SACRAMENTO ? After six months of wrangling, California lawmakers put the finishing touches on what they hope will be compromise foreclosure-prevention legislation.
The measure is part of a larger Homeowner Bill of Rights package of bills sponsored by state Atty. Gen. Kamala D. Harris aimed at helping borrowers who are behind on mortgage payments avoid foreclosures. A draft of the bill was made public late Friday.
The bill would lock into California law many of the terms of a national foreclosure lawsuit settlement with five big banks.
California has been hit hard by a wave of foreclosures that started in the recession of 2007-09. Last year, 38 of the nation's 100 most foreclosure-prone ZIP Codes were in the state.
"The California Homeowner Bill of Rights will help ensure that struggling California borrowers with the means and desire to stay in their homes will have real access to a process that will allow them to do so," Harris said in a statement.
A two-house legislative conference committee is expected to approve the bill, SB 900, next week and send the package to the floors of both the state Assembly and Senate for final debates and votes.
Passage by the conference committee, which has four majority Democratic and two Republican members, is considered assured now that a key, business-friendly Democrat, Sen. Ron Calderon of Montebello, has signaled his support.
"I followed two key principles throughout the development of the conference committee report: fair treatment of borrowers and the need to keep California's economic recovery on track," Calderon said. "Losing a home to foreclosure is a heartbreak that should be avoided whenever and wherever possible. Californians can rest assured that the conference committee report tackles the most egregious behavior displayed throughout the foreclosure crisis."
The bill contains a number of provisions that have rankled bankers, mortgage servicers and their allies in the real estate industry.
One such provision would require mortgage loan servicers to give their borrowers a single point of contact instead of bouncing them around from office to office.
A second would limit banks' ability to begin a foreclosure process if the borrowers have filed documents requesting a loan modification that would lower their monthly payments.
A third would give homeowners the ability to sue servicers, under certain restrictions, alleging that they were wrongly foreclosed upon.
"I think this is a product that represents a lot of significant compromises but, at the end of the day, is a step forward," said Paul Leonard, director of the Center for Responsible Lending in Oakland.
Mortgage bankers declined to comment on the substance of the bill, saying they had not fully reviewed the 23-page document.
However, Dustin Hobbs, a spokesman for the California Mortgage Bankers Assn., said his group's members were disappointed that the Democrat-dominated committee is "rushing" to a vote, "giving interested parties and the public virtually no time to digest the information and provide substantial feedback."
More than 400,000 Chevrolet Cruze sedans are covered by a new recall.
By Paul A. Eisenstein, The Detroit Bureau
It?s been a busy year for automotive safety regulators ? and dealer service shops ? with a growing number of makers announcing recalls including a series of problems that could potentially lead to vehicle fires.
The latest on that list is General Motors.? The Maker says it is recalling 413,418 late-model Chevrolet Cruze sedans to modify the engine shield under the vehicle.? And a small number of vehicles involved in that service action could be covered by a separate recall covering 249 vehicles that may not have had their fuel tank straps properly welded into place.?
Tesla Model S: The Battery Car Market?s Moon Shot?
?The most important thing for our customers to know is that we are proactively working to assure the Cruze is the safe and durable car they purchased,? said GM vice president of Global Quality Alicia Boler-Davis. ?We are sorry for any inconvenience caused by these actions.?
The maker says it knows of no crashes, fatalities or injuries connected with either recall, though reports of two fires spurred the bigger recall. ?
Details Leak on New 2013 Honda Accord?
The larger of the two recalls covers all Chevy Cruze vehicles built at the Lordstown plant in Ohio between September 2010 and May 2012 and sold during the 2011 and 2012 model-years.? Information identifying where and when a vehicle was assembled can be found on a plate in the driver?s door jamb. Chevrolet also plans to notify owners of the affected vehicles.
The problem with the faulty engine shield is two-fold.? First, if oil accidentally spills during an oil change it can contact hot engine or exhaust components and cause the shield, in turn, to catch fire.? For Cruze models equipped with a manual gearbox, leakage of transmission fluid could also cause a fire.?
Acura Went ?Overboard? Says New Design Chief?
