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1.
Nature ; 583(7814): 66-71, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32612224

RESUMO

Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.


Assuntos
Amelogênese , Esmalte Dentário/química , Ácidos/química , Cálcio/química , Carbonatos/química , Cristalização , Teoria da Densidade Funcional , Esmalte Dentário/ultraestrutura , Durapatita/química , Fluoretos/química , Humanos , Magnésio/química , Microscopia Eletrônica de Transmissão e Varredura , Sódio/química , Tomografia , Difração de Raios X
2.
Nature ; 568(7750): 122-126, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30867595

RESUMO

Pericyclic reactions are powerful transformations for the construction of carbon-carbon and carbon-heteroatom bonds in organic synthesis. Their role in biosynthesis is increasingly apparent, and mechanisms by which pericyclases can catalyse reactions are of major interest1. [4+2] cycloadditions (Diels-Alder reactions) have been widely used in organic synthesis2 for the formation of six-membered rings and are now well-established in biosynthesis3-6. [6+4] and other 'higher-order' cycloadditions were predicted7 in 1965, and are now increasingly common in the laboratory despite challenges arising from the generation of a highly strained ten-membered ring system8,9. However, although enzyme-catalysed [6+4] cycloadditions have been proposed10-12, they have not been proven to occur. Here we demonstrate a group of enzymes that catalyse a pericyclic [6+4] cycloaddition, which is a crucial step in the biosynthesis of streptoseomycin-type natural products. This type of pericyclase catalyses [6+4] and [4+2] cycloadditions through a single ambimodal transition state, which is consistent with previous proposals11,12. The [6+4] product is transformed to a less stable [4+2] adduct via a facile Cope rearrangement, and the [4+2] adduct is converted into the natural product enzymatically. Crystal structures of three pericyclases, computational simulations of potential energies and molecular dynamics, and site-directed mutagenesis establish the mechanism of this transformation. This work shows how enzymes are able to catalyse concerted pericyclic reactions involving ambimodal transition states.


Assuntos
Biocatálise , Produtos Biológicos/química , Produtos Biológicos/metabolismo , Reação de Cicloadição , Enzimas/metabolismo , Lactonas/química , Lactonas/metabolismo , Cristalografia por Raios X , Teoria da Densidade Funcional , Enzimas/química , Enzimas/genética , Simulação de Dinâmica Molecular , Conformação Proteica , Termodinâmica
3.
Nature ; 574(7779): 516-521, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31645723

RESUMO

Methods for selective C-H bond functionalization have provided chemists with versatile and powerful toolboxes for synthesis, such as the late-stage modification of a lead compound without the need for lengthy de novo synthesis1-5. Cleavage of an sp3 C-H bond via hydrogen atom transfer (HAT) is particularly useful, given the large number of available HAT acceptors and the diversity of reaction pathways available to the resulting radical intermediate6-17. Site-selectivity, however, remains a formidable challenge, especially among sp3 C-H bonds with comparable properties. If the intermediate radical could be further trapped enantioselectively, this should enable highly site- and enantioselective functionalization of C-H bonds. Here we report a copper (Cu)-catalysed site- and enantioselective allylic C-H cyanation of complex alkenes, in which a Cu(II)-bound nitrogen (N)-centred radical plays the key role in achieving precise site-specific HAT. This method is shown to be effective for a diverse collection of alkene-containing molecules, including sterically demanding structures and complex natural products and pharmaceuticals.


Assuntos
Carbono/química , Cobre/química , Hidrogênio/química , Alcenos/química , Produtos Biológicos/química , Catálise , Teoria da Densidade Funcional , Nitrogênio/química , Oxirredução , Preparações Farmacêuticas/química , Especificidade por Substrato
4.
Nature ; 575(7782): 336-340, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31723273

RESUMO

Organoboron reagents are important synthetic intermediates that have a key role in the construction of natural products, pharmaceuticals and organic materials1. The discovery of simpler, milder and more efficient approaches to organoborons can open additional routes to diverse substances2-5. Here we show a general method for the directed C-H borylation of arenes and heteroarenes without the use of metal catalysts. C7- and C4-borylated indoles are produced by a mild approach that is compatible with a broad range of functional groups. The mechanism, which is established by density functional theory calculations, involves BBr3 acting as both a reagent and a catalyst. The potential utility of this strategy is highlighted by the downstream transformation of the formed boron species into natural products and drug scaffolds.


