Molecules

24 pages, 7215 KiB

Open AccessArticle

Insights into the Antimicrobial Mechanisms of a Scorpion Defensin on Staphylococcus aureus Using Transcriptomic and Proteomic Analyses

by Xuhua Yang, Haozhen Zhang, Sijia Lu, Yiyuan Guo, Yitong Li, Chenhu Qin, Zheng Zuo, Yingliang Wu and Zhijian Cao

Molecules 2025, 30(7), 1542; https://doi.org/10.3390/molecules30071542 (registering DOI) - 30 Mar 2025

Abstract

Defensins constitute a family of cationic antimicrobial peptides that act against different bacteria; however, global information regarding their antibacterial mechanisms from omics-based analyses is highly limited. In this study, transcriptomics and proteomics were used to explore the antibacterial mechanisms of defensin (BmKDfsin4) originally [...] Read more.

Defensins constitute a family of cationic antimicrobial peptides that act against different bacteria; however, global information regarding their antibacterial mechanisms from omics-based analyses is highly limited. In this study, transcriptomics and proteomics were used to explore the antibacterial mechanisms of defensin (BmKDfsin4) originally isolated from a scorpion on a common Gram-positive bacterium. Staphylococcus aureus (AB94004) was treated with BmKDfsin4 for 15, 30, or 45 min based on its ability to moderately inhibit bacterial growth for one hour. Compared with those in the control group, more than 1000 genes and nearly 500 proteins in S. aureus were significantly differentially expressed after BmKDfsin4 treatment. In-depth analysis revealed that BmKDfsin4 significantly upregulated bacterial ribosome-related pathways and ribosomal components. In contrast, BmKDfsin4 also significantly downregulated the synthesis and metabolism pathways of bacterial amino acids. Moreover, BmKDfsin4 inhibited the synthesis pathways of teichoic acid and peptidoglycan, which are the key components of the cell wall in S. aureus. Furthermore, glycolysis and other metabolic processes in S. aureus were markedly reduced by BmKDfsin4. Overall, the global information detected from S. aureus revealed the multiple antibacterial mechanisms of BmKDfsin4, which could encourage the exploration of global bacterial information from the defensin family with high degrees of sequence variability and accelerate the research and development of defensins as new antibacterial agents. Full article

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13 pages, 1345 KiB

Open AccessArticle

Preparation and Modification of Sucrose-Based Non-Isocyanate Polyurethane Adhesives for Plywood Bonding

by Hongyi Zhong, Qianyu Zhang, Hong Lei, Xiaojian Zhou, Jun Zhang, Guanben Du, Antonio Pizzi and Xuedong Xi

Molecules 2025, 30(7), 1541; https://doi.org/10.3390/molecules30071541 (registering DOI) - 30 Mar 2025

Abstract

The production of non-isocyanate polyurethane (NIPU) resins using recyclable biomass materials and no isocyanates as a substitute for traditional polyurethane (PU) materials has become a research focus in the polyurethane industry. The development of such NIPU resins for application as wood adhesives has [...] Read more.

The production of non-isocyanate polyurethane (NIPU) resins using recyclable biomass materials and no isocyanates as a substitute for traditional polyurethane (PU) materials has become a research focus in the polyurethane industry. The development of such NIPU resins for application as wood adhesives has also emerged as an interesting new research topic. In this study, sucrose was used to react with dimethyl carbonate, and then polymerized with an amine to prepare sucrose-based non-isocyanate polyurethane (SNIPU) adhesives and evaluate their suitability for use in plywood. Four amines, namely polyethylene amine (PEI) of molecular weight (MW) 10,000, PEI of MW 1800, diethylenetriamine, and hexanediamine were tested in the preparation of SNIPU adhesives to determine a more suitable amine showing optimal adhesion performance. The effect of the amount of the amine added on adhesive properties was further investigated. The results showed that the SNIPU adhesive prepared with PEI-10000 as amine presents a good bonding performance. The SNIPU prepared with a PEI-10000 content of 45% (w/w on sucrose) presented the highest bonding strength. The dry strength, 24 h cold water (23 °C) wet strength, and 3 h hot water (63 °C and 93 °C) wet strengths of its bonded plywood were 1.26 MPa, 0.90 MPa, 0.84 MPa, and 0.80 MPa, respectively. Furthermore, the addition of 13% (w/w on SNIPU adhesive) of ethylene glycol diglycidyl ether (EGDE) as a modifier showed a significant decrease of 20 °C of the curing temperature of the SNIPU adhesive. Full article

(This article belongs to the Special Issue Advances in Polymer Materials Based on Lignocellulosic Biomass)

18 pages, 9139 KiB

Open AccessArticle

Identification and Validation of Urea Transporter B Inhibitor from Apium graveolens L. Seeds In Vitro and In Silico

by Guanzhong Chen, Xin Li, Xinhui Pan, Li Guo, Wei Wei, Xiaoying Sun, Hongtao Wei, Xue Qin, Ke Zhang, Wei Zhang, Lili Wei, Pinghua Sun and Xiaoda Yang

Molecules 2025, 30(7), 1540; https://doi.org/10.3390/molecules30071540 (registering DOI) - 30 Mar 2025

Abstract

Celery (Apium graveolens L.) seeds are rich in carbohydrates and protein, and they are widely used in diuretic drugs among Uyghur doctors. However, the diuretic mechanism is still unclear. To explore the possible diuretic mechanism of celery seeds, urea transporters, a potential [...] Read more.