Repairs under both recalls will be handled at no charge.? GM says the engine shield work will require about 30 minutes.? If a vehicle is also found to have faulty fuel tank strap welds that work will take an additional three hours.
Among the other makers recently involved in recalls or preliminary investigations linked to potential fire hazards are Toyota and Jeep.? Last week, the National Highway Traffic Safety expanded the Toyota recall from 800,000 to 1.4 million vehicles, including some Camry and RAV4 models, due to defective driver window switches.? NHTA also expanded to 5 million the number of Jeep vehicles under investigation due to potential problems with rear-mounted fuel tanks.
CelebrityPress, a leading fitness and health book publishing company, has recently signed a publishing deal with several leading health and fitness professionals from around the world to release ? The Fad Free Fitness Formula.?
Orlando, Fla. ? June 20, 2012 - A select group of the world?s leading health and fitness entrepreneurs have joined together to co-author the forthcoming book titled, The Fad Free Fitness Formula: The World?s Leading Fitness Professionals Reveal Fad Free, Tried and True Strategies to Become Lean, Fit and Healthy. Nick Nanton, Esq. along with business partner, JW Dicks, Esq., the leading agents to Celebrity Experts? worldwide, recently signed a publishing deal with each of these authors to contribute their expertise to the book, which will be released under their CelebrityPress? imprint.
The forthcoming book will feature top advice from health, fitness and wellness experts from across the globe on the subjects of total body health, fitness and nutrition. The Fad Free Fitness Formula: The World?s Leading Fitness Professionals Reveal Fad Free, Tried and True Strategies to Become Lean, Fit and Healthy will feature topics such as setting up a training system, the best exercise for fat loss, reducing stress, aging and training myths, fitness as a form of health care, interval training and helping entrepreneurs fit fitness into their work day, among others. The book is expected to be published later this year.
Some of the authors contributing to The Fad Free Fitness Formula include: Matt Hancocks,? Nicholas Osborne, Stephen Holt, Matt Luxton, Callie E. Durbrow, Jon Le Tocq, Dax Moy, Bruce Kelly, Ryan P. Toth, John David Eberley, Sean Millhouse, George Sinclair Comack, Aleksandra Stanic, Dewayne Holifield, Shawn Guiney, Priscilla Freed, Nick Berry and Pat Rigsby.
Other books recently released by CelebrityPress? include:
The Wellness Code: Your Ultimate Guide to Health, Fitness and Nutrition
The Definitive Guide To Burning Fat and Building Muscle
Total Body Breakthroughs: The World?s Leading Experts Reveal Proven Health, Fitness & Nutrition Secrets To Help You Achieve The Body You?ve Always Wanted But Couldn?t Until Now!
Champions: Knockout Strategies For Health, Wealth and Success From Today?s Leading Experts
The Definitive Guide to Youth Athletic Strength, Conditioning and Performance
3 Steps To Your Best Body in Record Time
About Celebrity Press?:
Celebrity Press? is a leading business, health and wellness book publisher that publishes books from thought leaders around the world. Celebrity Press? has published books alongside Jack Canfield, Brian Tracy, Dan Kennedy, Dr. Ivan Misner, Robert Allen and many of the biggest experts across diverse fields. CelebrityPress? has helped launch over 600 best-selling authors to date.
If you?d like to learn more about Celebrity Press? or to see if we?re a good fit for your book project, please visit http://www.celebritypresspublishing.com/contact-us
?
Sign Up Here to Stay Up To Date
on New Releases and News
from Your Favorite Authors!
Claim Your FREE SPECIAL REPORT - "The New Rules of Becoming An Author - The 7 Myths of Publishing Success"
There are many misconceptions people about what publishing is all about - and just what is needed (or not needed) to get a book published. We'd like to dispel all that misinformation from our extensive combined experience publishing over the last three decades and give you the lowdown on the "7 Myths of Publishing Success". For FREE. Just complete the short form below and we will send you your report right away.
