On-line monitoring of the dopamine-based molecular imprinting processes for protein templates with the assistance of a fluorescent indicator

Capillary electrochromatography synergistic enantioseparation system for racemate malic acid based on a novel nanomaterial synthesized by chiral molecularly imprinted polymer and chiral metal-organic framework

BACKGROUND

Chirality is one of the most fundamental features of nature. In terms of biological activities, pharmacological effects, etc., enantiomers often show great differences among each other. Therefore, it is important to develop highly efficient enantioseparation and analysis methods. Capillary electrochromatography (CEC) is one of the most popular methods in the field of enantioseparation. In the chiral stationary phase of CEC, chiral molecularly imprinted polymers (CMIPs) and chiral metal-organic frameworks (CMOFs) have shown great potential of enantioseparation. However, the enantioseparation performance of CMOFs and CMIPs alone as chiral separation media is less satisfactory.

RESULTS

In this work, a novel nanomaterial synthesized by CMOFs and CMIPs was used as stationary phase in CEC synergistic enantioseparation system and the relevant reports have not been internationally found by authors. As a proof-of-concept demonstration, a coated capillary column was prepared by a one-step method using l-malic acid (template), [Cu2(D-Cam)2Dabco] (Cu-MOF) and dopamine (functional monomer/cross-linking agent), which greatly simplified the modification process of the capillary columns. Compared with Cu-MOF and CMIP alone, the CEC synergistic enantioseparation system based on Cu-MOF@MIP has significantly better enantioseparation performance of malic acid enantiomers (resolution: 1.03/0.58 → 4.22), and there is also a satisfactory performance in the quantitative analysis in real samples. Finally, through molecular docking and adsorption experiments, it was systematically proved that Cu-MOF@MIP had a significantly stronger binding ability for l-malic acid than d-malic acid.

SIGNIFICANCE

Cu-MOF with chiral recognition ability have synergize with CMIPs to greatly improve the chiral selectivity of Cu-MOF@MIP, which is firstly used for the construction of the CEC chiral separation system. This pioneering synergistic chiral separation system creates a potential direction for efficient enantioseparation. Considering the diversity of CMOFs and CMIPs, the stationary phases hold great promise in chiral separation science.

Exploring the Complex Impact of Proteins on Dopamine Polymerization: Mechanisms and Strategies for Modulation

Polydopamine (pDA) is a valuable material with wide-ranging potential applications. However, the complex and debated nature of dopamine polymerization complicates our understanding. Specifically, the impact of foreign substances, especially proteins, on pDA formation adds an additional layer of subtlety and complexity. This study delves into specific surface features of proteins that predominantly shape their impact on dopamine polymerization. Notably, the biotin-binding site emerges as a critical region responsible for the pronounced inhibitory effect of avidin and neutravidin on the dopamine polymerization process. The binding of biotin successfully mitigates these inhibitory effects. Moreover, several nucleases demonstrated a significant hindrance to pDA formation, with their impact substantially alleviated through the introduction of DNA. It is speculated that hydrogen bonding, electrostatic, cation-π, and/or hydrophobic interactions may underlie the binding between protein surfaces and diverse oligomeric intermediates formed by the oxidation products of dopamine. Additionally, we observed a noteworthy blocking effect on the dopamine polymerization reaction induced by erythropoietin (EPO), a glycoprotein hormone known for its role in stimulating red blood cell production and demonstrating neuroprotective effects. The inhibitory influence of EPO persisted even after deglycosylation. These findings not only advance our comprehension of the mechanisms underlying dopamine polymerization but also provide strategic insights for manipulating the reaction to tailor desired biomaterials.

