Biomolecular machines

[Phronesis]

First a clutch and now brakes:
Molecular Brake for the Bacterial Flagellar Nano-Motor

ScienceDaily (Mar. 19, 2010) — Biozentrum researchers have now discovered that Escherichia coli bacteria harness a sophisticated chemosensory and signal transduction machinery that allows them to accurately control motor rotation, thereby adjusting their swimming velocity in response to changing environments. The research results that were published online in Cell on March 18, 2010, may foster the development of novel strategies to fight persistent infections.

Trajectories of swimming E.Coli bacteria. (Credit: Image courtesy of University of Biozentrum Basel)​

Bacteria can swim through liquids at speeds up to 30 times their body length per second. It has been known for a long time that different bacterial species swim at different speeds, but it was not known if this is a species specific trait and if bacteria can actively adjust their velocity.

The research team from Switzerland and Germany, led by Alex Böhm and Urs Jenal from the Biozentrum has now discovered that E. coli, and probably many other bacteria can actively regulate their swimming velocity.

This behaviour is governed by a molecular motor-brake protein that upon binding of the bacterial second messenger cyclic dimeric GMP interacts with a specific subunit of the flagellar nano-motor and thereby curbs motor output. The intracellular concentration of cyclic dimeric GMP is controlled by a network of signaling proteins. When bacteria are faced with nutrient depletion this network is actived, produces more cyclic dimeric GMP and triggers motor-brake engagement. Because slow swimming enhances the probability of a bacterial cell to permanently attach to surfaces, this behaviour might prime bacteria to switch into a sessile life style.

Colonization of epithelial surfaces in the human host can lead to the formation of antibiotic tolerant and immune system resistent 'biofilms' that are the basis of many chronic bacterial infections. Thus, understanding the molecular basis of surface colonization and biofilm formation may foster the development of novel strategies to fight persistent infections. In addition, the discovery of flagellar motor curbing could be exploited for biotechnological applications, for example to engineer nanopumps in microfluidics or to build cell-based microrobots.

Unconscious goal-directed regulation of bacterial swimming is obvious.

 

[Techne]

For those interested in how cells work... more codes, circuits, repair and quality control mechanisms, switches, cool pictures etc.

Newly Discovered DNA Repair Mechanism

ScienceDaily (Oct. 5, 2010) — Tucked within its double-helix structure, DNA contains the chemical blueprint that guides all the processes that take place within the cell and are essential for life. Therefore, repairing damage and maintaining the integrity of its DNA is one of the cell's highest priorities.

Why chromosomes never tie their shoelaces

In the latest issue of the journal Nature, Miguel Godinho Ferreira, Principal Investigator at the Instituto Gulbenkian de Ciencia (IGC) in Portugal, lead a team of researchers to shed light on a paradox that has puzzled biologists since the discovery of telomeres, the protective tips of chromosomes: while broken chromosome ends generated by DNA damage (such as radiation or cigarette smoke) are quickly joined together, telomeres are never tied to each other, thus allowing for the correct segregation of the genetic material into all cells in our body.

Scientists solve long-standing mystery of protein 'quality control' mechanism

Scientists from The Scripps Research Institute have solved a long-standing mystery of how cells conduct "quality control" to eliminate the toxic effects of a certain kind of error in protein production. The findings may lead to a better understanding of a host of neurodegenerative diseases.

At the crossroads of chromosomes: Study reveals structure of cell division's key molecule

(PhysOrg.com) -- On average, one hundred billion cells in the human body divide over the course of a day. Most of the time the body gets it right but sometimes, problems in cell replication can lead to abnormalities in chromosomes resulting in many types of disorders, from cancer to Down Syndrome.

Art of Dividing: Researchers Decode Function and Protein Content of the Centrosome

ScienceDaily (Sep. 21, 2010) — A basic requirement for growth and life of a multicellular organism is the ability of its cells to divide. Chromosomes in the cells duplicate and are then distributed among the daughter cells. This distribution is organized by a protein complex made up of several hundred different proteins, called the centrosome. In cancer cells, the centrosome often assumes an unnatural shape or is present in uncontrolled numbers. The reasons for this were previously largely unknown

Genetic switch underlies noisy cell division

(PhysOrg.com) -- While scientists have spent the past 40 years describing the intricate series of events that occur when one mammalian cell divides into two, they still haven't agreed on how the process begins.