Hey my friend, I just want to let you know that we were on the news this past weekend for Child Abduction Prevention and will be on the Dr. Veronica Show this coming Tuesday. The ...read more
[ [ [['Connery is an experienced stuntman', 2]], 'http://yhoo.it/KeQd0p', '[Slideshow: See photos taken on the way down]', ' ', '630', ' ', ' ', ], [ [['Connery is an experienced stuntman', 7]], ' http://yhoo.it/KpUoHO', '[Slideshow: Death-defying daredevils]', ' ', '630', ' ', ' ', ], [ [['know that we have confidence in', 3]], 'http://yhoo.it/LqYjAX ', '[Related: The Secret Service guide to Cartagena]', ' ', '630', ' ', ' ', ], [ [['We picked up this other dog and', 5]], 'http://yhoo.it/JUSxvi', '[Related: 8 common dog fears, how to calm them]', ' ', '630', ' ', ' ', ], [ [['accused of running a fake hepatitis B', 5]], 'http://bit.ly/JnoJYN', '[Related: Did WH share raid details with filmmakers?]', ' ', '630', ' ', ' ', ], [ [['accused of running a fake hepatitis B', 3]], 'http://bit.ly/KoKiqJ', '[Factbox: AQAP, al-Qaeda in Yemen]', ' ', '630', ' ', ' ', ], [ [['have my contacts on or glasses', 3]], 'http://abcn.ws/KTE5AZ', '[Related: Should the murder charge be dropped?]', ' ', '630', ' ', ' ', ], [ [['have made this nation great as Sarah Palin', 5]], 'http://yhoo.it/JD7nlD', '[Related: Bristol Palin reality show debuts June 19]', ' ', '630', ' ', ' ', ], [ [['have made this nation great as Sarah Palin', 1]], 'http://bit.ly/JRPFRO', '[Related: McCain adviser who vetted Palin weighs in on VP race]', ' ', '630', ' ', ' ', ], [ [['A JetBlue flight from New York to Las Vegas', 3]], 'http://yhoo.it/GV9zpj', '[Related: View photos of the JetBlue plane in Amarillo]', ' ', '630', ' ', ' ', ], [ [['the 28-year-old neighborhood watchman who shot and killed', 15]], 'http://news.yahoo.com/photos/white-house-stays-out-of-teen-s-killing-slideshow/', 'Click image to see more photos', 'http://l.yimg.com/cv/ip/ap/default/120411/martinzimmermen.jpg', '630', ' ', 'AP', ], [ [['He was in shock and still strapped to his seat', 6]], 'http://news.yahoo.com/photos/navy-jet-crashes-in-virginia-slideshow/', 'Click image to see more photos', 'http://l.yimg.com/cv/ip/ap/default/120406/jet_ap.jpg', '630', ' ', 'AP', ], [ [['xxxxxxxxxxxx', 11]], 'http://news.yahoo.com/photos/russian-grannies-win-bid-to-sing-at-eurovision-1331223625-slideshow/', 'Click image to see more photos', 'http://l.yimg.com/a/p/us/news/editorial/1/56/156d92f2760dcd3e75bcd649a8b85fcf.jpeg', '500', ' ', 'AP', ] ]
[ [ [['did not go as far his colleague', 8]], '29438204', '0' ], [ [[' the 28-year-old neighborhood watchman who shot and killed', 4]], '28924649', '0' ], [ [['because I know God protects me', 14], ['Brian Snow was at a nearby credit union', 5]], '28811216', '0' ], [ [['The state news agency RIA-Novosti quoted Rosaviatsiya', 6]], '28805461', '0' ], [ [['measure all but certain to fail in the face of bipartisan', 4]], '28771014', '0' ], [ [['matter what you do in this case', 5]], '28759848', '0' ], [ [['presume laws are constitutional', 7]], '28747556', '0' ], [ [['has destroyed 15 to 25 houses', 7]], '28744868', '0' ], [ [['short answer is yes', 7]], '28746030', '0' ], [ [['opportunity to tell the real story', 7]], '28731764', '0' ], [ [['entirely respectable way to put off the searing constitutional controversy', 7]], '28723797', '0' ], [ [['point of my campaign is that big ideas matter', 9]], '28712293', '0' ], [ [['As the standoff dragged into a second day', 7]], '28687424', '0' ], [ [['French police stepped up the search', 17]], '28667224', '0' ], [ [['Seeking to elevate his candidacy back to a general', 8]], '28660934', '0' ], [ [['The tragic story of Trayvon Martin', 4]], '28647343', '0' ], [ [['Karzai will get a chance soon to express', 8]], '28630306', '0' ], [ [['powerful storms stretching', 8]], '28493546', '0' ], [ [['basic norm that death is private', 6]], '28413590', '0' ], [ [['songwriter also saw a surge in sales for her debut album', 6]], '28413590', '1', 'Watch music videos from Whitney Houston ', 'on Yahoo! Music', 'http://music.yahoo.com' ], [ [['keyword', 99999999999999999999999]], 'videoID', '1', 'overwrite-pre-description', 'overwrite-link-string', 'overwrite-link-url' ] ]
All Critics (58) | Top Critics (10) | Fresh (56) | Rotten (1) | DVD (9)
It's among the most understated anti-war films ever made, effortlessly humanistic but far too subtle to indulge in preaching.
