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1.
Proc Natl Acad Sci U S A ; 118(19)2021 05 11.
Artículo en Inglés | MEDLINE | ID: mdl-33947817

RESUMEN

DNA damage plays a central role in the cellular pathogenesis of polyglutamine (polyQ) diseases, including Huntington's disease (HD). In this study, we showed that the expression of untranslatable expanded CAG RNA per se induced the cellular DNA damage response pathway. By means of RNA sequencing (RNA-seq), we found that expression of the Nudix hydrolase 16 (NUDT16) gene was down-regulated in mutant CAG RNA-expressing cells. The loss of NUDT16 function results in a misincorporation of damaging nucleotides into DNAs and leads to DNA damage. We showed that small CAG (sCAG) RNAs, species generated from expanded CAG transcripts, hybridize with CUG-containing NUDT16 mRNA and form a CAG-CUG RNA heteroduplex, resulting in gene silencing of NUDT16 and leading to the DNA damage and cellular apoptosis. These results were further validated using expanded CAG RNA-expressing mouse primary neurons and in vivo R6/2 HD transgenic mice. Moreover, we identified a bisamidinium compound, DB213, that interacts specifically with the major groove of the CAG RNA homoduplex and disfavors the CAG-CUG heteroduplex formation. This action subsequently mitigated RNA-induced silencing complex (RISC)-dependent NUDT16 silencing in both in vitro cell and in vivo mouse disease models. After DB213 treatment, DNA damage, apoptosis, and locomotor defects were rescued in HD mice. This work establishes NUDT16 deficiency by CAG repeat RNAs as a pathogenic mechanism of polyQ diseases and as a potential therapeutic direction for HD and other polyQ diseases.


Asunto(s)
Apoptosis/genética , Daño del ADN , Enfermedad de Huntington/genética , Péptidos/genética , Pirofosfatasas/genética , ARN/genética , Expansión de Repetición de Trinucleótido/genética , Animales , Apoptosis/efectos de los fármacos , Benzamidinas/metabolismo , Benzamidinas/farmacología , Línea Celular Tumoral , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Humanos , Proteína Huntingtina/genética , Proteína Huntingtina/metabolismo , Enfermedad de Huntington/metabolismo , Enfermedad de Huntington/prevención & control , Ratones Endogámicos C57BL , Ratones Transgénicos , Simulación de Dinámica Molecular , Pirofosfatasas/metabolismo , ARN/metabolismo , Interferencia de ARN , ARN Mensajero/genética , ARN Mensajero/metabolismo
2.
Chembiochem ; 23(17): e202200260, 2022 09 05.
Artículo en Inglés | MEDLINE | ID: mdl-35790065

RESUMEN

Small molecule targeting of DNA and RNA sequences has come into focus as a therapeutic strategy for diseases such as myotonic dystrophy type 1 (DM1), a trinucleotide repeat disease characterized by RNA gain-of-function. Herein, we report a novel template-selected, reversible assembly of therapeutic agents in situ via aldehyde-amine condensation. Rationally designed small molecule targeting agents functionalized with either an aldehyde or an amine were synthesized and screened against the target nucleic acid sequence. The assembly of fragments was confirmed by MALDI-MS in the presence of DM1-relevant nucleic acid sequences. The resulting hit combinations of aldehyde and amine inhibited the formation of r(CUG)exp in vitro in a cooperative manner at low micromolar levels and rescued mis-splicing defects in DM1 model cells. This reversible template-selected assembly is a promising approach to achieve cell permeable and multivalent targeting via in situ synthesis and could be applied to other nucleic acid targets.


Asunto(s)
Distrofia Miotónica , Aldehídos , Aminas , Secuencia de Bases , ADN , Humanos , Ligandos , Distrofia Miotónica/tratamiento farmacológico , Distrofia Miotónica/genética , ARN/genética , Expansión de Repetición de Trinucleótido
3.
Proc Natl Acad Sci U S A ; 116(18): 8709-8714, 2019 04 30.
Artículo en Inglés | MEDLINE | ID: mdl-30975744