Experiments Decipher Key Piece of the ‘histone Code’ In Cell Division

ScienceDaily (Sep. 22, 2010) — Reproduce or perish. That's the bottom line for genes. Because nothing lives forever, reproduction is how life sustains itself, and it happens most fundamentally in the division and replication of the cell, known as mitosis. Now new research at Rockefeller University has detailed a key role in mitosis for a chemical modification to histone proteins that package lengthy strings of DNA into compact chromosomes. The experiments, recently published in Science, add to an increasingly intricate picture of the precisely timed events that separate new copies of chromosomes to opposite ends of a cell just before the cell divides, one of the most fundamental processes involved in the reproduction of life.

 

[Techne]

Intracellular Express: Why Transport Protein Molecules Have Brakes

ScienceDaily (Oct. 11, 2010) — Every single one of our cells contains so-called motor proteins that transport important substances from one location to another. However, very little is known about how exactly these transport processes occur. Biophysicists at the Technische Universitaet Muenchen (TUM) and Ludwig Maximilians Universitaet Muenchen (LMU) have now succeeded in explaining fundamental functions of a particularly interesting motor protein.

They report their findings in the current issue of the Proceedings of the National Academy of Sciences (USA).

Motorized transport proteins are one of the keys to the development of higher organisms. It is they that enable the cell to transport important substances directly and quickly to a specific location in the cell. As bacteria cannot do this, they are not able to form larger cells or even large organisms with many cells. Particularly important are fast transport proteins in the primary cilia, the cell's antennas, with which they channel information from the surroundings into the cell.

Like trucks on a highway, kinesins transport cellular cargoes to their destinations. They do this by crawling along protein fibers, so-called microtubules, which extend through the entire cell. Kinesins consist of two long intertwined protein chains. At one end of every protein there is a head that can attach itself to certain structures on the surface of the microtubules; the freight is attached to the other end.

Very special kinesins are at work in the cilia of the Caenorhabditis elegans nematode: They consist of two different protein chains and are therefore especially suitable for investigating the transport mechanisms. As freight, the researchers attached small plastic beads to the ends of these motor proteins. They can manipulate these beads with "optical tweezers," a specially formed laser beam.

One end of the protein molecule was held with the optical tweezers; the other was able to walk on microtubules. This enabled the scientists to measure the force with which the motor protein can pull. In this experimental setup, the kinesin-2 with its freight walks as far as 1,500 nanometers in tiny steps measuring a mere eight nanometers. "If we didn't hold it back, it might still go a lot further," says Zeynep Ökten from the Institute for Cell Biology at LMU.

The kinesin-2 investigated consists of one KLP11 and one KLP20 protein. By exchanging the heads of the chains, the researchers were able to show that KLP11 is a non-processive motor protein. It only becomes a transport protein in combination with KLP20. In further experiments they were able to explain why nature chooses this unusual combination: KLP20 proteins have no "brakes." A transport protein made of two KLP20 units would be permanently on the go and would waste energy. The KLP11, in contrast, has a mechanism called autoinhibition, which makes sure that the transport protein is at a standstill if no freight is attached.

"Our results show that a molecular motor must take on a large number of functions over and above simple transport, if it wants to operate successfully in a cell," says Professor Matthias Rief from the Physics Department of the TU Muenchen. It must be possible to switch the motor on and off, and it must be able to accept a load needed at a specific location and hand it over at the destination. "It is impressive how nature manages to combine all of these functions in one molecule," Rief says. "In this respect it is still far superior to all the efforts of modern nanotechnology and serves as a great example to us all."

This work was supported by funds from the Cluster of Excellence Center for Integrated Protein Science Munich (CIPSM), a long-term European Molecular Biology Organization fellowship, and grants from the Deutsche Forschungsgemeinschaft (DFG) and the Friedrich-Baur-Stiftung.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.

Check out post #397 for nice animations about these kinesins.

Lol @ the editor's note...

 

[Techne]

More interesting research about how cells work:

Finger-Trap Tension Stabilizes Cells' Chromosome-Separating Machinery

ScienceDaily (Nov. 27, 2010) — Scientists have discovered an amazingly simple way that cells stabilize their machinery for forcing apart chromosomes.

Chromosomes (stained red) align and attach to microtubules (green) in the mitotic spindle before cell division. (Credit: Jason Stumpff)​

Their findings are reported Nov. 25 in Nature.

