On the face of it, cell biology is booming. Advances in laser optics and
multi-photon techniques are producing ever brighter and sharper pictures of
cells, even live ones. Fluorescent labels make it possible to find out which
regions of the genome are transcribed when; and to track any and every protein
in action within the cell.
These images are living chronicle of the astonishing diversity of
molecular species that the cell uses in signal transduction and
downstream processes; the multitude of genes and non-gene regions of the genome
transcribed, the coding messages translated into protein and transported to the
organelles to transform material and energy, to remodel the cells
cytoskeleton, to power arrays of molecular motors, not to mention the
battalions of molecular pumps in the cell membrane that must be energized to
keep out unwanted ions and metabolites, the receptors and gates that must be
flipped open to let the nutrients in through special channels and
to discharge secretions and wastes to the outside. And all that molecular
hardware the cell churns up and replaces with unseemly haste and
extravagance as it goes about its business of living.
It simply defies the imagination to figure out how the cell can keep
changing shape and substance yet maintain its unmistakable identity, or else,
even more mysteriously, manage to switch identity to become a different kind of
cell. And above all, no matter what it does, a cell never loses its sense of
being an organising, organized whole.
There is a dearth of new ideas that can lift cell biology out of the
pervasive molecular malaise that has infected all of the life sciences to
varying degrees in this post-genomics era: a proliferation of molecular
hardware and data, with no modicum of general understanding on the horizon.
Strong medicine needed
Strong medicine is needed; and I have no hesitation in recommending
Gilbert Lings latest book. But, like any strong medicine, it is not for
the faint-hearted. I only took it after plenty of encouragement, which is what
I hope to pass on to you.
I met Ling for the first time at the prestigious Gordon Research
Conference on Interfacial Water in Cell Biology in Mount Holyoke (Bradley,
Massachusetts, USA) in June 2004. He gave one of the two keynote lectures the
first evening, and speaker after speaker referred to him throughout the week.
He was the undisputed hero of the day. It was his moment of triumph after half
a century of relative obscurity. Everyone, including me, cheered silently for
him, and wished him well with all our heart, as though our own destiny and
repute depended on it.
Ling was the hero among a select bunch of fiercely independent and
original scientists in the true sense of the word, motivated by the quest for
knowledge of nature above all else, setting aside personal prestige, politics,
worldly success; often at great personal sacrifice and hardship. Many of the
scientists, like Gilbert Ling, have not been afraid to ask big questions, such
as posed by the celebrated quantum physicist Erwin Schrödinger sixty years
ago: "What is life?" It is indeed a mistake to call such scientists
mavericks and dissenters, because there is nothing
arbitrary about their refusal to accept the conventional theory thats
riddled with holes and falsehoods; and no coincidence that they are converging
on a more accurate view of what life is.
Lings thesis is so important, and so original, that his books
should have been read and understood by everyone at least ten, if not twenty
years ago. Sadly, to answer the big question he is after, or to recognize the
answer, requires an understanding of both physical and biological sciences to a
degree thats beyond most scientists. I know, because I had tried to read
an earlier book of his 20 years ago, before I was quite ready, and failed
almost completely to comprehend it.
This time round, I was determined to discover for myself what it was
that had inspired so many other scientists at the Gordon Conference; and I was
thrilled to get an autographed copy of the latest book from the author himself.
Yet, I had to put the book down five times before finishing it some
three months after I began. Ling has made even his latest book unnecessarily
difficult by reproducing innumerable graphs from his scientific papers, often
shrunk down to the point of illegibility and heavily annotated with small print
The subtitle "The Hidden History of a Fundamental Revolution in
Biology" may explain why Ling has gone to such lengths to document his own
work and the contribution of others with abundant notes and references (557 in
all), which also chopped up the text and spoiled the flow. My advice therefore
is to get on with the text, ignoring both the graphs and notes, only checking
them if you feel you must. You will be rewarded towards the end, as I was.