Celery (Apium graveolens L.) seeds are rich in carbohydrates and protein, and they are widely used in diuretic drugs among Uyghur doctors. However, the diuretic mechanism is still unclear. To explore the possible diuretic mechanism of celery seeds, urea transporters, a potential diuresis-related target, are used in this study. Urea transporters (UTs) play a key role of urine concentration. Selective knockout of UTs can concentrate urea without affecting water and electrolytes, resulting in selective diuresis, which is a promising new diuretic target. In the present study, we obtained different polar fractions by extracting and separating celery seed extract, characterized its polar fractions using UPLC-TOF-MS, and verified its action using an erythrocyte lysis model in vitro. Then, it was found that the isovaleric acid p-tolylester exhibited moderate activity (IC₅₀ = 80.34 μM). Finally, its inhibitory effect on UT-B was investigated by using molecular docking, a pharmacophore model, and molecular dynamics simulations. This study provides a new approach to developing novel diuretics. Full article

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18 pages, 4071 KiB

Open AccessArticle

Can We Unambiguously Define the Dipole Moment of Molecules in the Condensed Phase?

by Imre Bakó and Szilvia Pothoczki

Molecules 2025, 30(7), 1539; https://doi.org/10.3390/molecules30071539 (registering DOI) - 30 Mar 2025

Abstract

Various theoretical methods were applied and evaluated to determine the dipole moment of polar protic (methanol, ethanol) and aprotic (acetonitrile, pyridine, acetone) dipoles in the crystal phase. In mono-alcohols, the dipole moment is influenced by the hydrogen bonding (H-bonding) environment, similarly to earlier [...] Read more.

Various theoretical methods were applied and evaluated to determine the dipole moment of polar protic (methanol, ethanol) and aprotic (acetonitrile, pyridine, acetone) dipoles in the crystal phase. In mono-alcohols, the dipole moment is influenced by the hydrogen bonding (H-bonding) environment, similarly to earlier findings with liquid water. Using localization techniques without considering the effect of neighboring molecules gives similar results for the dipole moment of mono-alcohols than those obtained from the polarized continuum model (PCM). However, the PCM for polar aprotic molecules provides significantly different dipole moment values compared to localization methods. Our results clearly show that the magnitude of the dipole moment in the condensed phase cannot be unambiguously determined. Full article

(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules 2025)

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25 pages, 3475 KiB

Open AccessArticle

Structure Determination of Tegoprazan((S)-4-((5,7-difluorochroman-4-yl)oxy)-N,N,2-trimethyl-1H-benzo[d]imidazole-6-formamide) Polymorphs A and B by Laboratory X-Ray Powder Diffraction

by Seah Ryu, JooHo Lee, Jason Kim and Tokutaro Yamaguchi

Molecules 2025, 30(7), 1538; https://doi.org/10.3390/molecules30071538 (registering DOI) - 30 Mar 2025

Abstract

Tegoprazan is a potassium ion-competitive acid blocker (P-CAB) and a novel inhibitor of gastric acid secretion. The compound exists in two crystalline polymorphs, A and B, whose structures had not previously been reported. In this study, both polymorphs were analyzed by liquid- and [...] Read more.

Tegoprazan is a potassium ion-competitive acid blocker (P-CAB) and a novel inhibitor of gastric acid secretion. The compound exists in two crystalline polymorphs, A and B, whose structures had not previously been reported. In this study, both polymorphs were analyzed by liquid- and solid-state NMR, revealing identical tautomeric states. Using this information, the crystal structures were determined from laboratory powder X-ray diffraction data by simulated annealing and Rietveld refinement. Both forms were found to crystallize in the monoclinic space group P2₁, with Z = 4 and two independent molecules in the asymmetric unit (Z′ = 2). To assess the stability and reliability of the refined structures, we attempted geometry optimization and vibrational analysis using DFT-D methods. However, due to the high conformational complexity of Z′ = 2 systems, these calculations failed to converge or produced imaginary frequencies. Instead, single-point energy calculations were performed on the refined models. The resulting relative energy differences, together with solubility data, van’t Hoff enthalpies, and DSC profiles, consistently indicated that Polymorph A is more stable than Polymorph B. These results highlight the challenges of structure validation via DFT-D for complex molecular crystals and demonstrate the value of integrating experimental and computational approaches for polymorph characterization. Full article