A model of simplicity and grace, with emotional effects that move you when you least expect it, the kind of great film that only a master can pull off.
It's still one of the key humanist expressions to be found in movies: sad, funny, exalting, and glorious.
It's an excellent film, with Renoir's usual looping line and deft shifts of tone, though today the balance of critical opinion has shifted in favor of the greater darkness and filigree of The Rules of the Game.
An artistically masterful feature, the picture breathes the intimate life of warriors on both sides during the [First] World War.
Renoir has created a strange and interesting film, but he owes much to his cast.
Its very simplicity of utterance gives it a purity that makes other films that try to express similar sentiments feel forced and obvious.
Funny, heart-wrenching, nail-biting, caustic and profound, touting the futility of armed combat while turning imprisonment and escape into a microcosm for society's aspirations and contradictions.
Renoir's 1937 anti-war masterpiece created a new genre, the POW movie, and with his 1939 La R?gle du jeu constitutes a diptych of unparalleled excellence.
A timeless classic of acting and filmmaking genius that uses the artificiality of war to explore the very construct of society, and is a classic must-see.
The great illusion is that these men of the officer class are somehow different from the masses who suffered the bloodiest of wars. Renoir proves that they are not.
A vividly humanist, anti-war classic.
A sorrowful, acutely thoughtful, and wholly imperishable masterpiece...
Tragic. Moving. Funny. A pure joy.
The film makes its moral point about the futility of combat by emphasising the interconnectedness of all humanity via such shared experiences as hunger, desire and friendship. It's also a ripping yarn with a vein of charming and sometimes risqu? humour.
La Grande Illusion retains its power as an example of European camaraderie and co-operation.
It ranks proudly alongside The Rules Of The Game as Renoir at his stunning best.
La Grande Illusion is a sublimely poignant and lucidly insightful commentary on the social legacy of the Great War in Europe.
Poetically photographed and poignantly performed, this is a film rich in humour and, above all, humanity towards its characters. Even 60 years on, it remains deeply moving.
More Critic Reviews
No quotes approved yet for La Grande illusion (The Grand Illusion). Logged in users can submit quotes.
University of Utah chemists use nanopores to detect DNA damagePublic release date: 18-Jun-2012 [ | E-mail | Share ]
Contact: Lee Siegel lee.siegel@utah.edu 801-581-8993 University of Utah
New sequencing method finds gaps that can lead to disease
SALT LAKE CITY, June 18, 2012 Scientists worldwide are racing to sequence DNA decipher genetic blueprints faster and cheaper than ever by passing strands of the genetic material through molecule-sized pores. Now, University of Utah scientists have adapted this "nanopore" method to find DNA damage that can lead to mutations and disease.
The chemists report the advance in the week of June 18 online edition of the journal Proceedings of the National Academy of Sciences.
"We're using this technique and synthetic organic chemistry to be able to see a damage site as it flies through the nanopore," says Henry White, distinguished professor and chair of chemistry at the University of Utah and senior coauthor of the new study.
Strands of DNA are made of "nucleotide bases" known as A, T, G and C. Some stretches of DNA strands are genes.
The new method looks for places where a base is missing, known as an "abasic site," one of the most frequent forms of damage in the 3-billion-base human genome or genetic blueprint. This kind of DNA damage happens 18,000 times a day in a typical cell as we are exposed to everything from sunlight to car exhaust. Most of the damage is repaired, but sometimes it leads to a gene mutation and ultimately disease.
