Amino Groups Research Articles

Chiral amido-oxazoline functionalized MCM-41: A sustainable heterogeneous catalyst for enantioselective Kharasch–Sosnovsky and Henry reactions

In this study, a series of chiral amido-oxazoline ligands was synthesized with a primary focus on immobilizing the most effective ligands on MCM-41 mesoporous material. Following several attempts, the para-nitro group of the chiral amido-oxazoline ligands was successfully reduced to amino group, enabling their immobilization on MCM-41. The resulting chiral heterogeneous amido-oxazoline ligands were characterized using various techniques, including FT-IR, XRD, TGA, SEM, TEM, EDX, and BET-BJH, confirming the successful immobilization of the amido-oxazoline ligands. A comparison of the efficiency of the homogeneous and heterogeneous amido-oxazoline-based ligands in the Kharasch-Sosnovsky and Henry reactions revealed better performance of the heterogeneous ligand. The immobilized amido-oxazoline-copper complexes exhibited remarkable catalytic activity, achieving excellent yields and enantioselectivities (up to 88 % ee) in the Kharasch-Sosnovsky reaction, and delivering excellent yields with moderate enantioselectivities in the Henry reaction. Notably, the Henry reaction proceeded with moderate diastereoselectivity, favoring the syn diastereomer, under solvent-free conditions, highlighting the sustainability of the process. The heterogeneous nature of the catalysts facilitated effortless recovery and efficient reusability.

Exploring Secondary Amine Carnosine Derivatives: Design, Synthesis, and Properties.

Carnosine is a naturally occurring dipeptide that has been advocated by some authors as an interesting scaffold for the development of potential therapeutic agents in view of the positive outcomes of its supplementation in animal models of human diseases. Its mode of action seems to depend on the quenching of toxic electrophiles, such as 4-hydroxynonenal (HNE). However, carnosine's bioavailability in humans is lower than that in other mammals. The main reason for such an unfavorable pharmacokinetic profile is the activity of the enzyme human serum carnosinase (E.C. 3.4.13.20), which rapidly hydrolyzes carnosine upon absorption. Therefore, some studies have focused on the design of carnosinase-resistant derivatives that retain binding activity toward toxic electrophiles. Nevertheless, the structural modification of the N-terminus amino group of carnosine has rarely been considered, possibly because of its key role in the electrophile scavenging mechanism. This was proven, since some carnosine N-terminus modification generated inactive compounds, despite some derivatives retaining oral bioavailability and gaining resistance to carnosinase hydrolysis. Herein, we therefore report a study aimed at exploring whether the amino group of carnosine can be conveniently modified to develop carnosinase-resistant derivatives retaining the dipeptide activity toward toxic electrophiles.

 Synthesis and Characterization of Chitosan-Based Schiff Base and Cu(II) Complex from Shrimp Shells and its Application on Catalysis and Bio-sorption

In recent years, metal complexes and biopolymers have gained significant attention in environmental applications such as catalysis and heavy metal removal. Chitosan, a biopolymer derived from chitin, is well-known for its biodegradability, non-toxicity, and strong metal ion affinity, which can be further enhanced through Schiff bases to improve its catalytic and adsorption capabilities. The primary objectives of this study were to investigate whether Cu(II) complex of Chitosan Salicylaldehyde Schiff Base CSSB-Cu(II) can act as an efficient catalyst in hydrogen peroxide decomposition reaction and to find out the raw absorbent which has the highest Cadmium ion removal efficiency from among the absorbents Chitin (CT), Chitosan (CS) and Chitosan Salicylaldehyde Schiff Base (CSSB). CSSB was synthesized using the Schiff condensation reaction between the amino group of CS and the carbonyl compound of salicylaldehyde with the elimination of water molecules and it was complexed with Cu(II) ion to produce CSSB-Cu(II) complex. The catalytic effect of the CSSB-Cu(II) complex on the kinetics of the decomposition of hydrogen peroxide was investigated and compared with CSSB. CSSB-Cu(II) showed a better catalytic effect than CSSB and has a pseudo-first-order catalytic decomposition for H2 O2 . CT, CS, and CSSB were investigated as adsorbents for the Cd(II) removal to determine their cadmium removal efficiencies. This study concludes that the removal efficiency of CSSB was greater than that of CS and CT. The equilibrium data agreed more with the Langmuir model than with the Freundlich model. The IR and electronic spectral data confirm the presence of an imine bond and the existence of the complex in square planar geometry.