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20 pages, 6528 KiB

Open AccessArticle

Exploring the Performance Advantages of p-Aminobenzenesulfonate-Based Zwitterionic Gemini Surfactants in Oil Recovery

by Zhaozheng Song, Shiyuan Xia, Tongji Yang, Zhihong Li and Jiayi Li

Molecules 2025, 30(7), 1537; https://doi.org/10.3390/molecules30071537 (registering DOI) - 30 Mar 2025

Abstract

To investigate the specific performance enhancement of oilfield surfactants by using sodium p-aminobenzenesulfonate as a connecting group, cationic surfactant N,N-dimethyl-N-(oxiran-2-ylmethyl)dodecan-1-aminium (DDPA) and zwitterionic gemini surfactant sodium 4-[bis(3-(dodecyldimethylamino)-2-hydroxypropyl)amino]benzenesulfonate (DDBS) were synthesized. The oil recovery performance of these surfactants was compared, revealing that DDBS outperforms [...] Read more.

To investigate the specific performance enhancement of oilfield surfactants by using sodium p-aminobenzenesulfonate as a connecting group, cationic surfactant N,N-dimethyl-N-(oxiran-2-ylmethyl)dodecan-1-aminium (DDPA) and zwitterionic gemini surfactant sodium 4-[bis(3-(dodecyldimethylamino)-2-hydroxypropyl)amino]benzenesulfonate (DDBS) were synthesized. The oil recovery performance of these surfactants was compared, revealing that DDBS outperforms DDPA in thermal stability, wettability, adsorption, and resistance to temperature and salinity variations, as well as surface/interface activity, except for emulsification. Core flooding experiments, simulating the conditions of the Xinjiang oilfield, demonstrated that DDBS can achieve the same enhanced oil recovery effect at a concentration that is 1/15 of that of DDPA. Compared with water, DDBS and DDPA can incrementally enhance recovery rates by 7.9% and 8.5%. Furthermore, the synergistic formulation of DDBS with sodium dodecylbenzenesulfonate (SDS) significantly optimized performance, achieving a reduction in interfacial tension to 0.0301 mN m⁻¹. This study provides a research and data foundation for the application of new surfactants in petroleum extraction. Full article

(This article belongs to the Special Issue Surfactants at Liquid Interfaces: Applications in Enhanced Oil Recovery, 2nd Edition)

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20 pages, 5139 KiB

Open AccessArticle

Efficient Adsorption of Methylene Blue by Polyaminocarboxylated Modified Hydrochar Derived from Sugarcane Bagasse

by Xi Liu, Feng Zhou, Changrong Shi, Jerome Ramirez, Zhihua Liu, Fangxue Hang and Caifeng Xie

Molecules 2025, 30(7), 1536; https://doi.org/10.3390/molecules30071536 (registering DOI) - 30 Mar 2025

Abstract

Sugarcane bagasse (SCB) was transformed into polyaminocarboxylated modified hydrochar (ACHC) by hydrothermal carbonization (HTC), which was then followed by activation, etherification, amination, and carboxylation successively. ACHC was systematically characterized, and batch adsorption studies were used to assess its methylene blue (MB) adsorption capacity. [...] Read more.

Sugarcane bagasse (SCB) was transformed into polyaminocarboxylated modified hydrochar (ACHC) by hydrothermal carbonization (HTC), which was then followed by activation, etherification, amination, and carboxylation successively. ACHC was systematically characterized, and batch adsorption studies were used to assess its methylene blue (MB) adsorption capacity. Adsorption was analyzed by adsorption isotherm models, the adsorption mass transfer model, and the adsorption thermodynamics model. Density functional theory (DFT) was utilized to explain adsorption mechanisms. The findings demonstrated the adsorption was one type of endothermic, spontaneous, and homogenous monolayer adsorption with intra-particle diffusion, containing both chemical and physical adsorption, involving electrostatic attraction, hydrogen bonding, and π-π interaction. At 303 and 323 K, the highest adsorption capacity was 1017.29 and 1060.45 mg·g⁻¹, respectively. Furthermore, when the recycle time was 4, the equilibrium adsorption capacity remained at 665.43 mg·g⁻¹, which implied fairly good regeneration performance. The modification provided a simple, environmentally friendly, and economical solution for converting sugarcane bagasse into an efficient adsorbent for MB treatment. Full article

(This article belongs to the Special Issue Porous Carbon Materials: Preparation and Application)

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24 pages, 8064 KiB

Open AccessArticle

Design and Synthesis of Novel 6-(Substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole Compounds as Tyrosinase Inhibitors: In Vitro and In Vivo Insights

by Hyeon Seo Park, Hee Jin Jung, Hye Soo Park, Hye Jin Kim, Sang Gyun Noh, Yujin Park, Pusoon Chun, Hae Young Chung and Hyung Ryong Moon

Molecules 2025, 30(7), 1535; https://doi.org/10.3390/molecules30071535 (registering DOI) - 30 Mar 2025

Abstract

The 2,4-dihydroxyphenyl group is commonly present in the chemical structures of potent tyrosinase inhibitors. Based on this observation, a series of 6-(substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole compounds 1–13 were designed and synthesized as potential tyrosinase inhibitors. Among these, compounds 5 and 9 [...] Read more.