Assuntos
Compostos de Boro/química , Compostos de Boro/síntese química , Boro/química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Teoria da Densidade Funcional , Descoberta de Drogas , Indóis/química , Compostos Organometálicos/química , Preparações Farmacêuticas/síntese química , Preparações Farmacêuticas/química
5.
Biochemistry ; 63(9): 1118-1130, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38623827

RESUMO

Acyl capping groups stabilize α-helices relative to free N-termini by providing one additional C═Oi···Hi+4-N hydrogen bond. The electronic properties of acyl capping groups might also directly modulate α-helix stability: electron-rich N-terminal acyl groups could stabilize the α-helix by strengthening both i/i + 4 hydrogen bonds and i/i + 1 n → π* interactions. This hypothesis was tested in peptides X-AKAAAAKAAAAKAAGY-NH2, where X = different acyl groups. Surprisingly, the most electron-rich acyl groups (pivaloyl and iso-butyryl) strongly destabilized the α-helix. Moreover, the formyl group induced nearly identical α-helicity to that of the acetyl group, despite being a weaker electron donor for hydrogen bonds and for n → π* interactions. Other acyl groups exhibited intermediate α-helicity. These results indicate that the electronic properties of the acyl carbonyl do not directly determine the α-helicity in peptides in water. In order to understand these effects, DFT calculations were conducted on α-helical peptides. Using implicit solvation, α-helix stability correlated with acyl group electronics, with the pivaloyl group exhibiting closer hydrogen bonds and n → π* interactions, in contrast to the experimental results. However, DFT and MD calculations with explicit water solvation revealed that hydrogen bonding to water was impacted by the sterics of the acyl capping group. Formyl capping groups exhibited the closest water-amide hydrogen bonds, while pivaloyl groups exhibited the longest. In α-helices in the PDB, the highest frequency of close amide-water hydrogen bonds is observed when the N-cap residue is Gly. The combination of experimental and computational results indicates that solvation (hydrogen bonding of water) to the N-terminal amide groups is a central determinant of α-helix stability.


Assuntos
Amidas , Ligação de Hidrogênio , Conformação Proteica em alfa-Hélice , Estabilidade Proteica , Água , Água/química , Amidas/química , Peptídeos/química , Teoria da Densidade Funcional , Modelos Moleculares , Estrutura Secundária de Proteína
6.
J Struct Biol ; 216(2): 108094, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38653343

RESUMO

This study synthesized and evaluated a series of benzotriazole derivatives denoted 3(a-j) and 6(a-j) for their anti-HIV-1 RT activities compared to the standard drug efavirenz. Notably, compound 3 h, followed closely by 6 h, exhibited significant anti-HIV-1 RT efficacy relative to the standard drug. In vivo oral toxicity studies were conducted for the most active compound 3 h, confirming its nontoxic nature to ascertain the safety profile. By employing molecular docking techniques, we explored the potential interactions between the synthesized compounds (ligands) and a target biomolecule (protein)(PDB ID 1RT2) at the molecular level. We undertook the molecular dynamics study of 3 h, the most active compound, within the active binding pocket of the cocrystallized structure of HIV-1 RT (PDB ID 1RT2). We aimed to learn more about how biomolecular systems behave, interact, and change at the atomic or molecular level over time. Finally, the DFT-derived HOMO and LUMO orbitals, as well as analysis of the molecular electrostatic potential map, aid in discerning the reactivity characteristics of our molecule.


