11 research outputs found
Bifunctional Oxo-Tethered Ruthenium Complex Catalyzed Asymmetric Transfer Hydrogenation of Aryl <i>N</i>‑Heteroaryl Ketones
A facile
asymmetric transfer hydrogenation of <i>ortho</i>-substituted
aryl <i>N</i>-heteroaryl ketones and non-<i>ortho</i>-substituted <i>N</i>-oxide of aryl <i>N</i>-heteroaryl
ketones using a readily available oxo-tethered
ruthenium complex as a catalyst and sodium formate as a hydrogen source
in an aqueous solution has been discovered. A variety of chiral aryl <i>N</i>-heteroaryl methanols were obtained with up to 99.9% ee
Transformation of Alkynes into Chiral Alcohols via TfOH-Catalyzed Hydration and Ru-Catalyzed Tandem Asymmetric Hydrogenation
A novel full atom-economic
process for the transformation of alkynes
into chiral alcohols by TfOH-catalyzed hydration coupled with Ru-catalyzed
tandem asymmetric hydrogenation in TFE under simple conditions has
been developed. A range of chiral alcohols was obtained with broad
functional group tolerance, good yields, and excellent stereoselectivities
SPORL Pretreatment Spent Liquors Enhance the Enzymatic Hydrolysis of Cellulose and Ethanol Production from Glucose
This study investigated
the recycle utilization of SPORL pretreatment
spent liquor. Three lignosulfonates (LSs) were purified from the spent
liquor of SPORL pretreated Beetle-killed lodgepole pine (BKLP), Poplar
NE222 (NE222), and Douglas-fir (FS10). The structural characterization
showed that the apparent molecular mass and sulfur content of NE222-LS
were lowest, but the phenolic group content was highest. FS10-LS,
from a pH profiling SPORL pretreatment, had the highest apparent molecular
mass but medium sulfur and phenolic group content. The spectral analyses
exhibited that the guaiacyl unit was the main structure in BKLP and
FS10 LSs, while NE222-LS mainly contained both guaiacyl and syringyl
units. Both LSs and SPORL pretreatment spent liquors were used as
additives to enzymatic hydrolysis of Whatman paper and ethanol production
from glucose. LSs and liquors, from SPORL pretreated BKLP and NE222,
could obviously enhance the enzymatic saccharification. Nevertheless,
LS and liquor from SPORL pretreated FS10 presented a slight negative
effect on enzymatic saccharification. All LSs and liquors with low
concentration exhibited no inhibition on ethanol fermentation from
glucose. When whole spent liquors without any detoxification were
applied to prepare the fermentation medium with an initial glucose
concentration of 100 g/L, the ethanol yield was almost the same as
the control for BKLP and FS10 liquors. Nevertheless, the whole NE222
liquor without detoxification inhibited ethanol production thoroughly
Horseradish Peroxidase Modification of Sulfomethylated Wheat Straw Alkali Lignin To Improve Its Dispersion Performance
Wheat
straw alkali lignin (WAL), byproducts from the alkali pulping
process, is a low-value product with poor water solubility and limited
dispersion performance. Sulfomethylated wheat straw alkali lignin
(SWAL) was first prepared by sulfomethylation. In order to further
improve the dispersion performance of WAL, a commercially available
horseradish peroxidase (HRP) was then used to modify SWAL. Gel permeation
chromatography showed an obvious increase in molecular weight after
HRP modification by approximately 6 fold and 18 fold, compared with
SWAL and WAL, respectively. The structural characterization was investigated
by functional group content measurements and IR and <sup>1</sup>H
NMR analyses. After the HRP modification, the phenolic and methoxyl
group content decreased, while the sulfonic and carboxyl group content
increased. Because of the higher molecular weight and hydrophilic
group content, the HRP modification induced a significant improvement
in adsorption and dispersion performance of WAL
Rational Design of Magnetic Micronanoelectrodes for Recognition and Ultrasensitive Quantification of Cysteine Enantiomers
Driven by the urgent need for recognition
and quantification of
trace amino acids enantiomers in various biologic samples, we demonstrate
for the first time an ultrasensitive electrochemical chiral biosensor
for cysteine (Cys) based on magnetic nanoparticles (Fe<sub>3</sub>O<sub>4</sub>@PDA/Cu<sub><i>x</i></sub>O) as electrode
units. d-Cys-Cu<sup>2+</sup>-d-Cys formed in the
presence of cysteine exhibits strong stability and a shielding effect
on the redox current of indicator Cu<sup>2+</sup>, which can be used
to quantify and recognize d-Cys by square wave voltammetry.
