-calculated to RMS error less than 5 ppm also. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of density homogeneity on the dynamic response of powder bedsAICHE JOURNAL, Issue 8 2003T. Yanagida Homogeneous and inhomogeneous powder beds subjected to low-magnitude vibration are compared in terms of the dynamic response. The inhomogeneous samples were segregated into two phases: loose and dense phases, layering the two phases horizontally or vertically. An apparent mass, defined as a ratio of the base force to base acceleration, was measured. Comparison of homogeneous and segregated data demonstrated a significant density gradient dependence on the apparent mass data. First, homogeneous systems showed a resonant peak, which gave the longitudinal elastic modulus of the bed via the velocity of longitudinal stress wave propagation. Second, vertically segregated systems exhibited two significant peaks at low frequencies, corresponding to the resonance of each phase. In addition, the apparent mass values at the two peaks were related to the quantity of each phase. Third, horizontally segregated systems exhibited a resonant peak, whose frequency was approximately equal to homogeneous data, but the apparent mass value at the peak differed from homogeneous data. A model based on the fourth-power scaling law, two-phase theory and Rayleigh's energy method gave an interpretation for the insensitivity of the peak frequency to the density gradient in the vertical direction. [source] Analytical aspects of pharmaceutical grade chondroitin sulfatesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2007Nicola Volpi Abstract Chondroitin sulfate is a very heterogeneous polysaccharide in terms of relative molecular mass, charge density, chemical properties, biological and pharmacological activities. It is actually recommended by EULAR as a symptomatic slow acting drug (SYSADOA) in Europe in the treatment of knee osteoarthritis based on meta-analysis of numerous clinical studies. Chondroitin sulfate is also utilized as a nutraceutical in dietary supplements mainly in the United States. On the other hand, chondroitin sulfate is derived from animal sources by extraction and purification processes. As a consequence, source material, manufacturing processes, the presence of contaminants, and many other factors contribute to the overall biological and pharmacological actions of these agents. The aim of this review is to evaluate new possible more specific analytical approaches to the determination of the origin and purity of chondroitin sulfate preparations for pharmaceutical application and in nutraceuticals, such as the evaluation of the molecular mass values, the constituent disaccharides, and the specific and sensitive agarose-gel electrophoresis technique. Furthermore, a critical evaluation is presented, together with a discussion of the limits of these analytical approaches. Finally, the necessity for reference standards having high specificity, purity and well-known physico-chemical properties useful for accurate and reproducible quantitative analyses will be discussed. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3168,3180, 2007 [source] Isotopic pattern and accurate mass determination in urine drug screening by liquid chromatography/time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2006Suvi Ojanperä An efficient method was developed for toxicological drug screening in urine by liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry. The method relies on a large target database of exact monoisotopic masses representing the elemental formulae of reference drugs and their metabolites. Mass spectral identification is based on matching measured accurate mass and isotopic pattern (SigmaFitÔ) of a sample component with those in the database. Data post-processing software was developed for automated reporting of findings in an easily interpretable form. The mean and median of SigmaFitÔ for true-positive findings were 0.0066 and 0.0051, respectively. The mean and median of mass error absolute values for true-positive findings were 2.51 and 2.17,ppm, respectively, corresponding to 0.65 and 0.60,mTh. For routine screening practice, a SigmaFitÔ tolerance of 0.03 and a mass tolerance of 10,ppm were chosen. Ion abundance differences from urine extracts did not affect the accuracy of the automatically acquired SigmaFitÔ or mass values. The results show that isotopic pattern matching by SigmaFitÔ is a powerful means of identification in addition to accurate mass measurement. Copyright © 2006 John Wiley & Sons, Ltd. [source] Copper(I) chloride: a simple salt for enhancement of polystyrene cationization in matrix-assisted laser desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2001Sándor Kéki The possibility of using copper(I) chloride as a doping salt to enhance the cationization of polystyrene in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was investigated. It was shown that copper(I) chloride possesses sufficient solubility in tetrahydrofuran. The parameters of the MALDI mass spectra of different polystyrene samples, such as the number-average (Mn) and mass-average (Mw) molecular mass values, obtained by copper(I) cationization were compared with those obtained by means of silver(I) cationization, and good agreement was found. It was also shown that application of copper(I) chloride as a doping salt, and dithranol as a matrix, ensured good MALDI mass spectra of the sample spots even after storage for 1 month. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||