When a cell gets ready to split into new cells, this stable set-up permits its genetic material to be separated and distributed accurately. Otherwise, problem cells -- like cancer cells -- arise.

The human body contains more than a trillion cells, and every single cell needs to have the exact same set of chromosomes. Mistakes in moving chromosomes during cell division can lead to babies being born with genetic conditions like Down syndrome, where cells have an extra copy of chromosome 21.

"A striking hallmark of cancer cells," said one of the senior authors of the study, Sue Biggins, an investigator in the Basic Science Division, Fred Hutchinson Cancer Research Center in Seattle, "is that they contain the wrong number of chromosomes, so it is essential that that we understand how chromosome separation is controlled. This knowledge would potentially lead to ways to correct defects before they occur, or allow us to try to target cells with the wrong number of chromosomes to prevent them from dividing again."

The machine inside cells that moves the chromosomes is the kinetochore.

These appear on the chromosomes and attach to dynamic filaments during cell division. Kinetochores drive chromosome movement by keeping a grip on the filaments, which are constantly remodeling. The growth and shortening of the filaments tugs on the kinetochores and chromosomes until they separate.

"The kinetochore is one of the largest cellular machines but had never been isolated before," Biggins said, "Our labs isolated these machines for the first time. This allowed us to analyze their behavior outside of the cell and find out how they control movement."

"We demonstrated that attachments between kinetochores and microtubule filaments become more stable when they are placed under tension," noted Dr. Charles "Chip" Asbury, a University of Washington (UW) associate professor of physiology and biophysics. Originally trained in mechanical engineering, Asbury studies molecular motors in cells. He is also a senior author on the Nov. 25 Nature paper.

Asbury likened the stabilizing tension on the filament to a Chinese finger trap toy -- the harder you try to pull away, the stronger your knuckles are gripped.

Asbury explained how this tension-dependent stabilization helps chromosomes separate according to plan. As cell division approaches, a mitotic spindle forms, so named by 19th century scientists because the gathering microfilaments resemble a wheel spinning thread.

When chromosome pairs are properly connected to the spindle, with one attached to microtubules on the right and the other to microtubules on the left, the kinetochore comes under mechanical tension and the attachment becomes stabilized, sort of like steadying a load by tightening ropes on either side. This is a simple, primitive mechanism.

"On the other hand," Asbury said," if the chromosome pair is not properly attached, the kinetochores do not come under full tension. The attachments are unstable and release quickly, giving another chance for proper connections to form." Kinetochores are not just connectors, but also are regulatory hubs. They sense and fix errors in attachment. They emit "wait" signals until the microtubule filaments are in the right place.

The research team conducted this study using techniques to manipulate single molecules to see how they worked. These methods allow scientists to take measurements not possible in living cells. The native kinetochore particles were purified from budding yeast cells.

To the best of his knowledge, Asbury said, "Intact, functional kinetochores had not previously been isolated from any organism." The purification of the kinetochores allowed the research team to make the first direct measurements of coupling strength between individual kinetechore particles and dynamic microtubules.

The results of this study contribute to wider efforts to understand a puzzling phenomenon on which all life depends: How are motion and force produced to move duplicated chromosomes apart before cells divide?

The research was funded by grants from the National Institute of General Science at the National Institutes of Health, the National Science Foundation, the Packard Foundation, the Kinship Foundation and the Beckman Foundation.

In addition to senior authors Biggins and Asbury, the lead authors on this study are Bungo Akiyoshi, from the Molecular and Cellular Biology Program at the UW and the Division of Basic Sciences, Fred Hutchinson Cancer Research Center; and Krishna K, Sarangapani and Andrew F. Powers, both of the UW Department of Physiology & Biophysics. The research team included Christian R. Nelson, Fred Hutchinson Cancer Research Center; Steve L. Reichow, UW Department of Biochemistry; Hugo Arellano-Santoyo, Fred Hutchinson Cancer Research Center, UW Molecular and Cellular Biology Program, and UW Department of Physiology & Biophysics; Tamir Gonen of the UW Department of Biochemistry and the Howard Hughes Medical Institute; and Jeffrey N. Ranish of the Institute for Systems Biology in Seattle.

 

[Techne]

DNA and RNA are quite unstable, so a myriad of mechanisms exist to repair it.