Assuntos
Fármacos Anti-HIV , HIV-1 , Simulação de Acoplamento Molecular , Triazóis , Triazóis/química , Triazóis/farmacologia , Fármacos Anti-HIV/química , Fármacos Anti-HIV/farmacologia , HIV-1/efeitos dos fármacos , Transcriptase Reversa do HIV/antagonistas & inibidores , Transcriptase Reversa do HIV/química , Transcriptase Reversa do HIV/metabolismo , Humanos , Simulação de Dinâmica Molecular , Inibidores da Transcriptase Reversa/química , Inibidores da Transcriptase Reversa/farmacologia , Inibidores da Transcriptase Reversa/toxicidade , Modelos Moleculares , Teoria da Densidade Funcional , Relação Estrutura-Atividade , Alcinos/química , Animais , Ciclopropanos/toxicidade , Benzoxazinas/química , Benzoxazinas/farmacologia
7.
J Am Chem Soc ; 146(22): 15070-15084, 2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38768950

RESUMO

Despite the increased use of computational tools to supplement medicinal chemists' expertise and intuition in drug design, predicting synthetic yields in medicinal chemistry endeavors remains an unsolved challenge. Existing design workflows could profoundly benefit from reaction yield prediction, as precious material waste could be reduced, and a greater number of relevant compounds could be delivered to advance the design, make, test, analyze (DMTA) cycle. In this work, we detail the evaluation of AbbVie's medicinal chemistry library data set to build machine learning models for the prediction of Suzuki coupling reaction yields. The combination of density functional theory (DFT)-derived features and Morgan fingerprints was identified to perform better than one-hot encoded baseline modeling, furnishing encouraging results. Overall, we observe modest generalization to unseen reactant structures within the 15-year retrospective library data set. Additionally, we compare predictions made by the model to those made by expert medicinal chemists, finding that the model can often predict both reaction success and reaction yields with greater accuracy. Finally, we demonstrate the application of this approach to suggest structurally and electronically similar building blocks to replace those predicted or observed to be unsuccessful prior to or after synthesis, respectively. The yield prediction model was used to select similar monomers predicted to have higher yields, resulting in greater synthesis efficiency of relevant drug-like molecules.


Assuntos
Desenho de Fármacos , Bibliotecas de Moléculas Pequenas , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/síntese química , Aprendizado de Máquina , Teoria da Densidade Funcional , Estrutura Molecular , Química Farmacêutica/métodos
8.
J Am Chem Soc ; 146(27): 18689-18698, 2024 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-38935871

RESUMO

Persulfides (RSSH) are biologically important reactive sulfur species that are endogenously produced, protect key cysteine residues from irreversible oxidation, and are important intermediates during different enzymatic processes. Although persulfides are stronger nucleophiles than their thiol counterparts, persulfides can also act as electrophiles in their neutral, protonated form in specific environments. Moreover, persulfides are electrophilic at both sulfur atoms, and the reaction with a thiolate can lead to either H2S release with disulfide formation or alternatively result in transpersulfidation. Despite the broad acceptance of these reaction pathways, the specific properties that control whether persulfides react through the H2S-releasing or transpersulfidation pathway remain elusive. Herein, we use a combined computational and experimental approach to directly investigate the reactivity between persulfides and thiols to answer these questions. Using density functional theory (DFT) calculations, we demonstrate that increasing steric bulk or electron withdrawal near the persulfide can shunt persulfide reactivity through the transpersulfidation pathway. Building from these insights, we use a synthetic persulfide donor and an N-iodoacetyl l-tyrosine methyl ester (TME-IAM) trapping agent to experimentally monitor and measure transpersulfidation from a bulky penicillamine-based persulfide to a cysteine-based thiol, which, to the best of our knowledge, is the first direct observation of transpersulfidation between low-molecular-weight species. Taken together, these combined approaches highlight how the properties of persulfides are directly impacted by local environments, which has significant impacts in understanding the complex chemical biology of these reactive species.


