10 research outputs found
Synergistic Coordination and Hydrogen Bonding Interaction Modulate the Emission of Iridium Complex for Highly Sensitive Glutamine Imaging in Live Cells
Highly
selective detection of intracellular glutamine (Gln) is
very essential to understand the roles of Gln in some biological processes.
Here, we report a new fluorescent method for selective imaging of
Gln in live cells with an aldehyde-containing iridium complex, [IrÂ(pba)<sub>2</sub>(DMSO)<sub>2</sub>]ÂPF<sub>6</sub> (Hpba = 4-(2-pyridiyl)Âbenzaldehyde)
(Ir1), as the probe. Density functional theory (DFT) calculation and
experimental results suggest that the coordination and hydrogen bonding
interaction between Ir1 and Gln synergistically stabilize the Ir1–Gln
complex, modulate charge-transfer characteristics and emission of
Ir1, and as a consequence, enable Ir1 as the probe for the fluorescent
sensing of Gln. The sensing strategy is well-responsive to Gln without
interference from other amino acids or Gln-containing peptides and
is demonstrated to be useful for in situ Gln imaging in live cells.
The study provides a new method for fluorescent imaging of Gln in
live cells, which is envisioned to find interesting applications in
understanding the roles of Gln in some physiological processes
Zeolitic Imidazolate Framework-Based Electrochemical Biosensor for in Vivo Electrochemical Measurements
This
study demonstrates the first exploitation of zeolitic imidazolate
frameworks (ZIFs) as the matrix for constructing integrated dehydrogenase-based
electrochemical biosensors for in vivo measurement of neurochemicals,
such as glucose. In this study, we find that ZIFs are able to serve
as a matrix for coimmobilizing electrocatalysts (i.e., methylene green,
MG) and dehydrogenases (i.e., glucose dehydrogenase, GDH) onto the
electrode surface and an integrated electrochemical biosensor is readily
formed. We synthesize a series of ZIFs, including ZIF-7, ZIF-8, ZIF-67,
ZIF-68, and ZIF-70 with different pore sizes, surface areas, and functional
groups. The adsorption capabilities toward MG and GDH of these ZIFs
are systematically studied with UV–vis spectroscopy, confocal
laser scanning microscopy, and Fourier transfer-infrared spectroscopy.
Among all the ZIFs demonstrated here, ZIF-70 shows excellent adsorption
capacities toward both MG and GDH and is thus employed as the matrix
for our glucose biosensor. To construct the biosensor, we first drop-coat
a MG/ZIF-70 composite onto a glassy carbon electrode and then coat
GDH onto the MG/ZIF-70 composite. In a continuous-flow system, the
as-prepared ZIF-based biosensor is very sensitive to glucose with
a linear range of 0.1–2 mM. Moreover, the ZIF-based biosensor
is more highly selective on glucose than on other endogenous electroactive
species in the cerebral system. In the end, we demonstrate that our
biosensor is capable of monitoring dialysate glucose collected from
the brain of guinea pigs selectively and in a near real-time pattern
Photodecomposition of Ferrocenedicarboxylic Acid in Methanol to Form an Electroactive Infinite Coordination Polymer and Its Application in Bioelectrochemistry
Accurately
characterizing the product of photodecomposition of ferrocene derivatives
remains a longstanding challenge due to its structural complexity
and strong dependence on the solvent and the substituent. Herein,
photodecomposition of ferrocenedicarboxylic acid (FcDC) in methanol
is found for the first time to form an electroactive infinite coordinate
polymer (ICP) with uniform size, good water stability and photostability,
and excellent electrochemical activity. The possible mechanism for
the ICP formation is proposed based on the fission of the Fe-ring
bond and deprotonation of FcDC under light irradiation. The dissociated
Fe<sup>2+</sup> is first oxidized to Fe<sup>3+</sup> that consequently
coordinates with the deprotonated ferrocene dicarboxylate to produce
ICP nanoparticles. This work not only provides a new insight into
the product formation of the photodecomposition of ferrocene derivatives
but also offers a mild and simple route to the synthesis of electroactive
ICPs
Alkaline Post-Treatment of Cd(II)–Glutathione Coordination Polymers: Toward Green Synthesis of Water-Soluble and Cytocompatible CdS Quantum Dots with Tunable Optical Properties
In this study, we demonstrate a facile
and environmentally friendly
method for the synthesis of glutathione (GSH)-capped water-soluble
CdS quantum dots (QDs) with a high cytocompatibility and a tunable
optical property based on alkaline post-treatment of Cd–GSH
coordination polymers (CPs). Cd–GSH CPs are synthesized with
the coordination reaction of Cd<sup>2+</sup> with GSH at different
pH values, and the CdS QDs are then formed by adding NaOH to the aqueous
dispersion of the Cd–GSH CPs to break the coordination interaction
between Cd<sup>2+</sup> and GSH with the release of sulfur. The particle
size and optical property of the as-formed CdS QDs are found to be
easily tailored by simply adjusting the starting pH values of GSH
solutions used for the formation of Cd–GSH CPs, in which the
wavelengths of trap-state emission of the QDs red-shift with an increase
in the sizes of the QDs that is caused by an increase in the starting
pH values of GSH solutions. In addition, the use of GSH as the capping
reagent eventually endows the as-formed CdS QDs with enhanced water
solubility and good cytocompatibility, as demonstrated with HeLa cells.