RESUMEN

Developing highly active, multivalent ligands as therapeutic agents is challenging because of delivery issues, limited cell permeability, and toxicity. Here, we report intrinsically cell-penetrating multivalent ligands that target the trinucleotide repeat DNA and RNA in myotonic dystrophy type 1 (DM1), interrupting the disease progression in two ways. The oligomeric ligands are designed based on the repetitive structure of the target with recognition moieties alternating with bisamidinium groove binders to provide an amphiphilic and polycationic structure, mimicking cell-penetrating peptides. Multiple biological studies suggested the success of our multivalency strategy. The designed oligomers maintained cell permeability and exhibited no apparent toxicity both in cells and in mice at working concentrations. Furthermore, the oligomers showed important activities in DM1 cells and in a DM1 liver mouse model, reducing or eliminating prominent DM1 features. Phenotypic recovery of the climbing defect in adult DM1 Drosophila was also observed. This design strategy should be applicable to other repeat expansion diseases and more generally to DNA/RNA-targeted therapeutics.


Asunto(s)
Distrofia Miotónica/tratamiento farmacológico , Proteínas de Unión al ARN/metabolismo , Repeticiones de Trinucleótidos , Animales , ADN , Proteínas de Unión al ADN , Drosophila melanogaster , Células HeLa , Humanos , Ligandos , Hígado/metabolismo , Ratones , Mioblastos/fisiología , Distrofia Miotónica/genética , Proteínas con Motivos de Reconocimiento de ARN , Proteínas de Unión al ARN/química
4.
Acc Chem Res ; 53(6): 1244-1256, 2020 06 16.
Artículo en Inglés | MEDLINE | ID: mdl-32441091

RESUMEN

Cross-linking of polymers significantly alters their physical properties, greatly expanding their everyday utility. Indeed, the polymeric networks resulting from linkages between polymer chains are found in everyday materials from soft contact lenses and automobile tires to enamel coatings and high-performance adhesives. In contrast, intramolecularly cross-linked polymers have received far less attention until recent years, in large part because they are synthetically more challenging to prepare. In this Account, we trace our own efforts to develop the chemistry of intramolecularly cross-linked macromolecules, starting with dendrimers. Dendrimers provided an excellent starting point for investigating intramolecular cross-linking because they are single molecular entities. We showed that the end groups of dendrimers can be extensively cross-linked using the ring-closing metathesis reaction and that the discrete structure of the dendrimer provides unique opportunities for characterizing the number and location of the cross-links as well as some physical properties of the macromolecule such as its size and rigidity. Increasing the number of ring-closing metathesis reactions correlated with a reduction in size and an increase in rigidity. The general strategy applied to dendrimers was extended to star polymers and hyperbranched polyglycerols. Each of these macromolecules has a core or an initiating group from which the branches emanate. Linking the end groups or branches of these polymers presents a unique opportunity to chemically remove the core of the cross-linked macromolecule in a process that is reminiscent of that used to produce covalent molecular imprinted polymers. Recognizing this analogy, we sought a compelling application for cross-linked dendrimers, the first example of unimolecular imprinting, where a single polymer contains a single molecular imprint. The quality of the imprinting was mixed but pointed to an alternative general strategy for molecular imprinting in polymers. The effort also focused attention on synthetic antibodies and the general biomimicry provided by this class of macromolecules. Indeed, cross-linking of polymers either covalently or non-covalently bears a loose resemblance to folding of proteins into defined three-dimensional shapes. The synthesis and study of cross-linked linear polymers, often called single-chain nanoparticles (SCNPs), has emerged as a very active area of research in the past few years. Our experience with the cross-linking of branched polymers combined with an interest in performing organic synthesis within living cells led us to develop copper-containing SCNPs as artificial clickases. These polymeric clickases exhibit all of the hallmarks of enzymatic catalysis. One clickase containing a polyacrylamide backbone performs low-concentration copper-assisted alkyne-azide click reactions at unprecedented rates. Another performs click reactions within living cells. Other organic transformations can be performed intracellularly, and some of the most advanced SCNPs engage in concurrent and tandem catalysis with a naturally occurring biocatalyst. By tracing our own efforts, this Account provides a few entry points into the broader literature and also points to both the remaining challenges and overall promising future envisioned for this unique class of functional macromolecules.


