11 research outputs found
Electrocatalytic Efficiency Analysis of Catechol Molecules for NADH Oxidation during Nanoparticle Collision
Electrocatalysis of molecules is
a hot research topic in biological
and energy-related chemistry. Here, we develop a new system to study
the electrocatalytic efficiency of a single catechol molecule for
NADH oxidation by single functionalized nanoparticle collision at
ultramicroelectrodes (UMEs). The proposed system is composed of gold
nanoparticles (AuNPs) functionalized with catechol molecules and a
carbon-fiber ultramicroelectrode. In the absence of NADH, when a functionalized
AuNP collides with an UME at a suitable voltage, a small current spike
is generated due to the oxidation of catechol molecules modified on
the surface of AuNP. In the presence of NADH, the current spike is
significantly amplified by the combined effects of the oxidation and
electrocatalysis for NADH of catechol molecules. By analyzing the
variations of the average peak charges and durations without or with
NADH, we calculate that around five thousands NADH molecules could
be catalyzed per second by a single catechol molecule, suggesting
the successful establishment of this novel catalytic system. Thus,
the proposed strategy could be used as a promising platform for research
of other molecular electrocatalytic systems
Highly Selective Detection of Carbon Monoxide in Living Cells by Palladacycle Carbonylation-Based Surface Enhanced Raman Spectroscopy Nanosensors
A novel nanosensor was explored for
the highly selective detection
of intracellular carbon monoxide (CO) by surface enhanced Raman spectroscopy
(SERS) on the basis of palladacycle carbonylation. By assembling new
synthesized palladacycles (PC) on the surface of gold nanoparticles
(AuNPs), SERS nanosensors (AuNP/PC) were prepared with good SERS activity
and reactivity with CO. When the AuNP/PC nanosensors were incubated
with a CO-containing system, carbonylation of the PC assembled on
AuNPs was initiated, and the corresponding SERS spectra of AuNP/PC
changed significantly, which allowed the carbonylation reaction to
be directly observed <i>in situ</i>. Upon SERS observation
of CO-dependent carbonylation, this SERS nanosensor was used for the
detection of CO under physiological conditions. Moreover, benefiting
from the specificity of the reaction coupled with the fingerprinting
feature of SERS, the developed nanosensor demonstrated high selectivity
over other biologically relevant species. <i>In vivo</i> studies further indicated that CO in normal human liver cells and
HeLa cells at concentrations as low as 0.5 ÎŒM were successfully
detected with the proposed SERS strategy, demonstrating its great
promise for the analytical requirements in studies of physiopathological
events involved with CO
Electrocatalytic Oxidation of Tris(2-carboxyethyl)phosphine at Pyrroloquinoline Quinone Modified Carbon Nanotube through Single Nanoparticle Collision
Inspired
by the addition-elimination catalytic mechanism of natural
pyrroloquinoline quinone (PQQ) containing proteins, PQQ-modified hybrid
nanomaterials have been increasingly developed recently as biomimetic
heterogeneous electrocatalysts. However, up until now, no existing
electrochemical approach was able to assess the intrinsic catalytic
activity of PQQ sites, impeding the design of efficient PQQ-based
electrocatalysts. Herein, in this work, we introduced a new method
to calculate the turnover frequency (TOF) of any individual PQQ functional
group for electrocatalytic oxidation of trisÂ(2-carboxyethyl)Âphosphine
(TCEP), through the study of single PQQ-decorated carbon nanotube
(CNT) collisions at a carbon fiber ultramicroelectrode by chronoamperometry.
The core advantage of this approach is being able to resolve the number
of PQQ catalytic sites grafted on each individual CNT, so that the
charge of any CNT collision event can be accurately translated into
the intrinsic activity of the respective PQQ functional groups. The
resulting collision-induced current responses clearly showed that
the functionalization of CNTs with PQQ could indeed enhance its catalytic
performance by 3 times, reaching a TOF value of 133 s<sup>â1</sup> at 1.0 V vs Ag/AgCl. Such a single CNT collision technique, which
is proposed for the first time in this work, can open up a new avenue
for studying the intrinsic (electro)Âcatalytic performance at a molecular
level
Individual Modified Carbon Nanotube Collision for Electrocatalytic Oxidation of Hydrazine in Aqueous Solution
Collision at a single
molecule level was achieved based on the
nanoimpact of an individual pyrroloquinoline quinone (PQQ) modified
multiwalled carbon nanotube (MWCNT) at the carbon fiber ultramicroelectrode
(C UME). Electrocatalytic amplification of the current responses was
observed when the PQQ-modified MWCNT collided with C UME in the presence
of hydrazine (N<sub>2</sub>H<sub>4</sub>) in a Tris-HCl buffer solution,
which was also supported by the conventional cyclic voltammetry and
chronoamperometry techniques. The enhanced catalytic oxidation of
N<sub>2</sub>H<sub>4</sub> was due to the âaddition-eliminationâ
redox cycling mechanism of PQQ/PQQH<sub>2</sub>, where the oxidation
of N<sub>2</sub>H<sub>4</sub> occurred together with the reduction
of PQQ under an external bias, and the formed PQQH<sub>2</sub> intermediate
would be reoxidized back to PQQ simultaneously. The average collision
current, duration, and charge for PQQ-modified MWCNT at 1.0 V vs Ag/AgCl
were 105 pA, 0.45 ms, and 49 fC, respectively. As a result, the turnover
frequency of electrocatalytic oxidation of N<sub>2</sub>H<sub>4</sub> by PQQ was calculated to be 54 s<sup>â1</sup>. In this regard,
the proposed individual carbon nanotube collision method can not only
serve as a promising sensing technique to detect biochemical species,
but more importantly provide a robust approach to determine the intrinsic
catalytic activity as well
Effect of IR-A overexpression on downstream signaling pathways.
<p>A. Western blot analysis of IR protein expression and expression of downstream signaling proteins in RL95-2-CON, RL95-2âNC and RL95-2âIR-A cells. B. IR protein expression in RL95-2âIR-A cells is significantly higher than that in RL95-2âCON and RL95-2âNC cells. C. The relative expression of phospho-Akt is signiïŹcantly increased and the relative expression of phosphorylated ERK1/2 reduced in RL95-2âIR-A cells than controls. *, #, <i>P</i> < 0.05 vs. control.</p
IR-A expression in endometrial carcinoma cell lines.
<p>A. Expression of IR-A (444 bp), IRâB (480 bp), IGF-2 (214 bp) and GAPDH (226 bp) mRNA in endometrial carcinoma cell lines was measured by RT-PCR. The results indicates that two transcript isoforms of insulin receptors (IR-A and IRâB) and IGF-2 were co-expressed in HEC-1-A, Ishikawa, KLE and RL95-2âCON cells. RL95-2âCON has a much higher ratio of IRâB expressed than IR-A. B. Real-time RT-PCR indicates the relative levels of IR-A and total IR mRNA in endometrial carcinoma cell lines, normalized to GAPDH. C.The ratio of IR-A/ IR in endometrial cancer cell lines from real-time RT-PCR results. D. ELISA quantitation of IGF-2 protein secreted by RL95-2âCON, RL95-2âIR-A, KLE, HEC-1-A and Ishikawa cells.</p
Expression of IR-A/ IRâB in endometrial carcinoma tissues and control normal endometrium tissues.
<p>A. Representative examples of the endometrial carcinoma tissues (total 103cases). Lane M shown the DNA marker and Lanes T1âT19 correspond to 19 separate endometrial carcinoma patients B. Representative examples of control normal endometrium tissues(total 60 cases). Lanes N1âN25 correspond to 25 separate patients with normal endometrium.</p
IR-A overexpression increases cell proliferation rate.
<p>A. Proliferation of RL95-2âIR-A, RL95-2âCON and RL95-2âNC cells was measured over a 7-day period (plate 2000 cells/well as starting cells) B. Proliferation of the three cells was measured after 72 hours (plate 2000, 5000, 10000, 20000 cells/well as starting cells). 6 replicate wells were included per sample and the data points were present as means±SD. *, <i>P</i> < 0.05 vs. control.</p
Tumorigenicity of the RL95-2âIR-A, RL95-2âCON and RL95-2âNC cells in a xenograft model.
<p>A. Photographs of the inoculated BALB/c nude mice five weeks after inoculation, showing the tumor size. B. RL95-2âIR-A, RL95-2âCON and RL95-2âNC cells were injected groups of five mice and tumor volumes were measured using calipers every week after the inoculation. C. Five weeks after inoculation, tumors were excised, fixed, and stained by hematoxylin and eosin (H&E; 400Ă magnification). *, <i>P</i> < 0.05 vs. control.</p
PI3K inhibition reverses the effects of IR-A overexpression.
<p>A. Western blot analysis of phospho-Akt and total Akt levels 48 h after treatment with 5, 10, 20 and 40 ”M of LY294002. B. Growth curves of RL95-2âIR-A cells following treatment with 20 ”M LY294002 and without. C. Flow cytometry analysis indicating the proportion of RL95-2âIR-A cells containing S phase DNA at 48 h after treatment with 20 ”M LY294002. D. Flow cytometry analysis indicating the percentage of apoptotic cells in RL95-2âIR-A cells at 48 h after treatment with 20 ”M LY294002. *, <i>P</i> < 0.05 vs. control.</p