28 research outputs found
Characteristics of Potassium Prolinate + Water + Ethanol Solution as a Phase Changing Absorbent for CO<sub>2</sub> Capture
Potassium
prolinate + water + ethanol (ProK/W/Eth) solution has
potential use as a liquid-to-solid phase-changing absorbent for energy-efficient
CO<sub>2</sub> capture process. In this study, the equilibrium solubility
of CO<sub>2</sub> in ProK/W/Eth solutions was measured in a stirred
equilibrium cell at a temperature range from 293 to 343 K and CO<sub>2</sub> partial pressures up to 200 kPa. Density and viscosity were
also measured at temperatures from 293 to 333 K and ProK molality
up to 6.09 mol·kg<sup>–1</sup> ethanol. Moreover, the
CO<sub>2</sub> loading and cyclic capacity were compared with aqueous
monoethanolamine (MEA) and aqueous ProK solution. The solubility data
were well-represented using a Soft model with AAD within 8.0%. The
data of density and viscosity were also correlated with empirical
models. The predicted results matched well the experimental data with
AAD within 0.37% for density and 1.38% for viscosity
Physicochemical Properties of Aqueous Potassium Salts of Basic Amino Acids as Absorbents for CO<sub>2</sub> Capture
Aqueous
amino acid salt (AAS) solutions could be attractive absorbents
for CO<sub>2</sub> removal from flue gases. Density, viscosity, and
solubility of N<sub>2</sub>O in aqueous potassium salts of lysine,
histidine, and arginine were measured over the temperature range from
(293 to 353) K and molality concentration range from (0.26 to 3.6)
mol·kg<sup>–1</sup>. Experimental results were correlated
well with empirical correlations. The ion specific parameters (<i>h</i><sub>AA<sup>–</sup></sub>), based on the Weisenberger
and Schumpe model, were fitted using the solubility data of N<sub>2</sub>O in the aforementioned AAS systems, valid up to 328 K. The
models using temperature dependence of <i>h</i><sub>AA<sup>–</sup></sub> predict well within 2.5% AAD. The physical solubility
of CO<sub>2</sub> in the aqueous AAS solutions was also estimated
Kinetics of CO<sub>2</sub> Absorption into Aqueous Basic Amino Acid Salt: Potassium Salt of Lysine Solution
Aqueous amino acid
salts are considered as an attractive alternative
to alkanolamine solvents (e.g., MEA) for carbon dioxide (CO<sub>2</sub>) absorption. The kinetics of CO<sub>2</sub> into unloaded aqueous
solutions of potassium lysinate (LysK) was studied using a wetted
wall column at concentrations ranging from 0.25 to 2.0 M and temperatures
from 298 to 333 K. Physicochemical properties of aqueous LysK solutions
such as density, viscosity, and physical solubility of CO<sub>2</sub> were measured to evaluate the reaction rate constants. The reaction
pathway is described using zwitterion mechanism taking into account
the effect of ionic strength on the reaction rate. Under the fast
pseudo-first-order regime, the reaction rate parameters were obtained
and correlated in a power-law reaction rate expression. LysK shows
higher chemical reactivity toward CO<sub>2</sub> than the industrial
standard MEA and most of amino acid salts. Its reaction rate constants
increase considerably with concentration and temperature. The reaction
order is found to be an average value of 1.58 with respect to LysK.