By combining nanopore damage-detection with other chemical ways of altering DNA, the researchers hope to make this new technique capable of detecting other kinds of DNA damage by converting the damage to a missing base, says the study's other senior coauthor, Cynthia Burrows, a distinguished professor of chemistry at the University of Utah.
She adds: "Damage to the bases of DNA contributes to many age-related diseases, including melanoma; lung, colon and breast cancers; Huntington's disease; and atherosclerosis."
A patent is pending on the new method of doing chemistry on DNA that allows damage sites to be found using nanopore technology.
White and Burrows conducted the study with first author, Na An, a doctoral student in chemistry and Aaron Fleming, a postdoctoral research associate in chemistry. The study was funded by the National Institutes of Health, with equipment and software donations by Electronic BioSciences of San Diego.
Toward Cheaper, Faster DNA Sequencing
Sequencing is the process of determining the order of the nucleotide bases A, C, G and T in one of the two strands of bases that make up a DNA double helix. It is the basic method used to determine the genomes, or genetic blueprints, of living organisms and to identify disease-causing mutations in genes.
"Twenty years ago, it cost $1 billion to sequence the first human genome," while the cost now runs from $5,000 to $20,000, White says. "The National Institutes of Health has had the $1,000 genome project for a few years, and the price likely will go lower."
`
DNA sequencing is important in many ways. It is used by police to implicate or clear criminal suspects and by biologists to understand each living organism. "You can use it in agriculture if you modify a plant genome to produce a better plant," White says.
Faster, cheaper genomes of individual people promise an era of "personalized medicine," with treatments based on each person's genetic susceptibilities.
Nanopore sequencing is performed by passing a strand of DNA through a nanoscopic pore while both are bathed in an electrically charged solution known as an electrolyte. Some of that solution also is flowing through the pore. Researchers detect different current levels as differing DNA bases pass through the pore, blocking varying amounts of the electrified solution from passing through the pore.
Using Nanopores to Look for Damage
Unlike efforts to achieve nanopore sequencing of DNA, the Utah chemists are not reading the sequence of DNA bases as the strand move through a pore although they eventually want to do so but "we are detecting single base damage," White says.
"It's important to know how a damaged base leads to a mutation because that is the first step in a disease occurring," he adds. "Right now, we can see the damaged site and tell approximately where it is within the piece of DNA we're analyzing" to within about five or 10 bases. The goal is to pinpoint damage sites, and to understand how damage at specific sites leads to disease.
So far, the longest piece of DNA the Utah chemists put through a nanopore was about 100 bases long, and they were able to detect one or two damage sites.
"We've still got to do a lot of research and come up with ways of improving this," White says. "It's a very promising and new way of doing it. There are no other ways of doing what we're trying to do," namely, not only identify damage, but get sequence information to pinpoint damaged locations on a DNA strand.
The pore used by many DNA sequencers and by the Utah chemists is named alpha-hemolysin, and is a protein that comes from bacteria. To pass DNA through such a pore, a tiny hole only 400 nanometers wide, about a half percent as wide as a human hair is made in a glass membrane in the bottom of a glass tube. A soapy solution (known as a lipid bilayer) spreads out and forms film across that hole. The protein pore is embedded within the lipid bilayer.
The protein pore is somewhat mushroom shaped wider at the top where the DNA strand is captured and narrower at the bottom where the strand must pass through a tiny hole. The narrowest part of the pore measures 1.4 nanometers wide, not much wider than the 1-nanometer-wide single strand of DNA that must pass through the pore.
The billions of bases that make up a DNA strand are attached to a backbone of sugar and phosphate. To look for DNA damage in the form of a missing base, the researchers turn on the voltage, which makes current flow through the electrolyte. A positive electrode in the liquid outside the pore pulls DNA through the pore because the DNA has negatively charged phosphates making up its backbone.
The researchers created damage on some DNA by removing some bases. Where bases were missing, the sugar in the DNA backbone was exposed. The chemists attached a ring- or crown-shaped chemical known as an "18-crown-6 ether" to the sugar.
