| Fischer projection formula | <biochemistry> Of sugars, representations, by projection, of cyclic sugars, or derivatives thereof, in which the carbon chain is depicted vertically. The lowest-numbered asymmetric carbon atom (C-1 in aldoses; C-2 in 2-ketoses, e.g., fructose) is drawn at the top, and the rest of the carbon atoms of the chain are drawn in sequence below the top carbon atom. For each carbon atom, depicted in projection as lying in the plane of the paper, the carbon-to-carbon bond(s), which actually point away from the viewer, are drawn as vertical lines. The left-hand and right-hand bonds of each carbon atom, which actually point toward the viewer, are, in projection, depicted as horizontal lines. The conventions for the Fischer formulas of cyclic sugars are as follows: 1) if the highest-numbered asymmetric carbon atom has its OH (or its replacement) lying to the right, as is the 2-OH of d-glyceraldehyde, the sugar has the d configuration; if the OH is to the left, the sugar has the l configuration. 2) On the anomeric carbon atom (C-1 in the aldoses; C-2 in the 2-ketoses), an OH or substituted OH that lies to the right, with the OH of the highest-numbered asymmetric carbon atom also to the right is defined to be a; if it is to the left, with the OH of the highest-numbered carbon atom still to the right, it is b; the reverse applies if the latter OH is to the left. 3) The orientation of a terminal CH2OH group in the aldoses carries no configurational significance, as it contains no asymmetric carbon atom. (05 Mar 2000) |
|---|---|
| lateral projection | Radiographic projection with the X-ray beam in a coronal plane. (05 Mar 2000) |
| frog-leg lateral projection | A lateral projection of the femoral neck made with the thigh maximally abducted. (05 Mar 2000) |
| 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) |
| base composition | <biochemistry> In reference to nucleic acid, the proportion of the total bases consisting of guanine plus cytosine or thymine plus adenine base pairs. Usually expressed as a guanine + cytosine (G+C) value, for example 60% G+C. (09 Oct 1997) |
| base deficit | A decrease in the total concentration of blood buffer base, indicative of metabolic acidosis or compensated respiratory alkalosis. (05 Mar 2000) |
| base dissociation constant | <chemistry> This is the equilibrium constant for the reaction in which a weak base breaks apart in water to form its conjugate acid and hydroxide ion. (09 Oct 1997) |