The frequent emergence of drug-resistant bacteria has created an urgent demand for new antimicrobial agents. Traditional methods of novel antibiotic development are almost obsolete. Antimicrobial ...peptides (AMPs) are now regarded as a potential solution to revive the traditional methods of antibiotic development, although, until now, many AMPs have failed in clinical trials. A comprehensive database of AMPs with information about their antimicrobial activity and cytotoxicity will help promote the process of finding novel AMPs with improved antimicrobial activity and reduced cytotoxicity and eventually accelerate the speed of translating the discovery of new AMPs into clinical or preclinical trials. LAMP, a database linking AMPs, serves as a tool to aid the discovery and design of AMPs as new antimicrobial agents. The current version of LAMP has 5,547 entries, comprising 3,904 natural AMPs and 1,643 synthetic peptides. The database can be queried using either simply keywords or combinatorial conditions searches. Equipped with the detailed antimicrobial activity and cytotoxicity data, the cross-linking and top similar AMPs functions implemented in LAMP will help enhance our current understanding of AMPs and this may speed up the development of new AMPs for medical applications. LAMP is freely available at: http://biotechlab.fudan.edu.cn/database/lamp.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We study the stability of the feedback interconnection of two impedance passive linear time-invariant systems, of which one is finite dimensional. The closed-loop system is well known to be impedance ...passive, but no stability properties follow from this alone. We are interested in two main issues: 1) the strong stability of the operator semigroup associated with the closed-loop system, 2) the input-output stability (meaning transfer function in H ∞ ) of the closed-loop system. Our results are illustrated with the system obtained from the nonuniform SCOLE (NASA Spacecraft Control Laboratory Experiment) model representing a vertical beam clamped at the bottom, with a rigid body having a large mass on top, connected with a trolley mounted on top of the rigid body, via a spring and a damper. Such an arrangement, called a tuned mass damper (TMD), is used to stabilize tall buildings. We show that the SCOLE-TMD system is strongly stable on the energy state space and that the system is input-output stable from the horizontal force input to the horizontal velocity output.
Classic nucleophilic substitution reactions (S
1 and S
2) are not generally amenable to the enantioselective variants that use simple and racemic alkyl halide electrophiles. The merging of transition ...metal catalysis and radical chemistry with organometallic nucleophiles is a versatile method for addressing this limitation. Here, we report that visible light-driven catalytic asymmetric photoredox radical coupling can act as a complementary and generic strategy for the enantioconvergent formal substitution of alkyl haldies with readily available and bench-stable organic molecules. Single-electron reductive debrominations of racemic α-bromoketones generate achiral alkyl radicals that can participate in asymmetric C
-C
bonds forming cross-coupling reactions with α-amino radicals derived from N-aryl amino acids. A wide range of valuable enantiomerically pure β
- and β
-amino ketones were obtained in satisfactory yields with good-to-excellent enantioselectivities by using chiral phosphoric acid catalysts to control the stereochemistry and chemoselectivity. Fluoro-hetero-quaternary and full-carbon quaternary stereocenters that are challenging to prepare were successfully constructed.
Pyridine, one of the most important azaarenes, is ubiquitous in functional molecules. The electronic properties of pyridine have been exploited to trigger asymmetric transformations of prochiral ...species as a direct approach for accessing chiral pyridine derivatives. However, the full potential of this synthetic strategy for the construction of enantioenriched γ-functionalized pyridines remains untapped. Here, we describe the first enantioselective addition of prochiral radicals to vinylpyridines under cooperative photoredox and asymmetric catalysis mediated by visible light. The enantioselective reductive couplings of vinylpyridines with aldehydes, ketones, and imines were achieved by employing a chiral Brønsted acid to activate the reaction partners and provide stereocontrol via H-bonding interactions. Valuable chiral γ-secondary/tertiary hydroxyl- and amino-substituted pyridines were obtained in high yields with good to excellent enantioselectivities.
Key message
Although night-time transpiration occurs most of the time, stem refilling contributed more to the amount of night-time sap flux, which indicates that there was no water loss in
Schima ...superba
at night-time.
It has been historically shown to be difficult to identify the night-time transpiration (
E
n
) and stem refilling (
R
n
) components from night-time sap flux (NF
t
). We applied an autoregressive moving-average (ARMA) model with exogenous variables (ARMAX) fitting
E
n
to distinguish NF
t
of
Schima superba
for avoiding autocorrelation. In total, 23 optimum models were chosen at the node moments of the night in the dry and wet seasons. Models performed seasonal variations in involving environmental factors and build time. Vapor pressure deficit (VPD
t
) alone or with wind speed (WS
t
) drove positively NF
t
in most of the time in both seasons. SM
t
dominated NF
t
only at the beginning of the night-time in the dry season.
