key: cord-0308588-9w8be65s authors: Tagliapietra, Luca J.; Adlish, John I.; Neuhold, Piero; Surrente, Riccardo title: RNA Identification and Detection of Nucleic Acids as Aerosols in Air Samples by Means of Photon and Electron Interactions date: 2021-05-01 journal: nan DOI: 10.3390/instruments5020023 sha: ca89dd53e3e6f3852e23a25c62d02b533db86e35 doc_id: 308588 cord_uid: 9w8be65s This study presents a methodology to reveal traces of viral particles, as aerosol with known chemical and molecular structure, in a sample by means of photon and electron interactions. The method is based on Monte Carlo simulations and on the analysis of photon-electron fluxes-spectra through energy channels counts as a function of different aerosol viral concentrations in the air sample and looking at the peculiar photon/electron interactions with the potential abnormal atomic hydrogen (H), oxygen (O), carbon (C), and phosphorus (P) compositions present in the air sample as a function of living and nonliving matter with PO4 group RNA/DNA strands in a cluster configuration. Viruses are intracellular parasites composed of a nucleic acid surrounded by a protein coat, the capsid. Some viruses contain a lipid envelope, derived from the host, surrounding the capsid. The nucleic acid found in viruses can consist of either RNA or DNA. The Coronaviridae, for example contain a single molecule of RNA consisting of about 30 Kilobases in length where Kb stands for unit of measurement of DNA or RNA length used in genetics [1, [2] [3] [4] [5] [6] . RNA is composed of nucleotides, each containing a sugar (deoxyribose), a Nitrogen containing Base (Adenine, Uracil, Guanine, and Cytosine), and a phosphate group PO4. Members of the family Coronoviridae measure 80-160 nm in diameter. The phosphate group it is also present in ambient bacterial DNA and RNA which measure more than one μm in diameter, and containing different chemical components in fraction term, thus giving us the ability to distinguish between the two weighting the different spectrum and flux contribution. Most of the Phosphorus is present in the genetic strand of RNA and in particular in the phosphate group but trace amounts are also in viral proteins that contain the amino acid methionine. Phosphorus, on the other hand, is absent in the EPA pollutants listed in Table 1 . Therefore, Phosphorus, as part of the PO4 group, has been assumed as a marker of no living matter, potentially a virus. A physical model has been designed in order to detect PO4 groups amount changes related to different viral clusters. The present study aims to detect, by means of the particle Monte Carlo computer code Fluka 2020 [7-8] a cluster element spectrum with concentrations from 1 ppm in air to 0.1%, according to a composition of air in Table 1 and a simplified chemical form of a virus as a biological matter in air as reported in Figure 1 [1] with its own atom modelling. The proposed methodology is based on a subatomic coupled particle analysis (photon-electron) and the subsequent detection on top of their spectra (i.e., fluxes as a function of PO4 group contamination ppm). The present study refers to previous works by the same authors [1, 2] regarding RNA-DNA modelling and their identification through the interactions of particles such as muons and photons. The purpose of this work is among some preliminary activities in view of experimental work to be performed using a photon beam with energy between 110-150 keV energy range due to a cross sections evaluation and its consequent discrimination ability on top of shielding requirements. In order to justify the involved physics and the results in the 130 keV beam energy configuration a cross sections analysis for nitrogen and phosphorus content in the PO4 group has been performed taking into account the EPDL97 Library [8] . Those two elements have a primary role from a photo atomic contribution point of view in the microscopic and macroscopic cross sections acting in the cluster mixture. The model proposed is based on multiple spherical geometry clusters in grid cells whose spheres (11) have different sizes (as a function of ppm viral contamination). However, those clusters are immersed in a 75% Nitrogen composition system which has a weighting factor as far as macroscopic cross section evaluation. The microscopic cross section represents the effective target area of a single target nucleus for an incident particle and units are given in barn (1. barn = 10 -24 cm 2 ) or cm 2 , while the macroscopic cross-section represents the effective target area of all of the nuclei contained in the volume of the material and units are given in cm -1 . The macroscopic cross section can be obtained from the microscopic according to the following equation where N stands for nuclei density: In a mixture case with different chemical elements, it is necessary to determine the macroscopic cross section for each isotope and therefore sum all the individual macroscopic cross-sections. Moreover, both factors (different atomic densities and different cross-sections) must be considered in the calculation of the macroscopic cross-section of the mixture taken into account. The Avogadro's number N0 = 6.022 x 10 23 , is the number of particles that is contained in the amount of substance given by one mole. Thus, if M is the molecular weight, the ratio N0/M equals to the number of molecules in 1g of the mixture. The number of molecules per cm 3 in the material of density ρ and the macroscopic cross-section for mixtures are given by following equations: In the photon energy (Ep) interval 0.01 keV