Asunto(s)
Anticuerpos/metabolismo , Materiales Biomiméticos/química , Enzimas/metabolismo , Polímeros/química , Materiales Biomiméticos/síntesis química , Dendrímeros , Impresión Molecular , Polímeros/síntesis química , Relación Estructura-Actividad
5.
Biochemistry ; 59(37): 3463-3472, 2020 09 22.
Artículo en Inglés | MEDLINE | ID: mdl-32856901

RESUMEN

There are few methods available for the rapid discovery of multitarget drugs. Herein, we describe the template-assisted, target-guided discovery of small molecules that recognize d(CTG) in the expanded d(CTG·CAG) sequence and its r(CUG) transcript that cause myotonic dystrophy type 1. A positive cross-selection was performed using a small library of 30 monomeric alkyne- and azide-containing ligands capable of producing >5000 possible di- and trimeric click products. The monomers were incubated with d(CTG)16 or r(CUG)16 under physiological conditions, and both sequences showed selectivity in the proximity-accelerated azide-alkyne [3+2] cycloaddition click reaction. The limited number of click products formed in both selections and the even smaller number of common products suggests that this method is a useful tool for the discovery of single-target and multitarget lead therapeutic agents.


Asunto(s)
ADN/antagonistas & inhibidores , Distrofia Miotónica/tratamiento farmacológico , Distrofia Miotónica/genética , ARN/antagonistas & inhibidores , Bibliotecas de Moléculas Pequeñas/farmacología , Expansión de Repetición de Trinucleótido/efectos de los fármacos , Células Cultivadas , ADN/genética , ADN/metabolismo , Humanos , Distrofia Miotónica/patología , ARN/genética , ARN/metabolismo , Expansión de Repetición de Trinucleótido/genética
6.
J Biol Chem ; 294(8): 2757-2770, 2019 02 22.
Artículo en Inglés | MEDLINE | ID: mdl-30593503

RESUMEN

Polyglutamine (polyQ) diseases are a group of dominantly inherited neurodegenerative disorders caused by the expansion of an unstable CAG repeat in the coding region of the affected genes. Hallmarks of polyQ diseases include the accumulation of misfolded protein aggregates, leading to neuronal degeneration and cell death. PolyQ diseases are currently incurable, highlighting the urgent need for approaches that inhibit the formation of disaggregate cytotoxic polyQ protein inclusions. Here, we screened for bisamidine-based inhibitors that can inhibit neuronal polyQ protein inclusions. We demonstrated that one inhibitor, AQAMAN, prevents polyQ protein aggregation and promotes de-aggregation of self-assembled polyQ proteins in several models of polyQ diseases. Using immunocytochemistry, we found that AQAMAN significantly reduces polyQ protein aggregation and specifically suppresses polyQ protein-induced cell death. Using a recombinant and purified polyQ protein (thioredoxin-Huntingtin-Q46), we further demonstrated that AQAMAN interferes with polyQ self-assembly, preventing polyQ aggregation, and dissociates preformed polyQ aggregates in a cell-free system. Remarkably, AQAMAN feeding of Drosophila expressing expanded polyQ disease protein suppresses polyQ-induced neurodegeneration in vivo In addition, using inhibitors and activators of the autophagy pathway, we demonstrated that AQAMAN's cytoprotective effect against polyQ toxicity is autophagy-dependent. In summary, we have identified AQAMAN as a potential therapeutic for combating polyQ protein toxicity in polyQ diseases. Our findings further highlight the importance of the autophagy pathway in clearing harmful polyQ proteins.


Asunto(s)
Autofagia , Modelos Animales de Enfermedad , Furanos/farmacología , Cuerpos de Inclusión/patología , Enfermedades Neurodegenerativas/prevención & control , Neuronas/patología , Péptidos/metabolismo , Animales , Citoprotección , Drosophila melanogaster/fisiología , Furanos/química , Humanos , Cuerpos de Inclusión/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Enfermedades Neurodegenerativas/patología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Péptidos/química , Ratas
7.
J Am Chem Soc ; 142(10): 4565-4569, 2020 03 11.
Artículo en Inglés | MEDLINE | ID: mdl-32100539

RESUMEN

Combining synthetic chemistry and biocatalysis is a promising but underexplored approach to intracellular catalysis. We report a strategy to codeliver a single-chain nanoparticle (SCNP) catalyst and an exogenous enzyme into cells for performing bioorthogonal reactions. The nanoparticle and enzyme reside in endosomes, creating engineered artificial organelles that manufacture organic compounds intracellularly. This system operates in both concurrent and tandem reaction modes to generate fluorophores or bioactive agents. The combination of SCNP and enzymatic catalysts provides a versatile tool for intracellular organic synthesis with applications in chemical biology.


