RESUMEN
A combined experimental and theoretical study shows how the interaction of VUV radiation with cyclo-(alanine-alanine), one of the 2,5-diketopiperazines (DKPs), produces reactive oxazolidinone intermediates. The theoretical simulations reveal that the interaction of these intermediates with other neutral and charged fragments, released in the molecular decomposition, leads either to the reconstruction of the cyclic dipeptide or to the formation of longer linear peptide chains. These results may explain how DKPs could have, on one hand, survived hostile chemical environments and, on the other, provided the seed for amino acid polymerization. Shedding light on the mechanisms of production of such prebiotic building blocks is of paramount importance to understanding the abiotic synthesis of relevant biologically active compounds.
Asunto(s)
Dicetopiperazinas/química , Péptidos Cíclicos/química , Péptidos/síntesis química , Dicetopiperazinas/efectos de la radiación , Simulación de Dinámica Molecular , Oxazolidinonas/síntesis química , Péptidos Cíclicos/efectos de la radiación , Fotólisis , Polimerizacion , Rayos UltravioletaRESUMEN
A facile procedure for in situ peptide cyclization and phthalocyanine conjugation was developed by utilizing a bifunctional linker incorporated with a bis(bromomethyl)benzene unit and a cyclopentadiene moiety. These functional groups facilitated the nucleophilic substitution with the two cysteine residues of the linear peptides followed by the Diels-Alder reaction with the maleimide moiety attached to a zinc(II) phthalocyanine. With this approach, three cyclic peptide-phthalocyanine conjugates were prepared in 20-26% isolated yield via a one-pot procedure. One of the conjugates containing a cyclic form of the epidermal growth factor receptor (EGFR)-binding peptide sequence CMYIEALDKYAC displayed superior features as an advanced photosensitizer. It showed preferential uptake by two EGFR-positive cancer cell lines (HT29 and HCT116) compared with two EGFR-negative counterparts (HeLa and HEK293), resulting in significantly higher photocytotoxicity. Intravenous administration of this conjugate into HT29 tumor-bearing nude mice resulted in selective localization in tumor and effective inhibition of tumor growth upon photodynamic treatment.
Asunto(s)
Antineoplásicos/uso terapéutico , Neoplasias del Colon/tratamiento farmacológico , Receptores ErbB/metabolismo , Indoles/uso terapéutico , Péptidos Cíclicos/uso terapéutico , Fármacos Fotosensibilizantes/uso terapéutico , Animales , Antineoplásicos/síntesis química , Antineoplásicos/metabolismo , Antineoplásicos/efectos de la radiación , Línea Celular Tumoral , Neoplasias del Colon/metabolismo , Femenino , Células HEK293 , Humanos , Indoles/síntesis química , Indoles/metabolismo , Indoles/efectos de la radiación , Luz , Ratones Endogámicos BALB C , Péptidos Cíclicos/síntesis química , Péptidos Cíclicos/metabolismo , Péptidos Cíclicos/efectos de la radiación , Fotoquimioterapia , Fármacos Fotosensibilizantes/síntesis química , Fármacos Fotosensibilizantes/metabolismo , Fármacos Fotosensibilizantes/efectos de la radiación , Medicina de PrecisiónRESUMEN
Inverse photoconductance is an uncommon phenomenon observed in selective low-dimensional materials, in which the electrical conductivity of the materials decreases under light illumination. The unique material property holds great promise for biomedical applications in photodetectors, photoelectric logic gates, and low-power nonvolatile memory, which remains a daunting challenge. Especially, tunable photoconductivity for biocompatible materials is highly desired for interfacing with biological systems but is less explored in organic materials. Here, we report nanofibers self-assembled with cyclo-tyrosine-tyrosine (cyclo-YY) having voltage-regulated inverse photoconductance and photoconductance. The peptide nanofibers can be switched back and forth by a bias voltage for imitating biological sensing in artificial vision and memory devices. A peptide optoelectronic resistive random access memory (PORRAM) device has also been fabricated using the nanofibers that can be electrically switched between long-term and short-term memory. The underlying mechanism of the reversible photoconductance is discussed in this paper. Due to the inherent biocompatibility of peptide materials, the reversible photoconductive nanofibers may have broad applications in sensing and storage for biotic and abiotic interfaces.
