14 research outputs found
One-Pot Synthesis of Strained Macrocyclic Pyridone Hexamers and Their High Selectivity toward Cu<sup>2+</sup> Recognition
The removal of Cu<sup>2+</sup> ions
is relevant to environmental
pollution control and neurodegenerative disease treatment. A novel
family of strained macrocyclic pyridone hexamers, which exhibit highly
selective recognition of Cu<sup>2+</sup> ions and reduce copper content
in artificial seawater by 97% at a very low [host]:[CuCl<sub>2</sub>] molar ratio of 2:1, is documented
Surprisingly High Selectivity and High Affinity in Mercury Recognition by H‑Bonded Cavity-Containing Aromatic Foldarands
In the absence of macrocyclic ring
constraints, few synthetic systems,
possessing a mostly solvent-independent well-folded conformation that
is predisposed for highly selective and high affinity recognition
of metal ions, have been demonstrated. We report here such a unique
class of conformationally robust modularly tunable folding molecules
termed foldarands that can recognize Hg<sup>2+</sup> ions surprisingly
well over 22 other metal ions. Despite the lack of sulfur atoms and
having only oxygen-donor atoms in its structure, the best foldarand
molecule, i.e., tetramer <b>4</b>, exhibits a selectivity factor
of at least 19 in differentiating the most tightly bound Hg<sup>2+</sup> ion from all other metal ions, and a binding capacity that is ≥18
times that of thio-crown ethers. These two noteworthy binding characters
make possible low level removal of Hg<sup>2+</sup> ions. With a [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio of 5:1 and a single biphasic
solvent extraction, the concentration of Hg<sup>2+</sup> ions could
be reduced drastically by 98% (from 200 to 4 ppb) in pure water. <b>4</b> could also effect a highly efficient reduction in mercury
content by 98% (from 500 to 10 ppb) in artificial groundwater via
multiple successive extractions with an overall consumption of <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg<sup>2+</sup>]
molar ratio
Polar Solvent-Induced Unprecedented Supergelation of (Un)Weathered Crude Oils at Room Temperature
Use
of carrier solvents to assist dissolution of phase-selective
organogelators (PSOGs) before application in oil gelation is a common
approach for solution-based gelators. Because of the competition in
H-bonds by the polar carrier solvent, decreased gelling ability of
PSOGs was often observed. That is, while data are available, the previously
documented biphasic minimum gelling concentrations (BMGCs) are much
larger than the MGCs determined using heating–cooling cycle
for the same PSOG against the same oil. In this study, we show that,
by minimizing amount of polar carrier solvent used, the gelling ability
of PSOGs actually can be enhanced very substantially, rather than
being weakened. More specifically, we demonstrate that use of a minute
amount of polar carrier solvents of different types (e.g., ethyl acetate,
acetone, acetonitrile, and tetrahydrofuran) significantly enhances
the gelling ability of seven structurally different organogelators
in hydrophobic oil. In particular, with the use of 5 vol % essentially
nontoxic ethyl acetate, application of this previously unexplored
strategy onto four monopeptide-based PSOGs produces up to 11-fold
improvement in biphasic gelling ability toward seven (un)weathered
crude oils of widely ranging viscosities. While collectively overcoming
many problematic issues (slow gelling action, low gelling ability,
or a need to use hot or toxic solvent for dissolution of gelator)
associated with PSOGs, this surprisingly simple yet powerful and reliable
method produces unprecedented rapid supergelation of crude oil at
room temperature, with BMGCs of as low as 0.38 w/v % (e.g., 3.8 g
per liter of crude oil) and an averaged reduction in material cost
of gelators by 85–97%
Surprisingly High Selectivity and High Affinity in Mercury Recognition by H‑Bonded Cavity-Containing Aromatic Foldarands
In the absence of macrocyclic ring
constraints, few synthetic systems,
possessing a mostly solvent-independent well-folded conformation that
is predisposed for highly selective and high affinity recognition
of metal ions, have been demonstrated. We report here such a unique
class of conformationally robust modularly tunable folding molecules
termed foldarands that can recognize Hg<sup>2+</sup> ions surprisingly
well over 22 other metal ions. Despite the lack of sulfur atoms and
having only oxygen-donor atoms in its structure, the best foldarand
molecule, i.e., tetramer <b>4</b>, exhibits a selectivity factor
of at least 19 in differentiating the most tightly bound Hg<sup>2+</sup> ion from all other metal ions, and a binding capacity that is ≥18
times that of thio-crown ethers. These two noteworthy binding characters
make possible low level removal of Hg<sup>2+</sup> ions. With a [<b>4</b>]:[Hg<sup>2+</sup>] molar ratio of 5:1 and a single biphasic
solvent extraction, the concentration of Hg<sup>2+</sup> ions could
be reduced drastically by 98% (from 200 to 4 ppb) in pure water. <b>4</b> could also effect a highly efficient reduction in mercury