Asunto(s)
Nanopartículas/metabolismo , beta-Galactosidasa/metabolismo , Antineoplásicos/farmacología , Células Artificiales/metabolismo , Catálisis , Ingeniería Celular/métodos , Complejos de Coordinación/química , Complejos de Coordinación/metabolismo , Cumarinas/síntesis química , Doxorrubicina/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Endosomas/metabolismo , Colorantes Fluorescentes/síntesis química , Células HeLa , Humanos , Nanopartículas/química , Profármacos/metabolismo , Profármacos/farmacología , Prueba de Estudio Conceptual , Rodaminas/síntesis química , Rutenio/química , Estilbenos/farmacología
8.
J Am Chem Soc ; 142(32): 13966-13973, 2020 08 12.
Artículo en Inglés | MEDLINE | ID: mdl-32664734

RESUMEN

Synthetic polymer scaffolds may serve as gatekeepers preventing the adhesion of biomacromolecules. Herein, we use gating to develop a copper-containing single-chain nanoparticle (SCNP) catalyst as an artificial "clickase" that operates selectively on small molecules that are able to penetrate the polymeric shell. Whereas the analogous clickase with surface ammonium groups performs highly efficient copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reactions on both alkynylated proteins and small molecule substrates, the new SCNP clickase with polyethylene glycol (PEG) groups is only active on small molecules. Further, the new SCNP resists uptake by cells allowing extracellular click chemistry to be performed. We describe two proof of principle applications that illustrate the utility of the bioorthogonal activity. First, the SCNP catalyst is able to screen for ligands that bind proteins, including proteolysis targeting chimera (PROTAC)-like molecules. Second, the nonmembrane permeable SCNP can efficiently catalyze the click reaction extracellularly, thereby enabling in situ anticancer drug synthesis and screening without the catalyst perturbing intracellular functions.


Asunto(s)
Polímeros/química , Bibliotecas de Moléculas Pequeñas/química , Anhidrasa Carbónica II/química , Anhidrasa Carbónica II/metabolismo , Catálisis , Química Clic , Cobre/química , Células HeLa , Humanos , Ligandos , Nanopartículas del Metal/química , Modelos Moleculares , Estructura Molecular , Polímeros/síntesis química
9.
J Am Chem Soc ; 142(25): 11165-11172, 2020 06 24.
Artículo en Inglés | MEDLINE | ID: mdl-32478511

RESUMEN

The potent DNA-binding compound triaminotriazine-acridine conjugate (Z1) functions by targeting T:T mismatches in CTG trinucleotide repeats that are responsible for causing neurological diseases such as myotonic dystrophy type 1, but its binding mechanism remains unclear. We solved a crystal structure of Z1 in a complex with DNA containing three consecutive CTG repeats with three T:T mismatches. Crystallographic studies revealed that direct intercalation of two Z1 molecules at both ends of the CTG repeat induces thymine base flipping and DNA backbone deformation to form a four-way junction. The core of the complex unexpectedly adopts a U-shaped head-to-head topology to form a crossover of each chain at the junction site. The crossover junction is held together by two stacked G:C pairs at the central core that rotate with respect to each other in an X-shape to form two nonplanar minor-groove-aligned G·C·G·C tetrads. Two stacked G:C pairs on both sides of the center core are involved in the formation of pseudo-continuous duplex DNA. Four metal-mediated base pairs are observed between the N7 atoms of G and CoII, an interaction that strongly preserves the central junction site. Beyond revealing a new type of ligand-induced, four-way junction, these observations enhance our understanding of the specific supramolecular chemistry of Z1 that is essential for the formation of a noncanonical DNA superstructure. The structural features described here serve as a foundation for the design of new sequence-specific ligands targeting mismatches in the repeat-associated structures.


