Snapshots of
ribozyme reaction states
reveal structural switch
by Julie McCullough
RNA, like protein, can sometimes function
as an enzyme (ribozyme) to speed biochemical reaction rates.
But how does RNA, a simple polymer with just four different
chemical building blocks, enhance reaction rates by at least
a million fold? Recently, a group from the University of California,
Berkeley, and the Howard Hughes Medical Institute obtained
high-resolution x-ray crystallographic structures of a ribozyme
trapped in different states of its catalytic cycle, showing
how a change in the RNA conformation governs the reaction
mechanism. Most ribozymes catalyze the cutting and pasting
of RNA molecules at specific sites, snipping out (cleaving)
extraneous sequences not needed in the final functional form
of an RNA. In the hepatitis delta virus (HDV), a human pathogen
with a small circular RNA genome, a ribozyme contained within
the viral sequence cuts the RNA at a single site during replication
to enable packaging of new virions, the extracellular virus
particles that allow the virus to infect a host and replicate.
Understanding how the ribozyme works is of interest both for
defining the fundamental principles of RNA-catalyzed reactions
and for discovering a possible Achilles' heel in this deadly
pathogen. Full
story.
Publication about this research: A. Ke,
K. Zhou, F. Ding, J.H. Cate, and J.A. Doudna, "A conformational
switch controls hepatitis delta virus ribozyme catalysis,"
Nature 429, 201 (2004).
Contact: Jennifer Doudna, JDoudna@lbl.gov
Explosive experiment
explores
escaping electrons
by Bruce Balfour
Nothing in the universe stands still.
The study of particle motion in molecules allows physicists
to probe the fundamental properties of molecules and how they
work, which is crucial to understanding the driving forces
behind chemistry, biology, and pharmaceutical development.
Researchers from Berkeley Lab, Kansas State University, and
institutions in Germany, Australia, and Spain used a pulsed
beam of photons from the Advanced Light Source to ionize the
electrons in a deuterium molecule, causing it to fragment
in a "Coulomb explosion." The team then used position
and timing data to construct a three-dimensional "photograph"
of the simultaneous motion of all the electrons and nuclei
at the moment of fragmentation. In the process, they discovered
that even simple molecular hydrogen is full of surprises.
Full
story.
Publication about this research: Th.
Weber, A.O. Czasch, O. Jagutzki, A.K. Müller, V. Mergel,
A. Kheifets, E. Rotenberg, G. Meigs, M.H. Prior, S. Daveau,
A. Landers, C.L. Cocke, T. Osipov, R. Díez Muiño,
H. Schmidt-Böcking, and R. Dörner, "Complete
Photo-Fragmentation of the Deuterium Molecule," Nature
431, 437 (2004).
Contact: Thorsten Weber, weber@hsb.uni-frankfurt.de
Four new UEC
members to be
chosen by December 15
The 2004 UEC election is scheduled to
begin on Monday, November 29. This year, users will elect
four candidates: one student candidate and three regular candidates.
To view the final slate and their biographical information,
go to the UEC
Election Web page and click on "View Candidate Biographies."
All ALS users with current email addresses on file in our
user database are eligible to vote. The deadline for casting
your vote is December 15; results should be posted on the
election Web site by December 20.
The newly elected members will take office
for a three-year term beginning January 1, 2005. Rotating
off the committee at the end of 2004 are John Bozek (Berkeley
Lab), Alexander Moewes (Univ. of Saskatchewan, Canada), Yasuji
Muramatsu (Japan Atomic Research Institute), Eli Rotenberg
(Berkeley Lab), and Sophie Canton (student member).
Contact: Liz Moxon, EJMoxon@lbl.gov
Call for general
sciences proposals:
Due January 5
The User Services Office is accepting
general user proposals from scientists who wish to conduct
research in the general sciences at the ALS during the running
period from July through December 2005. The deadline for submissions
is Wednesday, January 5, 2005. (This deadline does not apply
to protein crystallography proposals, which have a separate
process and schedule.)
 Scientists
wishing to renew a previous proposal must download the short
"ALS
Experiment Report and Request for Beamtime" form
and email it as an attachment to the User Services Office
by the January 5 deadline. The form can be saved to your hard
disk, filled out, and attached in an email message to alsproposals@lbl.gov
with the key words "Experiment Report" in the subject
header. Proposals cannot be renewed for more than three six-month
cycles after they are first submitted. After three rollover
six-month cycles, a new proposal must be submitted. If your
proposal is designated ALS-01062 or lower, then you must submit
a new proposal to be eligible for beamtime.
The numeric rating for each proposal
will be communicated to the user along with any comments that
might have been added by the Proposal Study Panel. The cutoff
rating for each beamline in the previous proposal cycle is
published on the Web (see Item 5 below). The following resources
are available for further information:
ALS
User Services Administrator
General
user proposal process
ALS online forms
Beamline
information
Contact: alsproposals@lbl.gov
Scores for general
user
proposals posted
User proposals for the general sciences
submitted on June 1, 2004, have been reviewed by the Proposal
Study Panel and scored on a scale of one (highest) to
five. Beamtime for the run cycle January through June 2005
has been allocated based on each proposal's ranking in relation
to all other proposals for a given beamline. In cases where
proposal requests for a specific beamline exceeded available
beamtime, a cutoff score was assigned after which no beamtime
was allocated. To view the scoring for all beamlines and the
individual beamlines where cutoff scores were applied, see
General
User Proposal Scores: General Sciences.
Safety reminder:
Energized
electrical equipment
Users are reminded that they are expressly
not permitted to work on any system with accessible voltages
greater than 50 V, as well as high-current (greater than 100
A) systems at lower voltages, and systems with stored energy
components greater than 5 J. Such work is defined as "work
on energized electrical equipment" and can only be performed
by qualified persons under very controlled conditions. Should
you require any work on electrical equipment, please contact
the electronic maintenance shop at ext. 5457.
Contact: Georgeanna Perdue, GMPerdue@lbl.gov
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