Asunto(s)
Dipéptidos/química , Nanofibras/química , Péptidos Cíclicos/química , Equipos de Almacenamiento de Computador , Computadores Moleculares , Dipéptidos/efectos de la radiación , Conductividad Eléctrica , Nanofibras/efectos de la radiación , Péptidos Cíclicos/efectos de la radiaciónRESUMEN
A zinc(II) phthalocyanine substituted with three 2,4-dinitrobenzenesulfonate (DNBS) groups and a cyclic arginine-glycine-aspartic acid (cRGDfK) moiety was prepared and characterized. With three strongly electron-withdrawing DNBS groups, this compound was fully quenched in terms of fluorescence emission and singlet oxygen generation in N,N-dimethylformamide and phosphate buffered saline due to the strong photoinduced electron transfer effect. In the presence of glutathione (GSH), which is the most abundant intracellular thiol particularly in tumor cells, the DNBS moieties were cleaved, thereby restoring these photoactivities and making the conjugate as a GSH-activated photosensitizer. Being a well-known integrin antagonist, the cyclic RGD peptide sequence could enhance the localization of the conjugate in integrin-upregulated tumor cells. As shown by confocal laser scanning microscopy and flow cytometry, the intracellular fluorescence intensity of the conjugate was significantly higher in the integrin-positive A549 and MDA-MB-231â¯cells than in the integrin-negative MCF-7 and HEK293â¯cells. The photocytotoxicity of the conjugate against MDA-MB-231â¯cells was also higher than that toward MCF-7â¯cells. The results suggest that this dual-functional photosensitizer is a promising candidate for targeted photodynamic therapy.
Asunto(s)
Antineoplásicos/farmacología , Complejos de Coordinación/farmacología , Glutatión/metabolismo , Indoles/farmacología , Péptidos Cíclicos/farmacología , Fármacos Fotosensibilizantes/farmacología , Antineoplásicos/síntesis química , Antineoplásicos/metabolismo , Antineoplásicos/efectos de la radiación , Bencenosulfonatos/síntesis química , Bencenosulfonatos/metabolismo , Bencenosulfonatos/farmacología , Bencenosulfonatos/efectos de la radiación , Línea Celular Tumoral , Complejos de Coordinación/síntesis química , Complejos de Coordinación/metabolismo , Complejos de Coordinación/efectos de la radiación , Fluorescencia , Células HEK293 , Humanos , Indoles/síntesis química , Indoles/metabolismo , Indoles/efectos de la radiación , Integrinas/metabolismo , Luz , Péptidos Cíclicos/síntesis química , Péptidos Cíclicos/metabolismo , Péptidos Cíclicos/efectos de la radiación , Fármacos Fotosensibilizantes/síntesis química , Fármacos Fotosensibilizantes/metabolismo , Fármacos Fotosensibilizantes/efectos de la radiación , Oxígeno Singlete/metabolismo , Zinc/químicaRESUMEN
Dynamic substrates for cell culture control the spatial and temporal presentation of extracellular matrix ligands that interact with adherent cells. This paper reports a photoactive surface chemistry that can repeatedly activate regions of the substrate for cell adhesion, spreading, and migration. The approach uses self-assembled monolayers presenting the integrin ligand RGD that is caged with a nitrophenyl-based photoprotecting group. The group is also modified with a maltoheptaose oligosaccharide to prevent nonspecific protein adsorption and cell attachment. The peptide is uncaged when irradiated with a laser source at 405 nm on a microscope to reveal micron-size regions for single cell attachment. This method is applied to studies of gap junction-mediated communication between two neighboring cells and requires the patterning of an initial receiver cell population and then the patterning of a second sender population to give a culture wherein each pair of cells are separated by 30 µm. Finally, activation of the region between the cells permits cell-cell contact and gap junction assembly between the sender and receiver cells. This example demonstrates the broad relevance of this method to studying complex phenotypes in cell culture.
