Temporal photometric variations at near-infrared to submillimeter wavelengths have been found in low-mass young stellar objects. These phenomena are generally interpreted as accretion events of ...star-disk systems with varying accretion rates. There is growing evidence suggesting that similar luminosity flaring also occurs in high-mass star/cluster-forming regions. We report in this Letter the rise and fall of the 900 m continuum emission and the newly found 349.1 GHz methanol maser emission in the massive star-forming region S255IR SMA1 observed with the Submillimeter Array and the Atacama Large Millimeter/submillimeter Array. The level of flux variation at a factor of ∼2 at the submillimeter band and the relatively short 2 years duration of this burst suggest that the event is probably similar to those milder and more frequent minor bursts seen in 3D numerical simulations.
The dependence of the polarization fraction p on total intensity I in polarized submillimeter emission measurements is typically parameterized as p ∝ I− ( ≤ 1) and used to infer dust grain alignment ...efficiency in star-forming regions, with an index = 1 indicating near-total lack of alignment of grains with the magnetic field. In this work, we demonstrate that the non-Gaussian noise characteristics of the polarization fraction may produce apparent measurements of ∼ 1 even in data with significant signal-to-noise in Stokes Q, U, and I emission, and so with robust measurements of polarization angle. We present a simple model demonstrating this behavior and propose a criterion by which well-characterized measurements of the polarization fraction may be identified. We demonstrate that where our model is applicable, can be recovered by fitting the p-I relationship with the mean of the Rice distribution without statistical debiasing of the polarization fraction. We apply our model to JCMT BISTRO Survey POL-2 850 m observations of three clumps in the Ophiuchus molecular cloud, finding that in the externally illuminated Oph A region, 0.34, while in the more isolated Oph B and C, despite their differing star formation histories, ∼ 0.6-0.7. Our results thus suggest that dust grain alignment in dense gas is more strongly influenced by the incident interstellar radiation field than by star formation history. We further find that grains may remain aligned with the magnetic field at significantly higher gas densities than has previously been believed, thus allowing investigation of magnetic field properties within star-forming clumps and cores.
Many efforts have been made to develop inhibitors of MDM2 as potential drugs for cancer therapy. In this work, we use our previous developed conformational engineering technique to stabilize the ...binding conformation of the p53 transcription activation domain (TAD) peptide on gold nanoparticles (AuNPs), and create an AuNP‐based anti‐MDM2 artificial antibody, denoted as anti‐MDM2 Goldbody, that specifically binds MDM2. Though the free TAD peptide is unstructured, circular dichroism (CD) spectra confirm that its α‐helical conformation in the original p53 protein is restored on the anti‐MDM2 Goldbody, and surface plasmon resonance (SPR) experiments confirm that there is strong specific interaction between the anti‐MDM2 Goldbody and MDM2, demonstrating the anti‐MDM2 Goldbody as a potential inhibitor of MDM2. This work demonstrates that the conformational engineering technique is not limited to the antigen‐antibody systems, but can also be applied more widely in other protein‐protein interfaces to create increasingly more artificial proteins for various biomedical applications.
Proper conformation is key: An anti‐MDM2 artificial antibody, denoted as anti‐MDM2 Goldbody, is created by restoring the native conformation of the p53 transcription activation domain peptide on gold nanoparticles. The anchoring sites on the peptide are optimized to prevent interrupting the binding interface, thereby guaranteeing a strong specific interaction between MDM2 and the anti‐MDM2 Goldbody.
The massive young stellar object S255IR NIRS3 embedded in the star-forming core SMA1 has been recently observed with a luminosity burst, which is conjectured as a disk-mediated variable accretion ...event. In this context, it is imperative to characterize the gas properties around the massive young stellar object. With this in mind, we carried out high angular resolution observations with the Atacama Large Millimeter/submillimeter Array and imaged the 900 m dust continuum and the CH3CN J = 19−18 K = 0−10 transitions of S255IR SMA1. The integrated CH3CN emission exhibits an elongated feature with an extent of 1800 au in the northwest-southeast direction at a position angle of 165°, which is nearly perpendicular to the bipolar outflow. We confirm the presence of dense (a few cm−3) and hot (∼400 K) gas immediately surrounding the central protostar. The CH3CN emission features a velocity gradient along the elongated ridge, and by modeling the gas kinematics based on features in the position-velocity diagram, we infer that the gas is best described by a flattened rotating infalling envelope (or pseudo-disk). A mass infall rate of a few × 10−4 M yr−1 is derived. If there exists a putative Keplerian disk directly involved in the mass accretion onto the star and jet/outflow launching, it is likely smaller than 125 au and unresolved by our observations. We show qualitative resemblances between the gas properties (such as density and kinematics) in 255IR SMA1 inferred from our observations and those in a numerical simulation particularly tailored for studying the burst mode of massive star formation.
We report high angular resolution observations of NGC 1333 IRAS 4A, a protostellar binary including A1 and A2, at 0.84 mm with the Atacama Large Millimeter/submillimeter Array. From the continuum ...observations, we suggest that the dust emission from the A1 core is optically thick, and A2 is predominantly optically thin. The A2 core, exhibiting a forest of spectral lines including complex molecules, is a well-known hot corino, as suggested by previous works. More importantly, we report, for the first time, solid evidence of complex organic molecules (COMs), including CH3OH, 13CH3OH, CH2DOH, and CH3CHO, associated with the A1 core seen in absorption. The absorption features mostly arise from a compact region around the continuum peak position of the A1 core. Rather than originating from a larger common envelope surrounding the protobinary, the COM features are associated with individual cores A1 and A2. Considering the signatures observed in both continuum and spectral lines, we propose two possible scenarios for IRAS 4A1: the COM absorption lines may arise from a hot-corino-like atmosphere at the surface of an optically thick circumstellar disk around A1, or the absorption may arise from different layers of a temperature-stratified, dense envelope.