E.g.:
How Do DNA Components Resist Damaging UV Exposure?

ScienceDaily (Dec. 9, 2010) — The genetic material of DNA contains shielding mechanisms to protect itself from the exposure to the UV light emitted by the sun. This is of crucial importance, since without photostability -- i.e. without "programmed" defense mechanisms against UV irradiation -- there would be a rapid degradation of DNA and RNA.

The figure shows the special structures of DNA nucleobases, which – after exposure to solar radiation – are responsible for the ultrafast radiationless deactivation to the electronic ground state. (Credit: Felix Plasser, University of Vienna)​

As part of a project funded by the Austrian Science Fund (FWF) a group of researchers led by Hans Lischka, Quantum Chemist of the University of Vienna, Austria, could, for the first time, comprehensively unravel these ultra-fast processes of the photostability of the nucleobases.

The effect of sunlight on our skin not only leads to tanning, but it also initiates processes that can lead to serious health damage. A research team led by Hans Lischka, Professor at the Institute for Theoretical Chemistry, University of Vienna, Austria, investigated the shielding mechanisms that nature has provided to protect itself against such harmful effects. The strategy here is simple, yet highly complex: As soon as the UV light excites the electrons into a higher energy level, ultra-fast decay brings them back to its original state. In this way electronic energy is converted into heat. This process occurs in an incredibly short amount of time, in up to a quadrillionth of a second.

Computer simulations on the properties of light-active DNA components

In the group of Hans Lischka (Institute for Theoretical Chemistry, University of Vienna), together with Mario Barbatti (now Max-Planck-Institut for coal research, Mülheim/Ruhr, Germany) and in collaboration with colleagues of the Czech Academy of Sciences in Prague, Czech Republic, a vivid dynamic picture of the photostability of the nucleobases was given using innovative computer simulation techniques. It could be shown how the DNA components -- the nucleotides that are responsible in DNA and RNA for the formation of base pairs -- protect themselves against decomposition under UV irradiation.

New Quantum Chemical approaches for photophysical studies

The principal innovation of this work consists in the detailed calculation of the coupling of the electronic dynamics with that of the atomic nuclei. This goal was achieved with the help of worldwide unique quantum chemical methods developed at the Institute for Theoretical Chemistry, University of Vienna. The calculated states of motion of the nucleobases show a quite remarkable dynamic behavior in time that spans several orders of magnitude -- from the pico/trillionth to the femto/quadrillionth-second range.

The newly developed methods are suitable not only for elucidation of the above-described dynamics in DNA nucleobases, but they are also applicable to studies of photo-physical processes in DNA itself and in the area of photovoltaics which is of high technological interest. The new methods allow a better understanding of the fundamental processes of transport of electronic excitation energy and of charge separation for production of electricity.

 

[Techne]

Increases in our understanding of biomolecular machines inevitably result in medicinal advances and also aid in our own attempts at nano-engineering.
Pretty nifty computer engineering was also employed to help the scientists...

Scientists Ratchet Up Understanding of Cellular Protein Factory

ScienceDaily (Dec. 3, 2010) — Theoretical biologists at Los Alamos National Laboratory have used a New Mexico supercomputer to aid an international research team in untangling another mystery related to ribosomes -- those enigmatic jumbles of molecules that are the protein factories of living cells. The research, published December 2 in the journal Nature, could aid in development of new antibiotics used to fight multidrug resistant superbugs such as MRSA (methicillin-resistant Staphylococcus aureus infections) found in many U.S. hospitals. The work may also be important for combating engineered strains of anthrax and plague.

This is an inverse-color close-up representation of the transfer RNA binding regions in a bacterial ribosome, which was the topic of a paper released in Nature by Los Alamos researchers Karissa Sanbonmatsu and Paul Whitford and an international group of colleagues. In the image, a subunit of the ribosome is shown as dark blue ribbons, the transfer RNA as the brown ribbon and ribosomal residues that contact tRNAs at key sites within the ribosomal machinery appear as spheres of green, pink and light blue. (Credit: Image courtesy of DOE/Los Alamos National Laboratory)​

In the context of synthetic biology, understanding the ribosome could be key to developing nanofactories that produce designer biomolecules and polymers.