Debunking the membrane theory of cell biology
In case you are wondering about Lings credentials, he and Chinese
physicist C.N. Yang were co-winners of the Chinese national Boxer fellowship
that enabled them both to go to study in the United States. Yang won the Nobel
Prize in Physics in 1957, while Ling soon found himself at odds with the most
fundamental theory in cell biology: that the cell membrane is what keeps the
cell intact, by pumping sodium out in exchange for potassium which is
why the cell has a high concentration of potassium and low concentration of
sodium, precisely the opposite of the fluid outside - and acting as gate-keeper
for glucose and other metabolites, not to mention numerous receptors in the
membrane that are involved in signal transduction.
Armed with a thorough knowledge of physical chemistry and statistical
mechanics, Ling proceeded to debunk the conventional membrane theory with
meticulous experiments, based on which he developed several theories that fit
the observations much better than the cell membrane theory.
For example, cut muscle cells with big holes in their cell membrane
nevertheless excluded sodium in favour of potassium; furthermore, the cell
would need up to 30 times the ATP it has just to pump out the sodium, leaving
nothing for other activities.
Lings theories explain the most basic biology of the cell in terms
of the physicochemical state of the protoplasm, the matrix of the living cell.
I shall try to sketch the bare outlines to help orientate readers who will find
much, much more in the book itself. .
Cell water is organised in multiple layers on an extended protein
The first idea to grasp is that the 70% or so by weight of water
associated with the cell cell water is not like water in bulk
(even though thats mysterious enough, see SiS 23). Instead, the
water molecules are aligned in ordered layers over a matrix of extended
proteins in the protoplasm (see Fig. 1).
Figure one. The multiple layers of water molecules
aligned over a hydrophilic surface.
Most people nowadays accept that water molecules immediately next to the
hydrophilic (water loving) surface of proteins are bound in some
way to the surface, so their motion is much more restricted than it would be in
bulk water, but few believe this applies to more than one to several layers of
water molecules. Ling, however, believes that practically all the cell water is
restricted in motion and arranged in polarized multilayers.
This organised water has unusual properties, among which, its ability to
partially exclude molecules and ions with large hydration shells, which include
the sodium ion, Na+. That is essentially why the cytoplasm, even
without its cell membrane will bind the smaller potassium ion, K+ in
preference to Na+, and the latter need not be pumped out of the cell
by an energy consuming mechanism.
In fact, the bulk of potassium does not exist in free solution in the
cytoplasmic matrix. It is associated with fixed negative charges on the
carboxylic acid side chains of the proteins. That is the earliest of
Lings theories, which explains why K+ is not freely diffusible
even in a muscle cell that lacks an intact cell membrane, and externally
applied Na+ is still excluded from the cell.
In an astonishing, apparent confirmation of Lings polarized
multilayers or PM hypothesis, Gerald Pollack and colleagues in Washington
University, Seattle, USA, used a suspension of 0.5 to 2 micron diameter
microspheres that can be seen under the microscope, and showed up massive
exclusion zones clear of all or almost all microspheres extending
millions of layers of water molecules from the hydrophilic surfaces of gels
(see SiS 23). Perhaps other explanations are possible, but they are not
yet convincing. Pollack was inspired by Ling to write a highly readable book
that I have reviewed previously (see "Biology of least action", SiS
A confirmation of Lings fixed charge hypothesis that
K+ is associated with carboxylic acid side chains predominantly in
the myosinrich bands in muscle came from the work of Ludwig
Edelmann of Saarland University in Germany, who was also at the Gordon
Conference (see "What is the cell really like?" this issue).
The electronic cell
But still, a major difficulty for conventional biochemists is that the
proteins they know are never extended in solution, but folded up, almost
always, in globular conformation (see "The importance of cell water", this
issue for a different, but possibly complementary view on cell water); and
there is no evidence whatsoever that when such isolated proteins are in
solution, they preferentially bind K+ over Na+.
Lings answer is that purified isolated proteins are not at all
what they are like within the cell. Instead, within the cell, most, if not all
proteins are extended so that the peptide bonds along their polypeptide chains
are free to interact with the multiple layers of polarized water molecules, and
their carboxylic side chains similarly are free to bind preferentially
K+ over Na+. One reason may be the ubiquitous presence of
ATP in the living cell.