The method demonstrated here is advantageous in that the cadmium precursor
and the sulfur source are nontoxic and easily available, and the size,
optical properties, water solubility, and cytocompatibilty of the
as-formed CdS QDs are simply achieved and experimentally regulated.
This study offers a new and green synthetic route to water-soluble
and cytocompatible CdS QDs with tunable optical properties
An Electrochemical Method for Investigation of Conformational Flexibility of Active Sites of <i>Trametes versicolor</i> Laccase Based on Sensitive Determination of Copper Ion with Cysteine-Modified Electrodes
This study demonstrates a facile yet effective electrochemical
method to investigate the conformational flexibility of the active
sites of <i>Trametes versicolor</i> (<i>Tv</i>) laccase based on sensitive determination of copper ions (Cu<sup>2+</sup>) dissociated from the enzyme with the cysteine-modified
Au electrodes. In the native state, the multicopper active sites are
deeply buried in the polypeptide of <i>Tv</i> laccase and
are thus not electrochemically detectable even at the cysteine-modified
Au electrodes. Upon the unfolding of <i>Tv</i> laccase induced
by guanidine hydrochloride (GdnHCl), copper ions dissociate from the
peptide chain and, as a consequence, are electrochemically reduced
and thus detected at the cysteine-modified Au electrodes. Such a property
could be used to investigate the conformational flexibility of multicopper
active sites of <i>Tv</i> laccase in a simple way. We find
that both the conformation of the multicopper active sites in <i>Tv</i> laccase and the enzyme activity change with the presence
of a low concentration of GdnHCl denaturant (midpoint, where 50% of
the enzyme is unfolded, at 0.7 M). This concentration is lower than
that required to induce the conformational changes of <i>Tv</i> laccase molecule as a whole (midpoint at 3.4 M), as investigated
by the intrinsic fluorescence of <i>Tv</i> laccase. This
observation suggests that the multicopper active sites are formed
by relatively weak interactions and hence may be conformationally
more flexible than the intact enzyme. The electrochemical method demonstrated
in this study is technically simple yet effective and could be potentially
useful for investigation on the thermodynamics and kinetics of the
conformational changes of multicopper oxidases induced by different
denaturants
Aspartic Acid-Promoted Highly Selective and Sensitive Colorimetric Sensing of Cysteine in Rat Brain
Direct selective determination of cysteine in the cerebral
system
is of great importance because of the crucial roles of cysteine in
physiological and pathological processes. In this study, we report
a sensitive and selective colorimetric assay for cysteine in the rat
brain with gold nanoparticles (Au-NPs) as the signal readout. Initially,
Au-NPs synthesized with citrate as the stabilizer are red in color
and exhibit absorption at 520 nm. The addition of an aqueous solution
(20 μL) of cysteine or aspartic acid alone to a 200 μL
Au-NP dispersion causes no aggregation, while the addition of an aqueous
solution of cysteine into a Au-NP dispersion containing aspartic acid
(1.8 mM) causes the aggregation of Au-NPs and thus results in the
color change of the colloid from wine red to blue. These changes are
ascribed to the ion pair interaction between aspartic acid and cysteine
on the interface between Au-NPs and solution. The concentration of
cysteine can be visualized with the naked eye and determined by UV–vis
spectroscopy. The signal output shows a linear relationship for cysteine
within the concentration range from 0.166 to 1.67 μM with a
detection limit of 100 nM. The assay demonstrated here is highly selective
