N
1. symbol, newton. 2. chemical symbol, nitrogen. 3. symbol, normal (solution); the expressions 2N (double normal), 0.5N (half-normal), 0.1N (tenth- normal), etc., denote the strength of a solution in comparison with the normal.
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N banding
a staining technique for karyotypes; performed with Giemsa or silver stains; called N band because it identifies nucleolus organizer regions.
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N region
a highly variable region on the H chain of immunoglobulins.
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N’Dama
a West African small, humpless type of beef cattle, fawn, dun or light red in color, with lyre or crescent horns. There are a large number of varieties.
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N-3-pyridyl methyl N1-p-nitrophenyl urea
see valor.
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N5,N10A band
the wide (1.5–2 µm) anisotropic central zone in the sarcomere or contractile unit of the myofibril, made of both actin and myosin filaments.
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N5,N10-methylene H4 folate
form of tetrahydrolate essential to the synthesis of purines.
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NA
Nomina Anatomica.
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Na+
sodium ion.
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Na+,K+-ATPase
widely distributed enzyme consisting of two large ?-subunits and two smaller ?-subunits, whose function is to transport Na? and K? against their concentration gradients using hydrolysis of ATP as the thermodynamic couple. The stoichiometry of exchange is two K? for every three Na? pumped. Often called the sodium pump.
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