Asunto(s)
Adhesión Celular , Uniones Comunicantes/fisiología , Membranas Artificiales , Nitrobencenos/química , Péptidos Cíclicos/metabolismo , Línea Celular Tumoral , Fluoresceínas/metabolismo , Colorantes Fluorescentes/metabolismo , Células Endoteliales de la Vena Umbilical Humana , Humanos , Ligandos , Maleimidas/química , Nitrobencenos/efectos de la radiación , Péptidos Cíclicos/química , Péptidos Cíclicos/efectos de la radiación , Compuestos de Sulfhidrilo/química , Rayos UltravioletaRESUMEN
A new anticancer agent based on the conjugation of a photoactivatable Pt(IV) pro-drug to a cyclic RGD-containing peptide is described. Upon visible light irradiation, phototoxicity was induced preferentially in SK-MEL-28 melanoma cancer cells overexpressing αVß3 integrin compared to control DU-145 human prostate carcinoma cells.
Asunto(s)
Antineoplásicos , Integrina alfaVbeta3/metabolismo , Compuestos Organoplatinos , Péptidos Cíclicos , Profármacos , Antineoplásicos/química , Antineoplásicos/farmacología , Antineoplásicos/efectos de la radiación , Línea Celular Tumoral , Humanos , Luz , Compuestos Organoplatinos/química , Compuestos Organoplatinos/farmacología , Compuestos Organoplatinos/efectos de la radiación , Péptidos Cíclicos/química , Péptidos Cíclicos/farmacología , Péptidos Cíclicos/efectos de la radiación , Platino (Metal)/metabolismo , Profármacos/química , Profármacos/farmacología , Profármacos/efectos de la radiación , Receptores de Vitronectina/metabolismoRESUMEN
We have revisited the intramolecular Heck reaction and investigated the microwave-assisted macrocyclization on preformed peptides using a model series of ring-varying peptides acryloyl-Gly-[Gly](n)-Phe(4-I)NHR; n = 0-4. The method was applied to both solution and solid supported cyclizations. We demonstrate that the intramolecular Heck reaction can be performed in peptides both in solution and solid support using a modified domestic microwave within 1 to 30 minutes in DMF under reflux with moderate yields ranging from 15 to 25% for a scale between 2-45 mg of linear precursors. The approach was applied to the synthesis of a constrained biologically relevant peptidomimetic bearing an Arg-Gly-Asp (RGD) sequence. These results make the microwave-assisted Heck reaction an attractive renovated approach for peptidomimetics.
Asunto(s)
Péptidos Cíclicos/química , Péptidos Cíclicos/efectos de la radiación , Secuencia de Aminoácidos , Aminoácidos/química , Cromatografía Líquida de Alta Presión , Dimerización , Dimetilformamida/química , Cinética , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Microondas , Peso Molecular , Oligopéptidos/química , Péptidos Cíclicos/síntesis química , Conformación Proteica , Soluciones , Relación Estructura-ActividadRESUMEN
Urotensin-II (U-II) is a cyclic 11-amino acid peptide known as a potent mammalian vasoconstrictor. To study some purported intracellular actions of U-II, masked analogs of this peptide, becoming biologically active only upon UV exposure, were developed. Those analogs described as "caged" were derivatized with a photolabile 4,5-dimethoxynitrobenzyl group on the side chain of Lys-8 or Tyr-9. Both caged analogs of U-II showed a major decrease in their affinity towards the UT receptor. Nevertheless, upon UV irradiation, the native and biologically active U-II peptide was recovered. Thus, this work describes the development of new "caged" U-II derivatives and demonstrates that vasoactivity of U-II can be controlled by masking and unmasking two key residues.
