Spin Labels ESR NMR Electron Spin Resonance ESR

Spin Labels (ESR, NMR) Electron Spin Resonance (ESR), Nuclear Magnetic Resonance (NMR), & Magnetic Resonance Imaging (MRI) are covered in Guy & ffytche, An Introduction to The Principles of Medical Imaging, Imperial College Press, 2000, Chapter 2, pp 78 -88, & Chapter 6, pp 199 -264. Other coverage is also found in Smith, Shung, & Mosher, Chapter 4, Magnetic resonance imaging, in Shung, Smith, Tsui, Principles of Medical Imaging, Academic Press, 1992, pp 213 -271.

Electronic Quantum Spin Electrons usually occupy electronic shells in atoms as pairs. In such pairs the electrons have spins opposite one another so the associated magnetic fields cancel. In some ions, free radicals or paramagnetic materials, however, a single electron may occupy an orbital. Placing such an atom into a strong magnetic field will tend to cause the electrons to align with the field. Adding radiofrequency energy to the system in this situation cause the electron spins to “flip” so they oppose the magnetic field. This energy absorption can be detected by monitoring the energy input as radiofrequencies are scanned.

ESR Theory: http: //www. pharmainfo. net/reviews/electron-spinresonance-esr-principle-theory-and-applications http: //www. uottawa. ca/publications/ interscientia/inter. 2/spin. html http: //hyperphysics. phyastr. gsu. edu/hbase/molecule/esr. html ESR Illustrated: http: //www. physics. montana. edu/eprlab/n. Body_2. htm

ESR Spectral Information Because the exact energy absorption frequency of the unpaired electrons are sensitive to their molecular surroundings, the ESR spectra provide information on the nature of these surroundings. This is provided both by the position of major absorbance frequencies & by the splitting of these absorbances into hyperfine spectral features. While a free radical might have a characteristic ESR spectrum as a pure isolated entity, it may demonstrate specific spectral features when placed into a particular solvent or biological system.

Trace levels of Mn 2+ ions in dolomite, Ca. Mg(CO 3)2 http: //www. chem. memphis. edu/faculty/lloyd. htm

NMR Spectoscopy Similar to electrons, protons may also demonstrate quantal spins. If there are odd numbers of protons in the nucleus, the nucleus will demonstrate a nuclear magnetic moment capable of perturbation by radiofrequencies when in the presence of a strong external magnetic field. Here, however, the absorbed energy can be sensed either by the irradiating circuit or by a field coil as the nuclei flip back to their ground states. Again, resonant energy levels are characteristic of the nuclei involved & the molecular environment surrounding these nuclei.

Nuclei demonstrating accessible signals include: 1 H, 13 C, 17 O, 19 F, 23 Na, 31 P NMR Basics: http: //www. cis. rit. edu/htbooks/nmr/ http: //www. nobel. se/chemistry/ed ucational/poster/1991/nmr. html http: //www. wpi. edu/Academics/Depts/ Chemistry/Courses/CH 2670/nmr. html http: //www. brynmawr. edu/Acads/Chem/mnerzsto/The_B asics_Nuclear_Magnetic_Resonance%20_Spectroscop y_2. htm NMR Software: http: //www. spincore. com/nmrinfo/software_s. html

Basic Instrumental Layout for NMR http: //sis. bris. ac. uk/~sd 9319/spec/nmrspec. jpg

NMR Theory: http: //www. ipfw. edu/chem/262 spring 03/262 nt 0311. htm http: //www. shu. ac. uk/schools/sci/ chem/tutorials/molspec/nmr 1. htm http: //www. nuclear-magnetic-resonance. com/node 4. html http: //www. shef. ac. uk/chemistry/crystal/projectsug/sillitoe/html/theory. htm http: //www. resonancepub. com/magres. htm http: //www. avogadro. co. uk/analysis/nmr. htm Structural determination of proteins by NMR: http: //www. cryst. bbk. ac. uk/PPS 2/projects/schirra/html/ home. htm

MRI Analysis Magnetic Resonance Imaging (MRI) is the extrapolation of NMR to multiple dimensions. It extracts information on relative composition of body areas by assessing the strength & resonant frequency (& thus the chemical nature of absorbing molecules) of the NMR signals as part of a 3 or 4 dimensional evaluation of objects tested. The computationally intensive evaluation of MRI data sorts the vast volume of information collected during a scan & presents it in the form of an image that includes intensity data.

MRI basics: http: //www. mritutor. org/mritutor/ http: //health. howstuffworks. com/mri 2. htm http: //www. refindia. net/rlinks/reviewedlinks/mri. htm MRI instrumentation: http: //info. med. yale. edu/intmed/cardio /imaging/techniques/mri_diagram/

Medical applications: http: //www. gentili. net/diabeticfoot/mri. htm MRI analysis: http: //www. cis. rit. edu/research/thesis/ bs/1998/fetzner/Thesis_TF_thesis. html MRI contrast agents: http: //www. mritutor. org/mritutor/contrast. htm http: //www. mr-tip. com/serv 1. php? type=coa http: //adsabs. harvard. edu/abs/2008 mcpp. book. . 157 B

New Developments & Frontiers Long Range NMR/MRI Glover&Bowtell. MRIridesthewave. Nature 457 n 7232 p 971 Brunneretal. Travelingwave. NMRNature 457 n 7232 p 994 Long. Range. NMRNMeth 6 p 248 Intracellular NMR & MRI Midgley&Borkowski 2009 Electron. Tomography&Holographynma t 2406 Burz&Shekhtman 2009 Insidethe. Living. Cell. Nature 458 n 7234 p 37 Hammel 2009 Nanoscale. MRINature. Com 458 p 844 Inomata. Et. Al 2009 High. Resolution. Multi. Dimensional. NMRSpectros copy. Of. Proteins. In. Human. Cells. Nature 458 p 106 Sakakibara. Et. Al 2009 Protein. Structure. Determination. In. Living. Cells By. In. Cell. NMRSpectroscopy. Nature 458 p 07814