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1.
Chem Asian J ; 19(7): e202301033, 2024 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-38501888

RESUMO

Kinases are enzymes that play a critical role in governing essential biological processes. Due to their pivotal involvement in cancer cell signaling, they have become key targets in the development of anti-cancer drugs. Among these drugs, those containing the 2,4-dihalophenyl moiety demonstrated significant potential. Here we show how this moiety, particularly the 2-fluoro-4-iodophenyl one, is crucial for the structural stability of the formed drug-enzyme complexes. Crystallographic analysis of reported kinase-inhibitor complex structures highlights the role of the halogen bonding that this moiety forms with specific residues of the kinase binding site. This interaction is not limited to FDA-approved MEK inhibitors, but it is also relevant for other kinase inhibitors, indicating its broad relevance in the design of this class of drugs.


Assuntos
Antineoplásicos , Inibidores de Proteínas Quinases , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/química , Halogênios/química , Sítios de Ligação , Ligação Proteica , Antineoplásicos/farmacologia , MAP Quinase Quinase Quinases
2.
Environ Sci Technol ; 58(11): 5139-5152, 2024 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-38446791

RESUMO

Plasma has been proposed as an alternative strategy to treat organic contaminants in brines. Chemical degradation in these systems is expected to be partially driven by halogen oxidants, which have been detected in halide-containing solutions exposed to plasma. In this study, we characterized specific mechanisms involving the formation and reactions of halogen oxidants during plasma treatment. We first demonstrated that addition of halides accelerated the degradation of a probe compound known to react quickly with halogen oxidants (i.e., para-hydroxybenzoate) but did not affect the degradation of a less reactive probe compound (i.e., benzoate). This effect was attributed to the degradation of para-hydroxybenzoate by hypohalous acids, which were produced via a mechanism involving halogen radicals as intermediates. We applied this mechanistic insight to investigate the impact of constituents in brines on reactions driven by halogen oxidants during plasma treatment. Bromide, which is expected to occur alongside chloride in brines, was required to enable halogen oxidant formation, consistent with the generation of halogen radicals from the oxidation of halides by hydroxyl radical. Other constituents typically present in brines (i.e., carbonates, organic matter) slowed the degradation of organic compounds, consistent with their ability to scavenge species involved during plasma treatment.


Assuntos
Oxidantes , Sais , Poluentes Químicos da Água , Compostos Orgânicos , Radical Hidroxila/química , Oxirredução , Halogênios/química , Hidroxibenzoatos , Poluentes Químicos da Água/química
3.
J Med Chem ; 67(6): 4782-4792, 2024 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-38502551

RESUMO

Halogen bonds (XBs) are essential noncovalent interactions in molecular recognition and drug design. Current studies on XBs in drug design mainly focus on the interactions between halogenated ligands and target proteins, lacking a systematic study of naturally existing and artificially prepared halogenated residue XBs (hr_XBs) and their characteristics. Here, we conducted a computational study on the potential hr_XBs in proteins/peptides using database searching, quantum mechanics calculations, and molecular dynamics simulations. XBs at the protein-peptide interaction interfaces are found to enhance their binding affinity. Additionally, the formation of intramolecular XBs (intra_XBs) within proteins may significantly contribute to the structural stability of structurally flexible proteins while having a minor impact on proteins with inherently high structural rigidity. Impressively, introducing halogens without the formation of intra_XBs may lead to a decrease in the protein structural stability. This study enriches our understanding of the roles and effects of halogenated residue XBs in biological systems.


Assuntos
Halogênios , Proteínas , Halogênios/química , Proteínas/metabolismo , Peptídeos/metabolismo , Simulação de Dinâmica Molecular , Ligação Proteica
4.
Environ Sci Technol ; 58(8): 4008-4018, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38347702

