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ScienceWeek
SCIENCE-WEEK
SCIENCE-WEEK
A Free Weekly Digest of the News of Science
June 12, 1998
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Books must follow sciences, and not sciences books.
-- Francis Bacon (1561-1626)
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Contents of This Issue:
1. Physicist Edward Teller on Science and Morality
2. Rumblings of a New Scientific Fraud Scandal in Germany
3. On Quantum Computing with Molecules
4. A Silicon-Based Nuclear Spin Quantum Computer
5. On Simulated Evolution and Protein Folding
6. Host-Guest Encapsulation of Materials by Virus Protein Cages
7. A Superlattice Model for Red Cell Membrane Phospholipids
8. Cloned Transgenic Calves from Fetal Fibroblasts
---------------------------------------------
1. PHYSICIST EDWARD TELLER ON SCIENCE AND MORALITY
Edward Teller (Stanford University, US), one of the major
contributors to the physical theory and current explanation of
solar energy, is also well-known in the political arena as the
major proponent of the initial development of the hydrogen bomb
by the US. Teller was born in Hungary, became a physicist in
Germany, left Germany in 1933, and eventually became a partici-
pant in the US Manhattan Project 1941-1946 to develop the atomic
bomb. In a recent essay reviewing the political aspects of his
scientific career, Teller (who is now 90 years of age) makes the
following points: 1) Concerning the questions, What is true? What
is right? What is beautiful?: science considers what is true,
politics considers what is right, and art considers what is
beautiful. Truth, morality, and beauty thus produce activities in
science, politics, and art, but these activities diverge greatly,
and Teller proposes they can be pursued initially without regard
to each other, or without reconciling the possible conflicts that
may arise. 2) Teller says that in 1945, when the work on the
hydrogen bomb was discontinued, in addition to his disappointment
in having to stop a project on which he had been working, he was
disappointed for two other reasons: The first reason was his
belief that the pursuit of knowledge and the expansion of human
capabilities are intrinsically worthwhile; and the second reason
was his worry of what might result if the Soviets got too far
ahead of the US in military technology. 3) Of his long-standing
criticism of communism, Teller says that "by age 11 I had a non-
too-sweet taste of communism in Hungary." 4) Teller says that
when he met the physicist Lev Landau in 1930, Landau said he
could not imagine anything more ridiculous than a capitalist
government. Some years later, Teller learned that Landau had been
arrested by the Soviets as a capitalist spy, and Teller says this
event was for him (Teller) more defining than the Hitler-Stalin
pact, and that by 1940 he (Teller) had every reason to dislike
and distrust the Soviets. 5) Finally, concerning the question of
his role in producing the hydrogen bomb, Teller writes as
follows: "I am still asked on occasion whether I am not sorry for
having invented such a terrible thing as the hydrogen bomb. The
answer is, I am not."
QY: Edward Teller, Stanford University 415-723-2300.
(Science 22 May 98 280:1200) (Science-Week 12 Jun 98)
2. RUMBLINGS OF A NEW SCIENTIFIC FRAUD SCANDAL IN GERMANY
Another major scientific fraud scandal appears to have surfaced
in Germany, coming into view while the last scandal is still
fresh. This time the problem is fraudulent work at the Max Planck
Institute for Plant Breeding in Cologne. A laboratory head and
his technician have already resigned, the technician, Inge Czaja,
admitting fabrication of data in at least one scientific paper
while she worked in the laboratory of Richard Walden. A commiss-
ion is now investigating the possibility of systematic manipul-
ation of important experimental results for 6 years by this team.
Experiments in at least half a dozen papers have apparently
proved to be non-reproducible using specially developed tests.
The research involves the identification of certain enzymes in
the signaling system of the hormone auxin, a promoter of plant
cell growth. Walden claims no direct involvement in the fraud,
but admits responsibility, as group leader, for the quality of
work done by his group. Apparently, questions are also being
raised concerning the responsibility of Jeff Schell, one of the
institutes four directors and head of the department of plant
genetics, where the work was carried out. The fraud was first
revealed in March 1998.
(Nature 28 May 98 393:293) (Science-Week 12 Jun 98)
[Editor's note: Background material on the recent Herrmann-Brach
fraud scandal can be found in the SW issue of 5 Jun 98].
