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The proof of concept of BOLD-contrast imaging was provided by Seiji Ogawa and Colleagues in 1990, following an experiment which demonstrated that an in vivo change of blood oxygenation could be detected with MRI. [6] In Ogawa's experiments, blood-oxygenation-level–dependent imaging of rodent brain slice contrast in different components of the ...
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. [1] A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases.
The above reaction occurs between a 1,2-aminothiol and a 2-cyanobenzothiazole to make luciferin, which is fluorescent. This luciferin fluorescence can be then quantified by spectrometry following a wash, and used to determine the relative presence of the molecule bearing the 1,2-aminothiol.
Crossover experiments allow for experimental study of a reaction mechanism. Mechanistic studies are of interest to theoretical and experimental chemists for a variety of reasons including prediction of stereochemical outcomes, optimization of reaction conditions for rate and selectivity, and design of improved catalysts for better turnover number, robustness, etc. [6] [7] Since a mechanism ...
The actual sequence of the individual elementary reactions is known as reaction mechanism. An elementary reaction involves a few molecules, usually one or two, because of the low probability for several molecules to meet at a certain time. [14] Isomerization of azobenzene, induced by light (hν) or heat (Δ)
Not only is the reaction tolerant of water, but it has been found that the rate increases in aqueous media. Reactions have also been performed using norbornenes as dienophiles at second order rates on the order of 1 M −1 •s −1 in aqueous media. The reaction has been applied in labeling live cells [38] and polymer coupling. [39]
Autocrine signaling occurs when the chemical signal acts on the same cell that produced the signaling chemical. [1] Intracrine signaling occurs when the chemical signal produced by a cell acts on receptors located in the cytoplasm or nucleus of the same cell. [2] Juxtacrine signaling occurs between physically adjacent cells. [3]
Biosynthesis occurs due to a series of chemical reactions. For these reactions to take place, the following elements are necessary: [1] Precursor compounds: these compounds are the starting molecules or substrates in a reaction. These may also be viewed as the reactants in a given chemical process.