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Chemical composition

Cheemical composition refers to the specific arrangement and proportion of elements within a chemical substance.
Understanding chemical composition is crucial for accurately characterizing and studying the properties of materials, drugs, and other substances.
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Most cited protocols related to «Chemical composition»

All raw data were centroided and converted to 32-bit uncompressed mzXML file using Bruker Data Analysis. A script was developed to select all possible MS/MS spectra in each LC-MS/MS run that could correspond to a compound present in the sample. For each compound, we calculated the theoretical mass M from its chemical composition and searched for the M+H, M+2H, M+K, and M+Na adducts. Putative identifications included all MS/MS spectra whose precursor m/z had a ppm error <50 compared to the theoretical mass of each possible precursor m/z; all tandem MS/MS spectra with an MS1 precursor intensity of <1E4 were ignored. All candidate identifications were manually inspected and the most abundant representative spectrum for each compound was added to the corresponding library at the gold or bronze level based upon an expert evaluation of the spectrum quality. The best MS/MS spectrum per compound as added to the GNPS-Collections library without filtering or alteration from the mzXML files.
Publication 2016
cDNA Library chemical composition Gold Tandem Mass Spectrometry
The PDB archive contains comprehensive descriptions of structural models coming from crystallography, NMR, and 3DEM. Each archival entry is denoted by a 4-character PDB identifier (e.g., 1VTL). In addition to atomic coordinates, details regarding the chemistry of biopolymers and any bound small molecules are archived, as are metadata describing biopolymer sequence, sample composition and preparation, experimental procedures, data-processing methods/software/statistics, structure determination/refinement procedures and statistics, and certain structural features, such as the secondary and quaternary structure. Primary experimental data coming from crystallography (structure-factor amplitudes or intensities) and NMR (restraints and chemical shifts) must be archived in the PDB. Voluntary archiving of diffraction images is currently supported by two resources that operate independently of the PDB, including the Integrated Resource for Reproducibility in Macromolecular Crystallography (IRRMC; www.proteindiffraction.org) and the Structural Biology Data Grid Consortium (SBGrid; sbgrid.org [31 (link)]) both of which use digital object identifiers to make the data readily accessible. In addition, some synchrotron radiation facilities now store diffraction images in locally maintained repositories, with data retention and dissemination policies determined by the facility. BMRB [32 ] has long served as a public repository for NMR experimental data that are not stored in the PDB. Mass density maps used to derive structural models from 3DEM can be archived in EMDB [33 (link)]. Voluntary archival deposition of raw 3DEM images is currently supported by EMPIAR [34 (link)].
The first data format used by the PDB archive was established in the early 1970s, and was based on the 80-column Hollerith format used for punched cards [35 (link)]. Atom records included atom name, residue name, polymer chain identifier, and polymer sequence number. A set of “header records” contained limited metadata. The community readily accepted this format, because it was simple and both human- and machine-readable. However, the format also had limitations that became serious liabilities as structural biologists took the field to new heights. Structural models were limited to 99,999 atoms and relationships among various data items were implicit. These and other weaknesses of the legacy PDB format meant that deep subject matter expertise was required to both create and use software relying on this format. In the 1990s, the International Union of Crystallography (IUCr) charged a committee with creating a more informative and extensible data model for the PDB archive.
In response to the IUCR committee report, the Macromolecular Crystallographic Information File (mmCIF) was proposed [36 ]. mmCIF is a self-defining format in which every data item has attributes describing its features, including explicit definitions of relationships among data items. Most important, mmCIF has no limitations with respect to the size of the structural model to be archived. In addition, the mmCIF dictionary and mmCIF format data files are fully machine-readable, and no domain knowledge is required to read the files. At inception, the mmCIF dictionary contained over 3000 data items pertaining to crystallography. Over time, data items specific to NMR and 3DEM were added, and the dictionary was subsequently rebranded PDBx/mmCIF [37 ]. In 2007, it was decided that PDBx would be the PDB Master Format for data collected by the wwPDB. In 2011, major crystallographic structure determination software developers agreed to adopt this data model so that going forward all output from their programs would be available in PDBx/mmCIF.