RESUMO

The electrocatalytic hydrodehalogenation (EHDH) process mediated by atomic hydrogen (H*) is recognized as an efficient method for degrading halogenated organic pollutants (HOPs). However, a significant challenge is the excessive energy consumption resulting from the recombination of H* to H2 production in the EHDH process. In this study, a promising strategy was proposed to generate piezo-induced atomic H*, without external energy input or chemical consumption, for the degradation and dehalogenation of HOPs. Specifically, sub-5 nm Ni nanoparticles were subtly dotted on an N-doped carbon layer coating on BaTiO3 cube, and the resulted hybrid nanocomposite (Ni-NC@BTO) can effectively break C-X (X = Cl and F) bonds under ultrasonic vibration or mechanical stirring, demonstrating high piezoelectric driven dehalogenation efficiencies toward various HOPs. Mechanistic studies revealed that the dotted Ni nanoparticles can efficiently capture H* to form Ni-H* (Habs) and drive the dehalogenation process to lower the toxicity of intermediates. COMSOL simulations confirmed a "chimney effect" on the interface of Ni nanoparticle, which facilitated the accumulation of H+ and enhanced electron transfer for H* formation by improving the surface charge of the piezocatalyst and strengthening the interfacial electric field. Our work introduces an environmentally friendly dehalogenation method for HOPs using the piezoelectric process independent of the external energy input and chemical consumption.


Assuntos
Poluentes Ambientais , Hidrogênio/metabolismo , Halogênios/química
5.
J Mol Graph Model ; 127: 108680, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38039786

RESUMO

A detailed investigation of the σ-hole on the halogen atom present in the nido-heteroboranes is made by employing quantum mechanical methods. The bromide and the hydroxyl groups are incorporated in the exo-substituents of the nido-boranes. The potential of the bromide σ-hole was compared to that of electrostatic potential of hydroxyl group counterpart. The presence of a carbon atom vertex, in a different position of a system, influences the σ-hole and hence its binding abilities. Bromide substituted nido-carboranes have less potential and hence weaker binding ability compared to their closo-counterparts. Binding affinity with aliphatic is found to be more compared to that of aromatic system. The presence of solvent dampened the electrostatic interactions. Apart from the neutral system, the binding capabilities of charged nido-heteroboranes were also studied. The results of this study will be further useful for several applications viz., crystal engineering, drug designing (Pharmaceuticals), medicine, material science, energy storage devices, etc.


Assuntos
Boranos , Brometos , Compostos de Boro , Boranos/química , Halogênios/química
6.
J Mol Recognit ; 37(2): e3070, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37990248

RESUMO

Human interleukin-5 (IL-5) cytokine mediates the development of eosinophils and is involved in a variety of immune inflammatory responses that play a major role in the pathogenesis of childhood asthma, leukemia, and other pediatric allergic diseases. The immunomodulatory cytokine functions by binding to its cognate cell surface receptor IL-5R in a sheet-by-sheet manner, which can be conformationally mimicked and competitively disrupted by a double-stranded cyclic AF18748 peptide. In this study, we systematically examined the co-crystallized complex structure of human IL-5R with AF18748 peptide and rationally designed a halogen bond to glue at the protein-peptide complex interface by substituting the indole moiety of AF18748 Trp13 residue with a halogen atom (X = F, Cl, Br, or I). High-level theoretical calculations imparted presence of the halogen bond between the oxygen atom (O) of IL-5R Glu58 backbone and the halogen atom (X) of AF18748 Trp13 side chain. Experimental assays confirmed that the halogen bond can promote peptide binding moderately or considerably. More importantly, the halogen bond not only enhances peptide affinity to IL-5R, but also improves peptide selectivity for its cognate IL-5R over other noncognate IL-R proteins. As might be expected, the affinity and selectivity conferred by halogen bond increase consistently in the order: H < F < Cl < Br < I. Structural modeling revealed that the halogen bond plus its vicinal π-cation-π stacking co-define a ringed noncovalent system at the complex interface, which involves a synergistic effect to effectively improve the peptide binding potency and recognition specificity.