3. ON QUANTUM COMPUTING WITH MOLECULES
In general, in quantum mechanics, the "superposition principle"
holds that any two quantum mechanical states can be combined in
infinitely many ways to form states that have characteristics
intermediate between those of the two that are combined.
Entanglement is unique to quantum mechanics, and involves a
relationship (a "superposition of states") between the possible
quantum states of two entities such that when the possible states
of one entity collapse to a single state as a result of suddenly
imposed boundary conditions, a similar and related collapse
occurs in the possible states of the entangled entity no matter
where or how far away the entangled entity is located. The idea
of quantum computing received a significant impetus in 1994 when
Peter W. Shor of ATT (US) proposed that quantum entanglement and
superposition could in principle be used to accomplish many
numerical tasks, in particular the factoring of large numbers,
much faster than the best classical calculator. Since the
security of many important encryption systems depends on the
difficulty of factoring large numbers, quantum computing suddenly
became of great practical importance, and Shor's algorithm
provoked computer scientists to learn about quantum mechanics,
and physicists to begin serious considerations of the require-
ments of a quantum computer science. ... ... Gershenfeld and
Chuang (2 installations, US), review the theoretical bases and
current status of quantum computing, in particular their own work
applying nuclear magnetic resonance techniques. The authors point
out the following: 1) In classical computation, the state of a
bit (the fundamental unit of information) is specified by one
number, 0 or 1. An n-bit binary word in a typical computer is
thus described by string of n zeroes and ones. In contrast, in a
quantum computer, the qubit (the fundamental unit of information)
might be represented by an atom in one of two different states, 0
or 1, but unlike classical bits, qubits can exist simultaneously
as 0 or 1, with the probability for each state given by a
numerical coefficient. 2) A quantum computer promises to be
immensely powerful because it can be in multiple states at once
(superposition), and because it can act on all its possible
states simultaneously. Thus, a quantum computer could naturally
perform myriad operations in parallel, using only a single
processing unit. This is the essence of the idea of quantum
computing, although one must understand the expression here is
quite general. 3) The authors have investigated the construction
of a quantum computer based on the nuclear magnetic resonance
behavior of a simple molecular liquid [chloroform, CHCl(sub3)],
with the 2 possible quantum mechanical "spin" states of atoms as
the basic qubit states. Since chloroform is a simple molecule,
the fundamental limitation in this particular system is the small
number of qubits. The authors and other researchers are actively
working to increase the size of the basic molecule in
experimental quantum computing systems, and thus increase the
number of available qubits. 4) The authors conclude: "All along,
ordinary molecules have known how to do a remarkable kind of
computation. People were just not asking them the right
questions."
QY: Neil Gershenfeld, Massachusetts Institute of Technology 617-
253-1000.
(Scientific American June 1998) (Science-Week 12 Jun 98)
[Editor's note: Experimental details of the method and algorithm
used in the above mentioned NMR quantum computing technique were
recently presented by Chuang et al (5 authors 4 installations,
US) in Nature 14 May 1998 393:143]
4. A SILICON-BASED NUCLEAR SPIN QUANTUM COMPUTER
B.E. Kane (University of New South Wales, AU) presents an
analysis of quantum computing and a new scheme for implementing a
quantum mechanical computer. The author proposes: 1) Although the
concept of information underlying all modern computer technology
is essentially classical, "physicists know that nature obeys the
laws of quantum mechanics." The idea of a quantum computer has
been developed theoretically over several decades in order to
understand the capabilities and limitations of machines in which
information is treated quantum mechanically. 3) Logical
operations carried out on the qubits and their measurement to
determine the result of the computation must obey quantum-mech-
anical laws. 4) Quantum computation can in principal only occur
in systems that are almost completely isolated from their
environment and which consequently must dissipate no energy
during the process of computation, conditions that are extra-
ordinarily difficult to fulfill in practice. The author presents
a scheme for implementing a quantum computer on an array of
nuclear spins located on donors in silicon. Logical operations
and measurements can in principle be performed independently and
in parallel on each spin in the array. Specific electronic
devices are described for the manipulation and measurement of
nuclear spins, and the author suggests that the development of a
silicon-based quantum computer can benefit from already existing
highly developed silicon technology.