In collaboration with community stakeholders serving on the PDBx/mmCIF Working Group (wwpdb.org/task/mmcif), the wwPDB continues to extend and enhance archival data representations. As of December 2014, PDBx/mmCIF became the official format for distribution of PDB entries. At the time of writing, the PDBx/mmCIF dictionary contained more than 4400 data items, including ~250 and ~1200 specific to NMR and 3DEM, respectively. PDBML, an XML format based on PDBx/mmCIF [38 (link)] and the requisite RDF (Resource Description Framework) conversion have also been developed to facilitate integration of structural biology data with other life sciences data resources [39 (link)]. Recently, XML and RDF-formatted BMRB data have been provided as BMRB/XML and BMRB/RDF, respectively [40 (link)], by which a federated SPARQL query linking the BMRB is made available to other databases. Finally, other structural biology communities are building on the PDBx/mmCIF framework to establish their own controlled vocabulary and specialist data items. For example, SASbDB has been working in collaboration with wwPDB partners to develop sasCIF [41 ], which builds on PDBx/mmCIF. In addition to accelerating development of the SASbDB archive, creation of sasCIF will allow for facile inter-operation with the PDB archive using a common exchange protocol based on PDBx/mmCIF.
In 1996, BMRB adopted NMR-STAR (a version of mmCIF) as its archival format [42 ]. As noted above, this format has been harmonized with PDBx/mmCIF and now serves as the preferred deposition format for NMR structures [43 ]. Historically, most NMR experimental data have been deposited in “native” format provided by each software package and archived “as is” in the PDB. Format harmonization was addressed in part by the NMR Restraints Grid, which can process restraint files and convert them to the NMR-STAR or CCPN formats [44 (link), 45 (link)]. In 2013 and 2014, community stakeholders participating in a pair of NMR format meetings convened by the wwPDB NMR VTF, recommended that an NMR Exchange Format (NEF) be developed for facile data transfer among NMR software packages and faithful conversion to NMR-STAR [46 (link)]. BMRB-led efforts are now underway to complete harmonization of NEF with NMR-STAR/PDBx/mmCIF to support NMR data deposition, annotation, and validation using the wwPDB unified global system (deposit.wwpdb.org).
Prior to 2015, reliance on the original PDB format made it necessary for large structure depositions (e.g., ribosomes/ribosomal subunits) archived in the PDB to be “split” into multiple entries, each with its own 4-character PDB identifier and legacy PDB-format file. This stopgap arrangement was entirely suboptimal. Splitting depositions among multiple PDB entries effectively precluded routine visualization of some of the most interesting structural models in the PDB archive, owing to software limitations. With adoption of the PDBx/mmCIF standard, every PDB archival entry is now stored as a single PDBx/mmCIF file, including 277 large structures that had previously been “split.” At the time of writing (and for the foreseeable future), archival entries are made available as a public service in “stripped down,” best-effort PDB legacy format files wherever possible. In time, visualization, computational chemistry, etc. software providers will need to adjust to the new format and use PDBx/mmCIF files directly.
Publication 2017
Antioxidant (DPPH and ABTS radical scavenging, reducing power (CUPRAC and FRAP), phosphomolybdenum, and metal chelating (ferrozine method)) and enzyme inhibitory activities [cholinesterase (ChE) Elmann’s method], tyrosinase (dopachrome method), α-amylase (iodine/potassium iodide method), and α -glucosidase (chromogenic PNPG method)) were determined using the methods previously described by Zengin et al. (2014) (link) and Dezsi et al. (2015) (link).
For the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assay: Sample solution (1 mg/mL; 1 mL) was added to 4 mL of a 0.004% methanol solution of DPPH. The sample absorbance was read at 517 nm after a 30 min incubation at room temperature in the dark. DPPH radical scavenging activity was expressed as millimoles of trolox equivalents (mg TE/g extract).
For ABTS (2,2′-azino-bis(3-ethylbenzothiazoline) 6-sulfonic acid) radical scavenging assay: Briefly, ABTS+ was produced directly by reacting 7 mM ABTS solution with 2.45 mM potassium persulfate and allowing the mixture to stand for 12–16 in the dark at room temperature. Prior to beginning the assay, ABTS solution was diluted with methanol to an absorbance of 0.700 ± 0.02 at 734 nm. Sample solution (1 mg/mL; 1 mL) was added to ABTS solution (2 mL) and mixed. The sample absorbance was read at 734 nm after a 30 min incubation at room temperature. The ABTS radical scavenging activity was expressed as millimoles of trolox equivalents (mmol TE/g extract) (Mocan et al., 2016a (link)).
