Volume 25, Aug 22, 2006

Please see our “Did You Know?” section toward the end of this issue.

Topic: Surprise Finding For Stretched DNA

This issue of The DNA Informant includes stories addressing the future of DNA research and how it will become more and more helpful in police work, in detecting genetic diseases and of course how these advances will affect people’s privacy. Professor Buzz Scherr, from the Franklin Pierce Law Center has received a grant to “study the relationship between genetic science, police techniques and privacy rights.”

The Innocence Project has reopened 17 investigations. “The added cases, all of which were closed in the last decade after police said the evidence was lost or destroyed, bring to 23 the number of open investigations at the Innocence Project…” More efforts continue to be put on solving missing persons cases. In Los Angeles, “about $62,000 of a $882,399 federal grant is earmarked for the Missing Person DNA program”.

And again we are including a number of new and ongoing cases involving the use of DNA evidence.

Where DNA and law intersect  

As any fan of CSI knows, it's amazing what those forensic scientists can do. But as incredible as the feats are that investigators perform with hair, fibers and fingerprints, they will be better in the future.

One day, the police will be able to scan left behind cells for genetic information, such as a person's DNA signature or the likelihood that he or she has a certain disease or personality trait.

Buzz Scherr, a professor at Franklin Pierce Law Center, thinks that such advances are going to lead to increasingly complicated questions about constitutional privacy. He's just won a $50,000 grant from the National Institute of Health to study the relationship between genetic science, police techniques and privacy rights.

"As the technology continues to develop, as we're going to be able to take smaller and smaller amounts of trace DNA or body cells all over and mine those for all sorts of genetic information, we're going to have to start thinking about things that we don't have to think about now," he said.

The Fourth Amendment of the Constitution limits how the police can search for evidence. The courts have interpreted the amendment to mean, that in many cases, the police need to prove to a judge that there's good reason to believe a search can turn up important evidence of a crime. So, for example, the police can't search your home for a hidden weapon until they've gotten a search warrant.

But judges have interpreted the Fourth Amendment more loosely when it comes to things outside the home or person, where a defendant doesn't expect to have privacy. The police could search a public bus station for a weapon without a search warrant, or they could lift a fingerprint off of a soda can that a suspect used during an interrogation.

In the case of James Dale, who was convicted of raping and murdering 6-year-old Elizabeth Knapp of Contoocook in 1999, the police used saliva he left on a discarded cigarette butt to build their case. Dale had been picked up for violating parole conditions, but the police had no evidence linking him to the killing. All they knew was that he'd lived in the same building as Knapp at the time of the murder.

That probably wouldn't have been enough to persuade a judge to give them a warrant for a blood sample. But DNA that investigators took from Dale's cigarette matched crime scene evidence and provided probable cause for them to seek a warrant for more rigorous genetic tests. Ultimately, those tests linked Dale to the murdered girl.

In the future, Scherr said, the police may be able to pull DNA from even smaller samples, and they may be able to use those samples to find out increasingly detailed and personal information. In a few years, he said, they will be able to extract DNA from a used coffee cup you threw in the trash, or, perhaps, from skin cells you smeared on a doorknob. With your DNA, they may be able to uncover hints about your physical makeup, personality or health that they could use in court.

Those sorts of traits might invoke another constitutional issue: the Fifth Amendment's protections against self-incrimination. If genetic information can tell the police damning things about a suspect, shouldn't the suspect be able to keep that information to himself?

Scherr's study will draw on law, science and philosophy to consider whether such genetic information deserves special treatment. Under current case law, Scherr said, the police probably wouldn't need a search warrant to test a discarded coffee cup.

"Do we want to view the DNA on that coffee cup as abandoned property? Do we want to think about it as property that we've abandoned, or do we want to think about another paradigm?" he said. "Given that it's genetic information, should we be treating it differently?"

Scherr's grant comes from the NIH's Human Genome Project. Most of the project's money is used to fund scientific and medical research, but since its inception, it has set aside 5 percent to fund research into the ethical, legal and social issues surrounding genetic science.

"We also fund research that looks at sort of broader societal issues, and one set of those issues is how the information could be used or might be used in nonmedical settings," said Jean McEwen, a program director at the project.

Scherr's plan is to write and publish several law review articles on his findings and to speak at a number of academic conferences over the next two years. His hope is that his work will contemplate the constitutional questions surrounding genetic technology before they become commonplace.