Tea is the world＇s oldest and most popular caffeine-containing beverage with immense economic, medicinal, and cultural importance. Here, we present the first high-quality nucleotide sequence of the ...repeat-rich （80.9%）, 3.02-Gb genome of the cultivated tea tree Camellia sinensis. We show that an extraordinarily large genome size of tea tree is resulted from the slow, steady, and long-term amplification of a few LTR retrotransposon families. In addition to a recent whole-genome duplication event, lineage-specific expansions of genes associated with flavonoid metabolic biosynthesis were discovered, which enhance catechin production, terpene enzyme activation, and stress tolerance, important features for tea flavor and adaptation. We demonstrate an independent and rapid evolution of the tea caffeine synthesis pathway relative to cacao and coffee. A comparative study among 25 Camellia species revealed that higher expression levels of most flavonoid- and caffeinebut not theanine-related genes contribute to the increased production of catechins and caffeine and thus enhance tea-processing suitability and tea quality. These novel findings pave the way for further metabolomic and functional genomic refinement of characteristic biosynthesis pathways and will help develop a more diversified set of tea flavors that would eventually satisfy and attract more tea drinkers worldwide.
Abstract
Previous observations have shown that the ≲10 au, ≳400 K hot inner disk of the archetypal accretion outburst young stellar object, FU Ori, is dominated by viscous heating. To constrain dust ...properties in this region, we have performed radio observations toward this disk using the Karl G. Jansky Very Large Array in 2020 June–July, September, and November. We also performed complementary optical photometric monitoring observations. We found that the dust thermal emission from the hot inner disk mid-plane of FU Ori has been approximately stationary and the maximum dust grain size is ≳1.6 mm in this region. If the hot inner disk of FU Ori, which is inward of the 150–170 K water snowline, is turbulent (e.g., corresponding to a Sunyaev & Shakura viscous
α
t
≳ 0.1), or if the actual maximum grain size is still larger than the lower limit we presently constrain, then as suggested by the recent analytical calculations and the laboratory measurements, water-ice-free dust grains may be stickier than water-ice-coated dust grains in protoplanetary disks. Additionally, we find that the free–free emission and the Johnson
B-
and
V
-band magnitudes of these binary stars were brightening in 2016–2020. The optical and radio variability might be related to the dynamically evolving protostellar- or disk-accretion activities. Our results highlight that the hot inner disks of outbursting objects are important laboratories for testing models of dust grain growth. Given the active nature of such systems, to robustly diagnose the maximum dust grain sizes, it is important to carry out coordinated multiwavelength radio observations.
Abstract
We have conducted a line survey toward Orion KL using the
Q
-band receiver of the Tianma 65 m radio telescope (TMRT), covering 34.8–50 GHz with a velocity resolution between 0.79 and 0.55 km ...s
−1
, respectively. The observations reach a sensitivity of the level of 1–8 mK, proving that the TMRT is sensitive for conducting deep-line surveys. In total, 597 Gaussian features are extracted. Among them, 177 radio recombination lines (RRLs) are identified, including 126, 40, and 11 RRLs of hydrogen, helium, and carbon, with a maximum Δ
n
of 16, 7, and 3, respectively. The carbon RRLs are confirmed to originate from photodissociation regions with a
V
LSR
∼ 9 km s
−1
. In addition, 371 molecular transitions of 53 molecular species are identified. Twenty-one molecular species of this survey were not firmly detected in the
Q
band by Rizzo et al., including species such as H
2
CS, HCOOH, C
2
H
5
OH,
H
2
13
CO, H
2
CCO, CH
3
CHO, CH
2
OCH
2
, HCN
υ
2
= 1, and CH
3
OCHO
υ
t
= 1. In particular, the vibrationally excited states of ethyl cyanide (C
2
H
5
CN
υ
13/
υ
21) are for the first time firmly detected in the
Q
band. NH
3
(15,15) and (16,16) are identified, and they are so far the highest transitions of the NH
3
inversion lines detected toward Orion KL. All of the identified lines can be reproduced by a radiative transfer model.
The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)−H bonds has been impeded by the use of a base at elevated temperature that leads to ...racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)−H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzodoxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)−H bond and the involvement of alkyl radical species under the reaction conditions.
The use of a cinchona‐alkaloid‐derived N,N,P‐ligand leads to the direct enantioconvergent coupling of racemic alkyl bromides with azole C(sp2)−H bonds by copper catalysis. The key to success is the ligand‐enabled facile oxidative addition at approximately room temperature that suppresses product racemization at elevated temperature. This method provides a range of enantioenriched α‐chiral alkylated azoles.
A copper-catalyzed enantioconvergent Suzuki–Miyaura C(sp3)–C(sp2) cross-coupling of various racemic alkyl halides with organoboronate esters has been established in high enantioselectivity. ...Critical to the success is the use of a chiral cinchona alkaloid-derived N,N,P-ligand for not only enhancing the reducing capability of copper catalyst to favor a stereoablative radical pathway over a stereospecific SN2-type process but also providing an ideal chiral environment to achieve the challenging enantiocontrol over the highly reactive radical species. The reaction has a broad scope with respect to both coupling partners, covering aryl- and heteroarylboronate esters, as well as benzyl-, heterobenzyl-, and propargyl bromides and chlorides with good functional group compatibility. Thus, it provides expedient access toward a range of useful enantioenriched skeletons featuring chiral tertiary benzylic stereocenters.
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