QY: B.E. Kane (kane@newt.phys.unsw.edu.au)
EMAIL
(Nature 14 May 98 393:133) (Science-Week 12 Jun 98)
5. ON SIMULATED EVOLUTION AND PROTEIN FOLDING
Proteins are polymers consisting of long chains of amino acid
residues, but that is only the beginning of their functional
chemistry. In biological systems, proteins assume various complex
high-order configurations ("folding"), and it is these
configurations that usually determine the roles of proteins as
biochemical entities in the biological system. An important goal
of molecular biology is to understand the structural and
functional features of proteins, in particular the mechanisms
responsible for specific protein folding. The "bioinformatics"
approach is based on the idea of recognition and identification
in a protein of a new sequence of amino acids similar or
identical to other sequences in other proteins for which
structure and function are known. But this approach encounters
difficulties because of a lack of understanding of what features
of sequences have evolved to encode stability and fast folding in
proteins, and a lack of understanding of which features are
functional and which features are adventitious. Better
understanding of general principles that govern kinetics and
thermodynamics of protein folding can help to reveal the
signatures of protein sequences that are related to folding.
... ... Mirny et al (3 authors at Harvard University, US) report
a study of sequences of fast-folding model proteins 48 residues
long, the sequences generated by an "evolution-like selection"
toward fast folding. They report that such fast folding model
proteins exhibit a specific folding mechanism in which all
transition state conformations share a smaller subset of common
contacts (folding nucleus). The authors suggest their results and
analysis imply that for each protein structure there is a small
number of positions that are most crucial for fast folding into
that structure. Protein sequences that fold fast into that
structure may have evolved by placing into those strategic
folding-nucleus positions amino acids that provide stabilization
of the folding-nucleus.
QY: Eugene I. Shakhnovich (shakhnov@chemistry.harvard.edu)
EMAIL
(Proc. Natl. Acad. Sci. US 28 Apr 98 95:4976)
(Science-Week 12 Jun 98)
-------------------
Related Background:
BROWNIAN DYNAMICS SIMULATIONS OF PROTEIN FOLDING
Protein folding occurs on a time scale ranging from milliseconds
to minutes for a majority of proteins. Computer simulation of
protein folding, from a random configuration to the native
structure, is nontrivial due to the large disparity between the
simulation and folding time scales. In order to overcome this
limitation, simple models with idealized protein subdomains,
e.g., the diffusion-collision model, have gained some popularity.
The diffusion-collision protein-folding mechanism postulates the
early-stage formation of fluctuating quasiparticles (micro-
domains), which may be incipient secondary structures (alpha-
helices and beta-sheets) or hydrophobic clusters. These micro-
domains move via diffusion, and their coalescence leads to the
formation of folded proteins. Thus, the diffusion-collision model
reduces the complexity of the folding process from a consider-
ation of individual amino acids to that of the properties of a
few microdomains and their interactions. ... ... Rojnuckarin et
al (3 authors at 2 installations, US) present an analysis of the
folding of a 4-helix protein bundle within the framework of a
diffusion-collision model. Even with the simplifying assumptions
of a diffusion-collision model, a direct application of standard
Brownian dynamics methods would consume 10,000 processor-years on
current supercomputers. The authors circumvented this difficulty
by invoking a special Brownian dynamics simulation. They report
that a coarse-grained (i.e., crude) model of the 4-helix bundle
can be simulated in several days on current supercomputers, and
that such simulations yield folding times that are in the range
of time scales observed in experiments.