In the paper, "Head swivel on the ribosome facilitates translocation via intra-subunit tRNA hybrid sites," Los Alamos National Laboratory researchers Karissa Sanbonmatsu and Paul Whitford and José N. Onuchic at the University of California-San Diego join Christian Spahn, Andreas Ratje, and others from the Institute for Medical Physics and Biophysics, Berlin, Germany, to describe for the first time how a complicated swivel movement within a bacterial ribosome accommodates synthesis of proteins.

Ribosomes are composed of long chemical chains, called ribonucleic acids (RNA), and proteins. Each ribosome has two interlocked subunits, one large and one small, which behave as a single molecular machine. Because of its makeup, each ribosome resembles a tangle of threads or a handful of rubber bands tossed together. Despite the ribosome's outwardly disjointed appearance, researchers have found that the two subunits ratchet, un-ratchet, and swivel during protein synthesis to allow introduction of helper chemicals called transfer RNAs (tRNAs) into its folds to manufacture new chains of protein molecules. The proteins are used to create new cells or perform necessary functions within the host cell or organism.

Ribosomes build proteins by linking chemical segments fashioned from instructions delivered via messenger RNA, which is DNA's molecular cousin. Each segment, or amino acid, corresponds to a trio of bases in the message that, in turn, complement trios encoded in transfer RNA. Each base in the trio corresponds to a single chemical complement found on the RNA. In order for protein synthesis to occur, the tRNA must bind to the ribosome at two distinct sites -- one to decode the information and another to link the new amino acid to the emerging protein.

After each amino acid is added, the ribosome must crawl along the message to create additions. Exactly how this crawling occurs has been a mystery for several decades. Researchers have suspected that ratcheting motions of the two ribosomal subunits are key to allowing RNA and associated catalysts into the complex structure of the ribosome so the RNA and ribosome can couple at the crucial sites to create proteins. In the Nature paper, the researchers discovered that the majority of crawling (movement along messenger RNA) occurs during a new kind motion, "head swivel," rather than ratcheting.

The paper describes how an antibiotic was used to inhibit the full swivel and ratcheting motion of a ribosome from a bacterium called Thermus Thermophilus, which thrives in hot acidic environments. The ribosomes were flash-frozen at various mid-swivel and mid-ratchet configurations and examined under a powerful electron microscope.

The observed configurations were then coupled with a computer model newly developed at Los Alamos called MDFIT. The computer algorithm integrates molecular simulation with maps of ribosome structures obtained through the cryogenic microscopy. The Los Alamos team then used the Encanto supercomputer -- funded by the state of New Mexico and housed at the Intel plant in Rio Rancho -- to create molecular snapshots of the complicated motion of the ribosomal subunits during protein synthesis.

Previously, scientists were only able to observe the beginning or end states of the motion. These new images show the behavior of the ribosome through its range of motion -- much like early photographic motion studies that showed the entire fluid movement of a galloping horse. In addition to showing the importance of head swivel motion, the study showed that a key catalyst in the process acts as a dynamic pawl in the ribosomal machinery, providing directionality and acceleration for translocation of the tRNA. The understanding provided by the new model will help researchers to develop more effective antibiotics that target the ribosomal machinery of harmful organisms.

"While static images of the ribosome have revealed the detailed structure of the complex, we still don't know how all the parts of the machine work together to make proteins," said Janna Wehrle, Ph.D., who oversees Dr. Sanbonmatsu's and other structural biology grants at the National Institutes of Health. "By showing how the bacterial ribosome carries out a key step of protein synthesis, this study has begun to produce a more dynamic picture while offering a new way to target harmful, multi-drug resistant bacteria."

 

[Techne]

Nice compilation of various molecular animations from various companies and universities.
[video=youtube;FJ4N0iSeR8U]http://www.youtube.com/watch?v=FJ4N0iSeR8U[/video]

 

[Techne]

Structure of DNA Repair Complex Reveals Workings of Powerful Cell Motor

ScienceDaily (Mar. 28, 2011) — Over the last years, two teams of researchers at The Scripps Research Institute have steadily built a model of how a powerful DNA repair complex works. Now, their latest discovery provides revolutionary insights into the way the molecular motor inside the complex functions -- findings they say may have implications for treatment of disorders ranging from cancer to cystic fibrosis.