Asunto(s)
Urotensinas , Animales , Aorta Torácica/efectos de los fármacos , Aorta Torácica/efectos de la radiación , Humanos , Cinética , Masculino , Péptidos Cíclicos/síntesis química , Péptidos Cíclicos/farmacología , Péptidos Cíclicos/efectos de la radiación , Fotólisis/efectos de la radiación , Ratas , Ratas Sprague-Dawley , Factores de Tiempo , Rayos Ultravioleta , Urotensinas/síntesis química , Urotensinas/farmacología , Urotensinas/efectos de la radiaciónRESUMEN
UV radiation was applied to degrade cyanobacterial hepatotoxin, microcystin-LR in the presence of phycocyanin as a model natural sensitiser. The concentrations of both the toxin and the pigment used in the experiments were higher by several orders of magnitude than found in the environment. The photoreaction parameters were optimised. The process was found to be of limited use for water treatment due to its low efficacy. Additionally, pronounced UV-induced bleaching of the pigment significantly reducing the photoreaction rates of the toxin was observed for the highest UV radiation intensities applied.
Asunto(s)
Péptidos Cíclicos/metabolismo , Rayos Ultravioleta , Purificación del Agua/métodos , Biodegradación Ambiental , Cinética , Toxinas Marinas , Microcistinas , Modelos Biológicos , Péptidos Cíclicos/química , Péptidos Cíclicos/efectos de la radiación , Fotoblanqueo/efectos de la radiación , Fotólisis/efectos de la radiación , Pigmentos Biológicos/metabolismo , Pigmentos Biológicos/efectos de la radiación , Toxinas Biológicas/metabolismo , Toxinas Biológicas/efectos de la radiaciónRESUMEN
The thioredoxin reductase active-site fragment H-Ala-Cys-Ala-Thr-Cys-Asp-Gly-Phe-OH [134-141], which is known for its high tendency to assume an almost identical conformation as in the intact enzyme, was backbone cyclized with the photoresponsive (4-amino)phenylazobenzoic acid (APB) to produce a monocyclic and disulfide-bridged bicyclic APB-peptide. Light-induced reversible cis/trans isomerization occurs at identical extents in both the linear and the two cyclic forms. Nuclear magnetic resonance conformational analysis clearly revealed that in the bicyclic APB-peptide both as a trans- and cis-azo-isomer the constraints imparted by the bicyclic structure do not allow the molecule to relax into a defined low energy conformation, thus making the molecule a frustrated system that flip-flops between multiple conformational states. Conversely, the monocyclic APB peptide folds into a well-defined lowest energy structure as a trans-azo-isomer, which upon photoisomerization to the cis-azo configuration relaxes into a less restricted conformational space. First femtosecond spectroscopic analysis of the dynamics of the photoreaction confirm a fast first phase on the femtosecond time scale related to the cis/trans isomerization of the azobenzene moiety followed by a slower phase in the picosecond time scale that involves an adjustment of the peptide backbone. Due to the well- defined photoresponsive two-state transition of this monocyclic peptide molecule, it represents a model system well suited for studying the ultrafast dynamics of conformational transitions by time-resolved spectroscopy.
