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When the solvent is also a nucleophile such as dioxane two successive S N 2 reactions take place and the stereochemistry is again retention. With standard S N 1 reaction conditions the reaction outcome is retention via a competing S N i mechanism and not racemization and with pyridine added the result is again inversion. [5] [3]
The Hughes-Ingold symbol of the mechanism expresses two properties—"S N" stands for "nucleophilic substitution", and the "1" says that the rate-determining step is unimolecular. [1] [2] Thus, the rate equation is often shown as having first-order dependence on the substrate and zero-order dependence on the nucleophile. This relationship holds ...
The proposal that proteins were linear chains of α-amino acids was made nearly simultaneously by two scientists at the same conference in 1902, the 74th meeting of the Society of German Scientists and Physicians, held in Karlsbad. Franz Hofmeister made the proposal in the morning, based on his observations of the biuret reaction in proteins.
Walden inversion is the inversion of a stereogenic center in a chiral molecule in a chemical reaction. Since a molecule can form two enantiomers around a stereogenic center, the Walden inversion converts the configuration of the molecule from one enantiomeric form to the other.
The process for class 1 inteins begins with an N-O or N-S shift when the side chain of the first residue (a serine, threonine, or cysteine) of the intein portion of the precursor protein nucleophilically attacks the peptide bond of the residue immediately upstream (that is, the final residue of the N-extein) to form a linear ester (or thioester) intermediate.
Nucleotides are the monomers which polymerize into nucleic acids. All nucleotides contain a sugar, a phosphate, and a nitrogenous base. The bases found in nucleic acids are either purines or pyrimidines. In the more complex multicellular animals, they are both primarily produced in the liver but the two different groups are synthesized in ...
ER retention refers to proteins that are retained in the endoplasmic reticulum, or ER, after folding; these are known as ER resident proteins. Protein localization to the ER often depends on certain sequences of amino acids located at the N terminus or C terminus. These sequences are known as signal peptides, molecular signatures, or sorting ...
Interaction between branched-chain amino acids and the purine nucleotide cycle in muscles Fumarate , produced from the purine nucleotide cycle, is an intermediate of TCA cycle and enters the mitochondria by converting into malate and utilizing the malate shuttle where it is converted into oxaloacetic acid (OAA).