Assuntos
Teoria da Densidade Funcional , Sulfeto de Hidrogênio , Sulfetos , Sulfetos/química , Sulfeto de Hidrogênio/química , Compostos de Sulfidrila/química , Cisteína/química
9.
J Am Chem Soc ; 146(26): 18019-18031, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38888987

RESUMO

The membrane-bound hydrogenase (Mbh) from Pyrococcus furiosus is an archaeal member of the Complex I superfamily. It catalyzes the reduction of protons to H2 gas powered by a [NiFe] active site and transduces the free energy into proton pumping and Na+/H+ exchange across the membrane. Despite recent structural advances, the mechanistic principles of H2 catalysis and ion transport in Mbh remain elusive. Here, we probe how the redox chemistry drives the reduction of the proton to H2 and how the catalysis couples to conformational dynamics in the membrane domain of Mbh. By combining large-scale quantum chemical density functional theory (DFT) and correlated ab initio wave function methods with atomistic molecular dynamics simulations, we show that the proton transfer reactions required for the catalysis are gated by electric field effects that direct the protons by water-mediated reactions from Glu21L toward the [NiFe] site, or alternatively along the nearby His75L pathway that also becomes energetically feasible in certain reaction steps. These local proton-coupled electron transfer (PCET) reactions induce conformational changes around the active site that provide a key coupling element via conserved loop structures to the ion transport activity. We find that H2 forms in a heterolytic proton reduction step, with spin crossovers tuning the energetics along key reaction steps. On a general level, our work showcases the role of electric fields in enzyme catalysis and how these effects are employed by the [NiFe] active site of Mbh to drive PCET reactions and ion transport.


Assuntos
Hidrogênio , Hidrogenase , Simulação de Dinâmica Molecular , Pyrococcus furiosus , Hidrogenase/química , Hidrogenase/metabolismo , Hidrogênio/química , Hidrogênio/metabolismo , Pyrococcus furiosus/enzimologia , Prótons , Teoria da Densidade Funcional , Domínio Catalítico , Oxirredução
10.
J Am Chem Soc ; 146(20): 14213-14224, 2024 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-38739765

RESUMO

The formation of an amide bond is an essential step in the synthesis of materials and drugs, and in the assembly of amino acids to form peptides. The mechanism of this reaction has been studied extensively, in particular to understand how it can be catalyzed, but a representation capable of explaining all the experimental data is still lacking. Numerical simulation should provide the necessary molecular description, but the solvent involvement poses a number of challenges. Here, we combine the efficiency and accuracy of neural network potential-based reactive molecular dynamics with the extensive and unbiased exploration of reaction pathways provided by transition path sampling. Using microsecond-scale simulations at the density functional theory level, we show that this method reveals the presence of two competing distinct mechanisms for peptide bond formation between alanine esters in aqueous solution. We describe how both reaction pathways, via a general base catalysis mechanism and via direct cleavage of the tetrahedral intermediate respectively, change with pH. This result contrasts with the conventional mechanism involving a single pathway in which only the barrier heights are affected by pH. We show that this new proposal involving two competing mechanisms is consistent with the experimental data, and we discuss the implications for peptide bond formation under prebiotic conditions and in the ribosome. Our work shows that integrating deep potential molecular dynamics with path sampling provides a powerful approach for exploring complex chemical mechanisms.


Assuntos
Simulação de Dinâmica Molecular , Peptídeos , Água , Água/química , Peptídeos/química , Teoria da Densidade Funcional , Concentração de Íons de Hidrogênio , Alanina/química , Amidas/química
11.
J Am Chem Soc ; 146(25): 17009-17022, 2024 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-38820242

