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I posted this on another newsgroup:
This topic came up in discussions because of the claim that PUFAs are
necessary to "keep cell membranes flexible," though there is no
evidence that one must consume either omega 3 or omega 6 PUFAs in order
to accomplish this. Moreover, simple experiments could be done, to see
if the "cell membranes" of rats, for example, "stiffen up" if fed a fat
free diet. As long ago as 1948, such an experiment was done, and the
rats were fine. In any case, if anyone found this topic of interest,
here is some new information:
QUOTE: ...Gerald Pollack is only the messenger as far as what he has
written about the sodium pump is concerned. He actually tells a story
that was originally written by Gilbert Ling. I had to obtain a copy of
one of Gilbert Ling's recent publications (Physiol. Chem. Phys. &
Med. NMR 29: 123-198, 1997) to gain a glimpse of the turmoil that has
existed in the sodium pump field for about 50 years! Gilbert Ling
carried out some simple experiments (simple in terms of what he was
trying to observe: complex in terms of experimental design) as part of
his Ph.D work. His observations did not fit with the then current
understanding of the sodium pump. He writes that he was quietly advised
that the sodium pump was a 'Holy Cow' and that he should stay away
from it. He didn't. His research funding dried up. His research
students fled for fear of becoming unemployable. A smear campaign was
instigated to blacken his name. But his results are clear: if you
poison frog sartorius muscle with sodium iodoacetate, and/or provide a
nitrogen atmosphere and/or cool the muscle preparations down to 0°C,
ATP production should cease and the sodium pump should stop working.
This should result in intracellular sodium levels rising as the sodium
pump fails. But that is not what happens. If you want to see how Gerald
Pollack tells the story, get his book. Suffice it to say that the
sodium pump may well use ATP to do something that results in the
movement of sodium and potassium ions in opposite directions across
membranes, but that something has little if anything to do with
maintaining potassium at high level and sodium at low level
intracellularly. You don't need a sodium pump to achieve this end
because it happens spontaneously! If you are troubled by this
observation, you should get Gerald Pollack's book.
But there is much more to Gerald Pollack's book than a wish to
revisit the sodium pump and to focus, for a change, on the water in
living systems rather than on the proteins, carbohydrates,
phospholipids, salts, etc. He develops a story that eloquently moves
the reader towards a single unifying hypothesis built around phase
transitions that occur in the structured water environment of living
cells. The same phase transition phenomena can, it seems, provide
mechanistic explanations for a multitude of intracellular events that
are currently understood only in terms of the words that describe the
observable phenomena. Consider, for example, what it is that you
actually understand by the phrase 'secretion of a
neurotransmitter'. You could probably describe what is actually
observed during this process, but could you explain mechanistically how
secretion happens? Or how cell division happens? Or how muscle cells
contract? Or how action potentials propagate (yes, I too have read the
undergraduate textbooks, but the story about action potentials as it is
commonly told, like the sodium pump story, contains rather significant
omissions)? Or how transport of substances occurs through the
gelatinous mass that is the intracellular environment (this is, I would
submit, of fundamental significance to our understanding of
intracellular therapeutic targeting of bioactive molecules)? Or how ATP
works (yes, yes, I too have read the undergraduate textbooks and
lectured on the subject)? Gerald Pollack attempts to do all of this and
more. And I have to say that I find the case he makes compelling...
Richard J. Schmidt, J. Pharmacy and Pharmacology 55: 857-858, 2003
UNQUOTE.
QUOTE: In conclusion, the aqueous information transfer within the cell
involves the following:
Intracellular water favours K+ ions over Na+ ions.
Freely rotating proteins create zones of higher density water, which
tend towards a lower density clustering if the rotation is prevented.
Static charge-dense intracellular macromolecular structures prefer K+
ion pairs to freely soluble K+ ions.
Ion paired K+-carboxylate groupings prefer local clathrate water
structuring.
Clathrate water prefers local low density water structuring.
Low density water structuring can reinforce the low-density character
of neighbouring site water structuring.
Na+ and Ca2+ ions can destroy the low density structuring in a
cooperative manner.
Martin Chaplin [author of the above] is Professor of Applied Science,
London South Bank University, UK, with special interests in the
interactions between water and biological molecules. UNQUOTE.
