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ASTANA MEDICAL UNIVERSITYof “MEDICAL BIOPHYSICS AND THE BASICS OF LIFE SAFETY” STUDENT’SINDEPENDENT WORK: The usage of NMR and EPR in medical researches Performed by: Atayeva Nazerke: general medicine 2015

Contents: Introduction

. Physical meaning of EPR

2. Splitting of energy levels. Zeeman effect

. Electronic splitting. Hyperfine splitting

. Spectrometer of EPR. Device and mechanism of EPR

. Spin probes

. The usage of EPR specters in medico-biological researches

. Physical meaning of NMR

. Specters of NMR

. NMR introscopy. The usage of NMR in medico-biological researches

nuclear resonance spin spectrometer Introduction When atoms are placed in a magnetic field, the spontaneous transitions between their sublevels of the same level are unlikely. However, such transitions occur is induced under the influence of an external electromagnetic field. A necessary condition is the coincidence of the frequency of the electromagnetic field with the frequency of the photon corresponding to the energy difference between the split sublevels. It is possible to observe the absorption of electromagnetic energy, which is called magnetic resonance. Depending on the type of particles - carriers magnetic moment - distinguish electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR). Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a magnetic field absorb and re-emit electromagnetic radiation. This energy is at a specific resonance frequency, which depends on the strength of the magnetic field and the magnetic properties of the isotope of the atoms; in practical applications, the frequency is similar to VHF and UHF television broadcasts (60-1000 MHz). NMR allows the observation of specific quantum mechanical magnetic properties of the atomic nucleus.

Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a technique for studying materials with unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei. EPR spectroscopy is particularly useful for studying metal complexes or organic radicals. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944, and was developed independently at the same time by Brebis Bleaney at the University of Oxford. 1. Physical meaning of EPR The essence of the phenomenon of electron paramagnetic resonance is as follows. If you place a free radical with a resultant angular momentum J in a magnetic field with an intensity B0, then J, non-zero magnetic field the degeneracy, and the interaction with the magnetic field arises 2J + 1 levels, the situation is described by the expression: W = gβB0M, (where M = J +, + J-1, ... -J) and is determined by the Zeeman interaction of the magnetic field with the magnetic moment J.

If now to the paramagnetic center to make an electromagnetic field with a frequency ν, polarized in the plane perpendicular to the magnetic field vector B0, then it will cause magnetic dipole transitions, subject to the rules of selection ΔM = 1. At concurrence of the energy of electron transition with a photon energy of the electromagnetic wave will be resonant absorption of microwave radiation. Thus, the resonance condition is determined by the ratio of the fundamental magnetic resonance hν = gβB0. 2. Splitting of energy levels. Zeeman effect In the absence of an external magnetic field, the magnetic moments of the electrons are oriented randomly, and their energy does not differ from each other (E0). When an external magnetic field, the magnetic moments of the electrons are guided in the field depending on the magnitude of the spin magnetic moment, and their energy level is split into two. The interaction energy of the electron magnetic moment with the magnetic field is expressed by the equation: E = , where ∞ - magnetic moment of the electron, H - intensity of the magnetic field. From the equation the proportionality factor implies that:

,

the energy of electron interaction with an external magnetic field is .

equation describes the Zeeman effect, which can be expressed in the following words: the energy levels of electrons in a magnetic field, the field is split depending on the magnitude of the spin magnetic moment and magnetic field intensity. 3. Electronic splitting. Hyperfine splitting Most applications, including biomedical, based on the analysis of a group of lines (and not only singlentyh) in the absorption spectrum of EPR. The presence in the EPR spectrum of groups loved ones conventionally called cleavage lines. There are two basic types of splitting of the EPR spectrum. The first - an electronic splitting - occurs when a molecule or atom has not one, but several electrons, causing the ESR. Second - hyperfine splitting - is observed in the interaction of electrons with the magnetic moment of the nucleus. According to classical concepts, an electron orbiting the nucleus, as well as any moving in a circular orbit of a charged particle has a magnetic dipole moment.

Similarly, in quantum mechanics, the orbital angular momentum of the electron creates a certain magnetic moment. The interaction of the magnetic moment with the magnetic moment of the nucleus (due to the nuclear spin) leads to the hyperfine splitting (ie, creates a hyperfine structure). But the electron also has a spin, which contributes to its magnetic moment. Therefore, the hyperfine splitting has even terms with zero orbital angular momentum. The distance between the sublevels of the hyperfine structure of the order of 1000 times less than that between the levels of the fine structure (the order of magnitude is essentially due to the ratio of the electron mass to the mass of the nucleus). 4. Spectrometer of

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