and is free from the interference of other natural amino acids and
other thiol-containing species as well as the species commonly existing
in the brain such as lactate, ascorbic acid, and glucose. The basal
dialysate level of cysteine in the microdialysate from the striatum
of adult male Sprague–Dawley rats is determined to be around
9.6 ± 2.1 μM. The method demonstrated here is facile but
reliable and durable and is envisaged to be applicable to understanding
the chemical essence involved in physiological and pathological events
associated with cysteine
Water-Stable, Adaptive, and Electroactive Supramolecular Ionic Material and Its Application in Biosensing
Developing
water-stable and adaptive supramolecular materials is
of great importance in various research fields. Here, we demonstrate
a new kind of water-stable, adaptive, and electroactive supramolecular
ionic materials (SIM) that is formed from the aqueous solutions of
imidazolium-based dication and dianionic dye (i.e., 2,2′-azino-bisÂ(3-ethylbenzothiazoline-6-sulfonic
acid), ABTS) through ionic self-assembly. The formed SIM not only
shows good thermostability and unique optical and electrochemical
properties that are raised from precursors of the SIM, but also exhibits
good water-stability, salt-stability, and adaptive encapsulation properties
toward some heterocyclic cationic dye molecules. UV–vis and
FT-IR results demonstrate that this encapsulation property is essentially
based on the electrostatic interactions between the guest dye molecules
and ABTS in the SIM. The application of the SIM prepared here is illustrated
by the development of a new electrochemical sensor for NADH sensing
at a low potential. This study not only opens a new avenue to the
preparation of the supramolecular materials, but also provides a versatile
platform for electrochemical (bio)Âsensing
Real-Time Colorimetric Assay of Inorganic Pyrophosphatase Activity Based on Reversibly Competitive Coordination of Cu<sup>2+</sup> between Cysteine and Pyrophosphate Ion
In this study we demonstrate a new
colorimetric method for real-time
pyrophosphatase (PPase) activity assay based on reversible tuning
of the dispersion/aggregation states of gold nanoparticles (Au-NPs)
by controlling the coordination of Cu<sup>2+</sup> between cysteine
and pyrophosphate ion (PPi) with PPase. The addition of Cu<sup>2+</sup> to the cysteine-stabilized Au-NP dispersion results in the aggregation
of Au-NPs, while the further addition of PPi to this aggregation turns
the aggregated Au-NPs into their dispersed state because of the higher
coordination reactivity between Cu<sup>2+</sup> and PPi than that
between Cu<sup>2+</sup> and cysteine. The subsequent addition of PPase
to the PPi-triggered dispersed Au-NPs restores the aggregation state
of Au-NPs because PPase catalyzes the hydrolysis of PPi into orthophosphate
and thus consumes PPi in the reaction system. In this study, we utilize
this reversibility of the change between the aggregation/dispersion
states of Au-NPs for real-time colorimetric monitoring of PPase activity
by continuously measuring the ratio of absorbance at the wavelength
of 650 nm (<i>A</i><sub>650</sub>) to that at 522 nm (<i>A</i><sub>522</sub>) in the time-dependent UV–vis spectra
of Au-NP dispersions containing different activities of PPase. To
calculate the kinetics of the PPase-catalyzed hydrolysis of PPi, the <i>A</i><sub>650</sub>/<i>A</i><sub>522</sub> values
are converted into PPi concentrations to obtain the time-dependent
changes of PPi concentrations in the dispersions containing different
activities of PPase. The initial reaction rates (<i>v</i><sub>0</sub>) are thus achieved from the time-dependent logarithm
of PPi concentrations with the presence of different PPase activities.