Asunto(s)
Acridinas/química , ADN/química , Sustancias Intercalantes/química , Triazinas/química , Disparidad de Par Base , Emparejamiento Base , ADN/genética , Conformación de Ácido Nucleico , Timina/química , Repeticiones de Trinucleótidos
10.
Langmuir ; 36(34): 10103-10109, 2020 09 01.
Artículo en Inglés | MEDLINE | ID: mdl-32787037

RESUMEN

The surfactant properties of amphiphilic hyperbranched polyglycerols (HPGs) were investigated. The HPGs were prepared by ring-opening multibranching polymerization of glycidol using hydrophobic initiators of varying size and structure. The cloud points for all HPG surfactants were found to be >80 °C in deionized water with >1 wt % NaCl. The HPG surfactants with hydrophilic-lipophilic balance values between 16 and 18 were found to form stable octanol/water (o/w) emulsions within a 24 h period. Several surface properties, including critical micelle concentration (CMC), efficiency of surface tension reduction (pC20), effectiveness of surface tension reduction (γCMC), surface excess concentration at the CMC (Γmax), minimum area/molecule at the interface (Amin), and the CMC/C20 ratio of the HPG surfactants were measured in deionized water at 22.6 °C. In general, increasing HPG size was marked by an increase in minimum surface area per molecule (Amin) at the aqueous liquid/air interface. This increase in size also led to lower CMC and greater pC20 values of HPG surfactants prepared with Tergitol 15-S-7 initiator (HPG 5a-5d), a commercially available ethylene glycol oligomer with a branched hydrophobic tail.

11.
Chem Rev ; 118(4): 1664-1690, 2018 02 28.
Artículo en Inglés | MEDLINE | ID: mdl-29336552

RESUMEN

Biological cells are complex living machines that have garnered significant attention for their potential to serve as a new generation of therapeutic and delivery agents. Because of their secretion, differentiation, and homing activities, therapeutic cells have tremendous potential to treat or even cure various diseases and injuries that have defied conventional therapeutic strategies. Therapeutic cells can be systemically or locally transplanted. In addition, with their ability to express receptors that bind specific tissue markers, cells are being studied as nano- or microsized drug carriers capable of targeted transport. Depending on the therapeutic targets, these cells may be clustered to promote intercellular adhesion. Despite some impressive results with preclinical studies, there remain several obstacles to their broader development, such as a limited ability to control their transport, engraftment, secretion and to track them in vivo. Additionally, creating a particular spatial organization of therapeutic cells remains difficult. Efforts have recently emerged to resolve these challenges by engineering cell surfaces with a myriad of bioactive molecules, nanoparticles, and microparticles that, in turn, improve the therapeutic efficacy of cells. This review article assesses the various technologies developed to engineer the cell surfaces. The review ends with future considerations that should be taken into account to further advance the quality of cell surface engineering.


Asunto(s)
Tratamiento Basado en Trasplante de Células y Tejidos , Animales , Bioingeniería , Rastreo Celular , Propiedades de Superficie
12.
J Am Chem Soc ; 141(24): 9693-9700, 2019 06 19.
Artículo en Inglés | MEDLINE | ID: mdl-31124359

RESUMEN

Recent work has shown that polymeric catalysts can mimic some of the remarkable features of metalloenzymes by binding substrates in proximity to a bound metal center. We report here an unexpected role for the polymer: multivalent, reversible, and adaptive binding to protein surfaces allowing for accelerated catalytic modification of proteins. The catalysts studied are a group of copper-containing single-chain polymeric nanoparticles (CuI-SCNP) that exhibit enzyme-like catalysis of the copper-mediated azide-alkyne cycloaddition reaction. The CuI-SCNP use a previously observed "uptake mode", binding small-molecule alkynes and azides inside a water-soluble amphiphilic polymer and proximal to copper catalytic sites, but with unprecedented rates. Remarkably, a combined experimental and computational study shows that the same CuI-SCNP perform a more efficient click reaction on modified protein surfaces and cell surface glycans than do small-molecule catalysts. The catalysis occurs through an "attach mode" where the SCNPs reversibly bind protein surfaces through multiple hydrophobic and electrostatic contacts. The results more broadly point to a wider capability for polymeric catalysts as artificial metalloenzymes, especially as it relates to bioapplications.