Assuntos
Halogênios , Interleucina-5 , Humanos , Criança , Halogênios/química , Peptídeos/química , Proteínas
7.
Chem Biol Drug Des ; 103(1): e14387, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37926515

RESUMO

Human interleukin-5 (IL-5) functions as an important pro-inflammatory factor by binding to its specific receptor, IL-5Rα, which has been implicated in the pathogenesis of asthma. Previously, a disulfide-bonded cyclic peptide AF17121 obtained from random library screening and sequence variation was found to competitively disrupt the cognate IL-5Rα/IL-5 interaction with moderate potency. In this study, the crystal complex of IL-5Rα with AF17121 was investigated at structural and energetic levels. It is revealed that the side-chain indole moiety of the AF17121 Trp5 residue is a potential site for a stem putative halogen bond (X-bond) with IL-5Rα, which is just located within the key 3 EXXR6 motif region recognized specifically by IL-5Rα. We systematically examined four halogen substitution types at five positions of the indole moiety; QM/MM calculations theoretically unraveled that only halogenations at 5 and 6 positions can form effective X-bonds with the side-chain hydroxyl oxygen of the IL-5Rα Thr21 residue and the backbone carbonyl oxygen of Ala66 residue, respectively. Binding assays observed that I-substitution at the 5 position and Br-substitution at the 6 position can result in two potent halogenated peptides, [5I]AF17121 and [6Br]AF17121, which are improved by 1.6-fold and 3.5-fold relative to the native AF17121, respectively. 5I/6Br-double substitution, resulting in [5I/6Br]AF17121, can further enhance the peptide affinity by 7.5-fold. Structural analysis revealed that the X-bond stemming from 6Br-substitution is also involved in an orthogonal interaction system with a H-bond; they share a common backbone carbonyl oxygen acceptor of IL-5Rα Ala66 residue and exhibit a significant synergistic effect between them.


Assuntos
Asma , Peptídeos Cíclicos , Humanos , Receptores de Interleucina-5 , Peptídeos Cíclicos/química , Interleucina-5/metabolismo , Halogênios/química , Ligantes , Peptídeos/química , Indóis , Oxigênio
8.
J Chem Inf Model ; 63(23): 7464-7475, 2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-38010191

RESUMO

Compounds containing halogens can form halogen bonds (XBs) with biological targets such as proteins and membranes due to their anisotropic electrostatic potential. To accurately describe this anisotropy, off-center point-charge (EP) models are commonly used in force field methods, allowing the description of XBs at the molecular mechanics and molecular dynamics level. Various EP implementations have been documented in the literature, and despite being efficient in reproducing protein-ligand geometries and sampling of XBs, it is unclear how well these EP models predict experimental properties such as hydration free energies (ΔGhyd), which are often used to validate force field performance. In this work, we report the first assessment of three EP models using alchemical free energy calculations to predict ΔGhyd values. We show that describing the halogen anisotropy using some EP models can lead to a slight improvement in the prediction of the ΔGhyd when compared with the models without EP, especially for the chlorinated compounds; however, this improvement is not related to the establishment of XBs but is most likely due to the improvement of the sampling of hydrogen bonds. We also highlight the importance of the choice of the EP model, especially for the iodinated molecules, since a slight tendency to improve the prediction is observed for compounds with a larger σ-hole but significantly worse results were obtained for compounds that are weaker XB donors.


Assuntos
Halogênios , Teoria Quântica , Halogênios/química , Proteínas/química , Simulação de Dinâmica Molecular , Ligação de Hidrogênio
9.
Int J Mol Sci ; 24(19)2023 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-37834088

RESUMO

We designed 0D, 1D, and 2D supramolecular assemblies made of diaryliodonium salts (functioning as double σ-hole donors) and carboxylates (as σ-hole acceptors). The association was based on two charge-supported halogen bonds (XB), which occurred between IIII sites of the iodonium cations and the carboxylate anions. The sequential introduction of the carboxylic groups in the aryl ring of the benzoic acid added a dimension to the 0D supramolecular organization of the benzoate, which furnished 1D-chained and 2D-layered structures when terephthalate and trimesate anions, correspondingly, were applied as XB acceptors. The structure-directing XB were studied using DFT calculations under periodic boundary conditions and were followed by the one-electron-potential analysis and the Bader atoms-in-molecules topological analysis of electron density. These theoretical methods confirmed the existence of the XB and verified the philicities of the interaction partners in the designed solid-state structures.