Simultaneous detection of d-Cys and homocysteine (Hcy) is
achieved in the presence of other amino acids, demonstrating an excellent
selectivity of the sensor. Moreover, aided by the enrichment treatment
effect of magnetic micronanoelectrodes, an ultrahigh sensitivity up
to 102 μA μM<sup>–1</sup> cm<sup>–2</sup> was achieved, the detection limit is reduced to picomolar level
(83 pM) for d-Cys and can be used for the recognition of
cysteine enantiomers. The proposed method has been verified by real
sample analysis with satisfactory results. The results highlight the
feasibility of our proposed strategy for magnetic micronanoelectrode
sensor, electrochemical recognition, and quantification of d-Cys, which can be more broadly applicable than that with traditional
electrode structures and further advance the field of electrochemical
sensors
808 nm Excited Multicolor Upconversion Tuning through Energy Migration in Core–Shell–Shell Nanoarchitecture
NaGdF<sub>4</sub>: A (A = Eu, Tb)@NaGdF<sub>4</sub>: Yb, Tm@NaGdF<sub>4</sub>: Yb, Nd core–shell–shell is designed to achieve
808 nm excited upconversion emission tuning. On the basis of the above
core–shell–shell nanostructure, intense upconversion
emission has been realized for activators without long-lived intermediate
states (Eu<sup>3+</sup>, Tb<sup>3+</sup>) through Gd<sup>3+</sup>-mediated
energy migration under 808 nm irradiation, enriching the emission
colors. The spatial separation, where sensitizer (Nd<sup>3+</sup>),
accumulator (Tm<sup>3+</sup>), and activator (Eu<sup>3+</sup>, Tb<sup>3+</sup>) are doped into separated layers, effectively suppresses
nonradiative decays so that the doping concentration of Nd<sup>3+</sup> can reach to 40%, vastly enhancing the luminescence intensity. Notably,
when Gd<sup>3+</sup> ions are replaced by Nd<sup>3+</sup> or inert
Y<sup>3+</sup> in NaGdF<sub>4</sub>: Yb, Nd outer shell, without Gd<sup>3+</sup>-mediated energy migration, the deleterious energy transfer
from Tm<sup>3+</sup> in the interlayer to surface quenchers is suppressed,
and thus, more active energy is trapped by activators, which induces
the further change of upconversion emission color. Furthermore, the
multicolor upconversion tuning can also be realized via Tb<sup>3+</sup>-mediated energy migration. 808 nm excited multicolor upconversion
tuning, overcoming low tissue penetration and overheating effect under
980 nm excitation, improves the feasibility of upconversion nanoparticles
in multicolor imaging and multiplexed detection areas
Recycling Cellulase by a pH-Responsive Lignin-Based Carrier through Electrostatic Interaction
Enzymatic
conversion of lignocelluloses into fermentable sugars
is a key step in producing liquid fuels and chemicals in an ecofriendly
and sustainable manner. However, because of the large quantities of
cellulase required in enzymatic hydrolysis, the high cellulase cost
make the production cost of glucose still high. To reduce the overall
production cost and achieve the comprehensive utilization of lignocelluloses.
A new intensive production process for enzymatic saccharification
was developed: lignin, the residue of lignocellulosic substrates after
enzymatic hydrolysis, was modified to a pH-responsive carrier (pH-LC)
by simple graft reactions and used to recycle cellulase through electrostatic
interaction. pH-LC exhibited reversible soluble–insoluble property
as solution pH changed, and it did not inhibit cellulase activity.
By simply adjusting the pH of the solution contained pH-LC and cellulase,
cellulase could be precipitated or dissolved for recycling. pH-LC
could recover more than 90% of filter paper activity in solution for
cellulase CTec2. During the enzymatic hydrolysis of corncob residue,
pH-LC could not only recover more than 50% of cellulase but also increase
the yield of glucose from 78.1% to 93.0%. This new process is not
only green and convenient but also well integrated with existing processes
and easily applied
Media 1: Loop coupled resonator optical waveguides
Originally published in Optics Express on 06 October 2014 (oe-22-20-24202
Media 3: Loop coupled resonator optical waveguides
Originally published in Optics Express on 06 October 2014 (oe-22-20-24202
Media 4: Loop coupled resonator optical waveguides
Originally published in Optics Express on 06 October 2014 (oe-22-20-24202