540 research outputs found
CYP72A67 catalyses a key oxidative step in Medicago truncatula hemolytic saponin biosynthesis
In the Medicago genus, triterpenic saponins are bioactive secondary metabolites constitutively synthesized
in the aerial and subterranean parts of plants via the isoprenoid pathway. Exploitation of saponins
as pharmaceutics, agrochemicals and in the food and cosmetic industries has raised interest in identifying
the enzymes involved in their synthesis. We have identified a cytochrome P450 (CYP72A67) involved in
hemolytic sapogenin biosynthesis by a reverse genetic TILLING approach in a Medicago truncatula ethylmethanesulfonate
(EMS) mutagenized collection. Genetic and biochemical analyses, mutant complementation,
and expression of the gene in a microsome yeast system showed that CYP72A67 is responsible for
hydroxylation at the C-2 position downstreamof oleanolic acid synthesis. The affinity of CYP72A67 for substrates
with different substitutions at multiple carbon positions was investigated in the same in vitro yeast
system, and in relation to two other CYP450s (CYP72A68) responsible for the production of medicagenic
acid, the main sapogenin in M. truncatula leaves and roots. Full sib mutant and wild-type plants were
compared for their sapogenin profile, expression patterns of the genes involved in sapogenin synthesis,
and response to inoculation with Sinorhizobium meliloti. The results obtained allowed us to revise the
hemolytic sapogenin pathway in M. truncatula and contribute to highlighting the tissue specificities
(leaves/roots) of sapogenin synthesis
ELECTRON-DRIVEN REACTIONS IN PROTO-PLANETARY ATMOSPHERES: METASTABLE ANIONS OF GASEOUS o-BENZYNE
In this paper, we present an investigation into low-energy electron scattering (E < 15 eV) processes from a specific benzene-like polyatomic target such as ortho-benzyne, o-C6H4(1?), in order to gain a better understanding of the effects that possible low-lying metastable electron-attachment states could have on its nuclear fragmentation dynamics. The current importance of the dynamical evolution of this molecule lies in the fact that o-C6H4 is considered to be relevant for the circumstellar synthesis of large polycyclic aromatic hydrocarbons (PAHs), as a precursor for C6H6 production via ion-based ring closure reaction from C2H2. Our parameter-free scattering calculations are performed within the molecular reference frame, where we obtain the metastable anionic states for the nuclear equilibrium configuration and further characterize the properties of such transient anions with respect to those found earlier for the benzene molecule. Our quantum studies indicate that o-C6H4 is a more efficient producer of compact, fairly long-lived anionic intermediates than benzene itself; hence, this should more rapidly enter the chemical reaction cycles of PAHs formation, thereby disappearing from possible direct observation as a stable anion
Effect of cosmic rays on the resonant gravitational wave detector NAUTILUS at temperature T=1.5 K
The interaction between cosmic rays and the gravitational wave bar detector
NAUTILUS is experimentally studied with the aluminum bar at temperature of
T=1.5 K. The results are compared with those obtained in the previous runs when
the bar was at T=0.14 K. The results of the run at T = 1.5 K are in agreement
with the thermo-acoustic model; no large signals at unexpected rate are
noticed, unlike the data taken in the run at T = 0.14 K. The observations
suggest a larger efficiency in the mechanism of conversion of the particle
energy into vibrational mode energy when the aluminum bar is in the
superconductive status.Comment: 7 pages, 3 figures, 2 tables. Accepted by Physics Letters
An Optimal Tunable Josephson Element for Quantum Computing
We introduce a three-junction SQUID that can be effectively used as an
optimal tunable element in Josephson quantum computing applications. This
device can replace the simple dc SQUID generally used as tunable element in
this kind of applications, with a series of advantages for the coherence time
and for the tolerance to small errors. We study the device both theoretically
and experimentally at 4.2 K, obtaining a good agreement between the results.Comment: 3 pages, 4 figure
Evaluating case studies of community-oriented integrated care.
This paper summarises a ten-year conversation within London Journal of Primary Care about the nature of community-oriented integrated care (COIC) and how to develop and evaluate it. COIC means integration of efforts for combined disease-treatment and health-enhancement at local, community level. COIC is similar to the World Health Organisation concept of a Community-Based Coordinating Hub - both require a local geographic area where different organisations align their activities for whole system integration and develop local communities for health. COIC is a necessary part of an integrated system for health and care because it enables multiple insights into 'wicked problems', and multiple services to integrate their activities for people with complex conditions, at the same time helping everyone to collaborate for the health of the local population. The conversation concludes seven aspects of COIC that warrant further attention
Increasing the bandwidth of resonant gravitational antennas: The case of Explorer
Resonant gravitational wave detectors with an observation bandwidth of tens
of hertz are a reality: the antenna Explorer, operated at CERN by the ROG
collaboration, has been upgraded with a new read-out. In this new
configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz
about its frequency of operation of 919 Hz the spectral sensitivity is better
than 10^{-20} /sqrt(Hz) . We describe the detector and its sensitivity and
discuss the foreseable upgrades to even larger bandwidths.Comment: 4 pages- 4 figures Acceted for publication on Physical Review Letter
Study of the coincidences between the gravitational wave detectors EXPLORER and NAUTILUS in 2001
We report the result from a search for bursts of gravitational waves using
data collected by the cryogenic resonant detectors EXPLORER and NAUTILUS during
the year 2001, for a total measuring time of 90 days. With these data we
repeated the coincidence search performed on the 1998 data (which showed a
small coincidence excess) applying data analysis algorithms based on known
physical characteristics of the detectors. With the 2001 data a new interesting
coincidence excess is found when the detectors are favorably oriented with
respect to the Galactic Disk
Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope
We propose an under-ground experiment to detect the general relativistic
effects due to the curvature of space-time around the Earth (de Sitter effect)
and to rotation of the planet (dragging of the inertial frames or
Lense-Thirring effect). It is based on the comparison between the IERS value of
the Earth rotation vector and corresponding measurements obtained by a
tri-axial laser detector of rotation. The proposed detector consists of six
large ring-lasers arranged along three orthogonal axes.
In about two years of data taking, the 1% sensitivity required for the
measurement of the Lense-Thirring drag can be reached with square rings of 6
side, assuming a shot noise limited sensitivity ().
The multi-gyros system, composed of rings whose planes are perpendicular to one
or the other of three orthogonal axes, can be built in several ways. Here, we
consider cubic and octahedron structures. The symmetries of the proposed
configurations provide mathematical relations that can be used to study the
stability of the scale factors, the relative orientations or the ring-laser
planes, very important to get rid of systematics in long-term measurements,
which are required in order to determine the relativistic effects.Comment: 24 pages, 26 Postscript figure
- …