Surface imprinted bio-nanocomposites for affinity separation of a cellular DNA repair protein

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional DNA repair protein localized in different subcellular compartments. The mechanisms responsible for the highly regulated subcellular localization and "interactomes" of this protein are not fully understood but have been closely correlated to the posttranslational modifications in different biological context. In this work, we attempted to develop a bio-nanocomposite with antibody-like properties that could capture APE1 from cellular matrices to enable the comprehensive study of this protein. By fixing the template APE1 on the avidin-modified surface of silica-coated magnetic nanoparticles, we first added 3-aminophenylboronic acid to react with the glycosyl residues of avidin, followed by addition of 2-acrylamido-2-methylpropane sulfonic acid as the second functional monomer to perform the first step imprinting reaction. To further enhance the affinity and selectivity of the binding sites, we carried out the second step imprinting reaction with dopamine as the functional monomer. After the polymerization, we modified the nonimprinted sites with methoxypoly(ethylene glycol) amine (mPEG-NH₂ ). The resulting molecularly imprinted polymer-based bio-nanocomposite showed high affinity, specificity, and capacity for template APE1. It allowed for the extraction of APE1 from the cell lysates with high recovery and purity. Moreover, the bound protein could be effectively released from the bio-nanocomposite with high activity. The bio-nanocomposite offers a very useful tool for the separation of APE1 from various complex biological samples.

Tetrabutylammonium-chloride-glycerol of deep eutectic solvent functionalized MnO2: a novel mimic enzyme for the quantitative and qualitative colorimetric detection of L-cysteine

L-Cysteine is a common amino acid that plays an important role in human livelihood and production. Therefore, a novel method for the simultaneous quantitative and qualitative determination of L-cysteine by a colorimetric detection system is proposed. As a viable oxidase mimic, [N₄₄₄₄]Cl-G/MnO₂, which consisted of MnO₂ nanosheets functionalized by a tetrabutylammonium chloride-glycerol ([N₄₄₄₄]Cl-G) based deep eutectic solvent (DES) was fabricated. Owing to the oxidation of MnO₂ nanosheets, [N₄₄₄₄]Cl-G/MnO₂ could oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue product (oxTMB) with the characteristic UV-vis spectrum absorbance at 652 nm. The oxidation of TMB by DES/MnO₂ was inhibited when L-cysteine was introduced, and the absorbance decreased proportionally with the increase in L-cysteine concentration. Due to this inhibition effect, a colorimetric detection system ([N₄₄₄₄]Cl-G/MnO₂-TMB) was developed for the quantitative determination of L-cysteine. Under optimal conditions, the assay showed good linearity over the concentration range of 0.125-2.00 μg mL^-1 with a low detection limit of 5.96 ng mL^-1. A study of the inhibition mechanism demonstrated that the sulfhydryl group of L-cysteine could decompose [N₄₄₄₄]Cl-G/MnO₂ into Mn²⁺, thus limiting the conversion of TMB to oxTMB. In addition, the [N₄₄₄₄]Cl-G/MnO₂-TMB system was used in test strips for the visual qualitative detection of L-cysteine. The selectivity and test strip results demonstrated the high selectivity, simple operation, and rapid response of the [N₄₄₄₄]Cl-G/MnO₂-TMB system for the qualitative detection of L-cysteine. Given the satisfying performance of the detection strategy, colorimetric sensing based on the [N₄₄₄₄]Cl-G/MnO₂-TMB system is considered to have prospective application value in the quantitative and qualitative detection of L-cysteine.

Molecularly imprinted and cladded nanoparticles for high-affinity recognition of structurally closed gangliosides

A new method called reverse microemulsion-confined ganglioside-oriented surface imprinting and cladding (RM-GOSIC) is presented for controllable preparation of nanoscale binders for high-affinity targeting gangliosides. Using GM1a, an affordable ganglioside, as a representative ganglioside target, single-core quantum dot GM1a-imprinted and GM1a-cladded polymer (cMIP) nanoparticles were prepared. The prepared cMIP nanoparticles exhibited extremely high affinity towards GM1a, with dissociation constant at the nanomolar level (3-6 nM). The prepared cMIP nanoparticles also recognized structurally closed gangliosides while their cross-reactivity towards other gangliosides remained low. The potential of the cMIP nanoparticles in biomedical applications was demonstrated by cell and tissue imaging. Thus, this approach opened a new access to the synthesis of high-affinity nanoscale binders for targeting gangliosides.