The forward second-order kinetic rate constant, <i>k</i><sub>2</sub><sup>0</sup>, are obtained
as 31615 and 84822 m<sup>3</sup> kmol<sup>–1</sup> s<sup>–1</sup> at 298 and 313 K, respectively with activation energy of 51.0 kJ
mol<sup>–1</sup>. The contribution of water to the zwitterion
deprotonation seems to be more significant than that of LysK for the
above-mentioned kinetic conditions
Monolithic Capillary Column Based Glycoproteomic Reactor for High-Sensitive Analysis of N‑Glycoproteome
Despite the importance of protein N-glycosylation in
a series of
biological processes, in-depth characterization of protein glycosylation
is still a challenge due to the high complexity of biological samples
and the lacking of highly sensitive detection technologies. We developed
a monolithic capillary column based glycoproteomic reactor enabling
high-sensitive mapping of N-glycosylation sites from minute amounts
of sample. Unlike the conventional proteomic reactors with only strong-cation
exchange or hydrophilic-interaction chromatography columns, this novel
glycoproteomic reactor was composed of an 8 cm long C12 hydrophobic
monolithic capillary column for protein digestion and a 6 cm long
organic–silica hybrid hydrophilic monolithic capillary column
for glycopeptides enrichment and deglycosylation, which could complete
whole-sample preparation including protein purification/desalting,
tryptic digestion, enrichment, and deglycosylation of glycopeptides
within about 3 h. The developed reactor exhibited high detection sensitivity
in mapping of N-glycosylation sites by detection limit of horseradish
peroxidase as low as 2.5 fmol. This reactor also demonstrated the
ability in complex sample analysis, and in total, 486 unique N-glycosylation
sites were reliably mapped in three replicate analyses of a protein
sample extracted from ∼10<sup>4</sup> HeLa cells
Monolithic Capillary Column Based Glycoproteomic Reactor for High-Sensitive Analysis of N‑Glycoproteome
Despite the importance of protein N-glycosylation in
a series of
biological processes, in-depth characterization of protein glycosylation
is still a challenge due to the high complexity of biological samples
and the lacking of highly sensitive detection technologies. We developed
a monolithic capillary column based glycoproteomic reactor enabling
high-sensitive mapping of N-glycosylation sites from minute amounts
of sample. Unlike the conventional proteomic reactors with only strong-cation
exchange or hydrophilic-interaction chromatography columns, this novel
glycoproteomic reactor was composed of an 8 cm long C12 hydrophobic
monolithic capillary column for protein digestion and a 6 cm long
organic–silica hybrid hydrophilic monolithic capillary column
for glycopeptides enrichment and deglycosylation, which could complete
whole-sample preparation including protein purification/desalting,
tryptic digestion, enrichment, and deglycosylation of glycopeptides
within about 3 h. The developed reactor exhibited high detection sensitivity
in mapping of N-glycosylation sites by detection limit of horseradish
peroxidase as low as 2.5 fmol. This reactor also demonstrated the
ability in complex sample analysis, and in total, 486 unique N-glycosylation
sites were reliably mapped in three replicate analyses of a protein
sample extracted from ∼10<sup>4</sup> HeLa cells
Monolithic Capillary Column Based Glycoproteomic Reactor for High-Sensitive Analysis of N‑Glycoproteome
Despite the importance of protein N-glycosylation in
a series of
biological processes, in-depth characterization of protein glycosylation
is still a challenge due to the high complexity of biological samples
and the lacking of highly sensitive detection technologies. We developed
a monolithic capillary column based glycoproteomic reactor enabling
high-sensitive mapping of N-glycosylation sites from minute amounts
of sample. Unlike the conventional proteomic reactors with only strong-cation
exchange or hydrophilic-interaction chromatography columns, this novel
glycoproteomic reactor was composed of an 8 cm long C12 hydrophobic
monolithic capillary column for protein digestion and a 6 cm long
organic–silica hybrid hydrophilic monolithic capillary column
for glycopeptides enrichment and deglycosylation, which could complete
whole-sample preparation including protein purification/desalting,
tryptic digestion, enrichment, and deglycosylation of glycopeptides
within about 3 h. The developed reactor exhibited high detection sensitivity
in mapping of N-glycosylation sites by detection limit of horseradish
peroxidase as low as 2.5 fmol. This reactor also demonstrated the
ability in complex sample analysis, and in total, 486 unique N-glycosylation
sites were reliably mapped in three replicate analyses of a protein
sample extracted from ∼10<sup>4</sup> HeLa cells
A Comprehensive Differential Proteomic Study of Nitrate Deprivation in <i>Arabidopsis</i> Reveals Complex Regulatory Networks of Plant Nitrogen Responses
Nitrogen (N) is an important nutrient and signal for
plant growth and development. However, to date, our knowledge of how
plants sense and transduce the N signals is very limited. To better
understand the molecular mechanisms of plant N responses, we took
two-dimensional gel-based proteomic and phosphoproteomic approaches
to profile the proteins with abundance and phosphorylation state changes
during nitrate deprivation and recovery in the model plant <i>Arabidopsis thaliana</i>. After 7-day-old seedlings were N-deprived
for up to 48 h followed by 24 h recovery, a total of 170 and 38 proteins
were identified with significant changes in abundance and phosphorylation
state, respectively. Bioinformatic analyses implicate these proteins
in diverse cellular processes including N and protein metabolisms,
photosynthesis, cytoskeleton, redox homeostasis, and signal transduction.
Functional studies of the selected nitrate-responsive proteins indicate
that the proteasome regulatory subunit RPT5a and the cytoskeleton
protein Tubulin alpha-6 (TUA6) play important roles in plant nitrate
responses by regulating plant N use efficiency (NUE) and low nitrate-induced
anthocyanin biosynthesis, respectively. In conclusion, our study provides
novel insights into plant responses to nitrate at the proteome level,
which are expected to be highly useful for dissecting the N response
pathways in higher plants and for improving plant NUE
Determination of CK2 Specificity and Substrates by Proteome-Derived Peptide Libraries
Understanding
the specificity of kinases enables prediction of
their substrates and uncovering kinase functions in signaling pathways.