For CUPRAC (cupric ion reducing activity) activity assay: Sample solution (1 mg/mL; 0.5 mL) was added to premixed reaction mixture containing CuCl2 (1 mL, 10 mM), neocuproine (1 mL, 7.5 mM) and NH4Ac buffer (1 mL, 1 M, pH 7.0). Similarly, a blank was prepared by adding sample solution (0.5 mL) to premixed reaction mixture (3 mL) without CuCl2. Then, the sample and blank absorbances were read at 450 nm after a 30 min incubation at room temperature. The absorbance of the blank was subtracted from that of the sample. CUPRAC activity was expressed as milligrams of trolox equivalents (mg TE/g extract).
For FRAP (ferric reducing antioxidant power) activity assay: Sample solution (1 mg/mL; 0.1 mL) was added to premixed FRAP reagent (2 mL) containing acetate buffer (0.3 M, pH 3.6), 2,4,6-tris(2-pyridyl)-S-triazine (TPTZ) (10 mM) in 40 mM HCl and ferric chloride (20 mM) in a ratio of 10:1:1 (v/v/v). Then, the sample absorbance was read at 593 nm after a 30 min incubation at room temperature. FRAP activity was expressed as milligrams of trolox equivalents (mg TE/g extract).
For phosphomolybdenum method: Sample solution (1 mg/mL; 0.3 mL) was combined with 3 mL of reagent solution (0.6 M sulfuric acid, 28 mM sodium phosphate and 4 mM ammonium molybdate). The sample absorbance was read at 695 nm after a 90 min incubation at 95°C. The total antioxidant capacity was expressed as millimoles of trolox equivalents (mmol TE/g extract) (Mocan et al., 2016c (link)).
For metal chelating activity assay: Briefly, sample solution (1 mg/mL; 2 mL) was added to FeCl2 solution (0.05 mL, 2 mM). The reaction was initiated by the addition of 5 mM ferrozine (0.2 mL). Similarly, a blank was prepared by adding sample solution (2 mL) to FeCl2 solution (0.05 mL, 2 mM) and water (0.2 mL) without ferrozine. Then, the sample and blank absorbances were read at 562 nm after 10 min incubation at room temperature. The absorbance of the blank was sub-tracted from that of the sample. The metal chelating activity was expressed as milligrams of EDTA (disodium edetate) equivalents (mg EDTAE/g extract).
For ChE inhibitory activity assay: Sample solution (1 mg/mL; 50 μL) was mixed with DTNB (5,5-dithio-bis(2-nitrobenzoic) acid, Sigma, St. Louis, MO, United States) (125 μL) and AChE [acetylcholines-terase (Electric ell AChE, Type-VI-S, EC 3.1.1.7, Sigma)], or BChE [BChE (horse serum BChE, EC 3.1.1.8, Sigma)] solution (25 μL) in Tris–HCl buffer (pH 8.0) in a 96-well microplate and incubated for 15 min at 25°C. The reaction was then initiated with the addition of acetylthiocholine iodide (ATCI, Sigma) or butyrylthiocholine chloride (BTCl, Sigma) (25 μL). Similarly, a blank was prepared by adding sample solution to all reaction reagents without enzyme (AChE or BChE) solution. The sample and blank absorbances were read at 405 nm after 10 min incubation at 25°C. The absorbance of the blank was subtracted from that of the sample and the cholinesterase inhibitory activity was expressed as galanthamine equivalents (mgGALAE/g extract) (Mocan et al., 2016b (link)).
For Tyrosinase inhibitory activity assay: Sample solution (1 mg/mL; 25 μL) was mixed with tyrosinase solution (40 μL, Sigma) and phosphate buffer (100 μL, pH 6.8) in a 96-well microplate and incubated for 15 min at 25°C. The reaction was then initiated with the addition of L-DOPA (40 μL, Sigma). Similarly, a blank was prepared by adding sample solution to all reaction reagents without enzyme (tyrosinase) solution. The sample and blank absorbances were read at 492 nm after a 10 min incubation at 25°C. The absorbance of the blank was subtracted from that of the sample and the tyrosinase inhibitory activity was expressed as kojic acid equivalents (mgKAE/g extract) (Mocan et al., 2017 (link)).