The 2,4-dihydroxyphenyl group is commonly present in the chemical structures of potent tyrosinase inhibitors. Based on this observation, a series of 6-(substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole compounds 1–13 were designed and synthesized as potential tyrosinase inhibitors. Among these, compounds 5 and 9 strongly inhibited mushroom tyrosinase activity. Particularly, compound 9 exhibited nanomolar IC₅₀ values regardless of the substrate used, whereas kojic acid yielded IC₅₀ values of 15.99–26.18 μM. Kinetic studies on mushroom tyrosinase revealed that compounds 5 and 9 competitively inhibited tyrosinase activity, findings further corroborated by in silico docking analysis. In B16F10 cell-based experiments, both compounds effectively inhibited the cellular tyrosinase activity and melanin formation. These inhibitory effects were confirmed through in situ cellular tyrosinase activity assays. Compound 9 exhibited strong antioxidant activity by scavenging radicals, suggesting that its ability to reduce melanin production may be attributed to a combination of its antioxidant and tyrosinase inhibitory properties. Additionally, five compounds, including compound 5, demonstrated effective depigmentation activity in vivo in zebrafish embryos, and their depigmentation efficacy was similar to that of kojic acid, even at concentrations hundreds of times lower. These findings suggest that 6-(substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole compounds may be promising anti-melanogenic agents. Full article

(This article belongs to the Special Issue Heterocycles in Medicinal Chemistry III)

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23 pages, 3768 KiB

Open AccessArticle

DNA/BSA Binding Affinity and Cytotoxicity of Dinuclear Palladium(II) Complexes with Amino Acids as Ligands

by Stefan Jakovljevic, Petar Canovic, Marko Spasic, Marija Zivkovic, Milan Zaric, Radica Zivkovic Zaric, Andjela Franich, Snezana Rajkovic, Zeljko Todorovic, Nenad Relic, Milos Zivic and Nikola Mirkovic

Molecules 2025, 30(7), 1534; https://doi.org/10.3390/molecules30071534 (registering DOI) - 30 Mar 2025

Abstract

This study investigates the synthesis, characterization, and cytotoxicity of dinuclear palladium(II) complexes with glycine (Pd1), alanine (Pd2), and methionine (Pd3) as ligands. UV-Vis and fluorescence spectroscopy were used to investigate the complexes’ interactions with calf thymus DNA (CT-DNA) and bovine serum albumin. The [...] Read more.

This study investigates the synthesis, characterization, and cytotoxicity of dinuclear palladium(II) complexes with glycine (Pd1), alanine (Pd2), and methionine (Pd3) as ligands. UV-Vis and fluorescence spectroscopy were used to investigate the complexes’ interactions with calf thymus DNA (CT-DNA) and bovine serum albumin. The obtained measurements demonstrate that Pd1 and Pd2 have stronger binding affinities for CT-DNA compared to Pd3, with Pd3 exhibiting the most significant cytotoxicity against the MDA-MB-231 cancer cell line. The binding behavior was quantified by calculating intrinsic binding constants (K_b) and Stern–Volmer constants (K_sv), showing that Pd1 and Pd2 interact more effectively with DNA, possibly due to less steric hindrance in their chelation. Cytotoxic activity was evaluated using an MTT assay, and the results confirm that Pd3, with methionine as the ligand, exhibited superior antitumor effects, inducing apoptosis through caspase-3 activation. The complexes also showed a strong affinity for BSA, indicating their potential for biological interaction. These discoveries shed light on the processes of palladium(II) complexes in biological systems, highlighting their DNA and protein-binding capabilities, as well as their anticancer potential. Further research is required to explore their pharmacokinetics and possible clinical applications. Full article

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13 pages, 5241 KiB

Open AccessArticle

Manipulating Electronic Effect of Nitrogen Donor-Based Ligands for Efficient Complexation and Separation of Palladium from Highly Acidic Solution

by Yuyang Gan, Yimin Cai, Song Huang, Xiaowei Li, Wen Feng and Lihua Yuan

Molecules 2025, 30(7), 1533; https://doi.org/10.3390/molecules30071533 (registering DOI) - 30 Mar 2025

Abstract

Nitrogen donor-based ligands are highly promising extractants for palladium separation from high-level liquid waste (HLLW). However, the electronic effect of these ligands, a critical factor influencing their complexation ability with Pd(II), remains largely unexplored. Herein, three picolinamide-based ligands were designed and synthesized, each [...] Read more.

