Two or more coordination compounds in which the
donor atom of at least one of the ligands is different.
Linkage isomers have different physical and chemical
properties. Ligands that can form these isomers are
CN–, SCN–, and NO 2 –.
lipid A large group of HYDROPHOBIC(water insolu-
ble) molecules that are the building blocks of cell mem-
branes and liposomes (lipid vesicles) and contain fatty
acids; the principal components of fats, oils, waxes,
triglycerides, and cholesterol. They are insoluble in
water but soluble in solvents such as alcohol and ether.
The phospholipid bilayer of the plasma membrane is a
double layer of phospholipid molecules arranged so
that the hydrophobic “tails” lie between the
HYDROPHILIC“heads.” Also known as fat, they easily
store in the body and are an important source of fuel
for the body.
Lipmann, Fritz Albert (1899–1986) German/Ameri-
canBiochemist Fritz Albert Lipmann was born on
June 12, 1899, at Koenigsberg, Germany, to Leopold
Lipmann and his wife Gertrud Lachmanski.
From 1917 to 1922 he was educated at the Uni-
versities of Koenigsberg, Berlin, and Munich, where
he studied medicine and received a M.D. degree in
1924 at Berlin. In 1926 he was an assistant in Otto
Meyerhof’s laboratory at the Kaiser Wilhelm Institute,
Berlin, and received a Ph.D. in 1927. He then went
with Meyerhof to Heidelberg to conduct research on
the biochemical reactions occurring in muscle.
In 1930 Lipmann went back to the Kaiser Wil-
helm Institute in Berlin, then to a new institute in
Copenhagen in 1932. Between 1931 and 1932, he
served as a Rockefeller fellow at the Rockefeller Insti-
tute in New York and identified serine phosphate as
the constituent of phosphoproteins that contains the
phosphate.
He went to Copenhagen in 1932 as research asso-
ciate in the Biological Institute of the Carlsberg Foun-
dation. In 1939 he came to America and became a
research associate in the department of biochemistry at
Cornell Medical School, in Ithaca, New York, and in
1941 joined the research staff of the Massachusetts
General Hospital in Boston, first as a research associate
in the department of surgery, then heading his own
group in the biochemical research laboratory of the
hospital. In 1944 he became an American citizen. In
1949 he became professor of biological chemistry at
Harvard Medical School, Boston. In 1957 he was
appointed a member and professor of the Rockefeller
Institute, New York City.
In 1947 he isolated and named coenzyme A (or
CoA) as well as determining the molecular structure
(1953) of this factor that is now known to be bound to
acetic acid as the end product of sugar and fat break-
down in the absence of oxygen. It is one of the most
important substances involved in cellular metabolism,
since it helps convert amino acids, steroids, fatty acids,
and hemoglobins into energy. For his discovery of this
coenzyme, he was awarded the 1953 Nobel Prize for
physiology or medicine. He died on July 24, 1986, in
Poughkeepsie, New York.lipophilic Literally “fat-loving.” Applied to MOLECU-
LAR ENTITIES(or parts of molecular entities) having a
tendency to dissolve in fatlike (e.g., hydrocarbon) sol-
vents.
See also HYDROPHILIC; HYDROPHOBIC INTERAC-
TION.lipophilicity Represents the AFFINITYof a molecule
or a moiety (portion of a molecular structure) for a
LIPOPHILIC(fat soluble) environment. It is commonly
measured by its distribution behavior in a biphasic
system, either liquid-liquid (e.g., partition coefficient
in octan-1-ol/water) or solid-liquid (retention on
reversed-phase HIGH-PERFORMANCE LIQUID CHRO-
MATOGRAPHY[RP-HPLC] or thin-layer chromatogra-
phy [TLC] system).
See alsoHYDROPHOBICITY.lipoprotein Since lipids are hydrophobic, or water
insoluble, certain lipids like cholesterol and triglyc-
erides are coated or bonded with a protein so they can
be carried in the blood. Since it is not possible to deter-
mine the exact lipoprotein content in blood due to the
variety of lipoproteins, the medical profession talks
about low-density lipoproteins (LDLs) and high-density
lipoproteins (HDLs), which transport fats and choles-
terol through the blood.lipoprotein 167