For α-amylase inhibitory activity assay: Sample solution (1 mg/mL; 25 μL) was mixed with α-amylase solution (ex-porcine pancreas, EC 3.2.1.1, Sigma) (50 μL) in phosphate buffer (pH 6.9 with 6 mM sodium chloride) in a 96-well microplate and incubated for 10 min at 37°C. After pre-incubation, the reaction was initiated with the addition of starch solution (50 μL, 0.05%). Similarly, a blank was prepared by adding sample solution to all reaction reagents without enzyme (α-amylase) solution. The reaction mixture was incubated 10 min at 37°C. The reaction was then stopped with the addition of HCl (25 μL, 1 M). This was followed by addition of the iodine-potassium iodide solution (100 μL). The sample and blank absorbances were read at 630 nm. The absorbance of the blank was subtracted from that of the sample and the α-amylase inhibitory activity was expressed as acarbose equivalents (mmol ACE/g extract) (Savran et al., 2016 (link)).
For α-glucosidase inhibitory activity assay: Sample solution (1 mg/mL; 50 μL) was mixed with glutathione (50 μL), α-glucosidase solution (from Saccharomyces cerevisiae, EC 3.2.1.20, Sigma) (50 μL) in phosphate buffer (pH 6.8) and PNPG (4-N-trophenyl-α-D-glucopyranoside, Sigma) (50 μL) in a 96-well microplate and incubated for 15 min at 37°C. Similarly, a blank was prepared by adding sample solution to all reaction reagents without enzyme (α-glucosidase) solution. The reaction was then stopped with the addition of sodium carbonate (50 μL, 0.2 M). The sample and blank absorbances were read at 400 nm. The absorbance of the blank was subtracted from that of the sample and the α-glucosidase inhibitory activity was expressed as acarbose equivalents (mmol ACE/g extract) (Llorent-Martínez et al., 2016 (link)).
All the assays were carried out in triplicate. The results are expressed as mean values and standard deviation (SD). The differences between the different extracts were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s honestly significant difference post hoc test with α = 0.05. This treatment was carried out using SPSS v. 14.0 program.
Publication 2017
Generation rate, composition, and physical and chemical nature of both feces and urine were recorded as of Table 1. Each recorded datum was the mean of the data from the reported study. Some published papers reported two or more independent studies so these papers contributed more than one value to the data set. The mean and median of each variable were both calculated as measures of central tendency and data were checked for normality by calculating a coefficient of skewness (Young, 1962 ):


Measured variables for feces and urine
 Feces unitUrine unit
Variableof measureof measure
Generationg/cap/dayL/cap/day
Frequency of defecationmotions/24 hrurinations/24 hr
Water content% total mass% total mass
Organic composition% total mass% dry mass
Components of solids% total mass% total mass
Inorganic composition% dry mass% dry mass
Daily excretion of elementsg/cap/dayg/cap/day, mg/L
Chemical nature  
 pHpHpH
 COD and BODmg/g wet massmg/L
Physical form  
 Bristol stool formLinear scale (1–7) 
 Diarrhea prevalence% of population 
σ = Standard deviationn = Valid number of casesBox and whisker plots were created using Statistica 11 software (Statsoft Inc., Tulsa, OK, USA, 2011). Outliers of each data set were defined using a standard default outlier coefficient value (Burns et al., 2005 (link)).

No outliers were removed from the data set but were identified in the graphical output. Full statistical calculations were only conducted on variables that had at least seven values but a median value is given for data when there were less than seven values.
A summary of studies used in the statistical analysis are outlined in Table 2, including the location and number of studies. A large proportion (80%) of the data set was from studies conducted in Europe and North America. A distinction was therefore made between low and high income countries by the measure of development; using the Human Development Index (HDI), a composite index measuring average achievement in three basic dimensions of human development; life expectancy, education, and income (UNDP, 2011 ).