Asunto(s)
Aminobenzoatos/química , Aminobenzoatos/efectos de la radiación , Compuestos Azo/química , Compuestos Azo/efectos de la radiación , Péptidos Cíclicos/química , Dicroismo Circular , Isomerismo , Luz , Modelos Moleculares , Conformación Molecular/efectos de la radiación , Resonancia Magnética Nuclear Biomolecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/efectos de la radiación , Péptidos Cíclicos/efectos de la radiación , Fotoquímica/métodos , Estructura Secundaria de Proteína , Espectrofotometría Ultravioleta , Termodinámica , Reductasa de Tiorredoxina-Disulfuro/química , Factores de Tiempo , para-AminobenzoatosRESUMEN
It has been reported that backbone cyclization of octapeptides with the photoresponsive (4-aminomethyl)phenylazobenzoic acid imparts sufficient restraints to induce and stabilize ordered conformations of the peptide backbone in both the cis- and trans-azo-isomers (L. Ulysse, J. Cubillos, and J. Chmielewski, Journal of the American Chemical Society, 1995, Vol. 117, pp. 8466-8467). Correspondingly, the active-site octapeptide fragment H-Ala-Cys-Ala-Thr-Cys-Asp-Gly-Phe-OH [134-141] of thioredoxin reductase, with its high preference for a 3(10)-helix turn conformation centered on the Thr-Cys sequence, was backbone cyclized with this azobenzene moiety in the attempt to design a photoresponsive system where the conformational states of the peptide backbone are dictated by the configuration of the azobenzene and can be further modulated by the disulfide bridge. Nuclear magnetic resonance conformational analysis of the monocyclic compound clearly revealed the presence of two conformational families in both the cis- and trans-azo configuration. Of the higher populated conformational families, the structure of the trans-isomer seems like a pretzel-like folding, while the cis-isomer relaxes into a significantly less defined conformational state that does not exhibit any regular structural elements. Further restrictions imparted by disulfide bridging of the peptide moiety leads to an even better defined conformation for the trans-azo-isomer, whereas the cis-isomer can be described as a frustrated system without pronounced energy minima and thus with little conformational preferences. Our findings would suggest that this photoresponsive peptide template may not be of general usefulness for light-induced conformational transitions between two well-defined conformational states at least under the experimental conditions employed, even in the bicyclic form. However, trans --> cis isomerization of the bicyclic peptide is accompanied by a switch from a well-defined conformation to an ensemble of possible conformations.
Asunto(s)
Aminobenzoatos/química , Aminobenzoatos/efectos de la radiación , Compuestos Azo/química , Compuestos Azo/efectos de la radiación , Péptidos Cíclicos/química , Isomerismo , Luz , Modelos Moleculares , Conformación Molecular/efectos de la radiación , Resonancia Magnética Nuclear Biomolecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/efectos de la radiación , Péptidos Cíclicos/efectos de la radiación , Fotoquímica/métodos , Estructura Secundaria de Proteína , Espectrofotometría Ultravioleta , Termodinámica , Reductasa de Tiorredoxina-Disulfuro/química , Factores de Tiempo , para-AminobenzoatosRESUMEN
The microcystins are hepatotoxins produced by a number of cyanobacterial species (blue green algae) in fresh water systems. The increasing eutrophication of natural waters has led to an increase in the incidence of algal blooms and the consequent increased risk of microcystin contamination of water resources. The removal of microcystins LR, YR and YA from contaminated water was investigated using an experimental laboratory-scale photocatalytic 'falling film' reactor in which an oxygen purge, UV radiation and semiconductor titanium dioxide (TiO2) catalyst were used to oxidatively decompose the microcystin pollutants. Preliminary studies, using algal extracts spiked into distilled water, indicated that the microcystins were rapidly decomposed in this reactor. The decomposition followed first order reaction kinetics with half-lives of less than 5 min with the reactor operating in a closed-loop mode. Reaction rates were strongly dependent on the amount of TiO2 catalyst (O-5 g/l), but only marginally influenced by a change in gas purge from oxygen to compressed air. The use of lake water, rather than distilled water, showed that this process is feasible in natural waters, although increased levels of catalyst (up to 5 g/l) were required to achieve comparable decomposition rates.
