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EPR in biomedica

Nitric oxide

Binding of nitric oxide to oxyhemoglobin detected at 100 K.
Nitric Oxide (NO) is a highly reactive regulatory molecule which has many important physiological roles, such as a neurotransmitter in the central nervous system, a regulator of vasomotor tone in the cardiovascular system, and a cytotoxic mediator of the immune system. NO is a free radical and its short half-life (< 30 sec), has rendered direct measurement difficult. The instability of NO can be overcome by using a NO-trapping technique, in which a more stable complex is formed and subsequently detected by EPR. For example, the oxidation of nitric oxide (NO) to nitrate by oxyhemoglobin (oxyHb) is a fundamental reaction in NO biology and binding of NO to the heme can be characterized by EPR.

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Crystal structure of NO-Hb (4G51.pdb)
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EPR spectrum of NO-Hb complex at 100 K with VT unit

Detection of Reactive Oxygen Species (ROS) using spin traps

Quantitative EPR analysis of superoxide and hydroxyl radicals.
Oxidative stress and damage in cells is associated with the development of cancer, Alzheimer‘s disease, atherosclerosis, autism, infections and Parkinson‘s disease. Reactive Oxygen Species (ROSs) are the main cause of oxidative stress and damage in cells, causing damage to proteins, lipids and DNA. Two leading ROS are radicals such as the superoxide radical (O2•-) and the hydroxyl radical (HO) as shown here in the Xanthine/Xanthine oxidase system where their generation and decomposition can be accurately followed with the EMXnano.

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SpinCount provides a report showing the time evolution of the concentration of the radicals
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EPR spectra and SpinFit simulations of DMPO radical (superoxide and hydroxyl) adducts in xanthine/xanthine oxidase

Detection of Reactive Oxygen Species (ROS) using spin probes

Time course of superoxide formation using the spin probe CMH.
In vascular cells, increased generation of superoxide (O2•-) has been suggested to occur in hypertension, diabetes, and heart failure. Thus the accurate detection and ability to quantify O2•- are critically important in understanding the pathogenesis of these various cardiovascular disorders and other noncardiovascular diseases. As shown here the generation of superoxide over time can be easily monitored with the EMXnano.

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Detection of superoxide radical (O2•-) is confirmed by suppression of the EPR signal by superoxide dismutase (SOD)
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EPR spectrum of CM nitroxide due to the reaction: CMH + O2•- –» CM + H2O2