Structure of
telomere-
protecting proteins
by Art Robinson
Telomeres are specialized protein–DNA
complexes that cap the ends of linear chromosomes in eukaryotic
cells. Recent discoveries in organisms from yeasts to humans
have shown that Pot1 (protection of telomeres) proteins are
involved in the chromosome capping, but the molecular mechanism
for the binding between Pot1 and DNA remained unknown. A group
from the University of Colorado at Boulder and the Stowers
Institute for Medical Research has now obtained high-resolution
x-ray crystallography structures of complexes comprising a
DNA-binding domain of Pot1 and sections of DNA in yeast that
explain the binding specificity.
Full story.
Publication about this research: M. Lei,
E.R. Podell, P. Baumann, and T.R. Cech, "DNA
self-recognition in the structure of Pot1 bound to telomeric
single-stranded DNA,"  Nature
426, 198 (2003).
Contact: Thomas Cech, thomas.cech@colorado.edu
Pinning down
exchange bias
by Art Robinson
Exchange bias refers to a preferred direction
of magnetization of a ferromagnet in contact with an antiferromagnet.
It is due to a shift in the hysteresis loop (magnetization
vs. external magnetic field) when cooling the sample in an
external field (field-cooling) to below the antiferromagnet's
ordering (Néel) temperature. Magnetic devices based
on exchange bias are of considerable commercial importance
for data storage, but the mechanism behind it has evaded detection
for 50 years. A collaboration from the Stanford Synchrotron
Radiation Laboratory, the ALS, the Swiss Light Source, and
Hitachi Global Storage Technologies has now shown that a relatively
small number of "pinned" spins in the interface
layer of the antiferromagnet are the cause.
Full story.
Publication about this research: Publication
about this research: H. Ohldag, A. Scholl, F. Nolting,
E. Arenholz, S. Maat, A.T. Young, M. Carey,
and J. Stöhr, "Correlation between exchange
bias and pinned interfacial spins," Phys. Rev. Lett.
91, 017203 (2003).
Contact: Hendrik Ohldag, HOhldag@lbl.gov
Robots score
big with protein
crystallographers
A big step towards speeding up the process of solving protein
structures has been achieved by researchers with Berkeley
Lab who have developed and successfully demonstrated the first
automated system for mounting and aligning protein crystals
in an x-ray beamline at a synchrotron light source.
With genome sequencing becoming almost
a conveyer-belt process, one of the next big challenges in
biology is to determine the structures of the proteins being
assembled by all those genomes. In the architecturally loopy,
twisted world of proteins, knowing structural form is a key
to understanding molecular and cellular function. As there
may be more than 30,000 different kinds of human proteins,
and nearly a trillion different kinds of proteins on Earth,
solving protein structures is another process that screams
out for automation.
Full story.
Contact: Lynn Yarris, LCYarris@lbl.gov
Users' Meeting:
Mark your calendars,
send workshop ideas
Preparations have begun for this year's Users' Meeting, which
will be held October 18-20 at the ALS—mark your
calendars early and make plans to attend! Since last year's
meeting commemorated the 10th anniversary of ALS operations,
this year's theme will be "Looking Forward" to the
future. Workshops will again be an integral part of the meeting
program: many of the successful programs and technologies
of tomorrow will have their origins in the workshops of today.
As the ALS begins planning for the next 5 to 10 years, users
can help define the path forward by proposing workshop ideas.
To this end, the Users' Meeting planning
committee, chaired by Corie Ralston and Keith Jackson, is
interested in hearing from the user community what workshops
they would like to see offered. Workshops can range in scope
from basic scientific explanation to in-depth exploration
of highly specialized topics. Examples already on the program
include a workshop on microscopy organized by Carolyn Larabell
and a workshop on the Molecular Foundry chaired by Wayne Mitchell.
If you have a suggestion for a workshop, please contact Corie
Ralston (CYRalston@lbl.gov).
Hope to see you in October!
Contact: Corie Ralston, CYRalston@lbl.gov
UEC Corner: Notes
from the Users'
Executive Committee
by Dennis Lindle
On February 2, the President submitted his Fiscal Year
2005 (FY05) budget request to Congress. As you've probably
heard, the request cuts the DOE Office of Science budget by
2% from the FY04 budget (from $3.5 to $3.43 billion). I am
working in close collaboration with the leadership of the
users' groups of other facilities on strategies for responding
to the President's proposed science budget. If you would like
to learn more about how you can participate, a Web
page sponsored by the American Physical Society is available
for further information.
(Contact: Dennis Lindle, lindle@unlv.nevada.edu)
Proposal scores
and running schedule
available online
The general sciences beam time allocation process for the
running period from June through December 2004 is complete.
The number of proposals for the cycle was 230, up from 213
in the previous period. This running period will last seven
months, but the next running periods will all be 6 months
in duration: January–June and July–December. The
number of eight-hour shift requests for the upcoming cycle
was 4549. A total of 2508 shifts, equal to about 55% of the
total time requested in the proposals, was allocated. Competition
for beam time on insertion-device beamlines was especially
keen—requests for the insertion device beamlines will
continue to find the proposal process for general users competitive;
approximately 42% of the requested beam time was allocated.
For more detailed results, including beamline score distributions
and cutoff scores, go to the
proposal scores page of the ALS Web site.
The schedule
for the upcoming running period has also been posted on the
Web. Two-bunch operation will occur August 11–22.
Contact: Gary Krebs, GFKrebs@lbl.gov
ALS begins shutdown
this week
The ALS shut down at 8:00 A.M. on Monday, April 26, for
planned installations and maintenance. User operations will
resume at 8:00 A.M. on Thursday, June 10. One of the
first projects tackled during the shutdown was the replacement
of the 2300-gallon liquid nitrogen tank with a 6000-gallon
tank to accommodate the increased usage of liquid nitrogen
at the ALS. The old tank was removed on Monday. Other projects
scheduled include realignment of the storage ring, replacement
of the W16 wiggler in Sector 5 with a W11 insertion device,
and replacement of the superbend cold heads.
In the realignment process, surveyors
and engineers will carefully measure the position of each
sector arc in the storage ring, calculate their optimal positions,
move each arc girder as necessary to bring the ring back to
its nominal circumference and alignment, reposition the insertion
devices to minimize stresses on the flex bands, and finish
by reconfirming the position of each component. Beamlines
may see a shift in the source position as a result of these
moves. To ensure proper operation of the beamlines following
the storage ring realignment, 10 shifts of beam time have
been set aside at the end of the shutdown for testing and
alignment. Responsible scientists for each beamline are being
contacted separately and should make plans to ensure that
their beamlines are functioning properly with the aid of ALS
scientific and support staff.
Contact: Steve Rossi, SLRossi@lbl.gov |