QUOTE: In the course of developing these techniques, Edelmann also
confirmed a major prediction of AIH, that cellular potassium is
adsorbed at negatively charged sites of cellular proteins, and not
freely dissolved in cell water as was generally assumed. This
assumption inevitably led to the major dogma of contemporary cell
biology that Gilbert Ling has thoroughly deconstructed: that a sodium
/potassium pump is responsible for pumping sodium ions (Na+) out of the
cell and potassium ions (K+) into the cell, thereby keeping
intracellular K+ concentration high and Na+ concentration low.
The most spectacular visualization of potassium adsorption was achieved
using a method developed by Ling, which was to reversibly replace
potassium ions of living muscle cells with chemically similar heavy
ions such as caesium or thallium before cyrofixation and freeze-drying.
Electron micrographs of thin sections of this muscle demonstrated
directly the localisation of the electron-dense heavy metal ions at the
myosin protein bands as predicted (see Fig. 2). Edelmann has
demonstrated similar localised methods...
In his search of the protein structure in living cells, Edelmann
obtained images that have never been seen before. The outer membrane of
the cell as well as membranes inside the cell appear in negative
contrast, i.e., bright, as opposed to dark, as is usually seen, while
proteins of subcellular compartments appear very homogeneously
distributed instead of being heterogeneous or fibrous, suggesting that
the latter may be artefacts. UNQUOTE.
Source: http://www.i-sis.org.uk/WITCRL.php
QUOTE: ...where is the cytoskeleton? Using antibody-staining
techniques, Frank Mayer has found evidence of abundant fibrous proteins
that form a web-like structure just inside the inner membrane, to which
the ribosomes - organelles for synthesizing proteins - are
attached. UNQUOTE.
Written by Dr. Mae-Wan Ho. Source: http://www.i-sis.org.uk/WITBRL.php
QUOTE: "It is high time a good book was available to not only teach
biologists some physics, particularly bioenergetics, but make them sit
up and think a bit more deeply about it. This little volume is more
readable than other drier and much weightier books on the subject."
Cell Biology International UNQUOTE.
Source: http://www.i-sis.org.uk/rnbwwrm.php
A commentary on the book, The Rainbow And The Worm: The Physics of
Organisms,
by Mae-Wan Ho |
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QUOTE: "...Based on accepted theories, we expected crowding to affect proteins in the unfolded state," said Rice biochemist Pernilla Wittung-Stafshede, one of the study's co-authors. "We were surprised when both experimental evidence and computer simulations showed that crowding also acts directly upon proteins in the folded state."
Living cells are crowded places. They're filled with a chemical soup of 100-300 mg per mL of large molecules, such as DNA, proteins and ribosomes. This corresponds to about 40 percent of volume occupancy.
"The consistency is very viscous," said Wittung-Stafshede. "It's something like Jell-O or the freeway at rush hour..."
Using sucrose-based polymers (inert synthetic mimics of real macromolecules), the pair created several test environments designed to mimic the gooey milieu that proteins experience inside a cell. Using spectroscopic methods, Stagg and Wittung-Stafshede then probed how the structural content as well as the thermal stability of apoflavodoxin changed as a function of added crowding agents...
The researchers found the protein's native state becomes more compact and more ordered. The secondary structure of the folded protein increased by as much as 25 percent based on circular dichroism data...
Proteins are the workhorses of biology, and their form and function are intertwined. Proteins are chains of amino acids strung end-to-end like beads on a necklace. The order comes from DNA blueprints, but proteins fold into a 3-D shape as soon as the chain is complete, and scientists can determine a protein's function only by studying its folded shape. It is still an open question how a long floppy chain of amino acids is programmed to adopt a unique 3-D shape in a timely manner (often seconds to minutes)... UNQUOTE.
Source: http://www.sciencedaily.com/releases/2007/11/071112172136.htm |
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Though these scientists accept (without question) the "lipid bilayer membrane" notion (refuted directly long ago by Gilbert Ling and others), they have provided support for the alternative hypothesis:
QUOTE: The means by which proteins provide a 'border control' service, allowing cells to take up chemicals and substances from their surroundings, whilst keeping others out, is revealed in unprecedented molecular detail for the first time, 16 October in Science Express... UNQUOTE.