The trick was to get the DNA, with the crown ether attached, to pass through the nanopore slowly enough so missing bases can be detected.
Burrows compares the process to threading a needle. The DNA strand, once threaded through the eye of the needle, can be pulled through quickly and the presence of a tiny damage site a nick in the thread will never be noticed. Except in this case, chemists have converted the nick to a tiny loop in the thread, the crown ether. How fast the DNA can move through the tiny pore depends on the stiffness and size of the crown ether loop that marks the site of DNA damage. This can be changed with the addition of salts that attach to the loop.
The chemists tested different salts to find the best one to use as an electrolyte: potassium chloride, lithium chloride and sodium chloride, which is table salt. Whatever salt is used, the positive ion (potassium, lithium or sodium) gets bound inside the loop. That helps researchers read the current as a DNA strand moves through the pore.
But potassium was too big, making the ether loop so rigid it couldn't squeeze through the nanopore. Lithium was too small, making the ether loop slide through the nanopore too fast for damage to be detected.
But when Burrows and colleagues used sodium from table salt, the DNA and crown ether marking DNA damage sites both slid through the nanopore at just the right speed to be detected: about one-millionth of a second for an undamaged DNA base and about one-thousandth of a second for a crown ether loop marking where a base was missing, Burrows says.
###
University of Utah Communications
201 Presidents Circle, Room 308
Salt Lake City, Utah 84112-9017
(801) 581-6773 fax: (801) 585-3350
www.unews.utah.edu
[ | E-mail | Share ]
?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
University of Utah chemists use nanopores to detect DNA damagePublic release date: 18-Jun-2012 [ | E-mail | Share ]
Contact: Lee Siegel lee.siegel@utah.edu 801-581-8993 University of Utah
New sequencing method finds gaps that can lead to disease
SALT LAKE CITY, June 18, 2012 Scientists worldwide are racing to sequence DNA decipher genetic blueprints faster and cheaper than ever by passing strands of the genetic material through molecule-sized pores. Now, University of Utah scientists have adapted this "nanopore" method to find DNA damage that can lead to mutations and disease.
The chemists report the advance in the week of June 18 online edition of the journal Proceedings of the National Academy of Sciences.
"We're using this technique and synthetic organic chemistry to be able to see a damage site as it flies through the nanopore," says Henry White, distinguished professor and chair of chemistry at the University of Utah and senior coauthor of the new study.
Strands of DNA are made of "nucleotide bases" known as A, T, G and C. Some stretches of DNA strands are genes.
The new method looks for places where a base is missing, known as an "abasic site," one of the most frequent forms of damage in the 3-billion-base human genome or genetic blueprint. This kind of DNA damage happens 18,000 times a day in a typical cell as we are exposed to everything from sunlight to car exhaust. Most of the damage is repaired, but sometimes it leads to a gene mutation and ultimately disease.
By combining nanopore damage-detection with other chemical ways of altering DNA, the researchers hope to make this new technique capable of detecting other kinds of DNA damage by converting the damage to a missing base, says the study's other senior coauthor, Cynthia Burrows, a distinguished professor of chemistry at the University of Utah.
She adds: "Damage to the bases of DNA contributes to many age-related diseases, including melanoma; lung, colon and breast cancers; Huntington's disease; and atherosclerosis."
A patent is pending on the new method of doing chemistry on DNA that allows damage sites to be found using nanopore technology.
White and Burrows conducted the study with first author, Na An, a doctoral student in chemistry and Aaron Fleming, a postdoctoral research associate in chemistry. The study was funded by the National Institutes of Health, with equipment and software donations by Electronic BioSciences of San Diego.
Toward Cheaper, Faster DNA Sequencing
Sequencing is the process of determining the order of the nucleotide bases A, C, G and T in one of the two strands of bases that make up a DNA double helix. It is the basic method used to determine the genomes, or genetic blueprints, of living organisms and to identify disease-causing mutations in genes.
"Twenty years ago, it cost $1 billion to sequence the first human genome," while the cost now runs from $5,000 to $20,000, White says. "The National Institutes of Health has had the $1,000 genome project for a few years, and the price likely will go lower."