Nitrogen donor-based ligands are highly promising extractants for palladium separation from high-level liquid waste (HLLW). However, the electronic effect of these ligands, a critical factor influencing their complexation ability with Pd(II), remains largely unexplored. Herein, three picolinamide-based ligands were designed and synthesized, each featuring substituents with distinct electronic effects at the para-position of the pyridine (electro-donating methoxyl group for L-I, hydrogen for L-II, and electro-withdrawing ester group for L-III). The concurrent processes of Pd(II) coordination and ligand protonation enable the manipulation of pyridine nitrogen electronegativity, resulting in a tunable Pd(II) extraction performance. Notably, L-I exhibits the highest extraction efficiency at low acidities (≤1 M HNO₃) but the lowest extraction at high acidities (≥3 M HNO₃), whereas L-III shows the poorest efficiency at low acidities but the best performance at high acidities. The Job plot analysis and ESI-HRMS results reveal a 1:1 and 2:1 (L/Pd) stoichiometry in the Pd(II) complexation process. The single crystal X-ray analysis of Pd(NO₃)₂(L-II)₂ complex confirms a four-coordinated Pd(II) center, with two pyridine nitrogen atoms and two monodentate nitrate oxygens forming a quadrangular geometry. Density functional theory (DFT) calculations further indicate that the formation of 2:1 (L/Pd) complexes is energetically favored, and the stronger basicity of the nitrogen atoms correlates with a higher Pd(II) binding affinity and increased susceptibility to protonation. Full article

(This article belongs to the Special Issue 30th Anniversary of Molecules—Recent Advances in Inorganic Chemistry)

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18 pages, 1575 KiB

Open AccessArticle

Retrieval of Polyphenols Using Aqueous Two-Phase Systems Based on Ethyl Lactate and Organic Salts

by Gonçalo Perestrelo, Pedro Velho and Eugénia A. Macedo

Molecules 2025, 30(7), 1532; https://doi.org/10.3390/molecules30071532 (registering DOI) - 30 Mar 2025

Abstract

Food waste remains a critical global concern, with approximately one third of all food produced being ultimately discarded. Therefore, it is urgent to develop new techniques for the effective repurpose of waste. Aqueous two-phase systems (ATPSs) stand out as a simple and biocompatible [...] Read more.

Food waste remains a critical global concern, with approximately one third of all food produced being ultimately discarded. Therefore, it is urgent to develop new techniques for the effective repurpose of waste. Aqueous two-phase systems (ATPSs) stand out as a simple and biocompatible liquid–liquid extraction technique for the recovery of bioactive substances from food waste. In ATPSs, the target species partition between two liquid phases, according to affinity, which facilitates its extraction. This work aimed at extracting three polyphenols—chlorogenic acid (CA), ferulic acid (FA), and resveratrol (RV)—through the application of eco-friendly ATPSs composed of water, ethyl lactate (EL), and organic salts, namely disodium succinate (Na₂Succinate) and disodium tartrate (Na₂Tartrate), for future application in the valorisation of food waste. All partitions presented successful results, with values of partition coefficients (K) higher than 1 and extraction efficiencies (E) higher than 50%, indicating a preferential migration of the polyphenols to the top phase. The extraction of FA using the ATPS based on Na₂Tartrate presented the most promising results, with K = 19 ± 6 and E = (94.2 ± 0.9)% for the longest tie-line. Additionally, a comparison with previous works of the research group was drawn, with the extraction of RV exhibiting outstanding performance across all studied ATPSs. Therefore, the assessed ATPSs were shown to hold immense potential for the recovery of polyphenols. Full article

(This article belongs to the Special Issue Extraction and Analysis of Natural Products in Food—2nd Edition)

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13 pages, 5468 KiB

Open AccessArticle

A Bifunctional Fluorescence Probe for the Detection of Hypochlorous Acid and Viscosity in Living Cells and Zebrafish

by Xin Zhang, Yanmei Si, Xinpeng Chen, Xuqing Nie, Yiheng Zhang, Li Lin and Yehao Yan

Molecules 2025, 30(7), 1531; https://doi.org/10.3390/molecules30071531 (registering DOI) - 30 Mar 2025

Abstract

As two significant indicators in the microenvironment, hypochlorous acid and viscosity play important roles in multitudinous physiological metabolic processes. However, it is challenging to determine the dynamic levels of hypochlorous acid and viscosity in living cells and organisms because of the absence of [...] Read more.

As two significant indicators in the microenvironment, hypochlorous acid and viscosity play important roles in multitudinous physiological metabolic processes. However, it is challenging to determine the dynamic levels of hypochlorous acid and viscosity in living cells and organisms because of the absence of effective molecular tools that can simultaneously detect hypochlorous acid and viscosity in organisms. Herein, a molecular design strategy was presented to fabricate a single fluorescence probe that can simultaneously detect hypochlorous acid and viscosity by using two different emission channels. In JXR, TICT-based 4-(2-(5-(dimethylamino)thiophen-2-yl)vinyl)-1-methylpyridin-1-ium-iodide chromophore serves as energy acceptor in the FRET process and sensors for hypochlorous acid and viscosity. JXR showed a large Stokes shift, wide emission peak distance, high photostability, and low toxicity. JXR could detect hypochlorous acid and viscosity rapidly, sensitively, and selectively by emitting different fluorescence signals. Importantly, JXR was successfully applied to track the intracellular hypochlorous acid and viscosity in living cells. Meanwhile, the generation of endogenous hypochlorite in living cells can be observed by using JXR. Full article