Under the experimental conditions employed here, the <i>v</i><sub>0</sub> values are linear with the PPase activity within a range
from 0.025 to 0.4 U with a detection limit down to 0.010 U (S/N =
3). Moreover, the colorimetric method developed here is also employed
for PPase inhibitor evaluation. This study offers a simple yet effective
method for real-time PPase activity assay
Strong Interaction between Imidazolium-Based Polycationic Polymer and Ferricyanide: Toward Redox Potential Regulation for Selective In Vivo Electrochemical Measurements
This study effectively demonstrates a strategy to enable
the ferricyanide-based
second-generation biosensors for selective in vivo measurements of
neurochemicals, with glucose as an example. The strategy is based
on regulation of redox potential of ferricyanide mediator by carefully
controlling the different adsorption ability of ferricyanide (FeÂ(CN)<sub>6</sub><sup>3‑</sup>) and ferrocyanide (FeÂ(CN)<sub>6</sub><sup>4‑</sup>) onto electrode surface. To realize the negative
shift of the redox potential of FeÂ(CN)<sub>6</sub><sup>3‑/4‑</sup>, imidazolium-based polymer (Pim) is synthesized and used as a matrix
for surface adsorption of FeÂ(CN)<sub>6</sub><sup>3‑/4‑</sup> due to its stronger interaction with FeÂ(CN)<sub>6</sub><sup>3‑</sup> than with FeÂ(CN)<sub>6</sub><sup>4‑</sup>. The different
adsorption ability of FeÂ(CN)<sub>6</sub><sup>3‑</sup> and FeÂ(CN)<sub>6</sub><sup>4‑</sup> onto electrodes modified with a composite
of Pim and multiwalled carbon nanotubes (MWNTs) eventually enables
the stable surface adsorption of both species to generate integrated
biosensors and, more importantly, leads to a negative shift of the
redox potential of the surface-confined redox mediator. Using glucose
oxidase (GOD) as the model biorecognition units, we demonstrate the
validity of the ferricyanide-based second-generation biosensors for
selective in vivo neurochemical measurements. We find that the biosensors
developed with the strategy demonstrated in this study can be used
well as the selective detector for continuous online detection of
striatum glucose of guinea pigs, by integration with in vivo microdialysis.
This study essentially paves a new avenue to developing electrochemical
biosensors effectively for in vivo neurochemical measurements, which
is envisaged to be of great importance in understanding the molecular
basis of physiological and pathological events
Data_Sheet_1_Attention-deficit/hyperactive disorder updates.doc
BackgroundAttention-deficit/hyperactive disorder (ADHD) is a neurodevelopmental disorder that commonly occurs in children with a prevalence ranging from 3.4 to 7.2%. It profoundly affects academic achievement, well-being, and social interactions. As a result, this disorder is of high cost to both individuals and society. Despite the availability of knowledge regarding the mechanisms of ADHD, the pathogenesis is not clear, hence, the existence of many challenges especially in making correct early diagnosis and provision of accurate management.ObjectivesWe aimed to review the pathogenic pathways of ADHD in children. The major focus was to provide an update on the reported etiologies in humans, animal models, modulators, therapies, mechanisms, epigenetic changes, and the interaction between genetic and environmental factors.MethodsReferences for this review were identified through a systematic search in PubMed by using special keywords for all years until January 2022.ResultsSeveral genes have been reported to associate with ADHD: DRD1, DRD2, DRD4, DAT1, TPH2, HTR1A, HTR1B, SLC6A4, HTR2A, DBH, NET1, ADRA2A, ADRA2C, CHRNA4, CHRNA7, GAD1, GRM1, GRM5, GRM7, GRM8, TARBP1, ADGRL3, FGF1, MAOA, BDNF, SNAP25, STX1A, ATXN7, and SORCS2. Some of these genes have evidence both from human beings and animal models, while others have evidence in either humans or animal models only. Notably, most of these animal models are knockout and do not generate the genetic alteration of the patients. Besides, some of the gene polymorphisms reported differ according to the ethnic groups. The majority of the available animal models are related to the dopaminergic pathway. Epigenetic changes including SUMOylation, methylation, and acetylation have been reported in genes related to the dopaminergic pathway.ConclusionThe dopaminergic pathway remains to be crucial in the pathogenesis of ADHD. It can be affected by environmental factors and other pathways. Nevertheless, it is still unclear how environmental factors relate to all neurotransmitter pathways; thus, more studies are needed. Although several genes have been related to ADHD, there are few animal model studies on the majority of the genes, and they do not generate the genetic alteration of the patients. More animal models and epigenetic studies are required.</p