| ion exchange chromatography | <procedure> Separation of molecules by absorption and desorption from charged polymers. An important technique for protein purification. For small molecules the support is usually polystyrene, but for macromolecules, cellulose, acrylamide or agarose supports give less non-specific absorption and denaturation. Typical charged residues are CM carboxymethyl) or DEAE (diethylaminoethyl). (27 Oct 1998) |
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| ion exchange resin | <chemistry> A resin of polymers that havefixed charged groups which is used in chromatographic columns to separate ions. (27 Oct 1998) |
| ion exchange resins | <chemistry> High molecular weight, insoluble polymers which contain functional groups that are capable of undergoing exchange reactions (ion exchange) with either cations or anions. See: ion exchange, ion exchanger. (12 Dec 1998) |
| exchange | 1. To part with give, or transfer to another in consideration of something received as an equivalent; usually followed by for before the thing received. "Exchange his sheep for shells, or wool for a sparking pebble or a diamond." (Locke) 2. To part with for a substitute; to lay aside, quit, or resign (something being received in place of the thing with); as, to exchange a palace for cell. "And death for life exchanged foolishly." (Spenser) "To shift his being Is to exchange one misery with another." (Shak) 3. To give and receive reciprocally, as things of the same kind; to barter; to swap; as, to exchange horses with a neighbor; to exchange houses or hats. "Exchange forgiveness with me, noble Hamlet." (Shak) Synonym: To barter, change, commute, interchange, bargain, truck, swap, traffic. Origin: Cf.OF. Eschangier, F. Echanger. See Exchange. 1. The act of giving or taking one thing in return for another which is regarded as an equivalent; as, an exchange of cattle for grain. 2. The act of substituting one thing in the place of another; as, an exchange of grief for joy, or of a scepter for a sword, and the like; also, the act of giving and receiving reciprocally; as, an exchange of civilities or views. 3. The thing given or received in return; especially, a publication exchanged for another. 4. The process of setting accounts or debts between parties residing at a distance from each other, without the intervention of money, by exchanging orders or drafts, called bills of exchange. These may be drawn in one country and payable in another, in which case they are called foreign bills; or they may be drawn and made payable in the same country, in which case they are called inland bills. The term bill of exchange is often abbreviated into exchange; as, to buy or sell exchange. A in London is creditor to B in new York, and C in London owes D in New York a like sum. A in London draws a bill of exchange on B in New York; C in London purchases the bill, by which A receives his debt due from B in New York. C transmits the bill to D in New York, who receives the amount from B. 5. A mutual grant of equal interests, the one in consideration of the other. Estates exchanged must be equal in quantity, as fee simple for fee simple. 6. The place where the merchants, brokers, and bankers of a city meet at certain hours, to transact business. In this sense often contracted to 'Change. Arbitration of exchange. See Arbitration. Bill of exchange. See Bill. Exchange broker. See Broker. Par of exchange, the established value of the coin or standard of value of one country when expressed in the coin or standard of another, as the value of the pound sterling in the currency of France or the United States. The par of exchange rarely varies, and serves as a measure for the rise and fall of exchange that is affected by the demand and supply. Exchange is at par when, for example, a bill in new York, for the payment of one hundred pounds sterling in London, can be purchased for the sum. Exchange is in favor of a place when it can be purchased there at or above par. Telephone exchange, a central office in which the wires of any two telephones or telephone stations may be connected to permit conversation. Synonym: Barter, dealing, trade, traffic, interchange. Origin: OE. Eschange, eschaunge, OF. Eschange, fr. Eschangier, F. Echanger, to exchange; pref. Ex- out + F. Changer. See Change, and cf. Excamb. Source: Websters Dictionary (01 Mar 1998) |
| exchange transfusion | Removal of most of a patient's blood followed by introduction of an equal amount from donors. Synonym: exsanguination transfusion, substitution transfusion, total transfusion. (05 Mar 2000) |
| exchange transfusion, whole blood | Repetitive withdrawal of small amounts of blood and replacement with donor blood until a large proportion of the blood volume has been exchanged. Used in treatment of foetal erythroblastosis, hepatic coma, sickle cell anaemia, disseminated intravascular coagulation, septicaemia, burns, thrombotic thrombopenic purpura, and fulminant malaria. (12 Dec 1998) |
| acid-base balance | The normal balance between acid and base in the blood plasma, expressed in the hydrogen ion concentration or pH, resulting from the relative amounts of acidic and basic materials ingested and produced by body metabolism, compared to the relative amounts of acidic and basic materials excreted from the body and consumed by body metabolism; the normal state of acid-base balance is not one of neutrality, with equal concentrations of hydrogen and hydroxyl ions, but a more alkaline state with a certain excess of hydroxyl ions. Synonym: acid-base equilibrium. (05 Mar 2000) |
| acid-base equilibrium | A condition in which the net rate of acid or alkali production by the body is balanced by the net rate of acid or alkali excretion from the body, resulting in a stable concentration of hydrogen ions in the body fluids. (12 Dec 1998) |
| acid-base imbalance | Disturbances in the acid-base equilibrium of the body. (12 Dec 1998) |
| acrylic resin base | A form made of acrylic resin molded to conform to the tissues of the alveolar process and used to support the teeth of a prosthesis. (05 Mar 2000) |
| aldehyde base | An obsolete term for an imide. (05 Mar 2000) |
| anterior cranial base | The portion of the internal base of the skull, anterior to the sphenoidal ridges and limbus, in which the frontal lobes of the brain rest. Synonym: fossa cranii anterior, anterior cranial base. (05 Mar 2000) |
| Bandrowski's base | <chemical> Reported cause of anaphylactic reaction. Synonym: n',n'-bis(4-aminophenyl)-2,5-diamino-1,4-quinonediimine (26 Jun 1999) |
| base | <chemistry> The nonacid part of a salt, a substance that combines with acids to form salts, a substance that dissociates to give hydroxide ions in aqueous solutions, a substance whose molecule or ion can combine with a proton (hydrogen ion), a substance capable of donating a pair of electrons (to an acid) for the formation of a coordinate covalent bond. (13 Nov 1997) |
| base analogue | <biochemistry> A chemical which resembles a nucleotide base. They can substitute the Purine and pyrimidine bases that normally appear in DNA, despite minor differences in structure. May be used for inducing mutations, including point mutations. For example: 5 bromouracil can replace thymine or 2 aminopurine replace adenine. (13 Nov 1997) |