Featured Research

from universities, journals, and other organizations

Crowdsourcing the phase problem

Date:
June 17, 2014
Source:
International Union of Crystallography
Summary:
Compared with humans, computers have the capacity to solve problems at much greater speed. There are many problems, however, where computational speed alone is insufficient to find a correct or optimal solution.

Successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing.
Credit: Image courtesy of International Union of Crystallography

Compared with humans, computers have the capacity to solve problems at much greater speed. There are many problems, however, where computational speed alone is insufficient to find a correct or optimal solution, for example because the parameter "space" cannot be fully searched in a practical time. In contrast, the human mind can formulate expert knowledge specific for particular problems, providing a capacity to guide more efficient searches, although with more limited processing speed.

The power of the human contribution can be multiplied through the efforts of a greater number of individuals. The term `crowdsourcing', which combines the two domains of human and electronic computing, was coined in 2006 and since then has seen its definition broadened to a wide range of activities involving a network of people.

A challenging problem that might benefit from crowdsourcing is the phase problem in X-ray crystallography. Retrieving the phase information has plagued many scientists for decades when trying to determine the crystal structure of a sample.

In a diffraction experiment, the observed diffraction pattern allows measurement of the amplitudes of the reflection structure factors (as the square root of the intensities) but not their phases. The amplitudes and phases are both needed to reconstruct an electron-density map (by Fourier synthesis) so that a model of the crystallized molecule can be obtained.

There are a number of ways currently scientists try to solve the phase problem, all with varying degrees of success.

Regardless of the particular approach, most attacks on the phase problem can be viewed as having two sub-problems. One concerns how a high-dimensional space (i.e. of phases) can be efficiently searched, while the other concerns how a good solution can be recognized.

Crowdsourcing may be a route to solving these sub-problems, here scientists have developed a game based on a genetic algorithm (a powerful search-optimization technique), where players control the selection mechanism during the evolutionary process (by recognising the good solutions). The algorithm starts from a population of "individuals," in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals.

The game called CrowdPhase (http://www.crowdphase.com) was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30 degree phase error range and corresponding molecular envelopes showing agreement with the low-resolution models.

Successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing.


Story Source:

The above story is based on materials provided by International Union of Crystallography. Note: Materials may be edited for content and length.


Journal Reference:

  1. Julien Jorda, Michael R. Sawaya, Todd O. Yeates. CrowdPhase: crowdsourcing the phase problem. Acta Crystallographica Section D Biological Crystallography, 2014; 70 (6): 1538 DOI: 10.1107/S1399004714006427

Cite This Page:

International Union of Crystallography. "Crowdsourcing the phase problem." ScienceDaily. ScienceDaily, 17 June 2014. <www.sciencedaily.com/releases/2014/06/140617112224.htm>.
International Union of Crystallography. (2014, June 17). Crowdsourcing the phase problem. ScienceDaily. Retrieved August 23, 2014 from www.sciencedaily.com/releases/2014/06/140617112224.htm
International Union of Crystallography. "Crowdsourcing the phase problem." ScienceDaily. www.sciencedaily.com/releases/2014/06/140617112224.htm (accessed August 23, 2014).

Share This




More Computers & Math News

Saturday, August 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Apple iPhone 6 Screen Hits Snag Ahead of Launch

Apple iPhone 6 Screen Hits Snag Ahead of Launch

Reuters - Business Video Online (Aug. 22, 2014) Reuters has learned Apple is scrambling to get enough screens ready for the iPhone 6. Sources say it's unclear whether this could delay the launch. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Is Apple's iMessage Really Being Overrun By Spammers?

Is Apple's iMessage Really Being Overrun By Spammers?

Newsy (Aug. 21, 2014) A report says more than one third of all SMS spam over the past year came from a "single campaign" using iMessage and targeting iPhone users. Video provided by Newsy
Powered by NewsLook.com
Families Can Now Ask Twitter To Remove Photos Of Deceased

Families Can Now Ask Twitter To Remove Photos Of Deceased

Newsy (Aug. 20, 2014) In the wake of a high-profile harassment case, Twitter says family members can ask for photos of dying or dead relatives to be taken down. Video provided by Newsy
Powered by NewsLook.com
Ballmer Leaves Microsoft's Board, Has Advice For Nadella

Ballmer Leaves Microsoft's Board, Has Advice For Nadella

Newsy (Aug. 19, 2014) In a letter to Microsoft CEO Satya Nadella, Ballmer said he's leaving the board of directors and offered tips on how the company can be successful. 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