"I think it's inevitable that we're going to have the instinct that there's something different about this in the next five or 10 years," he said. "The legal system is always a step behind."

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref01.html

17 Cases Are Eyed Over Doubts On DNA Evidence

Using the momentum from the exoneration of a man who served 22 years of a 40-year sentence for rape before evidence surfaced that showed he was innocent, the Innocence Project has reopened 17 investigations.

The added cases, all of which were closed in the last decade after police said the evidence was lost or destroyed, bring to 23 the number of open investigations at the Innocence Project, a legal clinic at Cardozo Law School that helps people convicted of a crime get DNA tests.

At the heart of the reopenings is a concern that the New York Police Department does not properly store DNA evidence at the Pearson Place Warehouse in Long Island City, Queens, a staff attorney for the project, Vanessa Potkin, said.

The facility stores crime evidence for the five boroughs and contains more than 1.6 million invoices for property. A single invoice could represent dozens of items: A counterfeit shipment of hundreds of compact discs could be registered under one invoice, police officials said.

While in prison, Mr. Newton, 45, tried three times to get the rape kit's DNA evidence tested, which wasn't courtroom protocol when he was arrested and convicted, but police told his lawyers in a letter that the rape kit was destroyed at a previous facility. The evidence was eventually found — with the help of the chief sex crimes prosecutor in the Bronx, Elisa Koenderman — in the exact place it was supposed to be stored, Ms. Potkin said.

A spokesman for the police department, Assistant Chief Michael Collins, said Mr. Newton's evidence couldn't be found earlier because the property invoice was lost during one of two accidents at an old facility at the corner of Meeker and Morgan avenues in Brooklyn. The first incident was a fire in July 1995 that was started by sparks from a construction site at the Bronx-Queens Expressway, and the second was an asbestos leak in September 1995 after a truck crashed into the facility. Without an invoice, it is nearly impossible to determine where a piece of evidence is located in the warehouse, Chief Collins said.

The sergeant who contacted Mr. Newton's lawyers, Patrick McGuire, wrote similar letters to the Innocence Project in at least three of the cases that were recently reopened, Ms. Potkin said.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref02.html 

Grant aids DNA hunt for missing people

Tommy Bowman visited his aunt in Altadena and later went on a hike with relatives in the Angeles National Forest on a Saturday afternoon in 1957.

On the walk back, the 8-year-old went ahead of the group and told his cousins he would wait for them at the car. The Redondo Beach boy was never seen again.

His family is still waiting for Bowman 49 years after he vanished.

The Bowman case is among 28 missing-persons cases where Los Angeles County Sheriff's Department detectives have collected DNA samples from relatives that were included in a state DNA database. And detectives expect to collect more samples this year thanks to a grant from the National Institute of Justice.

About $62,000 of the $882,399 federal grant is earmarked for the Missing Person DNA program, according to sheriff's Sgt. Paul Mondry.

"We won't be hiring more people. Maybe utilizing more people to obtain the samples," said sheriff's Detective Diane Harris, who handles missing-person cases.

The Sheriff's Department has about 200 cases of missing adults and children dating as far back as the 1950s.

Under a 2001 law, officers must tell relatives of missing persons that they can choose to give DNA samples, which will be included in a database maintained by the state Department of Justice. Officers do the collecting.

The same law created the state's Missing Persons DNA program. DNA profiles from samples given by relatives and samples from the missing person are kept in one database called the family reference file. Another database holds DNA profiles generated from unidentified remains.

Police can use the family reference file to see if it matches any profiles in the other database. An agency trying to put a name to a John or Jane Doe case can also send in a sample to be checked against the database. State officials said a now grown kidnapped victim can also verify his identity with help from the database.

About 69 people have been identified, according to Aaron Carruthers, spokesman for the Attorney General's Office.

So far, Harris said there have been no matches on the databases in any of their cases.

The Department of Justice started receiving DNA samples in 2002, Carruthers said.

"Currently we have 961 samples that were either contributed by family members as reference samples or samples pulled from personal items belonging to the missing person, for example maybe a toothbrush," he said.

The program also has 836 samples from unidentified persons.

The Sheriff's Department started collecting DNA samples from relatives of missing adults and children in 2003. They've collected samples on 28 cases since then.

"We just did it in our spare time. Now with the grant we are able to have additional time to do this," Harris said.