Now comes perhaps Lings most original idea, and it makes a lot of
sense. ATP adenosine triphosphate is the universal intermediate in
all energy transformation processes, be it muscle contraction, protein
synthesis, DNA synthesis, transport, etc. It was once erroneously regarded as
the high energy intermediate, on account of its high
energy phosphate bonds, which turned out not to be the case. Living
protoplasm is full of ATP, which is bound to proteins at certain cardinal
sites, according to Ling. These ATP-bound sites then induce changes in
the electron density, ultimately of the entire polypeptide chain, including the
In the absence of ATP, proteins do tend to adopt secondary structures -
alpha helix, or a beta pleated sheet - due to hydrogen bonding between peptide
bonds in the same chain, which gives them a folded up conformation where they
dont interact maximally with water. However, when ATP is bound to the
cardinal site, it tends to withdraw electrons away from the protein chain,
thereby inducing the hydrogen bonds to open up, unfolding the chain and
enabling it to interact with water. This, Ling says, is the resting
living state of the protoplasm, a low-entropy state thats highly
organised, possessing what Schrödinger referred to as negative
entropy (see Fig. 2).
Figure 2. Phase transition of protein on binding or
It may be a misnomer to call the ATP-bound state of the protoplasm a
resting state, as it is also full of stored energy
ready to be released when ATP is hydrolysed to ADP. It so happens that ADP has
a much lower tendency to bind to protein, so it comes off the cardinal site,
and the protein naturally reverts to its folded state, an abrupt mechanical
process that releases a lot of energy. It is a thermodynamically downhill or
entropy-driven process because it produces disorder among the bound water
There could be other sites that bind molecules or ligands that have
electron-donating tendency, in which case, an extended protein chain
will abruptly adopt the folded up conformation, and at the same time, lose its
ability to selectively bind K+, or even reverse its preference for
binding Na+ over K+. The increase in electron density of
the side-chain carboxylic groups favours the formation of ionic bonds,
providing sufficiently strong attraction for the electropositive Na+
for it to give up its hydration shell.
No elaborate pumps or gates are needed to account for the high
concentration of potassium and low concentration of sodium inside the cell,
opposite to the situation in the extracellular medium. This is a plausible,
testable hypothesis, although no one has yet put it to the test. Ling himself
has lost his laboratory facilities at that point.
According to Ling, the abrupt transitions of state are what powers
living activities. The living cell is an exquisite "electronic machine", where
everything is done with the greatest of ease and the least bother, depending on
the electron density in specific protein chains.
Cell membrane and membrane potential demystified
According to Ling, cell membranes do exist, but they are not the
barriers to diffusion into and out of the cell, which, for far too long, has
been regarded little more than a bag of enzymes in free solution
that would instantly disintegrate were the membrane to disappear. Rather, the
cell membrane is more like the skin of an apple which itself constitutes a
phase similar to the bulk phase it encloses: the major constituents of
membranes are also proteins that behave in a similar way as proteins in the
cytoplasm. They too, preferentially bind K+ over Na+ in
the resting state. Membrane potentials are local surface potentials, while
action potentials simply reflect the changes of state that involves a release
of bound water and the temporary exchange of Na+ for K+
bound to the carboxylic acid groups in the protein side chains.
The living state is flexible and liquid crystalline
The picture of what Ling has referred to as the resting
living state with ATP and lots of associated water is very much like the liquid
crystalline state that I and my colleagues have discovered in cells and
organisms (see The Rainbow and
The Worm, The Physics of Organisms ), which is another reason why I
believe Ling may be largely correct. The living state as opposed to the state of death in
which ATP is exhausted, and rigor mortis sets in - is maximally hydrated
by polarized layers of bound water, and hence flexible and full of energy. This
idea of the truly living cell is beautifully brought to life in the inspired
portraits produced by Ludwig Edelmann (see "Whats the cell really
like?" this issue).