Assuntos
Ácidos Carboxílicos , Halogênios , Halogênios/química , Ânions , Teoria da Densidade Funcional , Ácido Benzoico
10.
Pharmacol Rev ; 76(1): 90-141, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37845080

RESUMO

Antimicrobial resistance presents us with a potential global crisis as it undermines the abilities of conventional antibiotics to combat pathogenic microbes. The history of antimicrobial agents is replete with examples of scaffolds containing halogens. In this review, we discuss the impacts of halogen atoms in various antibiotic types and antimicrobial scaffolds and their modes of action, structure-activity relationships, and the contributions of halogen atoms in antimicrobial activity and drug resistance. Other halogenated molecules, including carbohydrates, peptides, lipids, and polymeric complexes, are also reviewed, and the effects of halogenated scaffolds on pharmacokinetics, pharmacodynamics, and factors affecting antimicrobial and antivirulence activities are presented. Furthermore, the potential of halogenation to circumvent antimicrobial resistance and rejuvenate impotent antibiotics is addressed. This review provides an overview of the significance of halogenation, the abilities of halogens to interact in biomolecular settings and enhance pharmacological properties, and their potential therapeutic usages in preventing a postantibiotic era. SIGNIFICANCE STATEMENT: Antimicrobial resistance and the increasing impotence of antibiotics are critical threats to global health. The roles and importance of halogen atoms in antimicrobial drug scaffolds have been established, but comparatively little is known of their pharmacological impacts on drug resistance and antivirulence activities. This review is the first to extensively evaluate the roles of halogen atoms in various antibiotic classes and pharmacological scaffolds and to provide an overview of their ability to overcome antimicrobial resistance.


Assuntos
Antibacterianos , Anti-Infecciosos , Humanos , Antibacterianos/farmacologia , Antibacterianos/química , Anti-Infecciosos/farmacologia , Anti-Infecciosos/uso terapêutico , Halogênios/química , Halogenação , Relação Estrutura-Atividade
11.
ACS Biomater Sci Eng ; 9(11): 6094-6102, 2023 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-37856790

RESUMO

A polymer with high contents of ester bonds and iodine atoms was synthesized, exhibiting sufficient biodegradability and radioactivity for biomedical applications. The iodine moieties of the synthesized polyester can generate halogen bonding between molecules, which may develop additional functional properties through the bonding. In this study, poly(glycerol adipate) (PGA) was selected and synthesized as a polyester, which was then adequately conjugated with three different types of iodine compounds via the hydroxy groups of PGA. It was found that the iodine compounds could effectively work as donors of halogen bonding. The thermal analysis by differential scanning calorimetry (DSC) revealed that the glass transition temperature increased with the increase in the strength of interactions caused by π-π stacking and halogen bonding, eventually reaching 49.6 °C for PGA with triiodobenzoic groups. An elastomeric PGA with monoiodobenzoic groups was also obtained, exhibiting a high self-healing ability at room temperature because of the reconstruction of halogen bonding. Such multifaceted performance of the synthesized polyester with controllable thermal/mechanical properties was realized by halogen bonding, leading to a promising biomaterial with multifunctionality.


Assuntos
Compostos de Iodo , Iodo , Halogênios/química , Polímeros/química , Iodo/química , Poliésteres/química , Elasticidade
12.
J Labelled Comp Radiopharm ; 66(11): 362-368, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37530220

RESUMO

Halogenated, labeled with deuterium, tritium or doubly labeled with deuterium and tritium in the 3S position of the side chain isotopomers of L-phenylalanine and phenylpyruvic acid were synthesized. Isotopomers of halogenated L-phenylalanine were obtained by addition of ammonia from isotopically enriched buffer solution to the halogenated derivative of (E)-cinnamic acid catalyzed by phenylalanine ammonia lyase. Isotopomers of halogenated phenylpyruvic acid were obtained enzymatically by conversion of the appropriate isotopomer of halogenated L-phenylalanine in the presence of phenylalanine dehydrogenase. As a source of deuterium was used deuterated water, as a source of tritium was used a solution of highly diluted tritiated water. The labeling takes place in good yields and with high deuterium atom% abundance.