Their plan is to have a day when people can come in to give DNA samples, she said.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref03.html 

New and ongoing cases involving the use of DNA evidence include: 

International - DNA testing will decide whether John Mark Karr, the man arrested in Bangkok in connection with the 1996 murder of JonBenet Ramsey, was involved in the six-year-old's death or is a fantasist.

As prosecutors awaited Mr Karr's return to the US from Thailand doubts surfaced about the bizarre nature of his confession and remarks he made to Thai police during questioning.

Thai immigration police said he had confessed that he collected JonBenet from school and drugged her with chloroform before sexually assaulting her. But the child beauty queen's body was found on Boxing Day 1996, during the school holidays. No traces of chloroform were found in her autopsy and she had not been raped.

DNA was found beneath the girl's fingernails and on her clothing that came from a Caucasian white male. Authorities have never said whether the DNA matched anyone on an FBI database.

A DNA mouth swab test was carried out on Mr Karr in Bangkok. The results are unknown. He will be given another test when he is handed over to prosecutors in Boulder, Colorado, where the murder took place.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref05.html

California - Armed with fresh DNA evidence, prosecutors took two elderly women into custody today for befriending, insuring and then allegedly murdering two homeless men for $2.2 million in death benefits. 
Investigators said biological evidence taken from a car linked to the women, which was allegedly used to run down one of the victims, contained traces of his DNA.

"Our tests of biological material came back positive [to Kenneth McDavid, one of the victims] with a degree of certainty beyond a number that I can count to," said LAPD Lt. Paul Vernon. 
Helen Golay, 75, appeared in Los Angeles County Superior Court this morning wearing a blue jacket over a striped blouse, with her hair parted down the middle. She appeared animated as she consulted with her lawyer, Roger Jon Diamond. 
Co-defendant Olga Rutterschmidt, 73, remained seated through most of the hearing, at which Los Angeles County Superior Court Commissioner James N. Bianco ordered their arraignment delayed until Aug. 29. 
Prosecutors could seek the death penalty against the pair in the deaths of Paul Vados, 73, who was covered by more than a dozen life insurance policies when he was run down by a car on La Brea Avenue in 1999, and McDavid, 50, who was covered by 23 policies when he was run down and killed by an automobile. 

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref06.html 

California - A blood sample collected from the bottom of Pamela Vitale's right foot contained a mixture of DNA belonging to her and Scott Dyleski, her accused killer, a DNA expert said Tuesday during testimony in Contra Costa County Superior Court.

Analysts also found a mixture of Dyleski's and Vitale's DNA on a balaclava, or ski mask, found inside an abandoned van near Dyleski's home. Vitale's DNA was extracted from blood stains on the mask, while his genetic profile was taken from a saliva sample collected from the mask's mouth area.

David Stockwell, a senior DNA analyst for the Contra Costa County Sheriff's Department, said the genetic profiles derived from the ski mask were strong enough to statistically rule out their having been left there by any other living human being.

He estimated that only one in 13 quadrillion Caucasian women could match the sample left by Vitale, and that one in 780 trillion Caucasian men would match Dyleski's DNA sample.

"There have never been that many humans" on Earth, Stockwell said.

Dyleski, 17, watched the testimony with no visible emotion. His father, Kenneth Dyleski, sat in the seating gallery behind him.

Scott Dyleski is accused of murdering Vitale in the morning hours of Oct. 15 during a robbery at her home in Lafayette's Hunsaker Canyon. Prosecutor Harold Jewett has presented evidence that Dyleski stole the credit information of his neighbors in the canyon and bought pot-growing equipment on the Internet. In addition, a crime checklist was discovered in Dyleski's room that spelled out a plan to knock out, kidnap and steal financial information.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref07.html 

Michigan - Police said Tuesday they have linked the DNA of a 37-year-old man to a string of murders of prostitutes on the city's east side. 

The man was arrested July 30 on suspicion of criminal sexual conduct after he grabbed a suspected prostitute, police said. Investigators say the man was trying to kill the woman. 

A warrant has not yet been issued against the man in the prostitute killings, but he is in police custody. 

Police said the man, an east-side resident, fit the profile of a suspect they had been seeking since 1999. 

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref08.html 

Michigan - “I don't want to have to look at this stuff, I don't want to have to think about burying my little sister, but that's where we are," David Hosler said Monday, holding back tears as he stood next to a shrine of toys piled in honor of Raven Jeffries on a weedy, dusty field a few doors from her home. 