Asunto(s)
Cobre/química , Proteínas de la Membrana/química , Nanopartículas/química , Polímeros/química , Polisacáridos/química , Alquinos/química , Animales , Azidas/química , Catálisis , Bovinos , Línea Celular Tumoral , Química Clic , Reacción de Cicloadición , Humanos , Simulación de Dinámica Molecular
13.
J Am Chem Soc ; 141(7): 2838-2842, 2019 02 20.
Artículo en Inglés | MEDLINE | ID: mdl-30698426

RESUMEN

We describe the 3-iodopropyl acetal moiety as a simple cleavable unit that undergoes acid catalyzed hydrolysis to liberate HI (p Ka ∼ -10) and acrolein stoichiometrically. Integrating this unit into linear and network polymers gives a class of macromolecules that undergo a new mechanism of degradation with an acid amplified, sigmoidal rate. This trigger-responsive self-amplified degradable polymer undergoes accelerated rate of degradation and agent release.

14.
Bioorg Med Chem ; 27(13): 2978-2984, 2019 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-31113691

RESUMEN

We describe the molecular design, synthesis, and investigation of a series of acridine-triaminotriazine macrocycles that selectively bind to CTG trinucleotide repeats in DNA with minimal nonspecific binding. The limited conformational flexibility enforces the stacking of the triaminotriazine and acridine units. Isothermal titration calorimetry studies and Job plot analyses revealed that the ligands bound to d(CTG) mismatched sites. The acridine and triaminotriazine units were shown to intramolecularly π-stack in aqueous solutions. Compared to a noncyclic analog, the macrocycles showed an almost 10-fold lower cytotoxicity in HeLa cells and up to 4-fold higher transcription inhibition of d(CTG·CAG)74.


Asunto(s)
ADN/química , Repeticiones de Trinucleótidos/genética , Humanos
15.
Chem Soc Rev ; 47(5): 1811-1821, 2018 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-29367988

RESUMEN

The development of synthetic, metal-based catalysts to perform intracellular bioorthogonal reactions represents a relatively new and important area of research that combines transition metal catalysis and chemical biology. The ability to perform reactions in cellulo, especially those transformations without a natural counterpart, offers a versatile tool for medicinal chemists and chemical biologists. With proper modification of the metal catalysts, it is even possible to direct a reaction to certain intracellular sites. This review highlights advances in this new area, from early work on intracellular functional group conversions to recent advances in intracellular synthesis of drugs, including cytotoxic agents. Both the fundamental and applied aspects of this approach to intracellular synthesis are reviewed.


Asunto(s)
Técnicas de Química Sintética , Elementos de Transición/química , Catálisis
16.
J Am Chem Soc ; 140(42): 13695-13702, 2018 10 24.
Artículo en Inglés | MEDLINE | ID: mdl-30192530

RESUMEN

A major challenge in performing reactions in biological systems is the requirement for low substrate concentrations, often in the micromolar range. We report that copper cross-linked single-chain nanoparticles (SCNPs) are able to significantly increase the efficiency of copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reactions at low substrate concentration in aqueous buffer by promoting substrate binding. Using a fluorogenic click reaction and dye uptake experiments, a structure-activity study is performed with SCNPs of different size and copper content and substrates of varying charge and hydrophobicity. The high catalytic efficiency and selectivity are attributed to a mechanism that involves an enzyme-like substrate binding process. Saturation-transfer difference (STD) NMR spectroscopy, 2D-NOESY NMR, kinetic analyses with varying substrate concentrations, and computational simulations are consistent with a Michaelis-Menten, two-substrate, random-sequential enzyme-like kinetic profile. This general approach may prove useful for developing more-sustainable catalysts and agents for biomedicine and chemical biology.

17.
J Am Chem Soc ; 139(10): 3623-3626, 2017 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-28263067

RESUMEN

We describe the preparation of cross-linked, polymeric organic nanoparticles (ONPs) with a single, covalently linked DNA strand. The structure and functionalities of the ONPs are controlled by the synthesis of their parent linear block copolymers that provide monovalency, fluorescence and narrow size distribution. The ONP can also guide the deposition of chloroaurate ions allowing gold nanoparticles (AuNPs) to be prepared using the ONPs as templates. The DNA strand on AuNPs is shown to preserve its functions.


