Kilogram

Kilogram:

 The basic unit of mass (not of weight or of force). A kilogram is equal to the mass of 1.000028 cubic decimeters of water at the temperature of its maximum density.

Kilocalorie (kcal)

Kilocalorie (kcal):

 One kilocalorie is equal to 1,000 calories, which is based on the amount of heat energy required to raise the temperature of 1 kilogram of water by 1°C; used to measure the energy value in food
and labor. Usually just called calorie; 1 kilocalorie (kcal) = 1 Calorie (Cal) = 1,000 calories (cal). However, in the International System of Units (ISU), the universal unit of energy is the joule (J). One kilocalorie = 4.184 kilojoules (kJ).

Joule

Joule:

 The international unit of energy or work. The amount of work done when a force of 1 Newton is applied through a distance of 1 meter. One joule is 1kg·m2/s2 or 0.2390 calorie.

Iron-Sulfur Protein

Iron-Sulfur Protein:

 Proteins in which non-HEME iron is coordinated with cysteine sulfur and, usually, with inorganic sulfur. Divided into three major categories: RUBREDOXINs; simple iron-sulfur proteins, containing
only IRON-SULFUR CLUSTERs; and complex iron-sulfur proteins, containing additional active redox centers such as FLAVIN, molybdenum, or heme. In most iron-sulfur proteins, the clusters function as ELECTRON TRANSFER groups, but in others they have other functions such as catalysis of hydratase/dehydratase reactions, maintenance of protein structure, or REGULATION
of activity.

Ionization Energy

Ionization Energy:

 Ei (SI unit: kJ mol–1 or J per molecule) The minimum energy required to remove an electron from an isolated MOLECULAR ENTITY (in its vibrational GROUND STATE) in the gaseous phase. If the resulting molecular entity is considered to be in its
vibrational ground state, one refers to the energy as the
“adiabatic ionization energy.” If the molecular entity produced possesses the vibrational energy determined by the Franck-Condon principle (according to which the electron ejection takes place without an accompanying change in molecular geometry), the energy is called the “vertical ionization energy.” The name “ionization energy” is preferred to the somewhat misleading
earlier name “ionization potential.”

Ion Exchange

Ion Exchange:

 A reversible process where ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution. The direction of the exchange depends on (a) the affinities
of the ion exchanger for the ions present and (b) the concentrations of the ions in the solution. In water treatment, this process adds and removes ions from water. In nuclear chemistry, it is a common method for concentrating uranium from a solution. The uranium
solution is passed through a resin bed, where the uranium- carbonate complex ions are transferred to the resin by exchange with a negative ion like chloride. After buildup of the uranium complex on the resin, the uranium is eluted with a salt solution, and the uranium is precipitated in another process.

Intramolecular Catalysis

Intramolecular Catalysis:

 The acceleration of a chemical transformation at one site of a MOLECULAR ENTITY through the involvement of another FUNCTIONAL (“catalytic”) GROUP in the same molecular
entity, without that group appearing to have undergone change in the reaction product. The use of the term should be restricted to cases for which analogous INTERMOLECULAR CATALYSIS by CHEMICAL SPECIES bearing that catalytic group is observable. Intramolecular catalysis can be detected and expressed in quantitative form by a comparison of the reaction rate with
that of a comparable model compound in which the catalytic group is absent, or by measurement of the EFFECTIVE MOLARITY of the catalytic group.