Subscribe free to our newsletters via your
. 24/7 Space News .

Subscribe free to our newsletters via your

Light used to measure the 'big stretch' in spider silk proteins
by Staff Writers
Baltimore MD (SPX) Feb 17, 2016

Without the protein myosin to pull on it, vinculin can been seen to relax in this human cell (lower right) as the colors shift from blue to red as FRET increases. Image courtesy Taekjip Ha. Watch a video on the research here.

While working to improve a tool that measures the pushes and pulls sensed by proteins in living cells, biophysicists at Johns Hopkins say they've discovered one reason spiders' silk is so elastic: Pieces of the silk's protein threads act like supersprings, stretching to five times their initial length. The investigators say the tool will shed light on many biological events, including the shifting forces between cells during cancer metastasis.

"All other known springs, biological and nonbiological, lengthen in a way that is directly proportional to the force applied to them only until they have been stretched to about 20 percent of their original length," notes Taekjip Ha, Ph.D., the study's lead researcher.

"At that point, you have to apply more and more force to stretch them the same distance as before. But the piece of the spider silk protein we focused on continues to stretch in direct proportion to the force applied until it reaches its maximal stretch of 500 percent." Details of the research were published online in the journal Nano Letters.

Ha, a Bloomberg Distinguished Professor of biophysics and biophysical chemistry at the Johns Hopkins University School of Medicine, says the new discovery came during follow-up to research he and his team, then at the University of Illinois at Urbana-Champaign, described in the journal Nature in 2010, work done in collaboration with cell biologists led by Martin Schwartz, then at the University of Virginia.

The Virginia team set up those experiments by inserting a repeating amino acid sequence - taken from the spider silk protein known as flagelliform - into a human protein called vinculin. Vinculin is responsible for internalizing forces outside a cell by bridging the cellular membrane and the actin network within the cell, making it an important mechanical communicator within the cell.

The scientists also flanked the flagelliform insert in vinculin with two fluorescent proteins to light up and "report" what was going on through fluorescence resonance energy transfer, or FRET. FRET occurs when one fluorescent molecule is close enough to another that it activates the second.

So, when vinculin was relaxed within a cell, it "glowed" yellow, the color of the second fluorescent protein being activated by the first. As vinculin stretched, it began to glow blue - the color of the first fluorescent protein - because the lengthening distance between the two made FRET activation of the yellow protein impossible.

Using regular fluorescence microscopy, the scientists were able to watch the forces acting on vinculin in live cells in real time. But an issue remained: how to translate the changing colors into measurements of force "sensed" by vinculin.

That's where his team came in, says Ha. The researchers attached one end of modified vinculin to a glass plate and the other to a tether made of DNA with a small plastic bead at the end. They then pulled on the bead with what Ha describes as "chopsticks made of light," focusing a beam of light on a tiny spot nearby and generating an attractive force that pulled the bead toward the light source. That way, Ha says, his investigators could link the amount of FRET with the amount of force on vinculin, allowing them to measure the dynamic forces acting on proteins in live cells just by imaging them.

In that earlier study, the team inserted 40 flagelliform amino acids into vinculin, composed of eight repeats of the amino acid sequence GPGGA. In this new study, the scientists wanted to learn more about the flagelliform tool by varying its length, so they created inserts of five and 10 repeats to test alongside the original insert of eight. What they found is that the shortest insert was the most responsive to the widest range of forces, responding with linear increases in length to forces from 1 to 10 piconewtons. (Ha says that 1 piconewton is approximately the weight of a bacterium.)

The team wasn't expecting the spider silk inserts to show such linear behavior because, according to Ha, they don't form well-defined, three-dimensional structures. "Usually, unstructured proteins show disorderly, nonlinear behavior when we pull on them," says Ha. "The fact that these don't act that way means that they will be really useful tools for studying protein mechanics because their behavior is easy to understand and predict."

Already, Ha says, the flagelliform insert of eight repeats from the previous research has been used to study many biological phenomena, including the shifting forces between cells during cancer metastasis and the pushing and pulling of cells during the development of simple, multicelled organisms, like worms.

"Tension is important for many activities inside cells," says Ha. "Cells sense mechanical forces in their environments and change their behaviors and functions in response. Now we have a way to watch and understand these forces and how they are transmitted at a molecular level in living cells."

Other authors of the report include Michael Brenner and Ruobo Zhou of the University of Illinois at Urbana-Champaign; Daniel Conway of the University of Virginia; and Luca Lanzano and Enrico Gratton of the University of California, Irvine.


Related Links
Johns Hopkins Medicine
Space Technology News - Applications and Research

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Previous Report
UBC researchers discover new glass technology
Vancouver, Canada (SPX) Feb 12, 2016
Imagine if the picture window in your living room could double as a giant thermostat or big screen TV. A discovery by researchers at the University of British Columbia has brought us one step closer to this becoming a reality. Researchers at UBC's Okanagan campus in Kelowna found that coating small pieces of glass with extremely thin layers of metal like silver makes it possible to enhance ... read more

Edgar Mitchell, astronaut who walked on Moon, dead at 85

The forgotten moon landing that paved the way for today's space adventures

ASU satellite selected for NASA Space Launch System's first flight

Lunar Flashlight selected to fly as secondary payload on Exploration Mission-1

Becoming a Martian

Site of Martian lakes linked to ancient habitable environment

Opportunity climbing steeper slopes to reach science targets

Opportunity Reaches 12 Years on Mars!

Are private launches changing the rocket equation?

NASA tests solar sail deployment for asteroid-surveying CubeSat NEA Scout

Orion Crew Module processing begins for first mission

Mars or the Moon

China Conducts Final Tests on Most Powerful Homegrown Rocket

Last Launch for Long March 2F/G

China aims for the Moon with new rockets

China shoots for first landing on far side of the moon

Putting the Public in the Shoes of Space Station Science

Russians spacewalk to retrieve biological samples

Russia to Deliver Three Advanced Spacesuits to ISS in 2016

Russian spacewalk marks end of ESA's exposed space chemistry

SES-9 Launch Targeting Late February

Spaceflight Awarded First GSA Schedule Contract for Satellite Launch Services

Arianespace to launch two ViaSat high capacity satellites

SpaceX Conducts Hover Tests

Earth-like planets have Earth-like interiors

The frigid Flying Saucer

Astronomers discover largest solar system

Lonely Planet Finds a Mum a Trillion Km Away

Some 5,000 years ago, silver mining on the shores of the Aegean Sea

Chemical cages: New technique advances synthetic biology

Why not recycled concrete

UBC researchers discover new glass technology

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.