The new finding solves the long-standing mystery of how a single protein complex known as MRN (Mre11-Rad50-Nbs1, shown here) can repair DNA in a number of different ways. (Credit: Image courtesy of Scripps Research Institute)​

There are various DNA repair mechanisms. Here are a few videos describing these processes:
[video=youtube;g4khROaOO6c]http://www.youtube.com/watch?v=g4khROaOO6c[/video]
[video=youtube;XjNqqsvUXTw]http://www.youtube.com/watch?v=XjNqqsvUXTw[/video]
[video=youtube;bgUH9NfO2QM]http://www.youtube.com/watch?v=bgUH9NfO2QM[/video]
[video=youtube;jRGPxuo0H30]http://www.youtube.com/watch?v=jRGPxuo0H30[/video]

Companies are already starting to develop nanotechnologies based on these processes. E.g.:
[video=youtube;Q8tAj8A4pc0]http://www.youtube.com/watch?v=Q8tAj8A4pc0[/video]

And here is just a video of DNA replication:
[video=youtube;4jtmOZaIvS0]http://www.youtube.com/watch?v=4jtmOZaIvS0[/video]

 

[Techne]

Cells Send Signals Via Membrane Nanotubes

ScienceDaily (May 1, 2011) — Most of the body's cells communicate with each other by sending electrical signals through nano-thin membrane tubes. A sensational Norwegian research discovery may help to explain how cells cooperate to develop tissue in the embryo and how wounds heal.

Here a cell has coupled with another cell by growing a long nanotube which enables it to exchange electrical signals. (Credit: UiB)​

For nearly ten years, researchers have known that cells can "grow" ultra-thin tubes named tunnelling nanotubes (TNTs) between one another. These nanotubes -- the length of two to three cells and just 1/500th the thickness of a human hair -- are connections that develop between nearly all cell types to form a communication channel different from any previously known mechanisms.

In 2010, Dr. Xiang Wang and Professor Hans-Hermann Gerdes -- colleagues at the University of Bergen's Department of Biomedicine -- discovered that electrical signals were being passed through nanotubes from one cell to another at high speed (roughly 1-2 m/sec). Their research receives funding under the Research Council's large-scale research programme Nanotechnology and New Materials (NANOMAT).

The breakthrough

In their key experiment, Dr Wang used fluorescent dye that changes in intensity as the electric potential of the cell membrane changes. When two cells connected by forming a nanotube, he poked into one of them with a microinjection needle to depolarise that cell's membrane potential. This caused the fluorescent indicator on the cell membrane to light up like a firework, and it was soon followed by a similar light display in the cell on the other end of the nanotube.

The breakthrough discovery began with an experiment demonstrating intercellular transmission of electrical signals via nanotubes in 2007. The researchers then carried out similar trials with a number of other cell types, observing similar occurrences.

"We confirmed that this is a common phenomenon between cells," explains Professor Gerdes. "Still, this characteristic is not in every cell type."

The experiment was replicated a number of times to obtain statistically reliable data. The electrophysiology group at the University of Bergen took precise conductivity measurements of the cell systems to determine the strength of the electrical coupling. In autumn 2010 the results were published in Proceedings of the National Academy of Sciences (PNAS).

Short lifespan

Intercellular nanotubes are far from permanent. Most of them last only a few minutes. This means the researchers cannot predict where and when the cells will form nanotube connections.

"It is truly painstaking work," says Professor Gerdes. "You may sit there examining cells for hours through a microscope without seeing a single tube. If you are lucky, however, you catch sight of a nanotube being created and can film the event."

To raise the likelihood of finding nanotubes, the researchers developed a micro-matrix consisting of thousands of points and bridges on a plate surface. Smaller than a postage stamp, the plate is covered by a nano-structured material to which the cells adhere. The researchers place one cell onto each point and hope that nanotubes will form along the bridges between the points. The camera is focused on these bridges.

Once the nanotubes have been established, the researchers manipulate the cells at specified times; meanwhile the microscope is programmed to photograph, say, 50 preselected points every five minutes. The team can thus obtain data about many nanotube connections in a short time.

How do cells do this?

Dr. Wang quickly discovered that the mere presence of a nanotube was not sufficient to transmit an electrical signal. There had to be another mechanism involved as well.

Many cells form tiny membrane pores with each other called gap junctions, which are made up of ring-shaped proteins. Back in the 1960s it was discovered that directly adjacent cells could exchange electrical impulses through these gap junctions. What Dr Wang found was that one end of the nanotube was always connected to cells by a gap junctions before it transmitted its electrical impulses.