Effect of polydopamine-modified protease on shrink-resist properties of wool fiber

Dopamine is considered to have great potential in the field of immobilized enzymes due to its excellent biocompatibility and simple immobilization process. Herein, we propose a new shrink-resist treatment strategy for wool. The catechin in the dopamine structure is chemically cross-linked with the amino group in the enzyme molecule to control the hydrolysis reaction on the fiber surface. At the same time, using the characteristics of dopamine self-polymerization, excessive polydopamine is polymerized on the surface of wool fibers, forming multiple interactions between dopamine, protease, and wool. The structure and morphology of protease and polydopamine-protease-treated wool fibers were characterized by FTIR and scanning electron microscopy, and the effect of dopamine on protease activity was studied. Compared with untreated wool, this effective method can significantly improve the dimensional stability (2.34%) and wettability of wool fabric to felt, and can also make up for the strength loss caused by protease. However, affected by the color of dopamine itself, the treated wool is light gray, and the K/S value reaches 2.988. This study provides a new way for enzymatic modification of keratin-containing fibers such as wool using dopamine and other natural biopolymers with similar structures.

Enhancing Adsorption Performance of Ce(III) by Amine-Thiourea and Aniline-Modified Magnetic Chitosan Nanocomposites.

To enhance the adsorption performance of chitosan for rare earth ions, two novel magnetic chitosan-based adsorbents were prepared by using chitosan-coated magnetic silica nanoparticles modified with amine-thiourea and aniline. The structure of copolymers was analyzed using characterization methods such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis, confirming the successful synthesis of modified magnetic chitosan nanocomposites. The investigation explored the influence of pH, contact time, dosage, initial concentration, and temperature on the adsorption performance. Comparative studies revealed a significantly enhanced adsorption performance after modification. The chitosan-coated magnetic silica nanoparticles modified with aniline (PAN-CS/Fe3O4@SiO2) reached adsorption saturation in about 120 min with a capacity of 136 mg/g, while the chitosan-coated magnetic silica nanoparticles modified with amine-thiourea (TSC-CS/Fe3O4@SiO2) exhibited a higher adsorption capacity of 156 mg/g for Ce(III). Both materials demonstrated strong agreement with the Langmuir isotherm model and pseudo-second-order kinetics. Thermodynamic analysis indicated that Ce(III) adsorption is both spontaneous and endothermic. Examination of the adsorption mechanisms suggested that the effective adsorption of Ce(III) is due to the strong synergistic effects of chelation and electrostatic interactions involving amino, carboxyl, and hydroxyl groups. This study demonstrates that chitosan modified with amine-thiourea and aniline is an effective approach to significantly enhance the rare earth ion adsorption by chitosan.

Improving the Gelation Properties of Pea Protein Isolates Using Psyllium Husk Powder: Insight into the Underlying Mechanism.