Hours earlier, Hosler, 19, and his mother, Brenda Jeffries, 41, were notified that their 10-day vigil of hope was over. DNA tests confirmed that a badly burned body found Aug. 7 in a field in Romulus was that of 7-year-old Raven. 

Romulus Detective Lt. John Leacher said police are pursuing several leads. Although he would not comment, sources told The Detroit News that Raven was neither shot nor stabbed.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref09.html

Texas - It took more than 20 years, but two high-profile murder cases are now solved, and the killer is serving life sentences for the crimes. 
37-year-old Cedric Denell Compton admitted to the murders after DNA evidence proved he committed the crimes. 
Extra deputies were called into the courtroom as Compton pled guilty to the crimes. 
Prosecutor Nancy Mulder said, "Cedric Compton had threatened to take a bailiff's gun and shoot the judge and anybody else he could take down when he entered the courtroom." 
In shackles and chains, Compton admitted he killed 20-year-old Cathi Corken of Oklahoma.

Compton killed Cathi Corken when he was just 17 years old. Two years later he raped and strangled 25-year-old Tony Singleton. Her body was found under a house in south Dallas. 
Prosecutors say six weeks later he was convicted of aggravated robbery and received a 15 year sentence for the crime.  
They say DNA evidence in both cases is what led them to Compton. "DNA is truly a wonderful forensic tool in prosecution and as you've seen today it has brought closure to the families," Mulder said.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref10.html

Arkansas - Attorneys for condemned murderer Rickey Dale Newman say DNA tests on hairs prosecutors claim are from his victim are from someone else.

The attorneys, members of the federal public defenders office, said in a motion filed Thursday before U. S. District Judge Robert Dawson that DNA tests concluded that the hairs the state introduced as evidence as Marie Cholette’s did not match the DNA profile of blood samples taken from the 46-year-old transient.

The hairs were recovered from gloves belonging to Newman who was accused of murdering and mutilating Cholette in February 2001 at a homeless camp on the west edge of Van Buren. Newman initially confessed to the slaying.

“The results of this testing, which are fully exculpatory of Mr. Newman, provide significant support for Mr. Newman’s claims of actual innocence and ineffective assistance of counsel, as well as the applicability of the miscarriage of justice exception to any procedural defenses asserted by [the state ],” the motion states.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref11.html

North Carolina - DNA experts took the stand today in Barry Mintz's murder trial.

The experts testified that blood found on the shoes of Mintz and his friend David Allen matched the victim.

Prosecutors say Mintz and Allen beat Joe Bradshaw in a downtown Wilmington alley back in November 2004. Bradshaw died later from his injuries.

Allen pled guilty last week to second-degree murder. He is expected to testify against Mintz sometime next week.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref12.html

Kentucky - A central Kentucky man was found guilty of taking part in the killing a West Virginia truck driver.

A jury also found Jeremy D. Rice, 27, of Lexington guilty on Thursday of burglary in the Aug. 19, 2003 slaying of Carl Gene McClung, who was found shot to death in his cattle truck at a Scrub-A-Truck in Lexington.

Prosecutors said Rice wasn't the triggerman, but he could face up to life in prison for his part in the slaying.

Prosecutors and police said Rice and Marc Anthony Buchanan, 22, of Lexington, went to Scrub-a-Truck intent on robbing McClung, who was sleeping in the cab of his truck.

McClung fought off the robbery attempt, prompting Buchanan to shoot him, prosecutors said.

Buchanan is charged with murder, first-degree robbery and tampering with physical evidence. He is scheduled to stand trial Oct. 23.

Prosecutors said DNA and forensic evidence, including hair found at the scene and skin under McClung's fingernails, tied Rice to the slaying. Buchanan was arrested based on "testimonial evidence" said Lexington Police Sgt. Paul Williams. He declined to give details.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref13.html 

Massachusetts - The city of Boston has agreed to pay $3.2 million to a Roxbury man whose wrongful conviction in the shooting of a police officer in 1997 led to the temporary shutdown of the Police Department's fingerprint unit and sweeping changes in how such evidence is collected and analyzed.

Stephan Cowans spent 6 1/2 years in prison after police falsely linked him to a fingerprint left by the man who shot and wounded Sergeant Gregory Gallagher in a Roxbury backyard. While behind bars, he contracted hepatitis C, according to his lawyers, and missed his mother's funeral, before finally being exonerated by DNA evidence early in 2004 through the New England Innocence Project.