Asunto(s)
ADN de Cadena Simple/química , Oro/química , Nanopartículas del Metal/química , Polímeros/química , Estructura Molecular , Tamaño de la Partícula
18.
Nat Mater ; 15(7): 754-9, 2016 07.
Artículo en Inglés | MEDLINE | ID: mdl-27135859

RESUMEN

Many chemical and biological processes involve the transfer of both protons and electrons. The complex mechanistic details of these proton-coupled electron transfer (PCET) reactions require independent control of both electron and proton transfer. In this report, we make use of lipid-modified electrodes to modulate proton transport to a Cu-based catalyst that facilitates the O2 reduction reaction (ORR), a PCET process important in fuel cells and O2 reduction enzymes. By quantitatively controlling the kinetics of proton transport to the catalyst, we demonstrate that undesired side products such as H2O2 and O2(-) arise from a mismatch between proton and electron transfer rates. Whereas fast proton kinetics induce H2O2 formation and sluggish proton flux produces O2(-), proton transfer rates commensurate with O-O bond breaking rates ensure that only the desired H2O product forms. This fundamental insight aids in the development of a comprehensive framework for understanding the ORR and PCET processes in general.

19.
Biomacromolecules ; 18(4): 1393-1400, 2017 04 10.
Artículo en Inglés | MEDLINE | ID: mdl-28245360

RESUMEN

The extracellular matrix is an environment rich with structural, mechanical, and molecular signals that can impact cell biology. Traditional approaches in hydrogel biomaterial design often rely on modifying the concentration of cross-linking groups to adjust mechanical properties. However, this strategy provides limited capacity to control additional important parameters in 3D cell culture such as microstructure and molecular diffusivity. Here we describe the use of multifunctional hyperbranched polyglycerols (HPGs) to manipulate the mechanical properties of polyethylene glycol (PEG) hydrogels while not altering biomolecule diffusion. This strategy also provides the ability to separately regulate spatial and temporal distribution of biomolecules tethered within the hydrogel. The functionalized HPGs used here can also react through a copper-free click chemistry, allowing for the encapsulation of cells and covalently tethered biomolecules within the hydrogel. Because of the hyperbranched architecture and unique properties of HPGs, their addition into PEG hydrogels affords opportunities to locally alter hydrogel cross-linking density with minimal effects on global network architecture. Additionally, photocoupling chemistry allows micropatterning of bioactive cues within the three-dimensional gel structure. This approach therefore enables us to tailor mechanical and diffusive properties independently while further allowing for local modulation of biomolecular cues to create increasingly complex cell culture microenvironments.


Asunto(s)
Materiales Biocompatibles/química , Reactivos de Enlaces Cruzados/química , Módulo de Elasticidad , Glicerol/química , Hidrogeles/química , Polietilenglicoles/química , Polímeros/química , Animales , Fenómenos Bioquímicos , Materiales Biocompatibles/síntesis química , Fenómenos Biofísicos , Técnicas de Cultivo de Célula , Proliferación Celular/fisiología , Supervivencia Celular/fisiología , Células Cultivadas , Matriz Extracelular/química , Glicerol/síntesis química , Hidrogeles/síntesis química , Estructura Molecular , Polietilenglicoles/síntesis química , Polímeros/síntesis química , Células Madre/citología , Porcinos
20.
Phys Chem Chem Phys ; 19(10): 7086-7093, 2017 Mar 08.
Artículo en Inglés | MEDLINE | ID: mdl-28225090

RESUMEN

Proton-coupled electron transfer (PCET) reactions are ubiquitous in biochemistry and alternative energy schemes. Natural enzymes utilize quinones in proton transfer chains and energy conversion processes. Here, we utilize a bio-inspired hybrid bilayer membrane system to control the reaction mechanism of a quinone molecule covalently bound to an electrode surface. In particular, by impeding proton access to the quinone moiety, we change the reaction pathway from a PCET process to a pure electron transfer step. We further alter the reaction pathway to a stepwise PCET process by controlling the proton flux through the use of an alkyl proton carrier incorporated in the lipid membrane. By modulating proton availability, we control the quinone reaction pathway without changing the molecular structure of the redox species. This work provides unique insight into PCET reactions and a novel electrochemical platform for interrogating them.

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