content by 98% (from 500 to 10 ppb) in artificial groundwater via
multiple successive extractions with an overall consumption of <b>4</b> being 9:1 in terms of [<b>4</b>]:[Hg<sup>2+</sup>]
molar ratio
Proton Gradient-Induced Water Transport Mediated by Water Wires Inside Narrow Aquapores of Aquafoldamer Molecules
Hollow tubular aquapores inside aquafoldamers
can be created via
the “sticky” end-mediated formation of 1D chiral helical
stacks involving same-handed helices, and are capable of aligning
H-bonded water molecules in a chain-like fashion. These aquapores
uniquely feature a small cavity of ∼2.8 Å in diameter,
a size identical to that of the water molecule and also comparable
to the narrowest opening in naturally occurring aquaporins measuring
∼3 Å across, and hence allow not only proton transport
but also unique proton-gradient-induced water transport across the
lipid membranes in the presence of proton gradient
Intramolecularly Hydrogen-Bonded Aromatic Pentamers as Modularly Tunable Macrocyclic Receptors for Selective Recognition of Metal Ions
Despite
the tremendous progress that has been made in macrocyclic
chemistry since the discovery of corands, cryptands, and spherands
more than four decades ago, macrocyclic systems possessing a high
level of controllability in structural configuration concurrent with
a systematic tunability in function are still very rare. Employing
an inner design strategy to orient H-bonding forces toward a macrocyclic
cavity interior while convergently aligning exchangeable ion-binding
building blocks that dictate a near-identical backbone curvature,
we demonstrate here a novel pentagonal framework that not only enables
its variable interior cavity to be maintained at near-planarity but
also allows its ion-binding potential to be highly tunable. The H-bonded
macrocyclic pentamers thus produced have allowed a systematic and
combinatorial evolution of ion-selective pentamers for preferential
recognition of Cs<sup>+</sup>, K<sup>+</sup>, or Ag<sup>+</sup> ions
Low-Cost Phase-Selective Organogelators for Rapid Gelation of Crude Oils at Room Temperature
Frequent marine oil
spills pose a significant threat to the environment
and marine’s ecosystem. We have recently reported a highly
tunable molecular gelling scaffold, which enables us to identify a
few first examples of phase-selective organogelators (PSOGs) that
can instantly gel the crude oil of various types with room-temperature
operation. In this study, we demonstrate the high robustness and reliability
of this modular gelling scaffold in consistently and combinatorially
producing high capacity PSOGs. Such a unique feature has allowed us
to carry out a systematic study of 48 gelators via a two-step screening
process and to discover another powerful carboxybenzyl-based gelator
with comparable gelling properties but with a cost lowered by more
than 300%, pointing to a good commercial potential for rapid cleanup
of oil spills while effectively eliminating environmental pollution
caused by the spilled oil
Rh(III)-Catalyzed Carboamination of Propargyl Cycloalkanols with Arylamines via Csp<sup>2</sup>–H/Csp<sup>3</sup>–Csp<sup>3</sup> Activation
A Rh(III)-catalyzed
carboamination of alkynyl cycloalkanols with
arylamines has been developed. This transformation involves a novel
Csp<sup>2</sup>–H/Csp<sup>3</sup>–Csp<sup>3</sup> activation
relay and provides an efficient approach to versatile 1,2,3-trisubstituted
indoles with a broad range of functional group tolerance
Fusion Gene Vectors Allowing for Simultaneous Drug Selection, Cell Labeling, and Reporter Assay in Vitro and in Vivo
Vector systems allowing simultaneously for rapid drug selection, cell labeling, and reporter assay are highly desirable in biomedical research including stem cell biology. Here, we present such a vector system including pCVpf or pCVpr, plasmids that express <i>pf</i> or <i>pr</i>, a fusion protein between puromycin acetyltransferase and green or red fluorescent protein from CV, the human cytomegalovirus enhancer/promoter. Transfection with pCVpf or pCVpr produced a ∼10% efficiency of gene transfer. A 2-day pulse puromycin selection resulted in ∼13-fold enrichment for transgenic cells, and continuous puromycin selection produced stable transgenic stem cell clones with retained pluripotency. Furthermore, we developed a PAC assay protocol for quantification of transgene expression. To test the usefulness for cell labeling and PAC assay in vivo, we constructed pVASpf containing <i>pf</i> linked to the regulatory sequence of medaka germ gene <i>vasa</i> and generated transgenic fish with visible GFP expression in germ cells. PAC assay revealed the highest expression in the testis. Interestingly, PAC activity was also detectable in somatic organs including the eye, which was validated by fluorescence in situ hybridization. Therefore, the <i>pf</i> and <i>pr</i> vectors provide a useful system for simultaneous drug selection, live labeling, and reporter assay in vitro and in vivo