The award to Cowans equals what is believed to be the largest amount the city has ever paid in a wrongful conviction case. In the other case, the city agreed in March to pay $3.2 million to settle a lawsuit brought by Neil Miller, who served 10 years in prison after being convicted of raping a 19-year-old Emerson College student in 1989 before DNA tests proved another man had committed the crime.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref14.html

Alaska - The state must allow DNA testing on a piece of evidence from a 1993 rape case where one of the men convicted says he is innocent, a federal judge has ruled.

The order issued last week is a victory for William Osborne, who is serving a 26-year sentence after an Anchorage jury found him guilty of rape and kidnapping. Osborne has been fighting for years for the right to test a blue condom for evidence that someone else took part in a two-man Earthquake Park attack on a prostitute. The condom was used against Osborne at trial.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref15.html 

New York - A Syracuse University grad student was walking to her car two weeks ago in the middle of the day when she was dragged from the street into a nearby garage and raped. Because of the violent nature of the crime and the boldness of the suspect, police made the case a top priority.

Using evidence from a rape kit, analysts were able to create a DNA profile for the suspect and run it through the state's convicted offender database. 
"We were able to make a match, confirm that match, and let the police know and the District Attorney's Office know we had a hit to the case," said Dr. Kathleen Corrado, of the Center for Forensic Sciences.

The match was Robert Adams III, 21, who was released from a Buffalo-area prison just one day before the rape. He had been serving time for a burglary in Syracuse, and police said he returned to the area to see family.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref16.html

South Carolina - Stephen Stanko's lawyer is saying that his client was insane at the time of the killing and rape.

Stanko is charged with killing 43-year-old Laura Ling and raping a teenage girl last year. Prosecutors say he strangled Ling while he held down the teenage girl he had just beaten and raped.

In court Wednesday, psychiatrist James Thrasher testified. He says the frontal lobes of Stanko's brain do not function properly. That's the part of the brain that helps people make moral decisions.

Tuesday, a SLED agent said DNA samples taken from the crime scene matched Stanko.

The state is seeking the death penalty against 38-year-old Stanko.

Stanko is also charged with killing 74-year-old Henry Lee Turner. A trial date has not been set in that case.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref17.html 

Illinois - A federal jury Tuesday resoundingly rejected a $60 million lawsuit filed by a man who spent 27 years in prison before he was pardoned of kidnapping, raping and murdering a 9-year-old girl. 
Michael Evans, 47, seemed confounded as the verdict was read, exonerating 10 former Chicago police officers who Evans claimed conspired to convict him of Lisa Cabassa's murder by manipulating evidence and coercing an eyewitness. Evans glanced back and forth at the jury and his attorneys as the verdict was read. Afterward, Jonathan Loevy, his lead attorney, put an arm around Evans' shoulders and led him silently from the courtroom. 

Evans had sought $2 million for each year he spent in prison plus other damages. But Evans, who at one point was in settlement negotiations with the city, won't receive anything under the nine-member jury's verdict. 
Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref18.html

Virginia - A gun that authorities believe was used in the slaying of Midlothian teenager Allen "Chip" Ellis contained DNA evidence belonging to a former classmate accused of killing Ellis.

State forensic scientists obtained a DNA profile mixture that included the DNA of suspect Louis Shawn Lindenfeld from inside the gun's barrel, according to the Department of Forensic Science report, which also included an analysis of several items.

The report, filed with other documents in Henrico County Circuit Court late last week, says Lindenfeld cannot be eliminated as a contributor to this DNA mixture.

According to the documents, police recovered two guns in the case.

Investigators took swabs of material from both weapons. The DNA sample was found in the Colt pistol.

Lindenfeld's DNA was also found on a bloody gray tank top recovered by investigators.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref19.html 

California — A DNA "cold-hit" has led to the arrest of a man suspected of kidnapping and raping an Oakland woman more than seven years ago.

Shane Henry, 38, of Oakland, was charged Tuesday for the Jan. 13, 1999, rape of a 28-year-old woman.

According to police, the woman was walking on San Leandro Street when a man "approached the woman from behind with two guns, forced her across the street, down a driveway and into a garage, where he raped her..."

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref20.html 

Did You Know?