QY: Sangtae Kim (kim01@aa.WL.com)
EMAIL
(Proc. Natl. Acad. Sci. US 14 Apr 98 95:4288)
(Science-Week 15 May 98)
-------------------
Related Background:
A MODEL FOR BETA-HAIRPIN FOLDING IN PROTEINS
To be biologically active, proteins must adopt specific tertiary
configurations, a specific "folding". Although many natural
proteins spontaneously refold once they have been forced to
unfold, synthetic proteins are often produced in an insoluble
unfolded state and are thus inactive and useless until correctly
folded. One important aspect of protein folding is the kinetic
process, the rate at which folding occurs. Were a single
conformation to be found by random searching of all the possible
conformations, the number of years required would range from
10^(7) to 10^(66). In actuality, protein folding occurs on the
scale of microseconds, so there is clearly much yet to be learned
about these macromolecules. Probabilistic analysis of the
kinetics and energetics of a system of entities can be made
within the framework of the theory of statistical mechanics, and
the application of this theory is an important part of current
research into protein folding. In general, protein chains fold
into alpha-helices or beta-sheet structures, and the minimal
beta-structural element is the "beta-hairpin", a turning of the
polypeptide chain that has the shape of a hairpin. As far as
experimental methods are concerned, analysis of folding kinetics
in response to temperature variation is one of the key experi-
mental procedures, and there are now sophisticated methods for
temperature control provided by the coupling of computers and
laser physics. One such method is laser "temperature jump"
spectroscopy, which involves jump-heating (jump-discontinuity
heating) of a small volume of aqueous solution in a short time
domain coupled with spectroscopy in some part of the electro-
magnetic spectrum. Munoz et al (4 authors: National Institutes of
Health, US) used a nanosecond laser temperature jump apparatus
coupled with laser fluorescence excitation to study the kinetics
of folding of a protein beta-hairpin consisting of 16 amino acid
residues, and they report that folding of the beta-hairpin occurs
at 6 microseconds at room temperature, which is 30 times slower
than alpha-helix formation. The authors offer a statistical
mechanical model that provides a structural explanation for their
observations.
QY: Victor Munoz
(Nature 13 Nov 97) (Science-Week 5 Dec 97)
-------------------
Related Background:
A SYNTHETIC OLIGOMER THAT MIMICS PROTEIN FOLDING
The existence of helical folding in polymers such as proteins and
nucleic acids is of extreme importance in biological systems, but
biological polymers are not the only polymers to assume such
special folding arrangements. Beta-peptides, for example, non-
biological polymers synthesized from beta amino acids, form
helices stabilized by hydrogen bonds. Now Jeffrey S. Moore et al
(University of Illinois Urbana-Champaign, US) report that syn-
thetic oligomers with an all-carbon backbone, linear phenyl-
acetylenes with ester-substituted benzene rings linked to one
another by acetylene groups, spontaneously fold into a stable
helical configuration in acetonitrile, and that this apparently
involves a "solvophobic" mechanism similar to the hydrophobic
collapse model of protein folding in water. In both systems, the
phenylacetylene oligomers and biological proteins, hydrophobic
groups associate to form a compact structure that excludes the
solvent. The phenylacetylene oligomers have longitudinal cavities
that might be used for binding metals and other reactive species.
The authors also suggest such systems could be used in the design
and construction of synthetic enzymes.
QY: J. S. Moore, Univ. Illinois Urbana-Champaign, Chemistry (217)
333-0722 (Science 19 Sep 97) (Science-Week 3 Oct 97)
-------------------
Related Background:
PROTEIN-FOLDING MECHANISMS IN PROKARYOTES VS. EUKARYOTES
In biological systems, proteins are the molecules that do most of
the biological work, and the various proteins are the ultimate
expression of the genome of any organism. As polymers, proteins
are similar to the polymers known to polymer chemists, but the
chemical activities of proteins (and their biological functions)
depend mostly on higher-order folding into specific configur-
ations rather than on quasi-crystalline backbone arrays, as is
often the case in non-biological polymer chemistry. It is these
specific configurations that are responsible for the important
specificity and high catalytic power of the proteins that are
enzymes. The configurations, in turn, are an ultimate result of
amino acid sequences which form the backbone of proteins,
sequences which are not simple, as are the backbone sequences of
most non-biological polymers, but are specific, cryptic (coded),
and heterogenous. It is now recognized that complex proteins
usually have more than one folding domain, each involving a
sequence of 100 to 300 amino acids. The entire folding
architecture of a complex protein must be precisely constructed
in order for protein functionality to exist. Which provokes the
question of how the specific folding of particular proteins is
ensured by the biological system. The answer is evident for
simple proteins in vitro: the final configuration is
predetermined by the amino acid sequence, there being a single
energetically favored configuration that will always be attained
at equilibrium. This is Anfinsen's Rule, first proposed by the
protein biochemist C. B. Anfinsen more than 30 years ago. In
vivo, however, and particularly for complicated proteins, the
situation is more involved. This week W. J. Netzer and F. U.