Traditionally synthesized peptide libraries are used to determine
the kinase specificity. In this study, a proteomics-based method was
developed to determine the specificity of kinase by taking the advantages
of proteome-derived peptide libraries and quantitative proteomics.
Proteome-derived peptide libraries were constructed by digesting proteins
in total cell lysate followed with dephosphorylation of the resulting
peptides. After incubating the peptide libraries with/without CK2
for in vitro kinase assay, stable isotopic labeling based quantitative
phosphoproteomics was applied to distinguish the in vitro phosphosites
generated by CK2. By using the above approach, 404 CK2 in vitro phosphosites
were identified by 1D LC–MS/MS. Those sites allowed the statistic
determination of the CK2 specificity. In addition to the easy construction
of the proteome-derived peptide library, another significant advantage
of this method over the method with synthesized peptide libraries
is that the identified phosphosites could be directly mapped to proteins
for the screening of putative kinase substrates. It was found that
the confidence for substrate identification could be significantly
improved by comparing the in vitro CK2 sites with the in vivo sites
identified by phosphoproteomics analysis of the same cell lines. By
applying this integrated strategy, 138 phosphosites from 105 putative
CK2 substrates of high confidence were determined
Selective Enrichment of Cysteine-Containing Phosphopeptides for Subphosphoproteome Analysis
Among
the natural amino acids, cysteine is unique since it can
form a disulfide bond through oxidation and reduction of sulfhydryl
and thus plays a pervasive role in modulation of proteins activities
and structures. Crosstalk between phosphorylation and other post-translational
modifications has become a recurrent theme in cell signaling regulation.
However, the crosstalk between the phosphorylation and the formation
and reductive cleavage of disulfide bond has not been investigated
so far. To facilitate the study of this crosstalk, it is important
to explore the subset of phosphoproteome where phosphorylations are
occurred near to cysteine in the protein sequences. In this study,
we developed a straightforward sequential enrichment method by combining
the thiol affinity chromatography with the immobilized titanium ion
affinity chromatography to selectively enrich cysteine-containing
phosphopeptides. The high specificity and high sensitivity of this
method were demonstrated by analyzing the samples of Jurkat cells.
This “divide and conquer” strategy by specific analysis
of a subphosphoproteome enables identification of more low abundant
phosphosites than the conventional global phosphoproteome approach.
Interestingly, amino acid residues surrounding the identified phosphosites
were enriched with buried residues (L, V, A, C) while depleted with
exposed residues (D, E, R, K). Also, the phosphosites identified by
this approach showed a dramatic decrease in locating in disorder regions
compared to that identified by conventional global phosphoproteome.
Further analysis showed that more proline directed kinases and fewer
acidophilic kinases were responsible for the phosphorylation sites
of this subphosphoproteome
Selective Enrichment of Cysteine-Containing Phosphopeptides for Subphosphoproteome Analysis
Among
the natural amino acids, cysteine is unique since it can
form a disulfide bond through oxidation and reduction of sulfhydryl
and thus plays a pervasive role in modulation of proteins activities
and structures. Crosstalk between phosphorylation and other post-translational
modifications has become a recurrent theme in cell signaling regulation.
However, the crosstalk between the phosphorylation and the formation
and reductive cleavage of disulfide bond has not been investigated
so far. To facilitate the study of this crosstalk, it is important
to explore the subset of phosphoproteome where phosphorylations are
occurred near to cysteine in the protein sequences. In this study,
we developed a straightforward sequential enrichment method by combining
the thiol affinity chromatography with the immobilized titanium ion
affinity chromatography to selectively enrich cysteine-containing
phosphopeptides. The high specificity and high sensitivity of this
method were demonstrated by analyzing the samples of Jurkat cells.
This “divide and conquer” strategy by specific analysis
of a subphosphoproteome enables identification of more low abundant
phosphosites than the conventional global phosphoproteome approach.
Interestingly, amino acid residues surrounding the identified phosphosites
were enriched with buried residues (L, V, A, C) while depleted with
exposed residues (D, E, R, K). Also, the phosphosites identified by
this approach showed a dramatic decrease in locating in disorder regions
compared to that identified by conventional global phosphoproteome.
Further analysis showed that more proline directed kinases and fewer
acidophilic kinases were responsible for the phosphorylation sites
of this subphosphoproteome