NAD+ Oxidized form of nicotinamide adenine dinu-
cleotide. Note that despite the plus sign in the symbol,
the COENZYMEis anionic under normal physiological
conditions. NAD+is a coenzyme derived from the B
vitamin niacin. It is transformed into NADHwhen it
accepts a pair of high-energy electrons for transport in
cells and is associated with catabolic and energy-yield-
ing reactions.
NADH Reduced form of nicotinamide adenine dinu-
cleotide (NAD). Called coenzyme I and is an electron
donor essential for a variety of oxidation-reduction
reactions.
NADP+ Oxidized form of nicotinamide adenine din-
ucleotide phosphate. Note that despite the plus sign in
the symbol, the COENZYME is anionic under normal
physiological conditions. An enzyme commonly associ-
ated with biosynthetic reactions. NADP is a hydrogen
carrier in a wide range of redox reactions.
NADPH Reduced form of nicotinamide adenine din-
ucleotide phosphate. An energy-rich compound pro-
duced by the light-reaction of photosynthesis. It is used
to synthesize carbohydrates in the dark-reaction.
nanoparticle A molecule or other particle measured
in size on the order of tens of nanometers.
nanotube(buckytube) Any tube with nanoscale
dimensions. Used mostly to refer to carbon nanotubes
(sheets of graphite rolled up to make a tube).narcissistic reaction A CHEMICAL REACTIONthat
can be described as the conversion of a reactant into
its mirror image, without rotation or translation of
the product, so that the product ENANTIOMERactu-
ally coincides with the mirror image of the reactant
molecule. Examples of such reactions are cited under
the entries FLUXIONALand DEGENERATE REARRANGE-
MENT.native state The state when an element exists
uncombined in nature and free of other elements.natural gas A naturally occurring mixture of hydro-
carbon and nonhydrocarbon gases that are found in
porous/permeable geologic formations underneath the
Earth’s surface, and often found with petroleum.natural product High-value chemical entities
derived from plants or microbial sources.natural radioactivity Spontaneous decomposition
of an atom. Radioactivity associated with naturally191