RESUMO

Arsenic is highly toxic and a significant threat to human health, but certain bacteria have developed defense mechanisms initiated by AsIII binding to AsIII-sensing proteins of the ArsR family. The transcriptional regulator AfArsR responds to AsIII and SbIII by coordinating the metalloids with three cysteines, located in a short sequence of the same monomer chain. Here, we characterize the binding of AsIII and HgII to a model peptide encompassing this fragment of the protein via solution equilibrium and spectroscopic/spectrometric techniques (pH potentiometry, UV, CD, NMR, PAC, EXAFS, and ESI-MS) combined with DFT calculations and MD simulations. Coordination of AsIII changes the peptide structure from a random-coil to a well-defined structure of the complex. A trigonal pyramidal AsS3 binding site is formed with almost exactly the same structure as observed in the crystal structure of the native protein, implying that the peptide possesses all of the features required to mimic the AsIII recognition and response selectivity of AfArsR. Contrary to this, binding of HgII to the peptide does not lead to a well-defined structure of the peptide, and the atoms near the metal binding site are displaced and reoriented in the HgII model. Our model study suggests that structural organization of the metal site by the inducer ion is a key element in the mechanism of the metalloid-selective recognition of this protein.


Assuntos
Arsênio , Arsênio/química , Arsênio/metabolismo , Sítios de Ligação , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Metaloides/química , Metaloides/metabolismo , Teoria da Densidade Funcional , Simulação de Dinâmica Molecular , Ligação Proteica
12.
J Am Chem Soc ; 146(17): 11811-11822, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38635880

RESUMO

The development of novel agents with immunoregulatory effects is a keen way to combat the growing threat of inflammatory storms to global health. To synthesize pseudo-steroidal glycosides tethered by ether bonds with promising immunomodulatory potential, we develop herein a highly effective deoxygenative functionalization of a novel steroidal donor (steroidation) facilitated by strain-release, leveraging cost-effective and readily available Sc(OTf)3 catalysis. This transformation produces a transient steroid-3-yl carbocation which readily reacts with O-, C-, N-, S-, and P-nucleophiles to generate structurally diverse steroid derivatives. DFT calculations were performed to shed light on the mechanistic details of the regioselectivity, underlying an acceptor-dependent steroidation mode. This approach can be readily extended to the etherification of sugar alcohols to enable the achievement of a diversity-oriented, pipeline-like synthesis of pseudo-steroidal glycosides in good to excellent yields with complete stereo- and regiospecific control for anti-inflammatory agent discovery. Immunological studies have demonstrated that a meticulously designed cholesteryl disaccharide can significantly suppress interleukin-6 secretion in macrophages, exhibiting up to 99% inhibition rates compared to the negative control. These findings affirm the potential of pseudo-steroidal glycosides as a prospective category of lead agents for the development of novel anti-inflammatory drugs.


Assuntos
Anti-Inflamatórios , Glicosídeos , Esteroides , Glicosídeos/química , Glicosídeos/síntese química , Glicosídeos/farmacologia , Anti-Inflamatórios/química , Anti-Inflamatórios/farmacologia , Anti-Inflamatórios/síntese química , Esteroides/química , Esteroides/farmacologia , Esteroides/síntese química , Camundongos , Animais , Humanos , Teoria da Densidade Funcional , Estrutura Molecular , Interleucina-6/antagonistas & inibidores , Interleucina-6/metabolismo , Anti-Inflamatórios não Esteroides/química , Anti-Inflamatórios não Esteroides/farmacologia , Anti-Inflamatórios não Esteroides/síntese química , Macrófagos/efeitos dos fármacos
13.
Anal Chem ; 96(28): 11455-11462, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38968402

RESUMO

Efficient, mild, and reversible adsorption of nucleic acids onto nanomaterials represents a promising analytical approach for medical diagnosis. However, there is a scarcity of efficient and reversible nucleic acid adsorption nanomaterials. Additionally, the lack of comprehension of the molecular mechanisms governing their interactions poses significant challenges. These issues hinder the rational design and analytical applications of the nanomaterials. Herein, we propose an ultra-efficient nucleic acid affinity nanomaterial based on programmable lanthanide metal-organic frameworks (Ln-MOFs). Through experiments and density functional theory calculations, a rational design guideline for nucleic acid affinity of Ln-MOF was proposed, and a modular and flexible preparation scheme was provided. Then, Er-TPA (terephthalic acid) MOF emerged as the optimal candidate due to its pore size-independent adsorption and desorption capabilities for nucleic acids, enabling ultra-efficient adsorption (about 150% mass ratio) within 1 min. Furthermore, we elucidate the molecular-level mechanisms underlying the Ln-MOF adsorption of single- and double-stranded DNA and G4 structures. The affinity nanomaterial based on Ln-MOF exhibits robust nucleic acid extraction capability (4-fold higher than commercial reagent kits) and enables mild and reversible CRISPR/Cas9 functional regulation. This method holds significant promise for broad application in DNA/RNA liquid biopsy and gene editing, facilitating breakthroughs in analytical chemistry, pharmacy, and medical research.


Assuntos
DNA , Elementos da Série dos Lantanídeos , Estruturas Metalorgânicas , Estruturas Metalorgânicas/química , Elementos da Série dos Lantanídeos/química , Adsorção , DNA/química , DNA/isolamento & purificação , Ácidos Ftálicos/química , Nanoestruturas/química , Teoria da Densidade Funcional , Humanos
14.
J Comput Chem ; 45(24): 2059-2070, 2024 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-38741357

RESUMO

Graphene is the newest form of elemental carbon and it is becoming rapidly a potential candidate in the framework of nano-bio research. Many reports confirm the successful use of graphene-based materials as carriers of anticancer drugs having relatively high loading capacities compared with other nanocarriers. Here, the outcomes of a systematic study of the adsorption behavior of FDA approved PtII drugs cisplatin, oxaliplatin, and carboplatin on surface models of pristine, holey, and nitrogen-doped holey graphene are reported. DFT investigations in water solvent have been carried out considering several initial orientations of the drugs with respect to the surfaces. Adsorption free energies, calculated including basis set superposition error (BSSE) corrections, result to be significantly negative for many of the drug@carrier adducts indicating that tested layers could be used as potential carriers for the delivery of anticancer PtII drugs. The reduced density gradient (RDG) analysis allows to show that many kinds of non-covalent interactions, including canonical H-bond, are responsible for the stabilization of the formed adducts.


Assuntos
Antineoplásicos , Cisplatino , Teoria da Densidade Funcional , Portadores de Fármacos , Grafite , Grafite/química , Antineoplásicos/química , Cisplatino/química , Portadores de Fármacos/química , Carboplatina/química , Nanoestruturas/química , Oxaliplatina/química , Sistemas de Liberação de Medicamentos , Adsorção , Compostos Organoplatínicos/química
15.
Chembiochem ; 25(2): e202300652, 2024 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-37921481

RESUMO

The increase in antibacterial drug resistance is threatening global health conditions. Recently, antibacterial photodynamic therapy (aPDT) has emerged as an effective antibacterial treatment with high cure gain. In this work, three Zn(II) complexes viz., [Zn(en)(acac)Cl] (1), [Zn(bpy)(acac)Cl] (2), [Zn(en)(cur)Cl] (3), where en=ethylenediamine (1 and 3), bpy=2,2'-bipyridine (2), acac=acetylacetonate (1 and 2), cur=curcumin monoanionic (3) were developed as aPDT agents. Complexes 1-3 were synthesized and fully characterized using NMR, HRMS, FTIR, UV-Vis. and fluorescence spectroscopy. The HOMO-LUMO energy gap (Eg), and adiabatic splittings (ΔS1-T1 and ΔS0-T1 ) obtained from DFT calculation indicated the photosensivity of the complexes. These complexes have not shown any potent antibacterial activity under dark conditions but the antibacterial activity of these complexes was significantly enhanced upon light exposure (MIC value up to 0.025 µg/mL) due to their light-mediated 1 O2 generation abilities. The molecular docking study suggested that complexes 1-3 interact efficiently with DNA gyrase B (PDB ID: 4uro). Importantly, 1-3 did not show any toxicity toward normal HEK-293 cells. Overall, in this work, we have demonstrated the promising potential of Zn(II) complexes as effective antibacterial agents under the influence of visible light.