Assuntos
Halogênios , Fenilalanina , Ácidos Fenilpirúvicos , Deutério/química , Halogênios/síntese química , Halogênios/química , Hidrogênio , Trítio/química , Ácidos Fenilpirúvicos/síntese química , Ácidos Fenilpirúvicos/química
13.
Int J Mol Sci ; 24(15)2023 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-37569289

RESUMO

Statistical analysis of halogen...halogen intermolecular distances was performed for three sets of homomolecular crystals under normal conditions: C-Hal1...Hal2-C distances in crystals consisting of: (i) organic compounds (set Org); (ii) organometallic compounds (set Orgmet); and (iii) distances M1-Hal1...Hal2-M2 (set MHal) (in all cases Hal1 = Hal2, and in MHal M1 = M2, M is any metal). When analyzing C-Hal...Hal-C distances, a new method for estimating the values of van der Waals radii is proposed, based on the use of two subsets of distances: (i) the shortest distances from each substance less than a threshold; and (ii) all C-Hal...Hal-C distances less than the same threshold. As initial approximations for these thresholds for different Hal, the Ragg values previously introduced in investigations with the participation of the author were used (Ragg values make it possible to perform a statistical assessment of the presence of halogen aggregates in crystals). The following values are recommended in this work to be used as universal values for crystals of organic and organometallic compounds: RF = 1.57, RCl = 1.90, RBr = 1.99, and RI = 2.15 Å. They are in excellent agreement with the results of some other works but significantly (by 0.10-0.17 Å) greater than the commonly used values. For the Orgmet set, slightly lower values for RI (2.11-2.09 Å) were obtained, but number of the C-I...I-C distances available for analysis was significantly smaller than in the other subgroups, which may be the reason for the discrepancy with value for the Org set (2.15 Å). Statistical analysis of the M-Hal...Hal-M distances was performed for the first time. A Hal-aggregation coefficient for M-Hal bonds is proposed, which allows one to estimate the propensity of M-Hal groups with certain M and Hal to participate in Hal-aggregates formed by M-Hal...Hal-M contacts. In particular, it was found that, for the Hg-Hal groups (Hal = Cl, Br, I), there is a high probability that the crystals have Hg-Hal...Hal-Hg distances with length ≤ Ragg.


Assuntos
Halogênios , Compostos Organometálicos , Halogênios/química , Compostos Organometálicos/química
14.
J Med Chem ; 66(15): 10202-10225, 2023 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-37487500

RESUMO

As an orthogonal principle to the established (hetero)aryl halides, we herein highlight the usefulness of CF2X (X = Cl, Br, or I) moieties. Using tool compounds bearing CF2X moieties, we study their chemical/metabolic stability and their logP/solubility, as well as the role of XB in their small molecular crystal structures. Employing QM techniques, we analyze the observed interactions, provide insights into the conformational flexibilities and preferences in the potential interaction space. For their application in molecular design, we characterize their XB donor capacities and its interaction strength dependent on geometric parameters. Implementation of CF2X acetamides into our HEFLibs and biophysical evaluation (STD-NMR/ITC), followed by X-ray analysis, reveals a highly interesting binding mode for fragment 23 in JNK3, featuring an XB of CF2Br toward the P-loop, as well as chalcogen bonds. We suggest that underexplored chemical space combined with unconventional binding modes provides excellent opportunities for patentable chemotypes for therapeutic intervention.


Assuntos
Química Farmacêutica , Halogênios , Halogênios/química , Estrutura Molecular , Descoberta de Drogas , Biologia
15.
Phys Chem Chem Phys ; 25(26): 17692-17699, 2023 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-37367726

RESUMO

Hydrogen bonds (HBs) and halogen bonds (XBs) are two essential non-covalent interactions for molecular recognition and drug design. As proteins are heterogeneous in structure, the microenvironments of protein structures should have effects on the formation of HBs and XBs with ligands. However, there are no systematic studies reported on this effect to date. For quantitatively describing protein microenvironments, we defined the local hydrophobicities (LHs) and local dielectric constants (LDCs) in this study. With the defined parameters, we conducted an elaborate database survey on the basis of 22 011 ligand-protein structures to explore the microenvironmental preference of HBs (91 966 in total) and XBs (1436 in total). The statistics show that XBs prefer hydrophobic microenvironments compared to HBs. The polar residues like ASP are more likely to form HBs with ligands, while nonpolar residues such as PHE and MET prefer XBs. Both the LHs and LDCs (10.69 ± 4.36 for HBs; 8.86 ± 4.00 for XBs) demonstrate that XBs are prone to hydrophobic microenvironments compared with HBs with significant differences (p < 0.001), indicating that evaluating their strengths in the corresponding environments should be necessary. Quantum Mechanics-Molecular Mechanics (QM/MM) calculations reveal that in comparison with vacuum environments, the interaction energies of HBs and XBs are decreased to varying degrees given different microenvironments. In addition, the strengths of HBs are impaired more than those of XBs when the local dielectric constant's difference between the XB microenvironments and the HB microenvironments is large.