(This article belongs to the Special Issue Analytical Chemistry in Asia, 2nd Edition)

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14 pages, 1542 KiB

Open AccessArticle

Synthesis, Characterization, and Comparative Study on Norbornene Polymerization of CNN and PCN Pincer Palladium Complexes

by Huizhu Wang, Jin-Kui Liu, Yi-Dong Wang, Xin-Qi Hao, Mao-Ping Song, Jun-Fang Gong and Hui Jiang

Molecules 2025, 30(7), 1530; https://doi.org/10.3390/molecules30071530 (registering DOI) - 30 Mar 2025

Abstract

Several CNN pincer Pd(II) complexes including chiral complexes 1a–e with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones 2a–c with N-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition, the preparation of the achiral PCN pincer Pd(II) complexes 3a–e with aryl-based phosphinite–imine ligands and [...] Read more.

Several CNN pincer Pd(II) complexes including chiral complexes 1a–e with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones 2a–c with N-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition, the preparation of the achiral PCN pincer Pd(II) complexes 3a–e with aryl-based phosphinite–imine ligands and chiral 4a–c with aryl-based phosphinite–imidazoline ligands was also performed. Among them, the PCN Pd(II) pincers 3a–e were new complexes and were readily synthesized from commercially available materials in only two steps. The new complexes were characterized through elemental analyses, namely ¹H NMR, ¹³C{¹H} NMR, and ³¹P{¹H} NMR spectroscopies. Furthermore, the molecular structure of complex 3a was determined via X-ray single-crystal diffraction analysis. In the presence of EtAlCl₂, Et₂AlCl, or methylaluminoxane (MAO), the CNN pincer Pd(II) complexes and PCN pincer Pd(II) complexes exhibited excellent activities and monomer conversion rates in norbornene addition polymerization. Surprisingly, the CNN pincer Pd(II) complexes exhibited a higher conversion rate (99.5%) with Et₂AlCl as the cocatalyst, while the PCN pincer Pd(II) complexes showed a higher conversion rate (98.8%) with MAO. Full article

(This article belongs to the Special Issue Design, Synthesis and Applications of Novel Transition Metal Catalysts)

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33 pages, 4033 KiB

Open AccessReview

Advances in Antimicrobial Peptides: Mechanisms, Design Innovations, and Biomedical Potential

by He Zhang, Jiaxun Lv, Zhili Ma, Junfeng Ma and Jing Chen

Molecules 2025, 30(7), 1529; https://doi.org/10.3390/molecules30071529 (registering DOI) - 29 Mar 2025

Abstract

This comprehensive review explores the advancements in the study of antimicrobial peptides (AMPs), highlighting their potential as promising alternatives to conventional antibiotics in the context of growing antibiotic resistance. AMPs are small molecular proteins found ubiquitously in nature, exhibiting broad-spectrum antimicrobial activity, including [...] Read more.

This comprehensive review explores the advancements in the study of antimicrobial peptides (AMPs), highlighting their potential as promising alternatives to conventional antibiotics in the context of growing antibiotic resistance. AMPs are small molecular proteins found ubiquitously in nature, exhibiting broad-spectrum antimicrobial activity, including antibacterial, antiviral, and antifungal effects, and are vital components of the innate immune system. Due to their non-specific membrane-disrupting mechanism, AMPs are emerging as effective candidates for novel anti-infective agents. The integration of AMPs with biomaterials, such as nanoparticles, liposomes, polymers, and hydrogels, enhances their stability and efficacy while offering multifunctional therapeutic benefits. These combinations promote diverse antibacterial mechanisms, including membrane disruption, intracellular metabolic interference, cell wall modulation, and immune system activation. Despite challenges, such as toxicity, stability, and resistance, innovative strategies including computer-aided design and structural modification show promise in optimizing AMPs’ activity, targeting precision, and biocompatibility. The potential for AMPs in clinical applications remains highly promising, with significant opportunities for overcoming antimicrobial resistance through novel AMP-based therapeutic strategies. Full article

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11 pages, 2648 KiB

Open AccessArticle

Identification of Marker Peptides in Gelatins from Sika Deer (Cervus nippon) Using Ultra-High-Performance Liquid Chromatography–Quadrupole-Exactive-Orbitrap Mass Spectrometry

by Kouharu Otsuki, Aya Nomizo, Mi Zhang, Dongxia Li, Takashi Kikuchi and Wei Li

Molecules 2025, 30(7), 1528; https://doi.org/10.3390/molecules30071528 (registering DOI) - 29 Mar 2025

Abstract

Gelatin from deer has garnered attention as a high-value health-promoting resource given its history of usage as a traditional Chinese medicine and recent studies demonstrating its biological activities. Mass spectrometry-based methods have increasingly been employed for species identification in collagen-based materials, effectively addressing [...] Read more.