The geographical location and human development index ranking of studies used in statistical analysis
CountrynHDI*References
Africa23/4aCranston and Burkitt (1975 (link)), Burkitt et al. (1980 (link))
Australia21Birkett et al. (1996 (link)), Hovey et al. (2003 (link))
Burma14Myo-Kin et al. (1994 (link))
Canada31Burkitt et al. (1980 (link)), Vuksan et al. (1999 (link))
China32Jie et al. (2000 (link)), Chen et al. (2008 (link)), Bai and Wang (2010 )
Denmark21Maclennan and Jensen (1977 (link)), Jensen et al. (1982 (link))
Developing countries23/4aFeachem et al. (1978 )
Europe and North America11/2bFeachem et al. (1978 )
European11bMykkänen et al. (1998 (link))
Finland41Reddy et al. (1975 (link)), Reddy et al. (1978 (link)), Jensen et al. (1982 (link)), Mykkänen et al. (1998 (link))
Germany11Erhardt et al. (1997 (link))
Guatemala13Calloway and Kretsch (1978 (link))
Holland41Stasse-Wolthuis et al. (1980 (link)), Van Faassen et al. (1993 (link)), Gaillard (2002 ), Wierdsma et al. (2011 (link))
India13Shetty and Kurpad (1986 (link))
Iran12Adibi et al. (2007 (link))
Japan71Glober et al. (1977 ), Polprasert and Valencia (1981 ), Tarida et al. (1984 (link)), Saitoh et al. (1999 (link)), Danjo et al. (2008 (link)), Shinohara et al. (2010 (link)), Hotta and Funamizu (2009 (link))
Kenya14Cranston and Burkitt (1975 (link))
New Zealand11Pomare et al. (1981 )
North America11bVuksan et al. (2008 (link))
Peru12Crofts (1975 (link))
Singapore11Chen et al. (2000 (link))
South Africa23Burkitt et al. (1972 ), Walker (1975 (link))
Spain11Roig et al. (1993 (link))
Sweden41Reddy et al. (1978 (link)), Vinneras (2002 ), Vinnerås et al. (2006 )
Thailand22Danivat et al. (1988 ), Schouw et al. (2002 (link))
Tonga12Pomare et al. (1981 )
UK261Olmsted et al. (1934 ), Connell et al. (1965 (link)), Southgate and Durnin (1970 (link)), Burkitt et al. (1972 ), Goy et al. (1976 (link)), Wyman et al. (1978 (link)), Prynne and Southgate (1979 (link)), Stephen and Cummings (1980 (link)), Eastwood et al. (1984 (link)), Eastwood et al. (1986 (link)), Davies et al. (1986 (link)), Cummings et al. (1987 (link)), Sandler and Drossman (1987 (link)), Cummings et al. (1992 (link)), Murphy et al. (1993 (link)), Cummings et al. (1996 (link)), Lewis and Heaton (1997 (link)), Chen et al. (1998 (link)), Reddy et al. (1998 (link)), Rivero-Marcotegui et al. (1998 (link)), Aichbichler et al. (1998 (link)), Almeida et al. (1999 ), Magee et al. (2000 (link)), Chaplin et al. (2000 (link)), Woodmansey et al. (2004 (link)), Silvester et al. (2011 (link))
USA181Canfield et al. (1963 ), Watts et al. (1963 (link)), Diem and Lentner (1970 ), Goldsmith and Burkitt (1975 (link)), Cummings et al. (1978 ), Glober et al. (1977 ), Goldberg et al. (1977 (link)), Beyer and Flynn (1978 (link)), Reddy et al. (1978 (link)), Calloway and Kretsch (1978 (link)), Kien et al. (1981 (link)), Polprasert and Valencia (1981 ), Tucker et al. (1981 (link)), Schubert et al. (1984 (link)), Parker and Gallagher (1988 ), Zuckerman, et al. (1995 (link)), Aichbichler et al. (1998 (link)), McRorie et al. (2000)

*Human Development Index Classifications (UNDP, 2011 ): 1. Very high, 2. High, 3. Medium, 4. Low.aClassification not available, presumed to be ranking 3 or 4.bClassification not available, presumed to be ranking 1 or 2.

Preliminary data analysis indicated that fiber intake was a major cause of variation in fecal generation and composition. There were a sufficient number of studies that had examined the effects of fiber intake on fecal output to enable further analysis to be undertaken on these data. The total dietary fiber intake was related to the generation of feces in linear and nonlinear regression analyses.
