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Gadobenic Acid
Gadobenic acid (INN, brand name Multihance) is a complex of gadolinium with the ligand BOPTA. In the form of the methylglucamine salt meglumine gadobenate ( INNm) or gadobenate dimeglumine (USAN), it is used as a gadolinium-based MRI contrast medium. BOPTA is a derivative of DTPA in which one terminal carboxyl group, –C(O)OH is replaced by -C–O–CH2C6H5. Thus gadobenic acid is closely related to gadopentetic acid. BOPTA itself was first synthesized in 1995. In the "gadobenate" ion gadolinium ion is 9-coordinate with BOPTA acting as an 8-coordinating ligand. The ninth position is occupied by a water molecule, which exchanges rapidly with water molecules in the immediate vicinity of the strongly paramagnetic complex, providing a mechanism for MRI contrast enhancement. 139La NMR studies on the diamagnetic La-BOPTA2− complex suggest that the Gd complex maintains in solution the same kind of coordination as found, by X-ray crystallography X-ray crystallography is the expe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gadopentetic Acid
Gadopentetic acid, sold under the brand name Magnevist, is a gadolinium-based MRI contrast agent. It is usually administered as a salt of a complex of gadolinium with DTPA (''d''iethylene''t''riamine''p''ent''a''cetate) with the chemical formula A2 d(DTPA)(H2O) when cation A is the protonated form of the amino sugar meglumine the salt goes under the name "gadopentetate dimeglumine". It was described in 1981 by Hanns-Joachim Weinmann and colleagues and introduced as the first MRI contrast agent in 1987 by the Schering AG. It is used to assist imaging of blood vessels and of inflamed or diseased tissue where the blood vessels become "leaky". It is often used when viewing intracranial lesions with abnormal vascularity or abnormalities in the blood–brain barrier. It is usually injected intravenously. Gd-DTPA is classed as an acyclic, ionic gadolinium contrast medium. Its paramagnetic property reduces the T1 relaxation time (and to some extent the T2 and T2* relaxation times) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid-state Chemistry
Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, particularly, but not necessarily exclusively of, non-molecular solids. It therefore has a strong overlap with solid-state physics, mineralogy, crystallography, ceramics, metallurgy, thermodynamics, materials science and electronics with a focus on the synthesis of novel materials and their characterisation. Solids can be classified as crystalline or amorphous on basis of the nature of order present in the arrangement of their constituent particles. History Because of its direct relevance to products of commerce, solid state inorganic chemistry has been strongly driven by technology. Progress in the field has often been fueled by the demands of industry, sometimes in collaboration with academia. Applications discovered in the 20th century include zeolite and platinum-based catalysts for petroleum processing in the 1950s, high-pur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Complex
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the Periodic Table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from CT and PET scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft-tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, though "Open" MRI designs mostly relieve this. Additionally, implants and oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paramagnetic
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, diamagnetic materials are repelled by magnetic fields and form induced magnetic fields in the direction opposite to that of the applied magnetic field. Paramagnetic materials include most chemical elements and some compounds; they have a relative magnetic permeability slightly greater than 1 (i.e., a small positive magnetic susceptibility) and hence are attracted to magnetic fields. The magnetic moment induced by the applied field is linear in the field strength and rather weak. It typically requires a sensitive analytical balance to detect the effect and modern measurements on paramagnetic materials are often conducted with a SQUID magnetometer. Paramagnetism is due to the presence of unpaired electrons in the material, so most atoms wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordinate Covalent Bond
In coordination chemistry, a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal ions to ligands involves this kind of interaction. This type of interaction is central to Lewis acid–base theory. Coordinate bonds are commonly found in coordination compounds. Examples Coordinate covalent bonding is ubiquitous. In all metal aquo-complexes (H2O)''n'''m''+, the bonding between water and the metal cation is described as a coordinate covalent bond. Metal-ligand interactions in most organometallic compounds and most coordination compounds are described similarly. The term ''dipolar bond'' is used in organic chemistry for compounds such as amine oxides for which the electronic structure can be described in terms of the basic amine donating two electrons to an oxygen atom. : → O The arrow → indicates that both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxylic Acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion. Examples and nomenclature Carboxylic acids are commonly identified by their trivial names. They at oftentimes have the suffix ''-ic acid''. IUPAC-recommended names also exist; in this system, carboxylic acids have an ''-oic acid'' suffix. For example, butyric acid (C3H7CO2H) is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gadolinium
Gadolinium is a chemical element with the symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of is ferromagnetic, with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most paramagnetic element. It is found in nature only in an oxidized form. When separated, it usually has impurities of the other rare-earths because of their similar chemical properties. Gadolinium was discovered in 1880 by Jean Charles de Marignac, who detected its oxide by using spectroscopy. It is named after the mineral gadolinite, one of the minerals in which gadolinium is found, itself named for the Finnish chemist Johan Gadolin. Pure gadolinium was first isolated by the chemist Paul-Émile Lecoq de Boisbaudran around 1886. Gadoliniu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DTPA
Pentetic acid or diethylenetriaminepentaacetic acid (DTPA) is an aminopolycarboxylic acid consisting of a diethylenetriamine backbone with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA and is used similarly. It is a white solid with limited solubility in water. Coordination properties The conjugate base of DTPA has a high affinity for metal cations. Thus, the penta-anion DTPA5− is potentially an octadentate ligand assuming that each nitrogen centre and each –COO− group counts as a centre for coordination. The formation constants for its complexes are about 100 greater than those for EDTA.J. Roger Hart "Ethylenediaminetetraacetic Acid and Related Chelating Agents" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. As a chelating agent, DTPA wraps around a metal ion by forming up to eight bonds. Its complexes can also have an extra water molecule that coordinates the metal ion. Transition metals, however, u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Complete Drug Reference
''The'' () is a grammatical article in English, denoting persons or things that are already or about to be mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with nouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a consonant sound, and as (homophone of the archaic pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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