Gelatin from deer has garnered attention as a high-value health-promoting resource given its history of usage as a traditional Chinese medicine and recent studies demonstrating its biological activities. Mass spectrometry-based methods have increasingly been employed for species identification in collagen-based materials, effectively addressing challenges in quality control and authenticity verification. This study aims to identify characteristic marker peptides in gelatins from sika deer (Cervus nippon) to support their effective use as a health-promoting resource. Gelatin samples were enzymatically digested, and the resulting peptide mixtures were analyzed using ultra-high-performance liquid chromatography coupled with quadrupole Q-Exactive-Orbitrap mass spectrometry (UHPLC-Q-Exactive-Orbitrap MS). Marker peptide candidates were selected based on their high detection intensity and a literature review. Among the 28 selected marker peptide candidates, four peptides (P11, R2, R3, and R4) were defined as characteristic of sika deer gelatin. Comparative analyses with gelatins derived from donkey hide, bovine, porcine, and fish samples further confirmed the specificity of these peptides. These findings establish a robust analytical method for verifying the authenticity of sika deer gelatin, contributing to its safe and effective use as a health-promoting resource. Full article

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22 pages, 807 KiB

Open AccessArticle

Α Novel Liquid Chromatographic Time-of-Flight Tandem Mass Spectrometric Method for the Determination of Secondary Metabolites in Functional Flours Produced from Grape Seed and Olive Stone Waste

by Achilleas Panagiotis Zalidis, Natasa P. Kalogiouri, Ioannis Mourtzinos, Dimitris Sarris and Konstantinos Gkatzionis

Molecules 2025, 30(7), 1527; https://doi.org/10.3390/molecules30071527 (registering DOI) - 29 Mar 2025

Abstract

Agricultural by-products like grape pomace and olive stones are rich in bioactive compounds and can be processed into grape seed and olive stone flours.The phenolic composition of such flours still remains underexplored. This study introduces a liquid chromatographic time-of-flight tandem mass spectrometric method [...] Read more.

Agricultural by-products like grape pomace and olive stones are rich in bioactive compounds and can be processed into grape seed and olive stone flours.The phenolic composition of such flours still remains underexplored. This study introduces a liquid chromatographic time-of-flight tandem mass spectrometric method (LC-QTOF-MS/MS) to assess the phenolic profiles of functional flours from different origins and evaluate their potential use within the frame of a circular economy. Grape seed and olive stone flours from Lemnos and commercial sources were analyzed employing target, suspect, and non-target screening. Target screening resulted in the determination of 23 phenolic compounds. Suspect screening revealed phenolic diversity in flours produced in Lemnos island. Non-target screening resulted in the detection of 1042 and 1620 mass features in grape seed and olive stone flours, respectively. Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) successfully differentiated samples between commercially available and those produced in Lemnos. These results underscore the phenolic richness of grape seed and olive stone flours, supporting their use as functional ingredients and reinforcing sustainability and circular economy principles in the agri-food sector. Full article

(This article belongs to the Special Issue Chromatography—The Ultimate Analytical Tool, 3rd Edition)

15 pages, 7554 KiB

Open AccessArticle

TiO₂/LaFeO₃ Composites for the Efficient Degradation of Benzoic Acid and Hydrogen Production

by Isabella Natali Sora, Benedetta Bertolotti, Renato Pelosato, Andrea Lucotti, Matteo Tommasini and Marica Muscetta

Molecules 2025, 30(7), 1526; https://doi.org/10.3390/molecules30071526 (registering DOI) - 29 Mar 2025

Abstract

LaFeO₃/TiO₂ composites were prepared in the range 0–12.2 wt% of LaFeO₃, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal [...] Read more.

LaFeO₃/TiO₂ composites were prepared in the range 0–12.2 wt% of LaFeO₃, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal treatment. The composite materials presented agglomerates of LaFeO₃ with an average size from 1 to 5 μm, and the TiO₂ powder was well dispersed onto the surface of each sample. They showed varying activities for BA degradation depending on composition and light wavelength. The 6.2 wt% and 12.2 wt%-LaFeO₃/TiO₂ composites exhibited the highest activity under 380–800 nm light and could degrade BA in 300 min at BA concentration 13.4 mg L⁻¹ and catalyst 0.12 g L⁻¹. Using a 450 nm LED light source, all composites degraded less than 10% of BA, but in the presence of H₂O₂ (1 mM) the photocatalytic activity was as high as 96% in <120 min, 6.2 wt%-LaFeO₃/TiO₂ composite being the most efficient sample. It was found that in the presence of H₂O₂, BA degradation followed first order kinetic with a reaction rate constant of 4.8 × 10⁻⁴ s⁻¹. The hydrogen production rate followed a classical volcano-like behavior, with the highest reactivity (1600 μmol h⁻¹g⁻¹ at 60 °C) in the presence of 3.86%wt- LaFeO₃/TiO₂. It was also found that LaFeO₃/TiO₂ exhibited high stability in four recycled tests without losing activity for hydrogen production. Furthermore, a discussion on photogenerated charge-carrier transfer mechanism is briefly provided, focusing on lacking significant photocatalytic activity under 450 nm light, so p-n heterojunction formation is unlikely. Full article