Asunto(s)
Toxinas Bacterianas/metabolismo , Cianobacterias/fisiología , Péptidos Cíclicos/metabolismo , Contaminantes del Agua/metabolismo , Catálisis , Técnicas In Vitro , Luz , Microcistinas , Oxidación-Reducción , Óxidos/farmacología , Oxígeno/farmacología , Péptidos Cíclicos/efectos de la radiación , Factores de Tiempo , Titanio/farmacología , Purificación del Agua/métodosRESUMEN
When microcystin-LR was exposed to UV, three major nontoxic compounds were formed. These compounds were identified as [4(E),6(Z)-Adda5]- and [4(Z),6(E)-Adda5]microcystin-LR, which are geometrical isomers of the Adda [3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4(E),6(E)-decadienoic acid] moiety of microcystin-LR, and a novel compound, tricyclo-Adda [(2S,3S,1'R,3'S,4'S,5'R,6'R,7'R)-3-amino-5-(4',6'-dimethyl-3'-methoxy tricyclo[5.4.0.0(1',5')]undeca-8',10'-dien-6'-yl)-2-methy l-4(E)-pentenoic acid]-containing microcystin-LR ([tricyclo-Adda5]microcystin-LR), which was formed by [2 + 2] addition between the benzene ring and the double bond at position 6-7 of the Adda moiety of the microcystin. The geometrical isomers were formed reversibly, and their equilibrium constants were almost the same. [Tricyclo-Adda5]microcystin-LR was also formed reversibly and was decomposed under UV light. These results suggest that the breakdown of microcystin-LR by UV irradiation proceeds via [tricyclo-Adda5]microcystin-LR.
Asunto(s)
Inhibidores Enzimáticos/efectos de la radiación , Péptidos Cíclicos/efectos de la radiación , Animales , Cianobacterias , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/toxicidad , Espectroscopía de Resonancia Magnética , Toxinas Marinas , Ratones , Ratones Endogámicos BALB C , Microcistinas , Estructura Molecular , Péptidos Cíclicos/química , Péptidos Cíclicos/toxicidad , Estereoisomerismo , Rayos UltravioletaRESUMEN
The stability of the cyanobacterial hepatotoxin, nodularin, was determined during the incubation of purified toxin, and in nodularin-containing cell-free extracts and whole filaments of the nodularin-producer, Nodularia spumigena in sunlight and darkness. Levels of purified nodularin in aqueous solution remained approximately constant throughout the 9-day trials under all conditions, but decreased in cell-free extracts and whole filaments when incubated under all conditions, with losses being greatest in full sunlight, intermediate in sunlight minus ultraviolet wavelengths and lowest in continuous darkness. Photodegradation and detoxification in Artemia salina bioassays occurred when purified nodularin was irradiated with ultraviolet wavelengths using a laboratory lamp.
Asunto(s)
Toxinas Bacterianas/efectos de la radiación , Cianobacterias/efectos de la radiación , Toxinas Marinas/efectos de la radiación , Péptidos Cíclicos/efectos de la radiación , Luz Solar , Animales , Artemia , Toxinas Bacterianas/toxicidad , Cianobacterias/patogenicidad , Oscuridad , Relación Dosis-Respuesta en la Radiación , Estabilidad de Medicamentos , Toxinas Marinas/toxicidad , Péptidos Cíclicos/toxicidad , Factores de Tiempo , Pruebas de Toxicidad , Rayos UltravioletaRESUMEN
Microcystins are very potent hepatotoxins and strong liver tumor promoters produced by cyanobacteria, and their occurrence has been reported all over the world. They could threaten human health when toxic Microcystis occurs in water supply reservoirs. In this study, we examined the stability of microcystins during photolysis with UV light. The toxins were easily decomposed by UV light at wavelengths around the absorption maxima of the toxins and the decomposition depended on the intensity of the light. The half-life of microcystin LR by 147 microW/cm2 UV irradiation was 10 min, and the toxin was completely decomposed by 2550 microW/cm2 UV after 10 min. When the toxins were irradiated with weaker UV light, isomerization was also observed by a different mechanism from that during photolysis by sunlight and pigment, and several products including three geometrical isomers of the conjugated diene of Adda were detected. Microcystin RR showed almost the same behavior as that of microcystin LR under the same conditions. Since no noxious products were formed in the present study, a water treatment including UV irradiation is very possible for removing microcystins from raw water.