recommended owing to inconsistency with the terms
STEREOSELECTIVITYand STEREOSPECIFICITY.
See alsoCHEMOSELECTIVITY.
regulation Refers to control of activity of an
ENZYME(system) or GENE EXPRESSION.
Reichstein, Tadeus (1897–1996) Swiss Chemist
Tadeus Reichstein was born on July 20, 1897, at Wlo-
clawek, Poland, to Isidor Reichstein and Gastava Brock-
mann. He was educated at a boarding school at Jena
before his family moved to Zurich in 1906 (where he
was naturalized). He had a private tutor and then
attended the Oberrealschule (technical school of junior
college grade) and the Eidgenössische Technische
Hochschule (E.T.H.) (state technical college).
In 1916 he began to study chemistry at the E.T.H.
at Zurich and graduated in 1920. In 1922 he began a
nine-year research project on the composition of the
flavoring substances in roasted coffee.
In 1931 he turned to other scientific research, and
by 1938 he was professor in pharmaceutical chemistry
and director of the pharmaceutical institute in the Uni-
versity of Basel. From 1946 to 1967 he was professor
of organic chemistry at the University of Basel.
In 1933 he synthesized vitamin C (ascorbic acid)
and worked on plant glycosides. From 1953 to 1954
he worked with several other scientists and was the
first to isolate and explain the constitution of aldos-
terone, a hormone of the adrenal cortex. He also col-
laborated with E. C. KENDALL and P. S. Hench in
their work on the hormones of the adrenal cortex. For
this work, Reichstein, Kendall, and Hench were
jointly awarded the Nobel Prize for physiology or
medicine in 1950.
After 1967 he worked on the study of ferns and
published many papers on the subject. He died on
August 1, 1996, in Basel.
relative configuration The CONFIGURATIONof any
stereogenic (asymmetric) center with respect to any
other stereogenic center contained within the same
MOLECULAR ENTITY. A stereogenic unit is a grouping
within a molecular entity that can be considered a
focus of STEREOISOMERISM.
relaxation If a system is disturbed from its state of
equilibrium, it returns to that state, and the process is
referred to as relaxation.releaser A signal stimulus that functions as a commu-
nication signal between individuals of the same species
and initiates a fixed action pattern (FAP), a stereotyped
species-to-species behavior.reorganization energy In a one-electron transfer
reaction
A + D A.–+ D.+
the reorganization energy λis the energy required for
all structural adjustments (in the reactants and in the
surrounding solvent molecules) that are needed in
order that A and D assume the configuration required
for the transfer of the electron.
See alsoINTRINSIC BARRIER; MARCUS EQUATION.residence time The duration of time a specific
molecule of water remains in a particular flow system.
In geochemistry, it is the average time spent by an atom
or molecule within the reservoir (the mass of an ele-
ment or a compound within a defined “container”)
between the time it entered and exited it. Residence
time is calculated by dividing the reservoir size by the
input (or the output).resolving power A property of instruments like
microscopes and telescopes that distinguish objects that
are close to each other; the smaller the minimum dis-
tance at which two objects can be distinguished, the
greater the resolving power.resonance In the context of chemistry, the term refers
to the representation of the electronic structure of a
MOLECULAR ENTITYin terms of CONTRIBUTING STRUC-
TUREs. Resonance among contributing structures
means that the wave function is represented by “mix-
ing” the wave functions of the contributing structures.
The concept is the basis of the quantum mechanical
valence bond methods. The resulting stabilization is236 regulation