3,073 research outputs found
Lysine Biosynthesis in Bacteria: A Metallodesuccinylase as a Potential Antimicrobial Target
In this review, we summarize the recent literature on dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) enzymes, with an emphasis on structure–function studies that provide insight into the catalytic mechanism. Crystallographic data have also provided insight into residues that might be involved in substrate and hence inhibitor recognition and binding. These data have led to the design and synthesis of several new DapE inhibitors, which are described along with what is known about how inhibitors interact with the active site of DapE enzymes, including the efficacy of a moderately strong DapE inhibitor
An Analytical Method for Detecting Toxic Metal Cations Using Cyclotriveratrylene Derivative Capped Gold Nanoparticles
Cyclotriveratrylene-oxime (CTV-oxime) derivatives that terminate with a dithiolate linker were synthesized enabling the supramolecular scaffold to adhere to gold nanoparticles (AuNPs) with the bowl-shaped cavity of the CTV scaffold exposed for utilization in host–guest chemistry. Exposure of these CTV functionalized AuNPs to varying concentrations of di- and trivalent metal cations resulted in the formation of large CTV-AuNP polymeric clusters and an accompanying a shift in the plasmon resonance. These interactions between the CTV-AuNPs and the metal cations in solution provides proof-of-concept that supramolecular functionalized AuNPs can be used as a simple and straightforward, on-site detection system for toxic metal cations in solution. The order of binding affinity of the metals studied based on observed Kd values is Cu2+ \u3e Zn2+ \u3e Pb2+ \u3e Hg2+ \u3e Eu3+ \u3e Cd2+
Direct Patterning of a Cyclotriveratrylene Derivative for Directed Self-assembly of C60
A novel apex-modified cyclotriveratrylene (CTV) derivative with an attached thiolane-containing lipoic acid linker was directly patterned onto gold substrates via dip-pen nanolithography (DPN). The addition of a dithiolane-containing linker to the apex of CTV provides a molecule that can adhere to a gold surface with its bowl-shaped cavity directed away from the surface, thereby providing a surface-bound CTV host that can be used for the directed assembly of guest molecules. Subsequent exposure of these CTV microarrays to C60 in toluene resulted in the directed assembly of predesigned, spatially controlled, high-density microarrays of C60. The molecular recognition capabilities of this CTV template toward C60 provides proof-of-concept that supramolecular CTV scaffolds can be directly patterned onto surfaces providing a foundation for the development of organic electronic and optoelectronic materials
Red Sea Rifting Controls on Groundwater Reservoir Distribution: Constraints from Geophysical, Isotopic, and Remote Sensing Data
Highly productive wells in the Central
Eastern Desert of Egypt are tapping groundwater
in subsided blocks of Jurassic to
Cretaceous sandstone (Taref Formation of
the Nubian Sandstone Group) and Oligocene
to Miocene sandstone (Nakheil Formation),
now occurring beneath the Red Sea coastal
plain and within the proximal basement complex.
Aquifer development is related to Red
Sea rifting: (1) rifting was accommodated by
vertical extensional displacement on preexisting
NW-SE– to N-S–trending faults forming
a complex array of half-grabens and asymmetric
horsts; and (2) subsided blocks escaped
erosion accompanying the Red Sea–related
uplift. Subsided blocks were identifi ed and
verifi ed using satellite data, geologic maps,
and fi eld and geophysical investigations. Interpretations
of very low frequency (VLF)
measurements suggest the faults acted as
conduits for ascending groundwater from the
subsided aquifers. Stable isotopic compositions
(δD: –19.3‰ to –53.9‰; δ18O: –2.7‰ to
–7.1‰) of groundwater samples from these
aquifers are interpreted as mixtures of fossil
(up to 70%) and modern (up to 65%) precipitation.
Groundwater volumes in subsided
blocks are large; within the Central Eastern
Desert basement complex alone, they are estimated
at 3 × 109 m3 and 10 × 109 m3 for the
Nakheil and Taref Formations, respectively.
Results highlight the potential for identifying
similar rift-related aquifer systems along
the Red Sea–Gulf of Suez system, and in rift
systems elsewhere. An understanding of the
distribution of Red Sea rift–related aquifers
and modern recharge contributions to these
aquifers could assist in addressing the rising
demands for fresh water supplies and water
scarcity issues in the regio
Red Sea Rifting Controls on Groundwater Reservoir Distribution: Constraints from Geophysical, Isotopic, and Remote Sensing Data
Highly productive wells in the Central
Eastern Desert of Egypt are tapping groundwater
in subsided blocks of Jurassic to
Cretaceous sandstone (Taref Formation of
the Nubian Sandstone Group) and Oligocene
to Miocene sandstone (Nakheil Formation),
now occurring beneath the Red Sea coastal
plain and within the proximal basement complex.
Aquifer development is related to Red
Sea rifting: (1) rifting was accommodated by
vertical extensional displacement on preexisting
NW-SE– to N-S–trending faults forming
a complex array of half-grabens and asymmetric
horsts; and (2) subsided blocks escaped
erosion accompanying the Red Sea–related
uplift. Subsided blocks were identifi ed and
verifi ed using satellite data, geologic maps,
and fi eld and geophysical investigations. Interpretations
of very low frequency (VLF)
measurements suggest the faults acted as
conduits for ascending groundwater from the
subsided aquifers. Stable isotopic compositions
(δD: –19.3‰ to –53.9‰; δ18O: –2.7‰ to
–7.1‰) of groundwater samples from these
aquifers are interpreted as mixtures of fossil
(up to 70%) and modern (up to 65%) precipitation.
Groundwater volumes in subsided
blocks are large; within the Central Eastern
Desert basement complex alone, they are estimated
at 3 × 109 m3 and 10 × 109 m3 for the
Nakheil and Taref Formations, respectively.
Results highlight the potential for identifying
similar rift-related aquifer systems along
the Red Sea–Gulf of Suez system, and in rift
systems elsewhere. An understanding of the
distribution of Red Sea rift–related aquifers
and modern recharge contributions to these
aquifers could assist in addressing the rising
demands for fresh water supplies and water
scarcity issues in the regio
What Determines the Depth of BALs? Keck HIRES Observations of BALQSO 1603+300
We find that the depth and shape of the broad absorption lines (BALs) in
BALQSO 1603+3002 are determined largely by the fraction of the emitting source
which is covered by the BAL flow. In addition, the observed depth of the BALs
is poorly correlated with their real optical depth. The implication of this
result is that abundance studies based on direct extraction of column densities
from the depth of the absorption troughs are unreliable. Our conclusion is
based on analysis of unblended absorption features of two lines from the same
ion (in this case the Si IV doublet), which allows unambiguous separation of
covering factor and optical depth effects. The complex morphology of the
covering factor as a function of velocity suggests that the BALs are produced
by several physically separated outflows. The covering factor is ion dependent
in both depth and velocity width. We also find evidence that in BALQSO
1603+3002 the flow does not cover the broad emission line region.Comment: 13 pages, 2 figures, accepted for publication in Ap
Platelet Function Monitoring in Patients With Coronary Artery Disease
Studies focused on patient responsiveness to antiplatelet therapies, particularly aspirin and clopidogrel, have increased in recent years. However, the relations of in vivo platelet function and adverse clinical events to results of ex vivo platelet function tests remain largely unknown. This article describes current methods of measuring platelet function in various clinical and research situations and their advantages and disadvantages, reviews evidence for antiplatelet response variability and resistance, discusses the potential pitfalls of monitoring platelet function, and demonstrates emerging data supporting the positive clinical and treatment implications of platelet function testing
- …