Source: http://www.sciencedaily.com/releases/2008/10/081016140800.htm
Gilbert Ling has written a succinct and excellent review of how this impossible notion (that is, a structurally crucial "lipid bilayer membrane") came into existence:
QUOTE: ...In the early investigation of the living cell, mature plant cells were the preferred material for study. Plant materials were more readily available and they last well. Mature plant cells are large with well-delineated boundaries marked by walls. These characteristics were prized by the early observers because they assured the observers that they were looking at characteristic individual units rather than random artifacts. While these tangible advantages made the mature plant cells the preferred objects of study, the naturalists at the time could not and did not know that mature plant cells are highly unusual cells. They exhibit anatomical traits not shared by most living cells---but that perception came from a later chapter of investigations.
Of all the unusual features mature plant cells have, its possession of a gigantic central cavity or vacuole is the most striking--- occupying often close to the entire volume of the cell. This central vacuole is filled with a liquid hard to distinguish from ordinary water. Surrounding this central vacuole is a thin layer of gelatinous material later known as protoplasm. Still further outward, one finds the enclosing rigid cell wall.
Modern biology textbooks show that on the inner surface of the thin protoplasmic layer of a mature plant cell is a very thin membrane called the tonoplast (or vesicular membrane) and on the outside of the protoplasmic layer is another very thin membrane called the plasma membrane or the cell membrane. Both of these membranes are so thin, that one cannot see them with even the best light microscope available today. To visualize them, one must use an electron microscope ---a much later invention---and then only after the specimen has undergone special treatment and stained with electron-dense stains such as uranium or lead.
Since one cannot see the cell membrane even with the best light microscope today, it is an indisputable fact that naturalists in the 19th century with their much more primitive light microscopes could not have seen the cell membrane or the tonoplast. Common sense also dictates that those early naturalists had no reason to describe a structure which they could not and did not see. They must have seen something consistently; and that something must be thin but not invisible to them.
From these facts and reasoning , one is left with one and only one interpretation: What the 19th century naturalists called the cell membrane is in fact the thin layer of protoplasm, including the "invisible" plasma membrane and the equally "invisible" tonoplast surrounding the central vacuole, and what they thought was the cell substance is in fact the content of the big central vacuole---and there is no question that this central vacuole is filled with a watery liquid.
It is only in the light of this interpretation can one comprehend how Theodor Schwann (1810-1882), the founder of the "Cell Theory", could argue that "the containing membrane (of a cell) --was prior in importance to its contents. The content of the cellular cavity,....is typically a homogeneous, transparent liquid." (See Thomas S. Hall, "Ideas on Life and Matter, vol. 2, p. 194, 1969, Univ. Of Chicago Press, Chicago)
With the discovery of protoplasm by Felix Dujardin (1801-1860 ) and the extensive studies of many types of young and old plants as well as animal cells, the error of the earlier idea that the cells are membrane-enclosed bag of fluid became widely recognized. Thus in 1858-1860, Max Schultze defined the cell as a "naked little lump of protoplasm with a nucleus". In 1928, the eminent American cytologist, E. B.Wilson, in his monumental treatise, "The Cell in Development and Heredity" (Macmillan, New York, 3rd ed.,1928), further emphasized that cells "do not, in general, have the form of hollow chambers as the name suggests but are typically solid bodies."(p.4).
One would have expected that the erroneous notion that the cells are hollow chambers filled with watery liquid would be replaced soon after. It was the irony of history, that that was not to be the case.
For by this time another group of scientists interested in the living cell had taken over the perpetration of what I call the "Vesicular Doctrine", i.e., cells are empty chambers filled with a clear watery liquid.
That group of scientists were the early cell physiologists, beginning with the eminent French naturalist, Rene Dutrochet. Dutrochet's extensive study of "osmotic" movements of water into and out of mature plant cells set the direction of cell physiological research for the future. The long erroneous usage and the work of early cell physiologists drove deep into the psyche of biologists the belief that cells are hollow chambers filled with a watery liquid---- which lasted in the text books version of cell physiology to this very day... UNQUOTE.
Source: http://gilbertling.org/lp6.htm |
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