`
DNA sequencing is important in many ways. It is used by police to implicate or clear criminal suspects and by biologists to understand each living organism. "You can use it in agriculture if you modify a plant genome to produce a better plant," White says.
Faster, cheaper genomes of individual people promise an era of "personalized medicine," with treatments based on each person's genetic susceptibilities.
Nanopore sequencing is performed by passing a strand of DNA through a nanoscopic pore while both are bathed in an electrically charged solution known as an electrolyte. Some of that solution also is flowing through the pore. Researchers detect different current levels as differing DNA bases pass through the pore, blocking varying amounts of the electrified solution from passing through the pore.
Using Nanopores to Look for Damage
Unlike efforts to achieve nanopore sequencing of DNA, the Utah chemists are not reading the sequence of DNA bases as the strand move through a pore although they eventually want to do so but "we are detecting single base damage," White says.
"It's important to know how a damaged base leads to a mutation because that is the first step in a disease occurring," he adds. "Right now, we can see the damaged site and tell approximately where it is within the piece of DNA we're analyzing" to within about five or 10 bases. The goal is to pinpoint damage sites, and to understand how damage at specific sites leads to disease.
So far, the longest piece of DNA the Utah chemists put through a nanopore was about 100 bases long, and they were able to detect one or two damage sites.
"We've still got to do a lot of research and come up with ways of improving this," White says. "It's a very promising and new way of doing it. There are no other ways of doing what we're trying to do," namely, not only identify damage, but get sequence information to pinpoint damaged locations on a DNA strand.
The pore used by many DNA sequencers and by the Utah chemists is named alpha-hemolysin, and is a protein that comes from bacteria. To pass DNA through such a pore, a tiny hole only 400 nanometers wide, about a half percent as wide as a human hair is made in a glass membrane in the bottom of a glass tube. A soapy solution (known as a lipid bilayer) spreads out and forms film across that hole. The protein pore is embedded within the lipid bilayer.
The protein pore is somewhat mushroom shaped wider at the top where the DNA strand is captured and narrower at the bottom where the strand must pass through a tiny hole. The narrowest part of the pore measures 1.4 nanometers wide, not much wider than the 1-nanometer-wide single strand of DNA that must pass through the pore.
The billions of bases that make up a DNA strand are attached to a backbone of sugar and phosphate. To look for DNA damage in the form of a missing base, the researchers turn on the voltage, which makes current flow through the electrolyte. A positive electrode in the liquid outside the pore pulls DNA through the pore because the DNA has negatively charged phosphates making up its backbone.
The researchers created damage on some DNA by removing some bases. Where bases were missing, the sugar in the DNA backbone was exposed. The chemists attached a ring- or crown-shaped chemical known as an "18-crown-6 ether" to the sugar.
The trick was to get the DNA, with the crown ether attached, to pass through the nanopore slowly enough so missing bases can be detected.
Burrows compares the process to threading a needle. The DNA strand, once threaded through the eye of the needle, can be pulled through quickly and the presence of a tiny damage site a nick in the thread will never be noticed. Except in this case, chemists have converted the nick to a tiny loop in the thread, the crown ether. How fast the DNA can move through the tiny pore depends on the stiffness and size of the crown ether loop that marks the site of DNA damage. This can be changed with the addition of salts that attach to the loop.
The chemists tested different salts to find the best one to use as an electrolyte: potassium chloride, lithium chloride and sodium chloride, which is table salt. Whatever salt is used, the positive ion (potassium, lithium or sodium) gets bound inside the loop. That helps researchers read the current as a DNA strand moves through the pore.
But potassium was too big, making the ether loop so rigid it couldn't squeeze through the nanopore. Lithium was too small, making the ether loop slide through the nanopore too fast for damage to be detected.
But when Burrows and colleagues used sodium from table salt, the DNA and crown ether marking DNA damage sites both slid through the nanopore at just the right speed to be detected: about one-millionth of a second for an undamaged DNA base and about one-thousandth of a second for a crown ether loop marking where a base was missing, Burrows says.
###
University of Utah Communications
201 Presidents Circle, Room 308
Salt Lake City, Utah 84112-9017
(801) 581-6773 fax: (801) 585-3350
www.unews.utah.edu
[ | E-mail | Share ]
?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.