Publication 2015
The sequences of all the PPRs were identified with reference to the 11,938 sequences of Orthohepevirus A (including 338 complete HEV genomes) available in the Virus Pathogen Resource (VIPR) database.5 Selected sequences were systematically searched to identify insertions so that they could be used, together with those identified by PacBio sequencing, for further analysis. The compositions of HEV PPR insertions/duplications were determined and their post-translational modifications predicted by analyzing a range of parameters. Potential ubiquitination sites were identified using the BDM-PUB server6 with a threshold of >0.3 average potential score. Potential phosphorylation sites were identified using the NetPhos 3.1 server7 with a threshold of >0.5 average potential score. Potential acetylation sites were identified using the Prediction of Acetylation on Internal Lysines (PAIL) server8 with a threshold of >0.2 average potential score. Potential N-linked glycosylation sites were identified using the NetNGlyc 1.0 server9 with a threshold of >0.5 average potential score. Potential methylation sites were identified using the BPB-PPMS server10 with a threshold of >0.5 average potential score. Nuclear export signal (NES) sites were identified using the Wregex server11 with parameters NES/CRM1 and Relaxed. Nuclear localization signal (NLS) sites were identified using SeqNLS12 with a 0.86 cut-off. The amino acid composition (proportions of amino acids), physico-chemical composition, and net load were analyzed with R. Principal component analysis (PCA) is a mathematical algorithm that reduces the dimensionality of the data while retaining most of the variation in a data set. PCA allows to identify new variables, the principal components, which are linear combinations of the original variables (Ringner, 2008 (link)). PCA was done (excluding the amino acid composition due to redundancy with physico-chemical properties) to summarize and visualize the information on the variables in our data set (Abdi and Williams, 2010 (link)); each variable was then studied independently. An in-house R-pipeline based on the amino acid sequences and the results of each analysis was used to generate bar plots for amino acid composition. The amino acid compositions were assigned to one of two categories: sequences with insertions/duplications (including insertions of human genome and HEV genome duplications) and sequences without insertions/duplications. The other parameters were assigned to one of three categories: sequences with insertions, those with duplications, and sequences without insertion/duplication.
Publication 2020
Acetylation Amino Acids Amino Acid Sequence chemical composition chemical properties DNA Insertion Elements Genome Genome, Human Insertion Mutation Lysine Methylation Nuclear Export Signals Nuclear Localization Signals Pathogenicity Phosphorylation Protein Glycosylation Sequence Insertion Ubiquitination Virus

Most recents protocols related to «Chemical composition»

The chemical composition of the scaffolds was determined using X-ray diffractometry and Rietveld analysis. To determine the qualitative phase composition, three wedges of each composition were finely ground and placed in a cuvette of the diffractometer (D8 Advance, Bruker Corporations, Karlsruhe, Germany). The measurements were carried out under the following conditions: Cu-Kα radiation, measurement angle 2θ = 10–40°, measurement speed of 0.5 s/step and rotation of the cuvette of 15 rpm.
The phase composition was determined using DIFFRAC.EVA V.5.1.0.5. (Bruker Corporations, Billerica, MA, USA) based on ICDD reference patterns: MgHPO4·3H2O (newberyite; PDF Ref. 00-020-0153), CaHPO4·2H2O (brushite; PDF Ref. 00-009-0077), NH4MgPO4·6H2O (struvite; PDF Ref. 00-015-0762), Mg3(PO4)2 (farringtonite; PDF Ref. 00-033-0876), Ca4Mg5(PO4)6 (stanfieldite; PDF Ref. 00-011-0231) and MgO (magnesium oxide/periclase; PDF Ref. 00-004-0829). A quantitative phase analysis was carried out using the Rietveld method. The TOPAS V6 software (Bruker Corporations, Billerica, MA, USA) was used for this purpose.
Publication 2024
The chemical composition of the test sample was estimated using a JEOL JSM-6610LV (Tokyo, Japan) SEM (Scanning Electron Microscope) with an Oxford Instruments X-MAX 80 (Abingdon, Oxfordshire, England) module installed for energy dispersive X-ray (EDS) measurements using an accelerating voltage of 5 kV. Measurements were performed on pure Si samples, with a low accelerating voltage applied to minimize the depth from which the characteristic radiation originated, which was then used to measure qualitative and quantitative chemical composition.