Topic: Surprise Finding For Stretched DNA 

Author: Berkeley Lab 
Published on Aug 7, 2006

Most of us are familiar with the winding staircase image of DNA, the repository of a biological cell's genetic information. But few of us realize just how tightly that famous double helix is wound. Stretched to its full length, a single molecule of human DNA extends more than three feet, but, when wound up inside the nucleus of a cell, that same molecule measures about one millionth of an inch across. Biologists have long believed that as a molecule of DNA is stretched, its double helix starts to unwind. As much sense as this makes from an intuitive standpoint, a recent experiment proved it not to be the case. 
Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley used a combination of microscopic beads and magnetic tweezers to observe that when a DNA molecule is stretched, it actually begins to overwind. This overwinding continues until the force being applied to stretch the DNA exceeds about 30 picoNewtons. (One picoNewton is about a trillionth the force required to hold an apple against Earth's gravity.) Beyond the 30 picoNewton threshold, the DNA double helix did begin to unwind in accordance with predictions. 
"DNA's helical structure implies that twisting and stretching should be coupled, hence the prediction that DNA should unwind when stretched," said biophysicist Carlos Bustamante, who led this experiment. "That is why it was such surprise when we directly measured twist-stretch coupling to find instead DNA overwinds when stretched. The DNA molecule, when studied at close range, continues to surprise us!" 
Bustamante is a leading authority on the use of single-molecule visualization and manipulation techniques to study the dynamics, structure and kinetics of molecular motors and nucleo-protein assemblies. He holds joint appointments with Berkeley Lab's Physical Biosciences Division and UC Berkeley's Departments of Molecular & Cell Biology, Physics, and Chemistry. He is also a Howard Hughes Medical Institute (HHMI) investigator.  
The results of this study are reported in the journal Nature, in a letter entitled DNA Overwinds When Stretched, which is now available on-line. Coauthoring this letter with Bustamante were Jeff Gore, Zev Bryant, Marcelo Nöllmann, Mai Le and Nicholas Cozzarelli. 
The magic of DNA replication and the transcription of genetic information into the production of proteins depends upon the mechanical properties of the double helix. This is why understanding these mechanical properties has been a scientific priority since the double-helix was first discovered by Watson and Crick more than 50 years ago. Bustamante has been one of the foremost pioneers in this area of research. More than a decade ago, he and his research group tethered DNA molecules to tiny beads and measured their elasticity. Among the many breakthroughs he and his group have achieved is the development of the technique called "rotor bead tracking."  
In rotor bead tracking, a single DNA molecule is anchored to a surface and a magnetized bead is attached to the free end. A point along the double-helix is then biochemically "nicked" to create a single strand of DNA that acts as a free swivel. Immediately below this nick, a plastic bead is attached to the DNA to serve as a "rotor" that will spin in response to torque. Magnets are used to manipulate the magnetized bead, providing a measured and highly controlled amount of tension to stretch the DNA molecule. With the use of a fluorescent coating, the subsequent spinning of the rotor bead in response to the stretching can be recorded. 
"When we apply tension to the DNA molecule, changes in the rotor bead angle reflect changes in the twist of the lower DNA segment," Bustamante said. "The overwinding observed upon stretching, implies that contrary to the held belief, the stretch-torsion coupling constant of DNA is a negative value. This observation also implies that if we overwind the DNA, the molecule should get longer. Indeed, we found that Overwinding caused the DNA molecule to extend by about 0.5 nanometers per turn."

To explain the overwinding, Bustamante and his coauthors have proposed a simple "toy" model in which the radius of the DNA double-helix is allowed to shrink as the molecule is stretched. The model consists of an elastic rod that is wrapped around its outer surface by a stiff wire, analogous to DNA's sugar-phosphate backbone. The elastic rod is constructed from a material that conserves volume under stress. 
"As this system is stretched, the elastic rod decreases in diameter," said Bustamante. "This enables the outer wire to wrap a larger number of times over the length of the rod." 
The twist-stretch coupling results demonstrated by Bustamante and his collaborators holds important implications for how DNA-binding proteins are able to recognize their target sites along the helix. These proteins are known to bend, wrap, loop and twist DNA. Now it has been shown that they can achieve their goals by simultaneously stretching and overwinding a DNA molecule, or by compressing and underwinding it. 
"We believe that our work sheds new light on an old and important problem," said Bustamante, "and that, in addition to improving our understanding of DNA/protein interactions, it will also have implications in nanotechnology. For example, the DNA molecule might provide the energy to power future nanomotors." 
Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our Website at www.lbl.gov.

Source: http://www.dnalabsinternational.com/email_newsletter/vol_25_aug_06/vol25_ref21.html 

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