5 research outputs found
Real-time determination of volatile organic compounds (VOCs) by ion molecule reaction – mass spectrometry (IMR-MS)
Comprehensive analytical validation studies of a developed ion molecule reaction – mass spectrometer (IMR-MS) were undertaken for the real-time determination of volatile organic compounds (VOCs) in air. The instrument was developed with a focus on promoting chemical ionization (CI) in the reaction chamber by direct sample loading and enhancing maintenance efficiency and reliability of the results. Instrument stability was assessed through a system check and pre-performance check process, and consequently, the instrumental and analytical conditions including the plasma generation, pressure, temperature, and flow rate were successfully optimized. Relevant performance characteristics, such as mass resolution, mass detection range, accuracy, and precision were also investigated by VOC standards composed of benzene, toluene, perfluorotoluene, propylbenzene, and octane. To evaluate whether the performance of the technology is comparable to already accepted techniques, the quantitative results of the IMR-MS were compared with those of a commercial mass spectrometer. This evaluation was successful and suggests the applicability of the technology for spillage accidents of hazardous chemicals and identification of odor-causing substances as well as for real-time gas analysis.</p
Incorporation of Unnatural Amino Acids in Response to the AGG Codon
The
biological protein synthesis system has been engineered to
incorporate unnatural amino acid into proteins, and this has opened
up new routes for engineering proteins with novel compositions. While
such systems have been successfully applied in research, there remains
a need to develop new approaches with respect to the wider application
of unnatural amino acids. In this study, we reported a strategy for
incorporating unnatural amino acids into proteins by reassigning one
of the Arg sense codons, the AGG codon. Using this method, several
unnatural amino acids were quantitatively incorporated into the AGG
site. Furthermore, we applied the method to multiple AGG sites, and
even to tandem AGG sequences. The method developed and described here
could be used for engineering proteins with diverse unnatural amino
acids, particularly when employed in combination with other methods
Fungal Laccase-Catalyzed Oxidation of Naturally Occurring Phenols for Enhanced Germination and Salt Tolerance of <i>Arabidopsis thaliana</i>: A Green Route for Synthesizing Humic-like Fertilizers
Fungal
laccases have been highlighted as a catalytic tool for transforming
phenols. Here we demonstrate that fungal laccase-catalyzed oxidations
can transform naturally occurring phenols into plant fertilizers with
properties very similar to those of commercial humic acids. Treatments
of <i>Arabidopsis thaliana</i> with highly cross-linked
polyphenolic products obtained from a mixture of catechol and vanillic
acid were able to enhance the germination and salt tolerance of this
plant. These results revealed that humic-like organic fertilizers
can be produced via in vitro enzymatic oxidation reactions. In particular,
the root elongation pattern resulting from the laccase products was
comparable to that resulting from an auxin-like compound. A detailed
structural comparison of the phenol variants and commercial humic
acids revealed their similarities and differences. Analyses based
on SEM, EFM, ERP, and zeta-potential measurement showed that they
both formed globular granules bearing various hydrophilic/polar groups
in aqueous and solid conditions. Solid-phase <sup>13</sup>C NMR, FT-IR-ATR,
and elemental analyses showed that more nitrogen-based functional
and aliphatic groups were present in the commercial humic acids. Significant
differences were also identifiable with respect to particle size and
specific surface area. High-resolution (15 T) FT-ICR mass spectrometry-based
van Krevelen diagrams showed the compositional features of the variants
to be a subset of those of the humic acids. Overall, our study unraveled
essential structural features of polyaromatics that affect the growth
of plants, and also provided novel bottom-up ecofriendly and finely
tunable pathways for synthesizing humic-like fertilizers
One-Pot Transformation of Technical Lignins into Humic-Like Plant Stimulants through Fenton-Based Advanced Oxidation: Accelerating Natural Fungus-Driven Humification
Commercial
humic acids mainly obtained from leonardite are in increasing
demand in agronomy, and their market size is growing rapidly because
these materials act as soil conditioners and direct stimulators of
plant growth and development. In nature, fungus-driven nonspecific
oxidations are believed to be a key to catabolizing recalcitrant plant
lignins, resulting in lignin humification. Here we demonstrated the
effective transformation of technical lignins derived from the Kraft
processing of woody biomass into humic-like plant fertilizers through
one-pot Fenton oxidations (i.e., artificially accelerated fungus reactions).
The lignin variants resulting from the Fenton reaction, and manufactured
using a few different ratios of FeSO<sub>4</sub> to H<sub>2</sub>O<sub>2</sub>, successfully accelerated the germination of Arabidopsis thaliana seeds and increased the tolerance
of this plant to NaCl-induced abiotic stress; moreover, the extent
of the stimulation of the growth of this plant by these manufactured
lignin variants was comparable or superior to that induced by commercial
humic acids. The results of high-resolution (15 T) Fourier transform-ion
cyclotron resonance mass spectrometry, electrostatic force microscopy,
Fourier transform-infrared spectroscopy, and elemental analyses strongly
indicated that oxygen-based functional groups were incorporated into
the lignins. Moreover, analyses of the total phenolic contents of
the lignins and their sedimentation kinetics in water media together
with scanning electron microscopy- and Brunauer–Emmett–Teller-based
surface characterizations further suggested that polymer fragmentation
followed by modification of the phenolic groups on the lignin surfaces
was crucial for the humic-like activity of the lignins. A high similarity
between the lignin variants and commercial humic acids also resulted
from autonomous deposition of iron species into lignin particles during
the Fenton oxidation, although their short-term effects of plant stimulations
were maintained whether the iron species were present or absent. Finally,
we showed that lignins produced from an industrial-scale acid-induced
hydrolysis of wood chips were transformed with the similar enhancements
of the plant effects, indicating that our fungus-mimicking processes
could be a universal way for achieving effective lignin humification
Comparison of Phase States of PM<sub>2.5</sub> over Megacities, Seoul and Beijing, and Their Implications on Particle Size Distribution
Although the particle phase state is an important property,
there
is scant information on it, especially, for real-world aerosols. To
explore the phase state of fine mode aerosols (PM2.5) in
two megacities, Seoul and Beijing, we collected PM2.5 filter
samples daily from Dec 2020 to Jan 2021. Using optical microscopy
combined with the poke-and-flow technique, the phase states of the
bulk of PM2.5 as a function of relative humidity (RH) were
determined and compared to the ambient RH ranges in the two cities.
PM2.5 was found to be liquid to semisolid in Seoul but
mostly semisolid to solid in Beijing. The liquid state was dominant
on polluted days, while a semisolid state was dominant on clean days
in Seoul. These findings can be explained by the aerosol liquid water
content related to the chemical compositions of the aerosols at ambient
RH; the water content of PM2.5 was much higher in Seoul
than in Beijing. Furthermore, the overall phase states of PM2.5 observed in Seoul and Beijing were interrelated with the particle
size distribution. The results of this study aid in a better understanding
of the fundamental physical properties of aerosols and in examining
how these are linked to PM2.5 in polluted urban atmospheres