In chemistry, a dangling bond is an unsatisfied valence on an immobilized atom. An atom with a dangling bond is also referred to as an immobilized free radical or an immobilized radical, a reference to its structural and chemical similarity to a free radical.
Site-directed spin labeling (SDSL) is a technique for investigating the structure and local dynamics of proteins using electron spin resonance. The theory of SDSL is based on the specific reaction of spin labels with amino acids. A spin label's built-in protein structure can be detected by EPR spectroscopy. SDSL is also a useful tool in examinations of the protein folding process.
Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spins excited are those of the electrons instead of the atomic nuclei. EPR spectroscopy is particularly useful for studying metal complexes and 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.
Frémy's salt is a chemical compound with the formula (K4[ON(SO3)2]2), sometimes written as (K2[NO(SO3)2]). It a bright yellowish-brown solid, but its aqueous solutions are bright violet. The related sodium salt, disodium nitrosodisulfonate (NDS, Na2ON(SO3)2, CAS 29554-37-8) is also referred to as Frémy's salt.
Sodium diethyldithiocarbamate is the organosulfur compound with the formula NaS2CN(C2H5)2. It is a pale yellow, water soluble salt.
2-Methyl-2-nitrosopropane (MNP or t-nitrosobutane) is the organic compound with the formula (CH3)3CNO. It is a blue liquid that is used in chemical research as a spin trap, i.e. it binds to radicals.
EuFOD is the chemical compound with the formula Eu(OCC(CH3)3CHCOC3F7)3, also called Eu(fod)3. This coordination compound is used primarily as a shift reagent in NMR spectroscopy. It is the premier member of the lanthanide shift reagents and was popular in the 1970s and 1980s.
In organic chemistry, S-nitrosothiols, also known as thionitrites, are organic compounds or functional groups containing a nitroso group attached to the sulfur atom of a thiol. S-Nitrosothiols have the general formula R−S−N=O, where R denotes an organic group. Originally suggested by Ignarro to serve as intermediates in the action of organic nitrates, endogenous S-nitrosothiols were discovered by Stamler and colleagues and shown to represent a main source of NO bioactivity in vivo. More recently, S-nitrosothiols have been implicated as primary mediators of protein S-nitrosylation, the oxidative modification of cysteine thiol that provides ubiquitous regulation of protein function.
DPPH is a common abbreviation for the organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable free radical molecules. DPPH has two major applications, both in laboratory research: one is a monitor of chemical reactions involving radicals, most notably it is a common antioxidant assay, and another is a standard of the position and intensity of electron paramagnetic resonance signals.
Electron nuclear double resonance (ENDOR) is a magnetic resonance technique for elucidating the molecular and electronic structure of paramagnetic species. The technique was first introduced to resolve interactions in electron paramagnetic resonance (EPR) spectra. It is currently practiced in a variety of modalities, mainly in the areas of biophysics and heterogeneous catalysis.
Sulfur mononitride is an inorganic compound with the molecular formula SN. It is the sulfur analogue of and isoelectronic to the radical nitric oxide, NO. It was initially detected in 1975, in outer space in giant molecular clouds and later the coma of comets. This spurred further laboratory studies of the compound. Synthetically, it is produced by electric discharge in mixtures of nitrogen and sulfur compounds, or combustion in the gas phase and by photolysis in solution.
(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl, commonly known as TEMPO, is a chemical compound with the formula (CH2)3(CMe2)2NO. This heterocyclic compound is a red-orange, sublimable solid. As a stable aminoxyl radical, it has applications in chemistry and biochemistry. TEMPO is used as a radical marker, as a structural probe for biological systems in conjunction with electron spin resonance spectroscopy, as a reagent in organic synthesis, and as a mediator in controlled radical polymerization.