The industrial application of pea protein is limited due to its poor gelation properties. This study aimed to evaluate the effects of psyllium husk powder (PHP) on improving the rheological, textural, and structural properties of heat-induced pea protein isolate (PPI) gel. Scanning electron microscopy (SEM), intermolecular forces analysis, the quantification of the surface hydrophobicity and free amino groups, and Fourier transform infrared spectroscopy (FTIR) were conducted to reveal the inner structures of PPI-PHP composite gels, conformational changes, and molecular interactions during gelation, thereby clarifying the underlying mechanism. The results showed that moderate levels of PHP (0.5-2.0%) improved the textural properties, water holding capacity (WHC), whiteness, and viscoelasticity of PPI gel in a dose-dependent manner, with the WHC (92.60 ± 1.01%) and hardness (1.19 ± 0.02 N) peaking at 2.0%. PHP significantly increased surface hydrophobicity and enhanced hydrophobic interactions, hydrogen bonding, and electrostatic interactions in PPI-PHP composite gels. Moreover, the electrostatic repulsion between anionic PHP and negatively charged PPI in a neutral environment prevented the rapid and random aggregation of proteins, thereby promoting the formation of a well-organized gel network with more β-sheet structures. However, the self-aggregation of excessive PHP (3.0%) weakened molecular interactions and disrupted the continuity of protein networks, slightly reducing the gel strength. Overall, PHP emerged as an effective natural gel enhancer for the production of pea protein gel products. This study provides technical support for the development of innovative plant protein-based foods with strong gel properties and enriched dietary fiber content.

Enhancing the Interfacial Property Between UHMWPE Fibers and Epoxy Through Polydopamine and SiO2 Surface Modification.

Here, a combination of dopamine self-polymerization and epoxy modified SiO2 (M-SiO2) grafting was proposed, with the purpose of increasing interfacial adhesion of UHMWPE fiber. Inspired by mussel adhesion, polydopamine (PDA) was deposited onto the surface of UHMWPE fiber to form a thin layer with amino and hydroxyl groups. M-SiO2 nanoparticles were then adhered to fiber surface via chemical reactions by a "two-step" or "one-step" technology. In the "two-step" technique, the M-SiO2 nanoparticles were adhered to the surface of PDA modified UHMWPE fiber via reactions between epoxy and amino groups. In the "one-step" method, M-SiO2 and dopamine were added into the UHMWPE/Tris solution at the same time. Surface morphology and thermal properties of various UHMWPE fibers were tested by SEM and TGA, respectively. Surface wettability of different UHMWPE fibers were evaluated by dynamic contact angle. The results proved that PDA and M-SiO2 were successfully adhered to the surface of UHMWPE fibers. The mechanical property of modified UHMWPE/Epoxy composites was investigated, and 43.7 % improvement was obtained, compared with unmodified UHMWPE/Epoxy composite. Additionally, micro-bond test revealed that the interfacial property (IFSS value) of modified UHMWPE fiber via the "one-step" method was 6.08 MPa, significantly higher than that of unmodified UHMWPE fiber (2.47 MPa).

Direct Substitution of 2‐Aminotropones with Potassium Allyltrifluoroborates through Transition‐Metal‐Free C−N Bond Cleavage

AbstractThe poor nucleofugality of the amino group renders the C−N bond functionalization of primary aromatic amines highly challenging. Herein, we report a direct substitution reaction of 2‐aminotropones, bearing a unique non‐benzenoid seven‐membered aromatic ring that exists in some natural products and bioactive molecules, with potassium allyltrifluoroborates through C−N bond cleavage under transition‐metal‐free conditions. The amino group of 2‐aminotropones were directly substituted with potassium allyltrifluoroborates in the presence of sodium bicarbonate, delivering structurally diverse 2‐allyltropones in moderate to good yields. The reaction is free of directing groups, activating groups and transition metals, providing a convenient method to access substituted tropones.

Solid-phase electrochemiluminescence immunosensing platform based on bipolar nanochannel array film for sensitive detection of carbohydrate antigen 125.

