Composition of the human body | EPFL Graph Search

Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular type e.g., water, protein, fats (or lipids), hydroxylapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, connective tissue, muscle, bone, etc. In terms of cell type, the body contains hundreds of different types of cells, but notably, the largest number of cells contained in a human body (though not the largest mass of cells) are not human cells, but bacteria residing in the normal human gastrointestinal tract. Elements About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are thought

Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation

Julia Schmale, Yandong Tong

Online characterization of aerosol composition at the near-molecular level is key to understanding chemical reaction mechanisms, kinetics, and sources under various atmospheric conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) is capable of detecting a wide range of organic oxidation products in the particle phase in real time with minimal fragmentation. Quantification can sometimes be hindered by a lack of available commercial standards for aerosol constituents, however. Good correlations between the EESI-TOF and other aerosol speciation techniques have been reported, though no attempts have yet been made to parameterize the EESI-TOF response factor for different chemical species. Here, we report the first parameterization of the EESI-TOF response factor for secondary organic aerosol (SOA) at the near-molecular level based on its elemental composition. SOA was formed by ozonolysis of monoterpene or OH oxidation of aromatics inside an oxidation flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer reaction mass spectrometer (Vocus-PTR) and a high-resolution aerosol mass spectrometer (AMS) were used to determine the gas-phase molecular composition and the particle-phase bulk chemical composition, respectively. The EESI response factors towards bulk SOA coating and the inorganic seed particle core were constrained by intercomparison with the AMS. The highest bulk EESI response factor was observed for SOA produced from 1,3,5-trimethylbenzene, followed by those produced from d-limonene and o-cresol, consistent with previous findings. The near-molecular EESI response factors were derived from intercomparisons with Vocus-PTR measurements and were found to vary from 103 to 106 ion counts s−1 ppb−1, mostly within ±1 order of magnitude of their geometric mean of 104.6 ion counts s−1 ppb−1. For aromatic SOA components, the EESI response factors correlated with molecular weight and oxygen content and inversely correlated with volatility. The near-molecular response factors mostly agreed within a factor of 20 for isomers observed across the aromatics and biogenic systems. Parameterization of the near-molecular response factors based on the measured elemental formulae could reproduce the empirically determined response factor for a single volatile organic compound (VOC) system to within a factor of 5 for the configuration of our mass spectrometers. The results demonstrate that standard-free quantification using the EESI-TOF is possible.

2021

Biomass burning and marine aerosol processing over the southeast Atlantic Ocean: a TEM single-particle analysis

Athanasios Nenes, Lu Zhang

This study characterizes single-particle aerosol composition from filters collected during the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) and CLoud-Aerosol-Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) campaigns. In particular the study describes aged biomass burning aerosol (BBA), its interaction with the marine boundary layer and the influence of biomass burning (BB) air on marine aerosol. The study finds evidence of BBA influenced by marine boundary layer processing as well as sea salt influenced by BB air. Secondary chloride aerosols were observed in clean marine air as well as in BB-influenced air in the free troposphere. Higher-volatility organic aerosol appears to be associated with increased age of biomass burning plumes, and photolysis or oxidation may be a mechanism for the apparent increased volatility. Aqueous processing and interaction with the marine boundary layer air may be a mechanism for the presence of sodium on many aged potassium salts. By number, biomass burning potassium salts and modified sea salts are the most observed particles on filter samples. The most commonly observed BC coatings are inorganic salts. These results suggest that atmospheric processes such as photolysis, oxidation and cloud processing are key drivers in the elemental composition and morphology of aged BBA. Fresh BBA inorganic salt content, as it has an important role in the particles' ability to uptake water, may be a key driver in how aqueous processing and atmospheric aging proceed.

COPERNICUS GESELLSCHAFT MBH2022

Advances in Structural Elucidation of Small Molecules via High Performance Mass Spectrometry

Konstantin Zhurov

Qualitative and quantitative analyte analysis is omnipresent: from quality control in food, pharmaceutical, biotechnology industries, to new molecular syntheses, detection of explosives and drugs, as well as natural compound mixture analysis, such as crude oils or animal fluids. Of particular interest are analytes associated with human health and energy, both of synthetic and natural origin. Thus, a selection of synthetic analytes related to ongoing efforts in drug design and alternative energy sources, has been made for this Thesis. Additionally, for natural analytes, peptides and crude oil were selected as analytes of choice due to their central role in human health and energy sources, respectively. Mass spectrometry was chosen as the method of choice for analyte investigation (elemental composition and structural feature determination) due to its sensitivity, ability to obtain data on thousands of analytes simultaneously, and use of radical and photo chemistry to probe molecular structure. The thesis is split into three major parts, first investigating synthetic analytes, then peptides and, finally, crude oil fractions. In the first part, use of photoionization is discussed as an alternative to other common analyte ionization methods as most selected synthetic targets do not ionize with the latter. A rough guideline, based on analyte structural composition, is proposed to determine analyte photoionization response. In-source analyte reactions are analysed and used as indicators of various functional group presence. Finally, upper mass boundary on analytes is considered and extended with photoionization. In the second part, peptide-ion/electron and ion/radical anion interactions in tandem mass spectrometry experiments, along with in silico modelling are used to put forth a new mechanistic proposal, which is fundamentally different to all the other mechanistic proposals related to this type of fragmentation process. The proposal involves charge-driven, rather than radical driven peptide radical fragmentation. It is also additionally significantly influenced by the local 3D structure of the peptide. The proposal may be of particular interest when considering radiation damage effects on key biological systems. In the third part, several methods are proposed aimed at enhancing crude oil (and other complex mixture) analysis on a new type of high resolution mass spectrometer, the Orbitrap Elite FTMS, including maximising number of identifiable analytes and evaluating key parameters of mass spectra of complex mixtures. Additionally, a data visualization method is proposed, based on analyte heteroatom content, which creates a graphical representation of all the identified components in the complex mixture and how changes in bulk properties of the sample get reflected on its compositional makeup.