Assuntos
Complexos de Coordenação , Curcumina , Fotoquimioterapia , Humanos , Curcumina/farmacologia , Simulação de Acoplamento Molecular , Complexos de Coordenação/química , Teoria da Densidade Funcional , Células HEK293 , Antibacterianos/farmacologia , Antibacterianos/química , Zinco/química
16.
J Biol Inorg Chem ; 29(4): 441-454, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38753160

RESUMO

Five cationic ruthenium-arene complexes with the generic formula [Ru(SAc)(S2C·NHC)(p-cymene)](PF6) (5a-e) were prepared in almost quantitative yields using a straightforward one-pot, two-step experimental procedure starting from [RuCl2(p-cymene)]2, an imidazol(in)ium-2-dithiocarboxylate (NHC·CS2) zwitterion, KSAc, and KPF6. These half-sandwich compounds were fully characterized by various analytical techniques and the molecular structures of two of them were solved by X-ray diffraction analysis, which revealed the existence of an intramolecular chalcogen bond between the oxygen atom of the thioacetate ligand and a proximal sulfur atom of the dithiocarboxylate unit. DFT calculations showed that the C=S…O charge transfer amounted to 2.4 kcal mol-1. The dissolution of [Ru(SAc)(S2C·IMes)(p-cymene)](PF6) (5a) in moist DMSO-d6 at room temperature did not cause the dissociation of its sulfur ligands. Instead, p-cymene was slowly released to afford the 12-electron [Ru(SAc)(S2C·IMes)]+ cation that could be detected by mass spectrometry. Monitoring the solvolysis process by 1H NMR spectroscopy showed that more than 22 days were needed to fully decompose the starting ruthenium-arene complex. Compounds 5a-e exhibited a high antiproliferative activity against human glioma Hs683 and human lung carcinoma A549 cancer cells. In particular, the IMes derivative (5a) was the most potent compound of the series, achieving toxicities similar to those displayed by marketed platinum drugs.


Assuntos
Antineoplásicos , Complexos de Coordenação , Rutênio , Enxofre , Rutênio/química , Humanos , Ligantes , Antineoplásicos/farmacologia , Antineoplásicos/química , Antineoplásicos/síntese química , Complexos de Coordenação/química , Complexos de Coordenação/farmacologia , Complexos de Coordenação/síntese química , Enxofre/química , Linhagem Celular Tumoral , Cátions/química , Ensaios de Seleção de Medicamentos Antitumorais , Teoria da Densidade Funcional , Modelos Moleculares , Estrutura Molecular , Proliferação de Células/efeitos dos fármacos
17.
Chemistry ; 30(26): e202304079, 2024 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-38441909

RESUMO

The emerging role of Ribonucleic acids (RNAs) as therapeutics is alluring. However, RNAs are extremely labile under ambient conditions and typically need to be stored in cryogenic conditions (-20 °C to -80 °C). Hence, storage, stabilization, and transportation of RNA under ambient conditions have been an arduous task and remain an unsolved problem. In this work, a guanidinium-based ionic covalent organic framework (COF), TTGCl with nanotubular morphology, was synthesized and used as nano-reservoirs for room-temperature storage of RNA. To understand the role of the nanotubular morphology and chemical nature of TTGCl in stabilizing the RNA structure and for comparison purposes, a neutral COF, TMT-TT, is synthesized and studied. Further, density functional theory (DFT) studies confirmed non-covalent interaction between the COFs and the RNA nucleobases, facilitating reversible storage of RNA. RNA loaded in COFs was found to be resistant to enzymatic degradation when treated with RNase. Gel electrophoresis and sequencing confirmed the structural integrity of the recovered RNAs and their further processibility.