Hartl (Sloan Kettering Cancer Center, NY US; Max Planck Inst.
Biochemistry, Martinsried DE) report an analysis of the
differences between protein folding in prokaryotes (organisms,
such as bacteria, without membrane-bound organelles such as the
nucleus) and eukaryotes (organisms with membrane-bound
organelles). Perhaps the most interesting difference is that in
prokaryotes protein folding is delayed until translation (final
synthesis by the ribosome) is completed (post-translational
folding), while in eukaryotes folding of each protein domain
occurs as each domain is translated (co-translational folding).
One result is that new prokaryote proteins can often be
misfolded. There are helper proteins at work in both prokaryotes
and eukaryotes to chaperon the proteins to their final
configurations, but there is still more possibility for errors in
the prokaryotes. One important consequence of this analysis is
that when bacteria are genetically engineered to synthesize human
protein for clinical use, the susceptibility of prokaryote
protein synthesis to folding errors must be considered.
(Nature 24 Jul 97) (Science-Week 8 Aug 97)
6. HOST-GUEST ENCAPSULATION OF MATERIALS BY VIRUS PROTEIN CAGES
Self-assembled cage structures of nanometric dimensions can be
used as constrained environments of nanostructured materials and
the encapsulation of guest molecules, and these uses have
potential applications in drug delivery and catalysis. In
synthetic systems, the number of subunits contributing to cage
structures is typically small. But the protein coats of virions
(i.e., the entire virus as it exists before or after the
replication phase) usually consist of hundreds of subunits that
self-assemble into a cage for transporting viral nucleic acids.
Many virions, moreover, can undergo reversible structural changes
that open or close gated pores to allow switchable access to
their interior. ... ... Douglas and Young (2 installations, US)
now report that a virus (cowpea chlorotic mottle virus) can be
used as a host for the synthesis of materials. The authors report
the mineralization of two polyoxometalate species (paratungstate
and decavanadate) and the encapsulation of an anionic polymer
inside the virion, the processes controlled by pH-dependent
gating of the virion's pores. The authors suggest the diversity
in size and shape of such virus particles makes this a versatile
strategy for materials synthesis and molecular entrapment.
QY: Trevor Douglas (tdouglas@nimbus.ocis.temple.edu)
EMAIL
(Nature 14 May 98 393:152) (Science-Week 12 Jun 98)
7. A SUPERLATTICE MODEL FOR RED CELL MEMBRANE PHOSPHOLIPIDS
The biological phospholipids, which are essentially long-chain
fatty acids with a phosphate polar group at one end, are among
the most important chemical substances in biological systems,
responsible in various ways for the individualization of cells
and the compartmentalization of the interior of cells as a result
of the ability of phospholipids to form self-organizing layers in
surfaces, spheres, cylinders, and so on. Despite recent progress
in understanding the structure and function of biological
membranes, certain crucial issues remain unresolved. For example,
it is not well understood how the particular lipid composition of
cell membranes arise and are maintained. There is some evidence
that the components of bilayers have a tendency to acquire
regular superlattice-like lateral distributions, and a
consequence of such behavior would be that a number of
predictable critical compositions corresponding to optimal
lateral arrangements of the components occur.
... ... Virtanen et al (3 installations, US FI) report a study of
the possibility that such critical compositions play a role in
regulating lipid compositions of natural membranes. The authors
have compared the already known phospholipid compositions of the
erythrocyte (red cell) membrane from various mammals with the
critical compositions predicted by the superlattice model. The
erythrocyte membrane was selected because its composition has
been studied in considerable detail, because it may be close to
compositional equilibrium, and because it is commonly considered
as a model of mammalian cell membranes. The authors report a
highly significant agreement between the experimental and
predicted values of membrane phospholipid compositions, thus
supporting the involvement of superlattice formation in the
regulation of such compositions in the erythrocyte membrane.
