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Bifurcated H-bond systems are common in alpha-helical transmembrane proteins between the backbone amide C=O of residue i as the H-bond acceptor and two H-bond donors from residue i + 4: the backbone amide N−H and a side-chain hydroxyl or thiol H +. The energy preference of the bifurcated H-bond hydroxyl or thiol system is -3.4 kcal/mol or -2. ...
A compound can be transformed into a different substance by a chemical reaction, which may involve interactions with other substances. In this process, bonds between atoms may be broken or new bonds formed or both. There are four major types of compounds, distinguished by how the constituent atoms are bonded together.
The molecule's polarity, and especially its ability to form hydrogen bonds, makes ammonia highly miscible with water. The lone pair makes ammonia a base , a proton acceptor. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral ( pH = 7 ), 99.4% of ...
The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.
Hydrogen bonds of the form A--H•••B occur when A and B are two highly electronegative atoms (usually N, O or F) such that A forms a highly polar covalent bond with H so that H has a partial positive charge, and B has a lone pair of electrons which is attracted to this partial positive charge and forms a hydrogen bond. [23]: 702 Hydrogen ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 27 February 2025. Sweet-tasting, water-soluble carbohydrates This article is about the class of sweet-flavored substances used as food. For common table sugar, see Sucrose. For other uses, see Sugar (disambiguation). Sugars (clockwise from top-left): white refined, unrefined, brown, unprocessed cane ...
Pure water is an example of a chemical substance, with a constant composition of two hydrogen atoms bonded to a single oxygen atom (i.e. H 2 O). The atomic ratio of hydrogen to oxygen is always 2:1 in every molecule of water. Pure water will tend to boil near 100 °C
The notation "hydrated compound⋅n H 2 O", where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The n is usually a low integer, though it is possible for fractional values to occur. For example, in a monohydrate n = 1, and in a hexahydrate n = 6.