Development of simple solid-phase electrochemiluminescence (ECL) immunosensor with convenient fabrication for high-performance detection of tumor biomarkers is crucial. Herein, a solid-phase ECL immunoassay was constructed based on a bipolar silica nanochannel film (bp-SNA) modified electrode for highly sensitive detection of carbohydrate antigen 125 (CA 125). Inexpensive and readily available indium tin oxide (ITO) electrode was used as the supporting electrode for the growth of bp-SNA. bp-SNA consists of a bilayer SNA film with different functional groups and charge properties, including negatively charged inner layer SNA (n-SNA) and positively charged outer layer SNA (p-SNA). The nanochannels of bp-SNA were used for the immobilization of ECL emitter tris(bipyridine)ruthenium(II), while the outer surface was utilized for constructing the immunorecognition interface. Due to the dual electrostatic interaction composed of electrostatic attraction from n-SNA and electrostatic repulsion from p-SNA, ECL emitter could be stably confined within bp-SNA, providing stable and high ECL signals to the modified electrode. After amino groups on the outer surface of bp-SNA were derivatized with aldehyde groups, recognition antibodies could be covalently immobilized, and an immunosensor was obtained after blocking nonspecific sites. When CA 125 binds to the antibodies on the recognition interface, the formed complex reduces the diffusion of the co-reactant tripropylamine (TPrA) to the supporting electrode, decreasing the ECL signal. Based on this mechanism, the constructed immunosensor can achieve sensitive ECL detection of CA 125. The linear detection range is from 0.01 to 100U/mL, with a detection limit of 4.7mU/mL. CA 125 detection in serum is also achieved. The construction immunosensor has advantages including simple and convenient fabrication, high stability of the immobilized emitter, and high selectivity, making it suitable for CA 125 detection.

Binding of Glutamic Acid to Silver and Gold Nanoparticles Investigated by Surface-Enhanced Raman Spectroscopy

Glutamate is the most important excitatory neurotransmitter, which is relevant for the study of several diseases such as amyotrophic lateral sclerosis and Alzheimer. It is the form L-glutamic acid (Glu) takes at physiologically relevant pHs. The surface-enhanced Raman spectra of Glu obtained at pH values ranging from 3.3 to 12 are collected in the presence of silver and gold colloids and on solid substrates. The observed bands are compared with the positions of calculated normal modes for free neutral glutamic acid, glutamic acid monohydrate, glutamic acid bound to gold and silver atoms, and sodium glutamate. Although gold atoms prefer to bind to the NH2 group as compared to carbonyl groups, silver atoms prefer binding to hydroxyl groups more than binding to the amino group. SERS spectra of glutamic acid solutions with a pH value of 12, in which both carboxylic groups are deprotonated, indicate a complexation of the glutamic acid dianion with the sodium cation, which was introduced into the solution to adjust the pH value. Further research towards an optimal substrate is needed.

Antioxidant and anti-glycation activities of Mandevilla velutina extract and effect on parasitemia levels in Trypanosoma cruzi experimental infection: In vivo, in vitro and in silico approaches

Ethnopharmacological relevanceMandevilla velutina (Mart. Ex Stadelm.) Woodson, known in Brazil as "infalível" and "jalapa", is a medicinal plant native from the Cerrado region (Brazilian Savannah). The underground organ (xylopodium) of this species is prepared as ethanolic extract or infusion and it is commonly used in traditional medicine to treat snake venom. Although, locals and indigenous populations from Cerrado have used M. velutina for the treatment of infection by Trypanosoma cruzi (Chagas’ disease). Aim of the studyThis study aimed to evaluate the in vitro antioxidant and anti-glycation activities of the crude hydroethanolic extract of M. velutina xylopodium. Besides, it aimed to evaluate its effect on parasitemia levels in vivo T. cruzi experimental infection. In addition, this study aimed to determine possible interactions between the main compound of the extract and molecular targets associated with survival and virulence of T. cruzi in silico approaches. Materials and methodsDetermination of total polyphenols, flavonoids and steroidal aglycones content were performed. In addition, high performance liquid chromatography (HPLC) was carried out to identify main compounds of the extract. Antioxidant activity was determined by DPPH radical scavenging, ferric ion reducing power (FRAP), Thiobarbituric acid reactive species (TBARS) and Oxygen Radical Absorbance Capacity (ORAC) methods. Anti-glycation activity was demonstrated through relative mobility in electrophoresis (RME), determination of free amino groups and inhibition of AGEs formation. Determination of the action of extract in parasitemia levels was performed by T. cruzi experimental infection of mice and nitrite levels were measured in the serum of animals evaluated in this study. Molecular docking analyses of the main compound (Velutinol A) with DNA and molecular targets associated with survival and virulence of T. cruzi. ResultsPhytoconstituents evaluation exhibited the presence polyphenols, flavonoids and steroidal aglycone, and HPLC identified the major presence of Velutinol A. Antioxidant and anti-glycation evaluations showed that the extract present significant activity in all methods evaluated. In addition, extract reduced the number of trypomastigotes and increased the survival of treated animals. The treatment using extract showed an interference in the synthesis of physiological nitric oxide as an immune response to infection. In silico assays demonstrated interaction between Velutinol A and DNA and molecular targets of T. cruzi. ConclusionsThe results showed that the hydroethanolic extract of M. velutina xylopodium contains bioactive compounds including polyphenols, flavonoids and steroidal aglycones (mainly Velutinol A) of which may be responsible for the antioxidant, anti-glycation and anti-parasitic activity against T. cruzi. Trypanocidal activity of M. velutina compounds may be linked to their influence on NO synthesis during infection and/or their capacity to bind and inhibit molecules associated to virulence and survival of T. cruzi.