QY: P. Somerharju (pentti.somerharju@helsinki.fi)
EMAIL
(Proc. Natl. Acad. Sci. US 28 Apr 98 95:4964)
(Science-Week 12 Jun 98)
-------------------
Related Background:
ELECTRIC FIELD-INDUCED DEMIXING IN LIPID BILAYER MEMBRANES
In this report, the term "critical demixing" refers to the
formation of lateral concentration gradients in a two-dimensional
system at or near the critical point for the system -- the
thermodynamic state variable point at which the system is not
phase distinguishable. A "bilayer" membrane is a membrane
consisting of two contiguous monomolecular layers, and such
layers, involving lipid molecules with polar groups, are
important in biological systems. ... ... Groves et al (3 authors
at Stanford University, US) report a method to study critical
demixing in bilayer membranes by using an electric field applied
tangent to the plane of a confined patch of a supported lipid
bilayer, and provide a thermodynamic model of the system to
analyze the results. The steady-state distribution of lipids
under the influence of an electric field is very sensitive to
demixing effects, even at temperatures well above the critical
temperature for spontaneous phase separation. The authors suggest
this may have significant consequences for organization and
structural changes in natural cell membranes.
QY: Harden M. McConnell
(Proc. Natl. Acad. Sci. US 3 Feb 98)
-------------------
Related Background:
(from a SCIENCE-REPORT Focus Report 8.22.97)
... The idea of the protein-lipid bilayer as the basis of
biological membranes developed as the consensus model in the
1950s when the first electron micrographs of cell membranes
became available. As we will see, the consensus model has been
elaborated since then, but first let us consider the protein-
lipid bilayer membrane in its simplest form.
One of the essential aspects of this sort of bilayer is due
to the chemical geometry of its lipid constituents. Most of these
lipid constituents are long chain fatty acids whose polar groups
are the acid end of the molecule. A typical membrane fatty acid,
for example, may have 16 carbon atoms forming the backbone of
each of two tails, and a phosphate group as the main entity at
the polar end. The backbones are hydrocarbon backbones not
essentially different from the hydrocarbon backbones of molecules
that form oils and waxes, and as we have seen in a previous Focus
Report, there are important Van der Waals forces acting to couple
these hydrocarbon chains together. Water molecules cannot
dissolve this coupling, since the interaction of water molecules
with these hydrocarbon chains is not strong enough. So in the
absence of any solvent (or heat) to dissociate them, the
hydrocarbon chains tend to associate with each other. Because of
steric and other considerations, whether these chains are
saturated or unsaturated (containing double bonds) significantly
affects their Van der Waals association, and as expected, their
melting points. Molecules such as long-chain fatty acids, which
have one region (in this instance, the polar end) with a high
affinity for aqueous solvents, and another region (in this
instance, the hydrocarbon tails) with a high affinity for non-
aqueous solvents, are called amphiphiles, and one question which
is immediately suggested is what happens when we dump a batch of
these molecules into one or the other type of solvent? Well, if
we consider what we have said here and in previous reports, we
can more or less deduce what will happen with some confidence
that experimental observations will confirm our deductions. In
the first place, if we dump a batch of fatty acid molecules into
a non-aqueous solvent such as benzene and apply the principle
that the entire system benzene plus fatty acids must attempt to
rearrange itself to maximize all possible interaction energies,
then what we would expect is the fatty acid molecules will
agglomerate, polar groups interacting with each other in
exclusion, and hydrocarbon tails interacting both with each other
and with benzene molecules. There are various possible structures
that can accomplish this maximization of interaction energies,
sheets, spheres, and so on, all on a micro-scale involving
relatively small numbers of molecules, and that is precisely what
experimental observations confirm. In other words, these systems
tend to be self-organizing into small domains of molecules such
that the possible interaction energies can be maximized. In the
simplest case, that of a simple sphere (called a micelle), the
polar groups in this benzene-fatty acid system will be at the
center of the spheres and the hydrocarbon tails outward to
interact with the benzene molecules. And if we dump our batch of
fatty acid molecules into water, the same principles apply, and
in this case we can expect to obtain micelles with polar groups
outward to interact with water, and hydrocarbon tails inward to
interact with themselves. Another possible type of arrangement is
called a vesicle, a larger spherical entity, with some of the
solvent actually inside the sphere, and with the wall of the
sphere consisting of a double layer of fatty acid molecules --
again, everything arranged so as to maximize the possible
interaction energies for the given conditions and entities
