Related Experiment Video
Updated: Jun 25, 2026
08:04
A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry
Published on: March 13, 2014
The effective atomic numbers of some biomolecules calculated by two methods: a comparative study
S R Manohara1, S M Hanagodimath, L Gerward
1Department of Physics, Gulbarga University, Gulbarga, Karnataka 585 106, India.
Medical Physics
|February 25, 2009
Summary
The effective atomic number (Zeff) for biomolecules was calculated using two methods. The direct method yielded higher Zeff values than the interpolation method, especially at lower photon energies.
Area of Science:
- Medical Physics
- Computational Chemistry
- Radiation Physics
Background:
- The effective atomic number (Zeff) is crucial for understanding photon interactions in materials.
- Biomolecules like fatty acids and amino acids are fundamental components of biological systems.
- Accurate Zeff values are needed for radiation dosimetry and shielding in medical and biological applications.
Purpose of the Study:
- To calculate and compare the effective atomic numbers (Zeff) of fatty acids and amino acids.
- To evaluate two distinct numerical methods for Zeff determination.
- To provide insights into photon interaction properties of biomolecules using a modern database.
Main Methods:
- Calculated Zeff using a direct numerical method and an interpolation method.
- Utilized the WinXCom database for photon interaction cross-section data.
- Investigated the energy range from 1 keV to 20 MeV.
Main Results:
- The direct method consistently produced higher Zeff values compared to the interpolation method for all tested biomolecules.
- Significant differences between the methods were observed at low photon energies (1-100 keV).
- At medium energies (0.1-5 MeV), Zeff values from both methods converged and approximated the mean atomic number of the materials.
Conclusions:
- The choice of numerical method impacts Zeff calculations for biomolecules, particularly at low energies.
- The direct method offers a more comprehensive approach for determining Zeff in complex molecules.
- Findings contribute to a better understanding of radiation interactions in biological tissues.
More Related Videos
Related Concept Videos
01:13Mass Spectrometry: Isotope Effect
Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the mass differences between isotopes. Furthermore, the intensity of these signals is dependent on the...
01:12Atomic Number and Mass Number
The number of protons in the nucleus of an atom is its atomic number (Z). This is the defining trait of an element. Its value determines the identity of the atom. For example, any atom that contains six protons is the element carbon and has the atomic number 6, regardless of how many neutrons or electrons it may have. A neutral atom must contain the same number of positive and negative charges, so the number of protons equals the number of electrons. This means that the atomic number also...
01:52Atomic Mass
Atoms — and the protons, neutrons, and electrons that compose them — are extremely small. For example, a carbon atom weighs less than 2 × 10−23 g. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu). The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are...
01:15High-Resolution Mass Spectrometry (HRMS)
The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For example, the mass of helium...
01:25Atomic Weight
Protons and neutrons have approximately the same mass, about 1.67 × 10-24 grams. Scientists arbitrarily define this amount of mass as one atomic mass unit (amu) or one Dalton. Electrons are much smaller in mass than protons, weighing only 9.11 × 10-28 grams, or about 1/1800 of an atomic mass unit. As a result, they do not contribute much to an element's overall atomic mass. This means that, when considering atomic mass, it is customary to ignore the mass of any electrons and calculate the...
03:18Radioactivity and Nuclear Equations
Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for hydrogen, neutrons. The number of protons in the nucleus is called the atomic number (Z) of the element, and the sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are isotopes of the same element.
A nuclide of an element has a specific number of protons and...
A nuclide of an element has a specific number of protons and...