Assuntos
Halogênios , Proteínas , Halogênios/química , Ligação de Hidrogênio , Ligantes , Proteínas/química , Simulação de Dinâmica Molecular
16.
Arch Biochem Biophys ; 743: 109675, 2023 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-37343813

RESUMO

LinB and DhaA are well-known haloalkane dehalogenases (HLDs) capable of converting a plethora of halogenated alkanes, also those considered persistent pollutants. The dehalogenation reaction that these two enzymes catalyze has been studied to determine its rate-limiting step (rls) for the last two decades now. As a result, it has been determined that HLDs can show different rate-limiting steps for individual substrates, and at this point we do not have a basis for any generalization in this matter. Therefore, in this work we aimed at gaining insights into the enzymatic dehalogenation of selected dibromo- and bromochloro-ethanes and propanes by LinB and DhaA using computational approach to determine whether defined structural similarities of the substrates result in a unified mechanism and the same rls. By predicting halogen binding isotope effects (BIEs) as well as computing interaction energy for each HLD-ligand complex the nature of the protein-ligand interactions has been characterized. Furthermore, C and Br kinetic isotope effects (KIEs) as well as the minimum free energy paths (MFEPs) were computed to investigate the chemical reaction for the selected systems. Accuracy of the approach and robustness of the computational predictions were validated by measuring KIEs on the selected reactions. Overall results strongly indicate that any generalization with respect to the enzymatic process involving various ligands in the case of DhaA is impossible, even if the considered ligands are structurally very similar as those analyzed in the present study. Moreover, even small structural differences such as changing of one of the (non-leaving) halogen substituents may lead to significant changes in the enzymatic process and result in a different rls in the case of LinB. It has also been demonstrated that KIEs themselves cannot be used as rls indicators in the reactions catalyzed by the studied HLDs.


Assuntos
Alcanos , Hidrolases , Ligantes , Hidrolases/química , Halogênios/química
17.
Drug Des Devel Ther ; 17: 1247-1274, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37128274

RESUMO

Introduction: Therapeutic peptides are a significant class of drugs in the treatment of a wide range of diseases. To enhance their properties, such as stability or binding affinity, they are usually chemically modified. This includes, among other techniques, cyclization of the peptide chain by bridging, modifications to the backbone, and incorporation of unnatural amino acids. One approach previously established, is the use of halogenated aromatic amino acids. In principle, they are thereby enabled to form halogen bonds (XB). In this study, we focus on the -R-CF2X moiety (R = O, NHCO; X = Cl, Br) as an uncommon halogen bond donor. These groups enable more spatial variability in protein-protein interactions. The chosen approach via Fmoc-protected building blocks allows for the incorporation of these modified amino acids in peptides using solid-phase peptide synthesis. Results and Discussion: Using a competitive fluorescence polarization assay to monitor binding to Mdm4, we demonstrate that a p53-derived peptide with Lys24Nle(εNHCOCF2X) exhibits an improved inhibition constant Ki compared to the unmodified peptide. Decreasing Ki values observed with the increasing XB capacity of the halogen atoms (F ≪ Cl < Br) indicates the formation of a halogen bond. By reducing the side chain length of Nle(εNHCOCF2X) to Abu(γNHCOCF2X) as control experiments and through quantum mechanical calculations, we suggest that the observed affinity enhancement is related to halogen bond-induced intramolecular stabilization of the α-helical binding mode of the peptide or a direct interaction with His54 in human Mdm4.


