Featured Research

from universities, journals, and other organizations

Physicist's discovery alters conventional understanding of sight

Date:
June 24, 2011
Source:
Syracuse University
Summary:
Physicists shed new light on how the visual process is initiated. For almost 50 years, scientists have believed that light signals could not be initiated unless special light-receptor molecules in the retinal cells first changed their shape in a process called isomerization. However, researchers have now demonstrated that visual signals can be initiated in the absence of isomerization.

A discovery by a team of researchers led by a Syracuse University physicist sheds new light on how the visual process is initiated. For almost 50 years, scientists have believed that light signals could not be initiated unless special light-receptor molecules in the retinal cells first changed their shape in a process called isomerization. However, the SU research team, which includes researchers from Columbia University, has demonstrated that visual signals can be initiated in the absence of isomerization.

"We have demonstrated that chromophores (light-absorbing substances in retinal photoreceptor molecules), do not have to change shape in order to trigger the visual signal," says Kenneth Foster, professor of physics in SU's College of Arts and Sciences. "The shape-change that results from isomerization is actually the second step in the process. Historically, scientists have focused on isomerization without realizing there is an earlier and more crucial first step."

The research was published online June 23 in the journal Chemistry and Biology and is the cover article for the print version to appear June 24. The work was done in collaboration with Juree Saranak, research assistant professor in the Department of Physics; and Koji Nakanishi, professor of chemistry at Columbia University. Nakanishi's group was responsible for the synthetic chemistry that went into the compounds tested at SU. The National Institutes of Health funded the research.

Chromophores absorb light after it enters the eye, setting off an extremely rapid series of complex molecular changes that enable light signals to be transmitted to, and interpreted by, the brain so that we can visually perceive the world around us. Visual chromophores are composed of retinal (a type of vitamin A), which attaches to a protein (opsin) to form rhodopsin.

Foster's team of researchers discovered that the visual process is initiated by the redistribution of electrons on the chromophores, which occurs during the first few femptoseconds (one-quadrillionth of a second) after light enters the eye. Their experiments showed that when a chromophore absorbs a photon of light, electrons move from the chromophore's "free" end to the place where it attaches to opsin. The movement of the electrons causes a change in the electrical field surrounding the chromophore. That change is detected by nearby amino acids that are highly sensitive to changes in the electrical field. These amino acids, in turn, signal the rest of the rhodopsin molecule to initiate the visual process.

"We found that the complete blocking of isomerization of the chromophore does not preclude vision in our model organism," Foster says. "The signal is triggered as a result of an electronic coupling instead of a geometric change in the chromophore's structure as previously hypothesized. We believe this is a universal mechanism that activates all rhodopsins present in organisms from bacteria to mammals."

Foster attributes his findings to new technologies and scientific information not available 50 years ago when scientists first tried to understand how people see. "Fifty years ago, scientists had little knowledge of the structure of rhodopsins," he says. "Advances in technology have enabled scientists to determine the rhodopsin structure at the level of the amino acids, which enables us to design sensitive experiments to test our hypotheses."


Story Source:

The above story is based on materials provided by Syracuse University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kenneth W. Foster, Jureepan Saranak, Sonja Krane, Randy L. Johnson, Koji Nakanishi. Evidence from Chlamydomonas on the Photoactivation of Rhodopsins without Isomerization of Their Chromophore. Chemistry and Biology, Volume 18, Issue 6, 733-742, 24 June 2011 DOI: 10.1016/j.chembiol.2011.04.009

Cite This Page:

Syracuse University. "Physicist's discovery alters conventional understanding of sight." ScienceDaily. ScienceDaily, 24 June 2011. <www.sciencedaily.com/releases/2011/06/110623130137.htm>.
Syracuse University. (2011, June 24). Physicist's discovery alters conventional understanding of sight. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2011/06/110623130137.htm
Syracuse University. "Physicist's discovery alters conventional understanding of sight." ScienceDaily. www.sciencedaily.com/releases/2011/06/110623130137.htm (accessed April 24, 2014).

Share This



More Matter & Energy News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Air Force: $4.2B Saved from Grounding A-10s

Air Force: $4.2B Saved from Grounding A-10s

AP (Apr. 23, 2014) Speaking about the future of the United States Air Force, Chief of Staff Gen. Mark Welsh says the choice to divest the A-10 fleet was logical and least impactful. (April 23) Video provided by AP
Powered by NewsLook.com
Jets Fuel Jump in Boeing's Revenue

Jets Fuel Jump in Boeing's Revenue

Reuters - Business Video Online (Apr. 23, 2014) A sharp rise in revenue for commercial jets offset a decline in Boeing's defense business. And a big increase in deliveries lifted profitability. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins