The findings about online communities and more than 100 other issues are published in the 2007 Digital Future Project, the comprehensive annual examination of the impact of online technology on America.
The project surveys more than 2,000 individuals across the United States, each year contacting the same households to explore how online technology affects the lives of Internet users and non-users. It also examines how changing technology, such as the shift from Internet access by modem to broadband, affects behavior.
The 2007 Digital Future Project found that Internet use is growing and evolving as an instrument for personal engagement - through blogs, personal Web sites, and online communities.
Online communities: a catalyst for connection and activism
Online communities and offline action -- The Digital Future Project found that involvement in online communities leads to offline actions. More than one-fifth of online community members (20.3 percent) take actions offline at least once a year that are related to their online community. (An 'online community' is defined as a group that shares thoughts or ideas, or works on common projects, through electronic communication only.)
Social activism - Participation in online communities leads to social activism. Almost two-thirds of online community members who participate in social causes through the Internet (64.9 percent) say they are involved in causes that were new to them when they began participating on the Internet. And more than 40 percent (43.7 percent) of online community members participate more in social activism since they started participating in online communities.
Online communities: daily use -- A significant majority of members of online communities (56.6 percent) log into their community at least once a day.
Member interaction -- Online communities are online havens for interaction among members. In 2006, 70.4 percent of online community members say they sometimes or always interact with other members of their community while logged in.
Internet users: reaching out across the Web
Posting information -- Growing percentages of Internet users are going online to post information, whether on a blog, posting photos, or maintaining a personal Web site.
-- The number of Internet users in America who keep a blog has more than doubled in three years (now 7.4 percent of users, up from 3.2 percent in 2003).
-- Likewise, the number of Internet users who post photos online has more than doubled in three years (now 23.6 percent of users, up from 11 percent).
-- The number of users who maintain their own Web site continues to grow steadily (now 12.5 percent of users).
The Internet and social links
The Digital Future Project found continuing growth of the Internet for connection to family and friends - but with virtually no negative effects on time spent in person with them.
New friends, online and in person -- Internet users are finding growing numbers of online friends, as well as friends they first met online and then met in person. In 2006, Internet users report having met an average of 4.65 friends online whom they have never met in person. Internet users in 2006 report an average of 1.6 friends met in person whom they originally met online -- more than double the number when the Digital Future Project began in 2000.
Does the Internet increase regular contact with other users" -- Responding to a question last asked in 2002, 42.8 percent of Internet users agree that going online has increased the number of people they regularly stay in contact with -- marginally less than the 46.6 percent who voiced the same response four years ago.
Internet users and communication with family and friends -- Although more than 40 percent of users say that the Internet has increased the number of people with whom they stay in contact, a lower percent say that since starting to use the Internet they are communicating more with family and friends.
In 2006, 37.7 percent of Internet users agree that since they started to go online they are communicating more with family and friends -- down from 45.5 percent in 2002.
Does the Internet change the amount of time spent with friends and family face-to-face" -- While large percentages of Internet users say that going online increases contact with family and friends, almost all users report that the Internet has no effect on the time spent with close friends or family face-to-face.
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The USC-Annenberg Digital Future Project:
Six years of exploring the digital realm
The USC-Annenberg School Center for the Digital Future created and organizes the World Internet Project, which includes the Digital Future Project and similar studies in North America, South America, Europe, Asia, the Middle East and Australia. The center is supported by public foundations and private companies, including Accenture, America Online, Time Warner Companies, Sony, AT&T, Microsoft, and the Coca-Cola Company.
The Digital Future Project provides a broad year-to-year exploration of the influence of the Internet and online technology on Americans. Since 2000, the project has examined the behavior and views of a national sample of Internet users and non-users, as well as comparisons between new users (one year or less of experience) and very experienced users (more than nine years of experience).
Contact: Geoffrey Baum
University of Southern California
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Nobel Laureate Finds 'Elegant' Explanation For DNA Transcribing Enzyme's High Fidelity
Last month, Roger Kornberg of Stanford University won the Nobel Prize in Chemistry for his efforts to unravel the molecular basis of eukaryotic transcription, in which enzymes give 'voice' to DNA by copying it into the RNA molecules that serve as templates for protein in organisms from yeast to humans. Now, Kornberg and his colleagues report in the December 1, 2006 issue of the journal Cell, published by Cell Press, new structures that reveal another critical piece of the puzzle: how the so-called polymerase II enzyme discriminates among potential RNA building blocks to ensure the characteristic accuracy of the process.
The researchers found that a portion of the enzyme known as the trigger loop acts like a 'trap door,' swinging beneath a matching nucleoside triphosphate (NTP) building block, to close off the active center and form an extensive network of interactions with the NTP and other parts of the enzyme. Those interactions leave another side chain in the trigger loop precisely positioned, such that it may literally 'trigger' the formation of the chemical bonds that link components of the growing RNA chain together. If the NTP is even slightly misaligned, Kornberg said, those critical interactions fail.
The trigger loop mechanism therefore couples NTP recognition and catalysis, ensuring the fidelity of transcription, they reported.
"Of all revelations from the structure [of the transcription machinery] since it was first solved, this is perhaps the most fundamental since it gets at the underlying mechanisms," Kornberg said. "It's long known that the enzyme operates with high fidelity - selecting the correct base and sugar - but it's been a mystery how that is accomplished."
These findings offer "an unexpected and elegant explanation that's both beautiful and simple, as nature invariably proves to be."
The fundamental mechanism of transcription is conserved among cellular RNA polymerases, the researchers explained. Common features include an unwound region of about 15 base pairs of the DNA with some eight residues of the RNA transcript hybridized with the DNA in the center of the 'transcription bubble.' The enzyme polymerases involved are capable of moving both forward and backward on the DNA. Forward movement is favored by the binding of NTPs, while backtracking occurs especially when the enzyme encounters an impediment, such as damaged DNA.
Kornberg's group captured the first picture of the polymerase II transcribing complex by X-ray crystallography in 2001. Those structures revealed the complex with a nucleotide still in the enzyme's addition site, just after it had been added to the RNA transcript.
Later X-ray structures revealed the transcribing complex with the addition site available for entry of a matched NTP. Those crystals uncovered a second NTP-binding site on the transcribing enzyme, dubbed the entry site. While all NTPs can bind the entry site, only an NTP matched for base-pairing with the DNA template binds the addition site for attachment to the growing RNA strand, Kornberg said.
Yet the question of how the enzyme achieves such a high degree of discrimination between matched and mismatched NTPs remained unanswered.
The chemical attraction alone between RNA bases - adenine, cytosine, guanine, and uracil - and their complementary bases on the DNA template strand is far from sufficient to account for the incredible selectivity of polymerase II, Kornberg said. And the scientists didn't know either how the polymerase avoids substituting the NTPs that constitute DNA for the correct RNA building blocks, molecules that differ by only one oxygen atom.
In search of an explanation in the current study, the researchers screened hundreds of crystals to achieve higher data quality and resolution than ever before.
"In the course of the work, we saw something that had never been noticed before - additional protein density beneath the matching nucleotide," Kornberg said.
The team traced that protein density back to a portion of the polymerase II enzyme: the trigger loop.
"Of the 14 crystal structures now reported in which the trigger loop was observed, only in two is it seen in that location, directly beneath the NTP," Kornberg said. "Those were the only two crystals in which the NTP was correctly matched to the DNA template, evidence of the trigger loop's clear relationship to NTP selection."
Further study revealed that, when a matching NTP reaches the addition site, the trigger loop swings from its usual position some distance away until it rests parallel to the NTP. It then forms a network of interactions - some 20 to 30 in all - with components of the NTP, a process that serves to "recognize all features of the NTP in the addition site and detect its precise location," the researchers reported.
"The specificity is a result of the alignment with the NTP that is critically dependent upon the base, sugar, phosphate and location when the trigger loop swings into position," Kornberg said. "If it is misaligned even slightly, that set of contacts cannot occur."
As a consequence of that alignment, to angstrom (a unit of length equal to one hundred millionth of a centimeter) precision, a histidine side chain of the trigger loop rests on the phosphate, the chemical constituent that must have its bond broken in order for the NTP to join the RNA chain through the formation of a phosphodiester bond, Kornberg said. The finding suggested the side chain acts as a trigger for bond formation.
The whole decision-making process occurs extremely rapidly, he added, on the order of picoseconds. A picosecond is one trillionth of a second.
"The basis for the extraordinary specificity with which RNA polymerases transcribe DNA lies in a structural element termed the trigger loop, which makes both direct and indirect contact with all features of the nucleotide in the polymerase active center," the researchers concluded.
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The researchers include Dong Wang, David A. Bushnell, Kenneth D. Westover, Craig D. Kaplan, and Roger D. Kornberg of Stanford University School of Medicine in Stanford, CA.
This research was supported by NIH grants GM49985 and GM36559 to R.D.K. C.D.K. was supported by a Fellowship from the Helen Hay Whitney Foundation. Portions of the research were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program, and the National Institute of General Medical Sciences. Portions of this research were conducted at the Advanced Light Source, a national user facility operated by Lawrence Berkeley National Laboratory, on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The Berkeley Center for Structural Biology is supported in part by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Institute of General Medical Sciences.
Wang et al.: 'Structural Basis of Transcription: Role of the Trigger Loop in Substrate Specificity and Catalysis.' Publishing in Cell 127, 941 - 954, December 1, 2006. DOI 10.1016/j.cell.2006.11.023 http://www.cell.com
Contact: Heidi Hardman
Cell Press
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