E
n
occurred 1 h later and was lower in the wet than in the dry season (ca. 1.09 kg h
−1
vs 1.82 kg h
−1
), and
R
n
is the opposite (ca. 2.36 kg h
−1
vs 1.9 kg h
−1
). This may cause by greater water storage deficit in the trunk due to stronger day-time transpiration. We found that NF
t
was minor compared to day-time sap flux (DF
t
), and the mean ratio of night-time sap flow (
Q
n
) to daily sap flow (
Q
w
) was only 0.02. Our results showed that there were no seasonal differences on the contribution of NF
t
to the 24-h
F
t
, and no water loss at the daily scale in
Schima superba
in both seasons (
R
n
>
E
n
). This study first quantifies
E
n
and
R
n
, and reveals seasonal variations in tree night-time water use and provides a basis for better understanding of
E
n
function.
An enantioselective reduction of azaarene-based ketones through photoredox asymmetric catalysis is reported. With a transition metal-free dual catalytic system including a chiral phosphoric acid and ...a photosensitizer DPZ mediated by visible light, the transformations involved a tandem process involving double single-electron-transfer reductions and enantioselective protonation, providing valuable chiral alcohols in high yields (up to >99%) with good to excellent enantioselectivities (up to 97% ee).
Chiral hydrogen-bonding catalysis is a classic strategy in asymmetric organocatalysis, and it has been extensively used in a variety of fundamental chemical transformations. At the same time, visible ...light-driven photoredox catalysis is a powerful and sustainable tool commonly used in radical chemistry. The intriguing combination of these two catalysis platforms would open a new avenue for the direct and highly efficient synthesis of enantioenriched compounds. Inspired by the conceptual breakthrough of T. Bach, in recent years, significant progress has been made in cooperative photoredox and chiral hydrogen-bonding catalysis. By developing a variety of important types of reactions, a wide range of valuable chiral compounds have been successfully synthesized. In this review, the advances in this key area are systematically described, and the examples are organized according to the distinct bond-forming patterns in the construction of the stereocentres.
The development of organic fluorophores with efficient solid‐state emissions or aggregated‐state emissions in the red to near‐infrared region is still challenging. Reported herein are fluorophores ...having aggregation‐induced emission ranging from the orange to far red/near‐infrared (FR/NIR) region. The bioimaging performance of the designed fluorophore is shown to have potential as FR/NIR fluorescent probes for biological applications.
Twisted emissions: Fluorophores with aggregation‐induced emission (AIE) in the solid state are reported. The emissions range from the orange to far red/near‐infrared (FR/NIR) regions, and the molecules have twisted molecular conformations. The bioimaging performance of the designed fluorophores shows that they have potential as FR/NIR fluorescent probes for biological applications.
A powerful coronal mass ejection (CME) occurred on 2017 September 10 near the end of the declining phase of the historically weak solar cycle 24. We obtain new insights concerning the geometry and ...kinematics of CME-driven shocks in relation to their heliospheric impacts from the optimal, multispacecraft observations of the eruption. The shock, which together with the CME driver can be tracked from the early stage to the outer corona, shows a large oblate structure produced by the vast expansion of the ejecta. The expansion speeds of the shock along the radial and lateral directions are much larger than the translational speed of the shock center, all of which increase during the flare rise phase, peak slightly after the flare maximum and then decrease. The near simultaneous arrival of the CME-driven shock at the Earth and Mars, which are separated by 156 6 in longitude, is consistent with the dominance of expansion over translation observed near the Sun. The shock decayed and failed to reach STEREO A around the backward direction. Comparison between ENLIL MHD simulations and the multipoint in situ measurements indicates that the shock expansion near the Sun is crucial for determining the arrival or nonarrival and space weather impact at certain heliospheric locations. The large shock geometry and kinematics have to be taken into account and properly treated for accurate predictions of the arrival time and space weather impact of CMEs.
Lysine succinylation is a new kind of post-translational modification which plays a key role in protein conformation regulation and cellular function control. To understand the mechanism of ...succinylation profoundly, it is necessary to identify succinylation sites in proteins accurately. However, traditional methods, experimental approaches, are labor-intensive and time-consuming. Computational prediction methods have been proposed recent years, and they are popular because of their convenience and high speed. In this study, we developed a new method to predict succinylation sites in protein combining multiple features, including amino acid composition, binary encoding, physicochemical property and grey pseudo amino acid composition, with a feature selection scheme (information gain). And then, it was trained using SVM (Support Vector Machine) and an ensemble learning algorithm.
The performance of this method was measured with an accuracy of 89.14% and a MCC (Matthew Correlation Coefficient) of 0.79 using 10-fold cross validation on training dataset and an accuracy of 84.5% and a MCC of 0.2 on independent dataset.
The conclusions made from this study can help to understand more of the succinylation mechanism. These results suggest that our method was very promising for predicting succinylation sites. The source code and data of this paper are freely available at https://github.com/ningq669/PSuccE .
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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