(This article belongs to the Special Issue Research on Heterogeneous Catalysis—2nd Edition)

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25 pages, 4179 KiB

Open AccessArticle

Centrifugal Partition Chromatography Is a Powerful Tool for the Isolation of Antibiofilm Quantum Carbon Dots Synthesized by Hydrothermal Treatment of Avocado Peels

by Nandis Fiallos, Sergio Acuña, Diana Correa-Otero, Matías Venegas-Toloza, Tatiana Beldarrain, Josefina Burgos, Francisca Fuentes, Francisco Bustamante, Girlenne Christiansen, Vanesa Roa, Eduardo Schott, Julio Alarcón-Enos and Edgar Pastene-Navarrete

Molecules 2025, 30(7), 1525; https://doi.org/10.3390/molecules30071525 (registering DOI) - 29 Mar 2025

Abstract

Carbon quantum dots (CQD) are an emergent nanomaterial with unique optical and biological properties. However, the purification of CQD is one of the bottlenecks that makes it difficult to scale for application in different areas. In this work, we explore for the first [...] Read more.

Carbon quantum dots (CQD) are an emergent nanomaterial with unique optical and biological properties. However, the purification of CQD is one of the bottlenecks that makes it difficult to scale for application in different areas. In this work, we explore for the first time the potential of centrifugal partition chromatography (CPC) as an alternative preparative technology to achieve the purification of CQD at the gram scale. The hydrothermal method was used to synthesize CQD from avocado peels. After 6 h at 250 °C, a complex mix of strong blue-fluorescent CQDs were obtained and submitted to CPC fractionation without pretreatment. The best results were obtained with the solvent system n-hexane–ethyl acetate–methanol–water (1:2:1:2, v/v/v/v), in an elution-extrusion protocol. Nine fractions were obtained and were characterized by UV-VIS spectrophotometry, Fourier transform infrared (F-TIR), and field emission scanning electron microscopy (FESEM), confirming the presence of CQD of different sizes. CPC fractionations indicate that a polarity-based separation mechanism can be used to purify CQD. Interestingly, four fractions showed antibacterial and anti-biofilm effects on Pseudomonas putida and Listeria monocytogenes. Therefore, CPC allows for better refining of this type of nanomaterial, and in combination with other techniques, it would serve to obtain CQD of higher purity, facilitating the physicochemical and bioactivity characterization of these particles. CPC would also allow the use of waste, such as avocado peels, to obtain new materials. Full article

(This article belongs to the Special Issue Countercurrent Chromatography (CCC/CPC) as Versatile Separation ‘Tool-Box’ in the Field of Natural Product Recovery)

11 pages, 1130 KiB

Open AccessArticle

Local Interactions in Aqueous Ethanol Solution Revealed by the C=O Stretching Probe

by Zhiqiang Wang, Chi Chen, Ruiting Zhang, Lin Ma and Ke Lin

Molecules 2025, 30(7), 1524; https://doi.org/10.3390/molecules30071524 (registering DOI) - 29 Mar 2025

Abstract

Accurately identifying local interactions such as hydrophilicity and hydrophobicity is of critical importance in regulating the functions of amphiphilic biomolecules, but in situ identification methods for such interactions are still lacking. This study proposes a probe based on carbonyl (C=O) stretching vibration to [...] Read more.

Accurately identifying local interactions such as hydrophilicity and hydrophobicity is of critical importance in regulating the functions of amphiphilic biomolecules, but in situ identification methods for such interactions are still lacking. This study proposes a probe based on carbonyl (C=O) stretching vibration to study the hydrophilic and hydrophobic interactions in amphiphilic alcohol–water systems. A combination of theoretical calculations and Raman spectroscopy experiments is employed to investigate the molecular interactions of ethyl acetate C=O in an ethanol aqueous solution, as well as the reasons behind the splitting of spectral peaks. The results indicate that the spectral peak splitting of the C=O stretching vibration is attributed to ethyl acetate existing in different hydrophilic and hydrophobic environments. Specifically, the two low-wavenumber components arise from the formation of double and single hydrogen bonds between C=O and water or ethanol, respectively, while the high-wavenumber component is attributed to the interaction between C=O and the hydrophobic alkyl group. These findings suggest that the C=O stretching vibration of esters is sensitive to the surrounding hydrophilic and hydrophobic environments, thereby indicating its potential as a useful probe for identifying hydrophilic and hydrophobic interactions. Full article

(This article belongs to the Section Analytical Chemistry)

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