111 research outputs found
Phenol Nitration Induced by an {Fe(NO)\u3csub\u3e2\u3c/sub\u3e}\u3csup\u3e10\u3c/sup\u3e Dinitrosyl Iron Complex
Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs have been postulated, their chemical functionality outside of NO transfer has not been demonstrated thus far. Here we report the unprecedented dioxygen reactivity of a N-bound {Fe(NO)2}10 DNIC, [Fe(TMEDA)(NO)2] (1). In the presence of O2, 1 becomes a nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation of a putative iron-peroxynitrite [Fe(TMEDA)(NO)(ONOO)] (2) that is stable below −80 °C. Iron K-edge X-ray absorption spectroscopy on 2 supports a five-coordinated metal center with a bound peroxynitrite in a cyclic bidentate fashion. The peroxynitrite ligand of 2 readily decays at increased temperature or under illumination. These results suggest that DNICs could have multiple physiological or deleterious roles, including that of cellular nitrating agents
Auxin pretreatment promotes regeneration of sugarcane (Saccharum spp. hybrids) midrib segment explants
We have developed a new, simple,
quick and genotype-independent method for direct
regeneration of sugarcane using novel midrib
segment explants. Our protocol involves two
steps: the pretreatment of starting material on MS
(Murashige and Skoog (1962) Physiol Plant
15:473–497) medium containing 3.0 mg/l 2,4-
dichlorophenoxyacetic acid (2,4-D) for 8 days
under continuous dark and subsequent transfer of
the explants to MS medium augmented with
0.1 mg/l benzyladenine (BA) and 0.1 mg/l naphthaleneacetic
acid (NAA) under light-dark conditions.
On the regeneration medium, numerous
globular structures appeared from the explants
and subsequently differentiated into shoots.
Regenerated shoots attained 2–5 cm height
within 30 days of culture initiation and readily
rooted on MS basal medium. Hardened plants
were successfully established in the greenhouse.
The regulation of sugarcane morphogenesis by
auxin pretreatment is discussed
LEM All-Sky Survey: Soft X-ray Sky at Microcalorimeter Resolution
The Line Emission Mapper (LEM) is an X-ray Probe with with spectral
resolution ~2 eV FWHM from 0.2 to 2.5 keV and effective area >2,500 cm at 1
keV, covering a 33 arcmin diameter Field of View with 15 arcsec angular
resolution, capable of performing efficient scanning observations of very large
sky areas and enabling the first high spectral resolution survey of the full
sky. The LEM-All-Sky Survey (LASS) is expected to follow the success of
previous all sky surveys such as ROSAT and eROSITA, adding a third dimension
provided by the high resolution microcalorimeter spectrometer, with each 15
arcsec pixel of the survey including a full 1-2 eV resolution energy spectrum
that can be integrated over any area of the sky to provide statistical
accuracy. Like its predecessors, LASS will provide both a long-lasting legacy
and open the door to the unknown, enabling new discoveries and delivering the
baseline for unique GO studies. No other current or planned mission has the
combination of microcalorimeter energy resolution and large grasp to cover the
whole sky while maintaining good angular resolution and imaging capabilities.
LASS will be able to probe the physical conditions of the hot phases of the
Milky Way at multiple scales, from emission in the Solar system due to Solar
Wind Charge eXchange, to the interstellar and circumgalactic media, including
the North Polar Spur and the Fermi/eROSITA bubbles. It will measure velocities
of gas in the inner part of the Galaxy and extract the emissivity of the Local
Hot Bubble. By maintaining the original angular resolution, LASS will also be
able to study classes of point sources through stacking. For classes with
~ objects, it will provide the equivalent of 1 Ms of high spectral
resolution data. We describe the technical specifications of LASS and highlight
the main scientific objectives that will be addressed. (Abridged)Comment: White Paper in support of a mission concept to be submitted for the
2023 NASA Astrophysics Probes opportunity. This White Paper will be updated
when required. 30 pages, 25 figure
A highly N-doped carbon phase "dressing" of macroscopic supports for catalytic applications
© The Royal Society of Chemistry 2015. The straightforward "dressing" of macroscopically shaped supports (i.e. β-SiC and α-Al2O3) with a mesoporous and highly nitrogen-doped carbon-phase starting from food-processing raw materials is described. The as-prepared composites serve as highly efficient and selective metal-free catalysts for promoting industrial key-processes at the heart of renewable energy technology and environmental protection
High thermal conductive β-SiC for selective oxidation of H2S: A new support for exothermal reactions
International audienc
Revealing the excitation energy transfer network of Light-Harvesting Complex II by a phenomenological analysis of two-dimensional electronic spectra at 77 K
Energy equilibration in light-harvesting antenna systems normally occurs before energy is transferred to a reaction center. The equilibration mechanism is a characteristic of the excitation energy transfer (EET) network of the antenna. Characterizing this network is crucial in understanding the first step of photosynthesis. We present our phenomenology-based analysis procedure and results in obtaining the excitonic energy levels, spectral linewidths, and transfer-rate matrix of Light-Harvesting Complex II directly from its 2D electronic spectra recorded at 77 K with waiting times between 100 fs to 100 ps. Due to the restriction of the models and complexity of the system, a unique EET network cannot be constructed. Nevertheless, a recurring pattern of energy transfer with very similar overall time scales between spectral components (excitons) is consistently obtained. The models identify a "bottleneck" state in the 664-668 nm region although with a relatively shorter lifetime (similar to 4-6 ps) of this state compared to previous studies. The model also determines three terminal exciton states at 675, 677-678, and 680-681 nm that are weakly coupled to each other. The excitation energy equilibration between the three termini is found to be independent of the initial excitation conditions, which is a crucial design for the light-harvesting complexes to ensure the energy flow under different light conditions and avoid excitation trapping. We proposed two EET schemes with tentative pigment assignments based on the interpretation of the modeling results together with previous structure-based calculations and spectroscopic observables. Published under license by AIP Publishing
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