Assuntos
Aminoácidos , Proteína Supressora de Tumor p53 , Humanos , Peptídeos/química , Halogênios/química , Proteínas Proto-Oncogênicas c-mdm2/química , Proteínas Proto-Oncogênicas , Proteínas de Ciclo Celular
18.
J Magn Reson ; 352: 107472, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37186965

RESUMO

Inorganic metal halides offer unprecedented tunability through elemental variation of simple three-element compositions, but can exhibit complicated phase behaviour, degradation, and microscopic phenomena (disorder/dynamics) that play an integral role for the bulk-level chemical and physical properties of these materials. Understanding the halogen chemical environment in such materials is crucial to addressing many of the concerns regarding implementing these materials in commercial applications. In this study, a combined solid-state nuclear magnetic resonance, nuclear quadrupole resonance and quantum chemical computation approach is used to interrogate the Br chemical environment in a series of related inorganic lead bromide materials: CsPbBr3, CsPb2Br5, and Cs4PbBr6. The quadrupole coupling constants (CQ) were determined to range from 61 to 114 MHz for 81Br, with CsPbBr3 exhibiting the largest measured CQ and Cs4PbBr6 the smallest. GIPAW DFT was shown to be an excellent pre-screening tool for estimating the EFG of Br materials and can increase experimental efficiency by providing good starting estimates for acquisition. Finally, the combination of theory and experiment to inform the best methods for expanding further to the other quadrupolar halogens is discussed.


Assuntos
Brometos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética/métodos , Chumbo , Halogênios/química
19.
Int J Mol Sci ; 24(10)2023 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-37240403

RESUMO

The subjects of the article are halogen bonds between either XCN or XCCH (X = Cl, Br, I) and the carbene carbon atom in imidazol-2-ylidene (I) or its derivatives (IR2) with experimentally significant and systematically increased R substituents at both nitrogen atoms: methyl = Me, iso-propyl = iPr, tert-butyl = tBu, phenyl = Ph, mesityl = Mes, 2,6-diisopropylphenyl = Dipp, 1-adamantyl = Ad. It is shown that the halogen bond strength increases in the order Cl < Br < I and the XCN molecule forms stronger complexes than XCCH. Of all the carbenes considered, IMes2 forms the strongest and also the shortest halogen bonds with an apogee for complex IMes2⋯ICN for which D0 = 18.71 kcal/mol and dC⋯I = 2.541 Å. In many cases, IDipp2 forms as strong halogen bonds as IMes2. Quite the opposite, although characterized by the greatest nucleophilicity, ItBu2 forms the weakest complexes (and the longest halogen bonds) if X ≠ Cl. While this finding can easily be attributed to the steric hindrance exerted by the highly branched tert-butyl groups, it appears that the presence of the four C-H⋯X hydrogen bonds may also be of importance here. Similar situation occurs in the case of complexes with IAd2.


Assuntos
Halogênios , Metano , Humanos , Modelos Moleculares , Halogênios/química , Metano/química , Ligação de Hidrogênio
20.
Chem Asian J ; 18(12): e202300097, 2023 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-37095738

RESUMO

As a new type of non-covalent interaction similar to hydrogen bond, halogen bond has become an important supramolecular tool in crystal engineering, material chemistry, biological science, etc., due to its unique properties. In fact, halogen bond has been confirmed on the effect of molecular assemblies and soft materials, and widely used in various functional soft materials including liquid crystals, gels and polymers. In recent years, halogen bonding has aroused strong interest in inducing molecular assembly into low-molecular-weight gels (LMWGs). To the best of our knowledge, there is still a lack of in-depth review of this field. So, in this paper, the recent progress of LMWGs driven by halogen bonding is reviewed. According to the number of components forming halogen bonded gels, the structural characteristics of halogen bonded supramolecular gels, the relationship between halogen bonding and other non-covalent interactions, as well as the application fields of halogen bonded gels are introduced, respectively. In addition, the challenges faced by halogenated supramolecular gels at present and their development prospects in future have been proposed. We believe that the halogen bonded gel will have more impressive applications in the next few years, opening exciting new opportunities for the development of soft materials.


Assuntos
Halogênios , Polímeros , Halogênios/química , Géis/química , Polímeros/química
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