He also found that in some coupled cells voltage-gated calcium channels were involved in the forwarding of the incoming signals. When the electrical signal being sent through the nanotube reaches the membrane of the receiving cell, the membrane surface is depolarised, opening the calcium channel and allowing calcium -- a vital ion in cell signalling -- to enter.

"In other words," explains Professor Gerdes, "there are two components: a nanotube and a gap junction. The nanotube grows out from one cell and connects to the other cell through a gap junction. Only then can the two cells be coupled electrically."

Controls embryonic cells?

Now the scientists are seeking answers as to why the cells send signals to each other in this way.

"It's quite possible that the discovery of nanotubes will give us new insight into intercellular communication," asserts Professor Gerdes. "The process could explain how cells are coordinated during embryo growth. In that phase cells travel long distances -- yet they demonstrate a kind of collective behaviour, and move together like a flock of birds can."

Nanotubes may also be a factor in explaining cell movement associated with wound healing, since cells move toward a wound in order to close it. We already know that electrical signals are somehow involved in this process; scientists can only speculate as to whether nanotubes are involved here as well, stresses Professor Gerdes.

Perhaps brain cells, too?

In terms of electronic signal processing, the human brain surpasses all other organs. If this same signalling mechanism proves to be present in human brain cells, it could add a new dimension to understanding how the brain functions. Communication channels involving synapses and dendrites that are already identified differ widely from nanotubes.

The Bergen-based neuroscientists see this research as an opportunity to formulate better explanations for phenomena related to consciousness and electrical connections in the brain. In the project "Cell-to-cell communication: Mechanism of tunnelling nanotube formation and function," they are now studying precisely how nanotube mechanisms function in brain cells.

Professor Gerdes is currently conducting research at the European Molecular Biology Laboratory in Heidelberg. By studying the electrical connections in vivo he hopes to figure out how the mechanisms work in live subjects. The results could enhance understanding of diseases that occur when cell mechanisms fail to function properly.

Quite interesting!

 

[Techne]

A few good animations about Molecular Biology's Central Dogma

[video=youtube;GkdRdik73kU]http://www.youtube.com/watch?v=GkdRdik73kU[/video]

[video=youtube;-ygpqVr7_xs]http://www.youtube.com/watch?v=-ygpqVr7_xs[/video]

 

[Happy Camper]

I like your posts, please don't stop ++

 

[Techne]

New Insight On Molecular Motor Movement: Mini Cargo Transporters On a Rat Run

ScienceDaily (Apr. 26, 2012) — Kinesins assume a vital function in our cells: The tiny cargo transporters move important substances along lengthy protein fibers and ensure an effective transportation infrastructure. Biophysicists of the Technische Universitaet Muenchen (TUM) and the Ludwig Maximillians Universitaet Muenchen (LMU) have now discovered how some of these transporters can, like cars on a multi-lane motorway, change lanes. The researchers report on this hitherto unknown phenomenon in the current edition of the journal Molecular Cell.

Biophysicists of the Technische Universitaet Muenchen and the Ludwig Maximillians Universitaet Muenchen have discovered why some of these transporters can, like cars on a multi-lane motorway, change lanes: The heads of one kinesin (red) have a longer range than the other (blue) which allows "lane change" between the individual fibers (protofilaments) of the microtubule and results in a spiraling movement of the motor on the microtubule. A shorter range of the heads results in a straight movement of the motor. (Credit: Melanie Brunnbauer /TU Muenchen)​

Nice video demonstrating kinesin movement:
[video=youtube;8RULvE9rw6Y]http://www.youtube.com/watch?v=8RULvE9rw6Y[/video]

 

[Techne]

Another video from TED about all kinds of biomolecular machines:
[video=youtube;dMPXu6GF18M]http://www.youtube.com/watch?v=dMPXu6GF18M[/video]

 

[empirex]

Nano bio-machines, built in turn by other bio-machines, first transcribing the coded data, then translating / assembling the data into complex integrated 3D structures, from said library utilising a highly sophisticated "software" compression system. Which in turn is all coordinated within an "executive cell", itself featuring real-time feedback / adjustment systems according to interaction with it's environment. All operating at an unimaginably infinitesimal level.
Just one cell. Translate that to over two hundred and yeah I would say design is well in order.

