4 research outputs found
Tuning Metal–Organic Frameworks with Open-Metal Sites and Its Origin for Enhancing CO<sub>2</sub> Affinity by Metal Substitution
Reducing anthropogenic carbon emission is a problem that
requires
immediate attention. Metal–organic frameworks (MOFs) have emerged
as a promising new materials platform for carbon capture, of which
Mg-MOF-74 offers chemospecific affinity toward CO<sub>2</sub> because
of the open Mg sites. Here we tune the binding affinity of CO<sub>2</sub> for M-MOF-74 by metal substitution (M = Mg, Ca, and the first
transition metal elements) and show that Ti- and V-MOF-74 can have
an enhanced affinity compared to Mg-MOF-74 by 6–9 kJ/mol. Electronic
structure calculations suggest that the origin of the major affinity
trend is the local electric field effect of the open metal site that
stabilizes CO<sub>2</sub>, but forward donation from the lone-pair
electrons of CO<sub>2</sub> to the empty d-levels of transition metals
as in a weak coordination bond makes Ti and V have an even higher
binding strength than Mg, Ca, and Sc
Correction and Addition to “Tuning Metal–Organic Frameworks with Open-Metal Sites and Its Origin for Enhancing CO<sub>2</sub> Affinity by Metal Substitution”
Correction and Addition
to “Tuning Metal–Organic Frameworks with Open-Metal
Sites and Its Origin for Enhancing CO<sub>2</sub> Affinity by Metal
Substitution
Highly Efficient Catalytic Cyclic Carbonate Formation by Pyridyl Salicylimines
Cyclic
carbonates as industrial commodities offer a viable nonredox carbon
dioxide fixation, and suitable heterogeneous catalysts are vital for
their widespread implementation. Here, we report a highly efficient
heterogeneous catalyst for CO<sub>2</sub> addition to epoxides based
on a newly identified active catalytic pocket consisting of pyridine,
imine, and phenol moieties. The polymeric, metal-free catalyst derived
from this active site converts less-reactive styrene oxide under atmospheric
pressure in quantitative yield and selectivity to the corresponding
carbonate. The catalyst does not need additives, solvents, metals,
or co-catalysts, can be reused at least 10 cycles without the loss
of activity, and scaled up easily to a kilogram scale. Density functional
theory calculations reveal that the nucleophilicity of pyridine base
gets stronger due to the conjugated imines and H-bonding from phenol
accelerates the reaction forward by stabilizing the intermediate
Quantitative Proteomics Reveals Temporal Proteomic Changes in Signaling Pathways during BV2 Mouse Microglial Cell Activation
The
development of systematic proteomic quantification techniques
in systems biology research has enabled one to perform an in-depth
analysis of cellular systems. We have developed a systematic proteomic
approach that encompasses the spectrum from global to targeted analysis
on a single platform. We have applied this technique to an activated
microglia cell system to examine changes in the intracellular and
extracellular proteomes. Microglia become activated when their homeostatic
microenvironment is disrupted. There are varying degrees of microglial
activation, and we chose to focus on the proinflammatory reactive
state that is induced by exposure to such stimuli as lipopolysaccharide
(LPS) and interferon-gamma (IFN-Îł). Using an improved shotgun
proteomics approach, we identified 5497 proteins in the whole-cell
proteome and 4938 proteins in the secretome that were associated with
the activation of BV2 mouse microglia by LPS or IFN-Îł. Of the
differentially expressed proteins in stimulated microglia, we classified
pathways that were related to immune-inflammatory responses and metabolism.
Our label-free parallel reaction monitoring (PRM) approach made it
possible to comprehensively measure the hyper-multiplex quantitative
value of each protein by high-resolution mass spectrometry. Over 450
peptides that corresponded to pathway proteins and direct or indirect
interactors via the STRING database were quantified by label-free
PRM in a single run. Moreover, we performed a longitudinal quantification
of secreted proteins during microglial activation, in which neurotoxic
molecules that mediate neuronal cell loss in the brain are released.
These data suggest that latent pathways that are associated with neurodegenerative
diseases can be discovered by constructing and analyzing a pathway
network model of proteins. Furthermore, this systematic quantification
platform has tremendous potential for applications in large-scale
targeted analyses. The proteomics data for discovery and label-free
PRM analysis have been deposited to the ProteomeXchange Consortium
with identifiers and , respectively