Herein, we demonstrated a strategy to regulate the conductive metal−organic framework (MOF) surface, by the conjugated molecule wires for selective and sensitive determination of dopamine (DA) in the live brain. The MOFs were decorated at the carbon fiber electrode deposited by Au nanoleaves as the upper electric transducer to provide rich electrocatalytic sites for electron transfer of neurochemicals at the electrode surface, leading to greatly enhanced sensitivity for detection of neurochemicals. On the other hand, the conjugated molecular wire, 4-(thiophen-3ylethynyl)-benzaldehyde (RP1), was synthesized and assembled as an underlying bridge to regulate the electrochemical processes at the MOF-based electrode, specifically decreasing the reaction Gibbs free energy of DA oxidation, thus selectively promoting the heterogeneous electron transfer of DA from the MOF layer to the electrode surface. Owing to the electrocatalytic activity for DA oxidation, the present microsensor exhibited high selectivity for real-time tracking of DA in a good linear relationship in the range of 0.004−0.4 μM with a detection limit of 1 nM. Eventually, this functionalized electrode was successfully applied for in vivo monitoring of DA in mouse brains with Parkinson's disease (PD) model. The results indicated that the levels of DA were obviously decreased in both acute and subacute PD models. Moreover, the level of DA strongly depended on the amount of uric acid (UA), a physiological antioxidant, which rose as the UA amount was lower than 200 mg kg −1 but was downregulated again after treatment by a higher amount of UA.
The lack of reliable approaches for
real-time measurement and quantification
of polysulfides (H2S
n
) in vivo
greatly limits the exploration of their potential roles in brain functions.
Herein, an electrochemical probe, 4-(5-(1,2-dithiolan-3-yl)pentanamido)-1,2-phenylene
bis(2-fluoro-5-nitrobenzoate) (FP2), was rationally designed and created
for determination of H2S
n
.
The bis-electrophilic groups of FP2 could specifically recognize two
−SH groups in H2S
n
and
trigger the generation of an electroactive pyrocatechol moiety, resulting
in a well-defined faradic current signal at ∼0.24 V (vs Ag/AgCl).
Meanwhile, bidentate thiols were designed as anchoring sites to greatly
improve the assembled stability of FP2 at the Au surface, which efficiently
defended the interference of glutathione (GSH) with a current decrease
of less than 5.2% even after long-term measurements in 5 mM GSH for
3 h. In addition, a stable inner reference molecule with dithiols,
α-lipoic acid ferrocenylamide (FcBT), was synthesized to construct
a ratiometric electrochemical strategy for in vivo determination of
H2S
n
through one-step coassembling
with FP2 via double S–Au bonds. The present ratiometric strategy
demonstrated high selectivity for real-time tracking of H2S
n
in a linear range of 0.25–20
μM. Eventually, the developed microelectrode with high selectivity,
accuracy, and stability was employed for in vivo assaying of H2S
n
in mouse brains with ischemia.
The parameters for S-wave elastic scattering of near-zero-energy electrons and positrons by H 2 molecules are calculated using the stabilization method with explicitly correlated Gaussians. The confined variational method is applied to optimize the Gaussians to describe the short-range interaction of incident e ± with H 2 in the fixed-nuclei approximation. For e +-H 2 scattering the scattering length of previous work [Phys. Rev. Lett. 103, 223202 (2009)] is substantially improved. More importantly, for e −-H 2 scattering, from first principles, the scattering length is computed as a function of the internuclear distance. In the case that the two nuclei are at the equilibrium distance the results are in a good agreement with values derived from fitting experimental total and diffusion cross sections to the modified effective range theory.
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