Assuntos
RNA , Temperatura , RNA/química , Estruturas Metalorgânicas/química , Guanidina/química , Conformação de Ácido Nucleico , Estabilidade de RNA , Teoria da Densidade Funcional
18.
Chemistry ; 30(31): e202400009, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38446718

RESUMO

An effective, GFP-inspired fluorescent Zn2+ sensor is developed for two-photon microscopy and related biological application that features an 8-methoxyquinoline moiety. Excellent photophysical characteristics including a 37-fold fluorescence enhancement with excitation and emission maxima at 440 nm and 505 nm, respectively, as well as a high two-photon cross-section of 73 GM at 880 nm are reported. Based on the experimental data, the relationship between the structure and properties was elucidated and explained backed up by DFT calculations, particularly the observed PeT phenomenon for the turn-on process. Biological validation and detailed experimental and theoretical characterization of the free and the zinc-bound compounds are presented.


Assuntos
Corantes Fluorescentes , Proteínas de Fluorescência Verde , Quinolinas , Zinco , Zinco/química , Corantes Fluorescentes/química , Quinolinas/química , Proteínas de Fluorescência Verde/química , Humanos , Teoria da Densidade Funcional , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Fótons
19.
Chemistry ; 30(31): e202400723, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38623783

RESUMO

Glycoside hydrolases (glycosidases) take part in myriad biological processes and are important therapeutic targets. Competitive and mechanism-based inhibitors are useful tools to dissect their biological role and comprise a good starting point for drug discovery. The natural product, cyclophellitol, a mechanism-based, covalent and irreversible retaining ß-glucosidase inhibitor has inspired the design of diverse α- and ß-glycosidase inhibitor and activity-based probe scaffolds. Here, we sought to deepen our understanding of the structural and functional requirements of cyclophellitol-type compounds for effective human α-glucosidase inhibition. We synthesized a comprehensive set of α-configured 1,2- and 1,5a-cyclophellitol analogues bearing a variety of electrophilic traps. The inhibitory potency of these compounds was assessed towards both lysosomal and ER retaining α-glucosidases. These studies revealed the 1,5a-cyclophellitols to be the most potent retaining α-glucosidase inhibitors, with the nature of the electrophile determining inhibitory mode of action (covalent or non-covalent). DFT calculations support the ability of the 1,5a-cyclophellitols, but not the 1,2-congeners, to adopt conformations that mimic either the Michaelis complex or transition state of α-glucosidases.


Assuntos
Inibidores de Glicosídeo Hidrolases , alfa-Glucosidases , Inibidores de Glicosídeo Hidrolases/química , Inibidores de Glicosídeo Hidrolases/farmacologia , Inibidores de Glicosídeo Hidrolases/síntese química , alfa-Glucosidases/metabolismo , alfa-Glucosidases/química , Humanos , Conformação Molecular , Relação Estrutura-Atividade , Teoria da Densidade Funcional , Cicloexanóis
20.
Chemistry ; 30(39): e202401165, 2024 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-38752552

RESUMO

An Artificial Metalloenzyme (ArM) built employing the streptavidin-biotin technology has been used for the enantioselective synthesis of binaphthyls by means of asymmetric Suzuki-Miyaura cross-coupling reactions. Despite its success, it remains a challenge to understand how the length of the biotin cofactors or the introduction of mutations to streptavidin leads the preferential synthesis of one atropisomer over the other. In this study, we apply an integrated computational modeling approach, including DFT calculations, protein-ligand dockings and molecular dynamics to rationalize the impact of mutations and length of the biotion cofactor on the enantioselectivities of the biaryl product. The results unravel that the enantiomeric differences found experimentally can be rationalized by the disposition of the first intermediate, coming from the oxidative addition step, and the entrance of the second substrate. The work also showcases the difficulties facing to control the enantioselection when engineering ArM to catalyze enantioselective Suzuki-Miyaura couplings and how the combination of DFT calculations, molecular dockings and MD simulations can be used to rationalize artificial metalloenzymes.


Assuntos
Teoria da Densidade Funcional , Simulação de Dinâmica Molecular , Estreptavidina , Estereoisomerismo , Estreptavidina/química , Estreptavidina/metabolismo , Catálise , Biotina/química , Biotina/análogos & derivados , Ligantes , Simulação de Acoplamento Molecular , Metaloproteínas/química , Metaloproteínas/metabolismo
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