Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Biology meets geometry

31.10.2014

A UCSB biophysicist and deputy director of the Kavli Institute for Theoretical Physics collaborates with colleagues to describe the geometry of a common cellular structure

Architecture imitates life, at least when it comes to those spiral ramps in multistory parking garages. Stacked and connecting parallel levels, the ramps are replications of helical structures found in a ubiquitous membrane structure in the cells of the body.


Artist's rendering of Terasaki spiral ramps, helices that connect stacks of evenly spaced sheets in the rough endoplasmic reticulum.

Credit: Jemal Guven

Dubbed Terasaki ramps after their discoverer, they reside in an organelle called the endoplasmic reticulum (ER), a network of membranes found throughout the cell and connected to and surrounding the cell nucleus. Now, a trio of scientists, including UC Santa Barbara biological physicist Greg Huber, describe ER geometry using the language of theoretical physics. Their findings appear in print and online in the Oct. 31 issue of Physical Review Letters.

"Our work hypothesizes how the particular shape of this organelle forms, based on the interactions between Terasaki ramps," said Huber, who is deputy director of UCSB's Kavli Institute for Theoretical Physics. "A physicist would like to say there's a reason for the membrane's shape, that it's not just an accident. So by understanding better the physics responsible for the shape, one can start to think about other unsolved questions, including how its form relates to its function and, in the case of disease, to its dysfunction."

The rough ER consists of a number of more or less regular stacks of evenly spaced connected sheets, a structure that reflects its function as the shop floor of protein synthesis within a cell. Until recently, scientists assumed that the connections between adjacent sheets were like wormholes — that is, simple tubes.

Last year, however, it was discovered that these connections are formed by spiral ramps running up through the stack of sheets. According to lead author Jemal Guven of the Universidad Nacional Autónoma de México, this came as a surprise because spiral geometries had never previously been observed in biological membranes.

Attached to the membrane, ribosomes, which serve as the primary site for protein synthesis, dot the ER like cars populating a densely packed parking structure. "The ribosomes have to be a certain distance apart because otherwise they can't synthesize proteins," Huber explained.

"So how do you get as many ribosomes per unit volume as possible but not have them bump up against each other?" Huber asked. "The cell seems to have solved that problem by folding surfaces into layers that are nearly parallel to each other and allow a high density of ribosomes."

Different parts of the ER have different shapes: a network of tubes, a sphere that bounds the nucleus or a set of parallel sheets like the levels of a parking garage. The smooth ER consists of a tubular network of membranes meeting at three-way junctions. These junctions are also the location of lipid (or membrane) synthesis. As new lipids are produced within the smooth ER, they accumulate in these junctions, eventually cleaving apart the tubes meeting there.

In the rough ER, the parallel surfaces or stacks are connected by Terasaki spiral ramps. In some cases, one ramp is left-handed and the other right-handed — the parking-garage geometry — which is what Terasaki and colleagues (including Huber) found last year.

"We propose that the essential building blocks within the stack are not individual spiral ramps but a 'parking garage' organized around two gently pitched ramps, one of which is the mirror image of the other — a dipole," said Guven, who was assisted in his research by one of his students, Dulce María Valencia. "This architecture minimizes energy and is consistent with the laminar structure of the stacks but is also stable."

In physics, these helical structures, which connect one layer of the ER with the next, are called defects. That word, Huber noted, carries no negative connotation in this context. "When you look at this through the eyes of physics, there are certain mechanisms that suggest themselves almost immediately," Huber said. "The edge of an ER sheet is a region of high curvature because the sheet turns around and bends. The bend is actually the thing that's forming the helix."

The bend creates a U shape that looks like half of a tube. Huber and his colleagues applied the principles of differential geometry to this curved membrane. Pulling the halves of a tube apart creates a flat region spanning the two U-shaped halves, which then become part of a sheet.

The geometrical idea is that one can actually get a sheet by pulling apart a network of tubes in a certain way," Huber explained. "Imagine that each of the U-shaped edges wants to bend, but when you try to connect those two U shapes together, each one is now bent. That's what the color figure is trying to show. A tube can generate a sheet if the edges come apart and they're allowed to bend in space."

According to Huber, this theoretical work provides a deeper story and richer vocabulary for discussing the shapes found in cell interiors. "One suspects that their shape is related to their function," he concluded. "In fact, scientists know that the shape of the ER can be an indicator of abnormal functions seen in certain diseases."

Julie Cohen | EurekAlert!
Further information:
http://www.ucsb.edu/

Further reports about: Biology connections function geometry physics protein synthesis ribosomes smooth structure structures surfaces tubes

More articles from Life Sciences:

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>