 

[Techne]

Nano bio-machines, built in turn by other bio-machines, first transcribing the coded data, then translating / assembling the data into complex integrated 3D structures, from said library utilising a highly sophisticated "software" compression system. Which in turn is all coordinated within an "executive cell", itself featuring real-time feedback / adjustment systems according to interaction with it's environment. All operating at an unimaginably infinitesimal level.
Just one cell. Translate that to over two hundred and yeah I would say design is well in order.

The definition of "design" and what it actually is is still not clear and up for debate.

However, the common sense axiom of "every agent acts for an end" is nicely exemplified by these and other scientific studies.

 

[Techne]

Neat animation.

[video=youtube;TZuxuVJA36Q]http://www.youtube.com/watch?v=TZuxuVJA36Q&feature=player_embedded[/video]

More here:
http://catalog.nucleusinc.com/categories.php?CatID=000&TL=1&A=2&I=2
http://www.youtube.com/user/XVIVOAnimation

 

[RiaX]

sigh, thats a lot of complex stuff D: even for me cant we have nice videos (documentry) i dislike reading so much. Interesting read but I got a headache now :<

 

[Techne]

sigh, thats a lot of complex stuff D: even for me cant we have nice videos (documentry) i dislike reading so much. Interesting read but I got a headache now :<

Yeah, more documentaries about molecular biology is needed.

Thought this was pretty short and sweet though:
[video=youtube;V0Pqf2DyYWc]http://www.youtube.com/watch?v=V0Pqf2DyYWc[/video]

 

[Techne]

[video=youtube;AHwAZIHxiBk]http://www.youtube.com/watch?v=AHwAZIHxiBk[/video]

 

[Techne]

Laser Spotlight Reveals Machine 'Climbing' DNA

ScienceDaily (Oct. 26, 2012) — New imaging technology has revealed how the molecular machines that remodel genetic material inside cells 'grab onto' DNA like a rock climber looking for a handhold.

Imaging the molecular machine MukBEF using flourescent tags attached to its component parts. (Credit: Image courtesy of University of Oxford)​

The experiments, reported in this week's Science, use laser light to generate very bright patches close to single cells. When coupled with fluorescent tags this 'spotlight' makes it possible to image the inner workings of cells fast enough to see how the molecular machines inside change size, shape, and composition in the presence of DNA.

The Oxford team built their own light microscopy technology for the study, which is a collaboration between the research groups of Mark Leake in Oxford University's Department of Physics and David Sherratt in Oxford University's Department of Biochemistry.

The molecular machines in question are called Structural Maintenance of Chromosome (SMC) complexes: they remodel the genetic material inside every living cell and work along similar principles to a large family of molecules that act as very small motors performing functions as diverse as trafficking vital material inside cells to allowing muscles to contract.

The researchers studied a particular SMC, MukBEF (which is made from several different protein molecules), inside the bacterium E.coli. David Sheratt and his team found a way to fuse 'fluorescent proteins' directly to the DNA coding for MukBEF, effectively creating a single dye tag for each component of these machines.

Up until now conventional techniques of biological physics or biochemistry have not been sufficiently fast or precise to monitor such tiny machines inside living cells at the level of single molecules.

'Each machine functions in much the same way as rock-climber clinging to a cliff face,' says Mark Leake of Oxford University's Department of Physics, 'it has one end anchored to a portion of cellular DNA while the other end opens and closes randomly by using chemical energy stored in a ubiquitous bio-molecule called adenosine triphosphate, or 'ATP': the universal molecular fuel for all living cells.

'This opening and closing action of the machine is essentially a process of mechanical 'grabbing', in which it attempts to seize more free DNA, like the rock-climber searching for a new handhold.'

It is hoped that pioneering biophysics experiments such as this will give fresh insights into the complex processes which are vital to life, and pave the way for a whole new approach to biomedical research at the very tiny length scale for understanding the causes of many diseases in humans, and how to devise new strategies to combat them.

Journal Reference:

A. Badrinarayanan, R. Reyes-Lamothe, S. Uphoff, M. C. Leake, D. J. Sherratt. In Vivo Architecture and Action of Bacterial Structural Maintenance of Chromosome Proteins. Science, 2012; 338 (6106): 528 DOI: 10.1126/science.1227126