Due to the limitations of the EDS method (in particular, the inability to accurately quantify light and heavy elements simultaneously, as well as to accurately analyze the carbon content and the possibility of carbon contamination of both the walls of the vacuum chamber of the microscope and the surface of the samples), the results of the proportion of carbon relative to the other elements can be subject to large error. To minimize errors, an analysis of the relative ratio of carbon to silicon was carried out, comparing the results obtained with those obtained for reference samples of SiN coatings, for which the measured carbon content was considered to be the contamination standard noise. All coatings in terms of their chemical composition were measured during a single test, to obtain the same carbon contamination conditions. For each group of coatings, two samples of monocrystalline silicon with deposited coatings were examined by SEM-EDS [36 (link),37 ].
Publication 2024
Not available on PMC !
The basic chemical composition of the wines is shown below in Table 2. There were signi cant differences across all variables measured. In particular, alcohol %, TA and RS are deemed to have sensory implications. The difference in the alcohol of the wines were driven primarily by the brix of the grapes that was harvested (data not shown).
Publication 2024
The main chemical composition items of fish musles were estimated according to the guidelines of AOAC (2000), including the percentages of moisture and ash, in addition to the crude lipid content (Ether extract) which was analyzed using the Soxhlet system with ether as a solvent (SRPS ISO 1443 :1997) . Moreover, the crude protein was determined by Micro Klejdahl.
Publication 2024
Physio-chemical methods were used according to Porto and others (15) to determine the chemical composition of fish, feces, and feed ingredients. In an oven with a 105 °C setting, weight loss was used to measure moisture. Ash was produced by burning a known quantity of the sample at 550 °C to a constant weight. Crude protein was calculated by converting total nitrogen, which was measured using the Kjeldahl method, into protein. The 6.25 factor was applied. Using the Soxhlet procedure, petroleum ether was used to extract the total lipids. The total calorie content was determined using the equivalent caloric values for proteins, lipids, and carbohydrates, which were 5.5, 9.1, and 4.1 kcal/g, respectively. Carbohydrates were estimated using the following equation:
Carbohydrates = 100 -(moisture % + protein% + lipid% + ash%)
Publication 2024

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The JEM-2100 is a transmission electron microscope (TEM) manufactured by JEOL. It is designed to provide high-quality imaging and analysis of a wide range of materials at the nanoscale level. The instrument is equipped with a LaB6 electron source and can operate at accelerating voltages up to 200 kV, allowing for the investigation of a variety of samples.
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DPPH is a chemical compound used as a free radical scavenger in various analytical techniques. It is commonly used to assess the antioxidant activity of substances. The core function of DPPH is to serve as a stable free radical that can be reduced, resulting in a color change that can be measured spectrophotometrically.
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Methanol is a clear, colorless, and flammable liquid that is widely used in various industrial and laboratory applications. It serves as a solvent, fuel, and chemical intermediate. Methanol has a simple chemical formula of CH3OH and a boiling point of 64.7°C. It is a versatile compound that is widely used in the production of other chemicals, as well as in the fuel industry.

More about "Chemical composition"

Chemical composition refers to the specific arrangement and proportion of elements within a chemical substance.
Understanding this is crucial for accurately characterizing and studying the properties of materials, drugs, and other substances.
Researchers can leverage cutting-edge AI tools like PubCompare.ai to easily locate relevant protocols from scientific literature, pre-prints, and patents, then use AI-driven comparisons to identify the optimal approaches for their chemical composition research.
By streamlining this process, PubCompare.ai helps elevate the accuracy and efficiency of chemical composition studies, leading to more robust and reliable findings.
This is particularly important for advanced analytical techniques like ESCALAB 250Xi, S-4800, and D8 Advance, which provide detailed insights into the chemical composition of samples.
Similarly, mass spectrometry methods like K-Alpha and JEM-2100F can be used to precisely determine the elemental composition and molecular structure of compounds.
Other key subtopics in chemical composition research include the use of solvents like DMSO, the analysis of antioxidant activity using DPPH, and the quantification of compounds like Gallic acid using techniques like JEM-2100 and Methanol extraction.
Ultimately, by optimizing the protocols and approaches used in chemical composition studies, researchers can elevate the accuracy, efficiency, and reliability of their findings, leading to advancements in fields ranging from materials science to pharmaceutical development.