involved. And the principles are no different for the
organization of the entities in layers: monolayers, multilayers,
and multilayers called membranes. The basis, then, for the
structural integrity of the biological cell membrane is the fact
that its lipid molecules are amphiphiles consisting of a polar,
hydrophilic heads and nonpolar oleophilic fatty acid chains. One
interesting consideration is that in many aspects the biological
cell membrane resembles the membranes of soap bubbles. Soap
consists of various types of long chain fatty acids, and the
cleaning action of soaps depends on their ability to sequester
oil soluble dirt into the oleophilic interiors of their little
micelles. The exterior polar surface of the soap micelle
interacts strongly with water, is therefore soluble in water, and
the soap micelle plus its dirt baggage is carried away. The dirt
has, in essence, been solubilized by soap molecules constructing
microscopic oil phases. All of this is possible because of the
self-organizing tendency of the amphiphile soap molecules, and
when soap bubbles are produced it is that same self-organizing
tendency which is responsible for the special surface of the soap
bubble and its stability. As in biological cells, this special
surface of the soap bubble is about 10 nanometers in thickness,
enough for a bimolecular layer. In the 1930s, when many membrane
biologists were studying surface active substances such as soaps
and their films and bubbles, they were often derided by their
biology colleagues for working with soap bubbles rather than
living systems. But, as often happens in science, the people
doing the deriding were wrong: those years of careful investiga-
tion of the physical chemistry of biological surfactants by
membrane biologists laid the foundations for the understanding of
the structure of biological cell membranes that came decades
later...
(Science-Report 22 Aug 97)
8. CLONED TRANSGENIC CALVES FROM FETAL FIBROBLASTS
Research has been in progress for more than a decade to develop a
system for genetic modification and large-scale cloning in
cattle, an important species in agriculture, biotechnology, and
human medicine. During the past 18 months, there has been much
publicity concerning the cloning of sheep using somatic cell
donor cells, the research conducted by the Wilmut group in the
UK. ... ... Now Cibelli et al (8 authors at 3 installations, US)
report similar results (but with a different method) in cattle.
Actively dividing fetal fibroblasts were genetically modified
with a marker gene, a clonal line was selected, and the cells
were fused to enucleated mature oocytes. Out of 28 embryos
transferred to 11 recipient cows, three healthy, identical,
transgenic calves were generated. Furthermore, the life span of
near senescent donor fibroblasts could be significantly extended
by nuclear transfer. With the ability to extend the life-span of
these primary cultured cells, this system would be useful for
inducing complex genetic modification in cattle. The authors
suggest their somatic cell nuclear transfer procedure could
improve the efficiency of producing transgenic cattle and broaden
the scope of applications for transgenic cattle.
QY: James M. Robl (robl@vasci.umass.edu)
EMAIL
(Science 22 May 98 280:1256) (Science-Week 12 Jun 98)
-------------------
Related Background:
SHEEP CLONING RESEARCH RESULTS: QUESTIONS AND ANSWERS
In a rare public exposure of what is usually a private or at
least specialist-restricted dispute between researchers,
Sgaramella and Zinder (2 installations, IT US), in a letter to
the journal Science and in interviews with various news media,
have extensively criticized the Roslin (Scotland, UK) sheep
cloning group headed by Ian Wilmut. Sgaramella and Zinder focus
on the cloning of the sheep Dolly from an adult ovine cell, and
state there has been a lack of any confirmation of this experi-
ment, that the original experiment was poorly controlled, the
interpretations untested, corollary mitochondrial data not
provided, and so on. Sgaramella and Zinder suggest that endless
debates about cloning are less than correct in the face of both
"the scientific weaknesses of the experiment and the possible
impact on the societal credibility of science itself" by debates
based on "facts" only presumed. In a contiguous reply, Campbell
et al (including Ian Wilmut) provide details explaining the
protocols used in the original Dolly cloning, say the Dolly
cloning was an unexpected and unplanned tangent from other
research, say the fact that Dolly is a Finn Dorset ewe restricts
the origin of Dolly to a single laboratory culture existing at
the time, that corollary data have indeed been provided to third
parties, that only 11 months have passed since publication of the
results, and since the gestation period in sheep is 5 months,
there has not yet been enough time to complete similar experi-
ments and publish data. Despite this public conflict, the
apparent consensus among embryologists is that the work of the
Wilmut group will be confirmed. QY: Norton D. Zinder, Rockefeller
University, 1230 York Avenue, New York, NY 10021 US; Ian Wilmut,
Roslin Institute, Roslin, Midlothian E-125 9PS, Scotland, UK.