In chemistry, the amino radical, ·NH2, also known as the aminyl radical or azanyl radical, is the neutral form of the amide ion. Aminyl radicals are highly reactive and consequently short-lived, like most radicals; however, they form an important part of nitrogen chemistry. In sufficiently high concentration, amino radicals dimerise to form hydrazine. While NH2 as a functional group is common in nature, forming a part of many compounds, the radical cannot be isolated in its free form.
Paramagnetic nuclear magnetic resonance spectroscopy refers to nuclear magnetic resonance (NMR) spectroscopy of paramagnetic compounds. Although most NMR measurements are conducted on diamagnetic compounds, paramagnetic samples are also amenable to analysis and give rise to special effects indicated by a wide chemical shift range and broadened signals. Paramagnetism diminishes the resolution of an NMR spectrum to the extent that coupling is rarely resolved. Nonetheless spectra of paramagnetic compounds provide insight into the bonding and structure of the sample. For example, the broadening of signals is compensated in part by the wide chemical shift range (often 200 ppm in 1H NMR). Since paramagnetism leads to shorter relaxation times (T1), the rate of spectral acquisition can be high.
Aminoxyl denotes a radical functional group with general structure R2N–O•. It is commonly known as a nitroxyl radical or a nitroxide, however IUPAC discourages the use of these terms, as they erroneously suggest the presence of a nitro group. Aminoxyls are structurally related to hydroxylamines and N-oxoammonium salts, with which they can interconvert via a series of redox steps.
Wolfgang Lubitz is a German chemist and biophysicist. He is currently a director emeritus at the Max Planck Institute for Chemical Energy Conversion. He is well known for his work on bacterial photosynthetic reaction centres, hydrogenase enzymes, and the oxygen-evolving complex using a variety of biophysical techniques. He has been recognized by a Festschrift for his contributions to electron paramagnetic resonance (EPR) and its applications to chemical and biological systems.
A trivalent group 14 radical (also known as a trivalent tetrel radical) is a molecule that contains a group 14 element (E = C, Si, Ge, Sn, Pb) with three bonds and a free radical, having the general formula of R3E•. Such compounds can be categorized into three different types, depending on the structure (or equivalently the orbital in which the unpaired electron resides) and the energetic barrier to inversion. A molecule that remains rigidly in a pyramidal structure has an electron in a sp3 orbital is denoted as Type A. A structure that is pyramidal, but flexible, is denoted as Type B. And a planar structure with an electron that typically would reside in a pure p orbital is denoted as Type C. The structure of such molecules has been determined by probing the nature of the orbital that the unpaired electron resides in using spectroscopy, as well as directly with X-ray methods. Trivalent tetrel radicals tend to be synthesized from their tetravalent counterparts (i.e. R3EY where Y is a species that will dissociate).
Spectroelectrochemistry (SEC) is a set of multi-response analytical techniques in which complementary chemical information is obtained in a single experiment. Spectroelectrochemistry provides a whole vision of the phenomena that take place in the electrode process. The first spectroelectrochemical experiment was carried out by Theodore Kuwana, PhD, in 1964.
R. David Britt is the Winston Ko Chair and Distinguished Professor of Chemistry at the University of California, Davis. Britt uses electron paramagnetic resonance (EPR) spectroscopy to study metalloenzymes and enzymes containing organic radicals in their active sites. Britt is the recipient of multiple awards for his research, including the Bioinorganic Chemistry Award in 2019 and the Bruker Prize in 2015 from the Royal Society of Chemistry. He has received a Gold Medal from the International EPR Society (2014), and the Zavoisky Award from the Kazan Scientific Center of the Russian Academy of Sciences (2018). He is a Fellow of the American Association for the Advancement of Science and of the Royal Society of Chemistry.
Electron resonance imaging (ERI) is a preclinical imaging method, together with positron emission tomography (PET), computed tomography scan, magnetic resonance imaging (MRI), and other techniques. ERI is dedicated to imaging small laboratory animals and its unique feature is the ability to detect free radicals. This technique could also be used for other purposes such as material science, quality of food, etc.
