tein coated with a sugar is termed glycosylatedand is
described or named with the initials “gp” along with
its molecular weight, e.g., gp160. Several gps are asso-
ciated with HIV infection, since they are the outer-coat
proteins of HIV: gp41 plays a key role in HIV’s infec-
tion of CD4+ T cells by facilitating the fusion of the
viral and cell membranes. GP120 is one of the proteins
that forms the envelope of HIV, and projects from the
surface of HIV and binds to the CD4 molecule on
helper T cells. GPs are found in mucus and mucins, y-
globulins, al-globulins, a2-globulins, and transferrin,
an ion-transporting protein. They act as receptors for
molecular signals originating outside the cell. Attach-
ment of oligosaccharides to peptides increases solubil-
ity, covers the antigenic domains, and protects peptide
backbones against proteases.
gold drugs Gold COORDINATIONcompounds used in
the treatment of rheumatoid arthritis, examples being
auranofin, (tetraacetylthioglucosato-S)(triethylphos-
phane)gold(I), and myocrysin, disodium thiomalonato-
gold(I).
Graham’s law The rate of diffusion of a gas is
inversely proportional to the square root of its density
or molecular weight.
Greek letters used
α: SeeHELIX(for alpha helix); CYTOCHROME
β: SeeBETA SHEET; BETA STRAND; BETA TURN;
CYTOCHROME
γ: SeeSORET BAND(for gamma band)
η: SeeHAPTO; ASYMMETRY PARAMETER
κ: SeeDONOR ATOM SYMBOL(for kappa convention)
μ: SeeBRIDGING LIGAND(for mu symbol)
greenhouse effect The warming of an atmosphere
by its absorption of infrared radiation while shortwave
radiation is allowed to pass through.
Certain gaseous components of the atmosphere,
called greenhouse gases, transmit the visible portion of
solar radiation but absorb specific spectral bands of
thermal radiation emitted by the Earth. The theory is
that terrain absorbs radiation, heats up, and emits
longer wavelength thermal radiation that is prevented
from escaping into space by the blanket of carbon
dioxide and other greenhouse gases in the atmosphere.
As a result, the climate warms. Because atmospheric
and oceanic circulations play a central role in the cli-
mate of the Earth, improving our knowledge about
their interaction is essential.
See alsoCARBON DIOXIDE.ground state The state of lowest Gibbs energy of a
system.
See alsoEXCITED STATE; GIBBS ENERGY DIAGRAM.group A defined linked collection of atoms or a sin-
gle atom within a MOLECULAR ENTITY. This use of the
term in physical, organic, and general chemistry is less
restrictive than the definition adopted for the purpose
of nomenclature of organic compounds.
Also a vertical column in the periodic table.
See alsoSUBSTITUENT.group 119Greenhouse effect. The warming of an atmosphere by its
absorbing infrared radiation while allowing shortwave radiation
to pass through