(Science 30 Jan 98) (Science-Week 13 Feb 98)
-------------------
Related Background:
AN ESSAY ON THE CONFUSION OVER CLONING
Ever since Ian Wilmut introduced a cloned sheep to the world, the
subject has been a subject of media frenzy and political
brouhaha. The sheep Dolly was shown to the world on February 23,
1997, and the next day President Clinton called on the National
Bioethics Advisory Commission to undertake "a thorough review of
the legal and ethical issues". Three months later, the Commission
produced a 115 page report, and last week this report was
reviewed by Richard Lewontin, a well-known biologist (Harvard
University, US). Lewontin's conclusion: "It is impossible to
understand the incoherent and unpersuasive document produced by
the National Bioethics Advisory Commission except as an attempt
to rationalize a deep cultural prejudice, but it is also
impossible to understand it without taking account of the
pervasive error that confuses the genetic state of an organism
with its total physical and psychic nature as a human being."
Lewontin suggests that modern society is in the midst of a
widespread "genomania" fomented by the press and huckster
popularizers of science, a false view of modern biology that
proposes genetic dominance over human life. QY: R. Lewontin,
Harvard Univ. (617) 495-1551.
(New York Review of Books 23 Oct) (Science-Week 17 Oct 97)
-------------------
Related Background:
AN IMPORTANT NEW DEVELOPMENT IN GENETIC ENGINEERING
Predicting science is always hazardous. When the world learned of
the cloning of the sheep Dolly by Ian Wilmut (Roslin Institute,
Edinburgh, Scotland UK) last February, most genetics researchers
casually stated that in 5 or 10 years we might see genetically
engineered cloned sheep. The actuality, however, is not 5 or 10
years, but 5 months. This week, in a prepublication report to the
press, Ian Wilmut and Keith Campbell introduced Polly, born two
weeks ago, a cloned sheep that has an added human gene and an
added companion marker gene in every cell of her body. The human
gene will be identified in a forthcoming paper by the research
group. Two other lambs were born a few days ago, and are expected
to also have the human gene and marker gene. Still two others
have just the marker gene. The consequences are apparently as
follows: In short order, using these techniques, laboratories
will be cloning animals with human genes to produce hormones or
other products for use in human clinical medicine. Second, cloned
animals engineered to have human genetic diseases will be used
for research into these diseases. Third, cloned, engineered
animals will be produced with specific changes in their cell
surfaces that will reduce the probability of organ rejection and
thus give a great impetus to the use of animal organs in organ
transplantation in clinical medicine. The basic procedure used by
the Wilmut group is to take skin cells from fetal sheep, grow
them in the laboratory, add new genes, at least one of which is
human, then replace the genetic material of a sheep's egg with
that of one of the fetal skin cells that have incorporated the
new genes into their genome. After the fetal skin cell's genes
take up residence in the nucleus of a sheep egg cell, the fetal
cell's genes direct the development of a baby lamb whose every
cell contains the skin cell's genes, included the human gene and
its companion marker gene, and thus the cloning process is
complete. Although making predictions is indeed hazardous, one
feels compelled to make the following: Assuming that Wilmut's
achievements are soon replicated by independent laboratories,
during the next decade there will be a deluge of applications of
cloning research to human clinical medicine, and Ian Wilmut will
receive the Nobel Prize in Physiology and Medicine before the
decade is finished.
(New York Times 25 July) (Science-Week 1 Aug 97)
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