Preparation of Poly(allylamine Hydrochloride) Grafted Porous Boron Nitride Fibers for Efficient Cr(VI) Adsorption from Aqueous Solution.

Cr(VI) pollution poses great harm to the cyclic utilization of groundwater and surface water resources. Efficient adsorbent materials have great potential to change this situation and assist in the restoration of ecosystems. This work chooses porous boron nitride fibers (pBN) with stable physical and chemical properties as the matrix, 3-aminopropyltriethoxysilane (APTES) as the coupling agent, and uses a one-step crosslinking method to graft poly(allylamine hydrochloride) (PAH) onto pBN, forming pBN-AS@PAH with fascinating Cr(VI) adsorption capacity. PAH is uniformly covered and modified on the surface of pBN, and the composite with high specific surface area (383.33 m2/g), large pore volume (0.37 cm3/g), and abundant amino groups. Its equilibrium adsorption capacity for Cr(VI) can reach up to 123.32 mg/g, and the adsorption behavior follows the quasi second-order kinetic model and Langmuir model, indicating the chemical adsorption process of monolayer. The adsorption style belongs to a spontaneous exothermic process and has the optimal adsorption effect at a pH of ~2. Additionally, after cycling for 5 times, the decrease rate of adsorption capacity is less than 10 %, showing an excellent reusability.

Evaluation of Double Self-Immolative Linker-Based Antibody-Drug Conjugate FDA022-BB05 with Enhanced Therapeutic Potential.

Typical antibody-drug conjugates (ADCs) with valine-alanine linkage, often conjugated with the amino group in payloads, face challenges when interacting with hydroxyl group-containing payloads. Herein, we introduced a transformative Val-Ala-based double self-immolative linker-payload platform, reshaping ADCs by optimizing hydroxyl group-containing payload integration. Utilizing this platform, FDA022-BB05 was successfully conjugated with the hydroxyl group-containing payload DXd using trastuzumab (FDA022) as the monoclonal antibody (mAb). FDA022-BB05 demonstrated enhanced stability, effective cathepsin B sensitivity, reduced cell proliferation, increased bystander killing, and targeted delivery. Notably, acute toxicity evaluations in diverse preclinical models indicated favorable safety profiles and tolerability, with a broad therapeutic index in HER2-positive and -negative xenografts. Overall, these compelling findings support the promising therapeutic potential of FDA022-BB05, emphasizing the significance of diverse linker-payload platform strategies. This ADC is a valuable addition to targeted cancer therapy development, currently advancing through phase I clinical trials.

Acid Sensors Based on Luminochromism of Solid‐State Excimer Emission of Pyrene‐Modified Polyhedral Oligomeric Silsesquioxane

To obtain solid‐state fluorescence sensors, it is essential to simultaneously obtain solid‐state emission and stimuli‐responsiveness. In this research, the modified polyhedral oligomeric silsesquioxane (POSS) tethered with pyrenes was synthesized and we confirmed that both demands for developing solid‐state fluorescence sensors can be satisfied. The POSS derivative exhibited strong emission even in the solid state. In particular, we found that exposure of the POSS films to trifluoroacetic acid vapor resulted in a significant red‐shift of the peak wavelength of the emission band. Excitation spectroscopy and comparison with model compounds suggest that this significant red‐shift should be attributable to the formation of static excimer, meaning a preformed dimer in the ground state induced by protonation of the secondary amino groups. These results indicate that POSS is a promising scaffold for a solid‐state fluorescence sensor.

Synthesis of New Silylated and N-Si-N bridged Urea Derivatives from Aminosilanes and Diisocyanates.

Urea derivatives of the general motifs R1(N(SiMe3)C(O)NR2R3)2 and [R1(NC(O)NR2R3)2SiMe2]n (R1=difunctional organic linker, i. e., core of diisocyanate used; R2,R3= H,nPr; H,Ph; Et,Et) were synthesized by insertion of four different diisocyanates (1,6-HMDI, 2,4-TDI, 1,3-TMXDI and 4,4'-MDI) into aminotrimethylsilanes Me3SiNR2R3 and diaminodimethylsilanes Me2Si(NR2R3)2. The products obtained were analyzed by NMR and IR spectroscopy. Insertion into aliphatic aminosilanes was found to be favored for primary over secondary amino groups. For insertion into 4,4'-methylenebis(phenylisocyanate) (4,4'-MDI), good results were obtained for silanes derived from secondary amines as well. Insertion into aminosilanes with aromatic N-bound substituents turned out to be kinetically inhibited. Elucidation of molecular structures of the products by crystallography and NMR spectroscopy revealed interesting differences in N-Si connectivity, caused by steric and electronic effects of the reactants and migration of -SiMe3 and -(SiMe2)- moieties.

Modulating the cavity micro-environments of Fe-MOFs for high-performance gas chromatographic separations

Precise modulation of cavity micro-environment in metal-organic frameworks (MOFs) is important for achieving significant separation performance. Herein, the Fe-MOF (MIL-142-BTB-BDC) with different tridentate and bidentate ligands to form cavities, was chosen as the platform to precisely modulate the cavity micro-environment and investigate the influence of cavity windows and cavity walls on gas chromatographic separations. Changing tridentate ligands on the cavity walls led to MIL-142-TATB-BDC while changing bidentate ligands on the cavity windows produced MIL-142-BTB-BDC-NH2. Mechanism investigation revealed that for MIL-142-BTB-BDC and MIL-142-TATB-BDC, altering the ligands of cavity walls had little influence on the thermodynamic interactions between MOFs and analytes while slightly reducing the kinetic diffusion rate of analytes. On the contrary, introducing amino groups on cavity windows in MIL-142-BTB-BDC-NH2 not only increased the thermodynamic interactions with analytes but also slowed down the kinetic diffusion of analytes, which resulted in poor separation performance of the MIL-142-BTB-BDC-NH2 coated column. This work provides a guide to precisely modulating the cavity micro-environment and analyzing the relationship between the cavity micro-environment and application properties of MOFs.

A MOF@MOF S-scheme Heterojunction with Lewis Acid-Base Sites Synergistically Boosts Cocatalyst-Free CO2 Cycloaddition.

The photocatalytic cycloaddition reaction between CO2 and epoxide is one of the most promising green routes for CO2 utilization, for which high performance photocatalysts are intensely desired. Herein, we have constructed an S-scheme heterojunction of MIL-125@ZIF-67 modified by amino groups, which achieves a cyclic carbonate yield of as high as 99 % without employing any co-catalyst, outperforming the previously reported photocatalysts. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in-situ electron paramagnetic resonance (EPR) spectroscopy reveal the important role of photogenerated electron migration from Lewis acid (Co) sites to the O atom of epoxide in triggering its ring-opening (the rate-determining step of CO2 cycloaddition reaction) under the assistance of photogenerated hole. Synergistically and concurrently, the Lewis base (amino groups) sites activate CO2 to CO2*, facilitating the following CO2 cycloaddition. Such a synergistic effect provides a most favorable approach to design efficient heterogeneous photocatalysts with dual/multiple-active sites for CO2 cycloaddition reaction.

LiBr-Promoted Reaction of β-Ketodithioesters and Thioamides with Sulfoxonium Ylides to Synthesize Functionalized Thiophenes.

An operationally simple and highly efficient synthesis of functionalized thiophenes has been developed by LiBr promoted heteroannulation of β-ketodithioesters and thioamides with bench-stable sulfoxonium ylides in open air for the first time. This one-pot strategy involves formal Csp3-H bond insertion/intramolecular cyclization cascade, featuring readily accessible starting materials, TM and additive-free condition, broad substrate scope, high functional group compatibility, and scalability. Moreover, the carbonyl, thiomethyl, and amino groups in the resulting thiophene provide a good handle on downstream transformations.

Short Lysine-Containing Tripeptide as Analgesic Substance: The Possible Mechanism of Ligand–Receptor Binding to the Slow Sodium Channel

A possible molecular mechanism of the ligand–receptor binding of Ac-Lys-Lys-Lys-NH2 (Ac-KKK-NH2) to the NaV1.8 channel that is responsible for nociceptive signal coding in the peripheral nervous system is investigated by a number of experimental and theoretical techniques. Upon Ac-KKK-NH2 application at 100 nM, a significant decrease in the effective charge carried by the NaV1.8 channel activation gating system Zeff is demonstrated in the patch-clamp experiments. A strong Ac-KKK-NH2 analgesic effect at both the spinal and supraspinal levels is detected in vivo in the formalin test. The distances between the positively charged amino groups in the Ac-KKK-NH2 molecule upon binding to the NaV1.8 channel are 11–12 Å, as revealed by the conformational analysis. The blind docking with the NaV1.8 channel has made it possible to locate the Ac-KKK-NH2 binding site on the extracellular side of the voltage-sensing domain VSDI. The Ac-KKK-NH2 amino groups are shown to form ionic bonds with Asp151 and Glu157 and a hydrogen bond with Thr161, which affects the coordinated movement of the voltage sensor up and down, thus modulating the Zeff value. According to the results presented, Ac-KKK-NH2 is a promising candidate for the role of an analgesic medicinal substance that can be applied for pain relief in humans.

The facile preparation of polydopamine-modified sepiolite and its adsorption properties and microscopic mechanism for cadmium ion

Natural sepiolite (SEP) has the characteristics of cation exchange, abundant reserves, low cost, and environmental friendliness, but its adsorption capacity for heavy metal pollutants is limited. Because polydopamine (PDA) molecules contain rich functional groups such as phenolic and amino groups, in the present work, dopamine and natural sepiolite were utilized as raw materials to prepare polydopamine-modified sepiolite composite (SEP/PDA) by simple co-precipitation method. According to Langmuir isotherm model, the maximum adsorption capacity of SEP/PDA for Cd2+ can reach 203.21 mg/g at 298 K. At the initial concentration of 100 mg/L, the adsorption capacity was 2.9 times that of natural sepiolite. The composite material has good reusability and anti-cationic interference performance and has 100 % removal ability of low concentration Cd2+ in actual electroplating wastewater. Density Functional Theory (DFT) calculations were performed to obtain the electronic structure information. To elucidate the microscopic mechanism, molecular surface analyses, Interaction Region Indicator (IRI), Atom In Molecules (AIM) theory, Bond Order Density (BOD), and Electron Localization Function (ELF) were conducted. These analyses revealed that the amino nitrogen and phenolic oxygen atoms in the dopamine molecules donate lone pair electrons to coordinate with cadmium ions. Polydopamine, which possesses multiple oxidation states, contains catechol, quinone, and indole or a lesser extend pyrrole groups that can complex with cadmium ions, resulting in the formation of a surface complex. This coordination significantly enhances the adsorption properties of the SEP/PDA composite.