RESUMEN
Large immune complexes formed by the cross-linking of antibodies with polyvalent antigens play critical roles in modulating cell-mediated immunity. While both the size and the shape of immune complexes are important determinants in Fc receptor-mediated signaling responsible for phagocytosis, degranulation, and, in some instances, autoimmune pathologies, their characterization remains extremely challenging due to their large size and structural heterogeneity. We use native mass spectrometry (MS) supplemented with limited charge reduction in the gas phase to determine the stoichiometry of immune complexes formed by a bivalent (homodimeric) antigen, a 163 kDa aminopeptidase P2 (APP2), and a monoclonal antibody (mAb) to APP2. The observed (APP2·mAb)n complexes populate a wide range of stoichiometries (n = 1-4) with the largest detected species exceeding 1 MDa, although the gas-phase dissociation products are also evident in the mass spectra. While frequently considering a nuisance that complicates interpretation of native MS data, limited dissociation provides an additional dimension for characterization of the immune complex quaternary structure. APP2/mAb associations with identical composition but slightly different elution times in size exclusion chromatography exhibit notable differences in their spontaneous fragmentation profiles. The latter indicates the presence of both extended linear and cyclized (APP2·mAb)n configurations. The unique ability of MS to distinguish between such isomeric structures will be invaluable for a variety of applications where the biological effects of immune complexes are determined by their ability to assemble Fc receptor clusters of certain density on cell surfaces, such as platelet activation by clustering the low-affinity receptors FcγRIIa on their surface.
RESUMEN
The orphan nuclear receptors estrogen-related receptors (ERRs) bind to the estrogen-related receptor response element (ERRE) to regulate transcriptional programs in cellular metabolism and cancer cell growth. In this study, we evaluated the potential for a pyrrole-imidazole polyamide to block ERRα binding to ERREs to inhibit gene expression. We demonstrated that the ERRE-targeted polyamide 1 blocked the binding of ERRα to the consensus ERRE and reduced the transcriptional activity of ERRα in cell culture. We further showed that inhibiting ERRα transcriptional activity with polyamide 1 led to reduced mitochondrial oxygen consumption, a primary biological effect regulated by ERRα. Finally, our data demonstrated that polyamide 1 is an inhibitor for cancer cell growth.
RESUMEN
Age-related macular degeneration (AMD) is associated with dysfunction and death of retinal pigment epithelial (RPE) cells. Cell-based approaches using RPE-like cells derived from human pluripotent stem cells (hPSCs) are being developed for AMD treatment. However, most efficient RPE differentiation protocols rely on complex, stepwise treatments and addition of growth factors, whereas small-molecule-only approaches developed to date display reduced yields. To identify new compounds that promote RPE differentiation, we developed and performed a high-throughput quantitative PCR screen complemented by a novel orthogonal human induced pluripotent stem cell (hiPSC)-based RPE reporter assay. Chetomin, an inhibitor of hypoxia-inducible factors, was found to strongly increase RPE differentiation; combination with nicotinamide resulted in conversion of over one-half of the differentiating cells into RPE. Single passage of the whole culture yielded a highly pure hPSC-RPE cell population that displayed many of the morphological, molecular, and functional characteristics of native RPE.
Asunto(s)
Diferenciación Celular/efectos de los fármacos , Células Madre Pluripotentes/efectos de los fármacos , Epitelio Pigmentado de la Retina/citología , Ensayos Analíticos de Alto Rendimiento , Humanos , Células Madre Pluripotentes/citología , Reacción en Cadena de la PolimerasaRESUMEN
The development of novel antitumor agents that have high efficacy in suppressing tumor growth, have low toxicity to nontumor tissues, and exhibit rapid localization in the targeted tumor sites is an ongoing avenue of research at the interface of chemistry, cancer biology, and pharmacology. Supramolecular metal-based coordination complexes (SCCs) have well-defined shapes and geometries, and upon their internalization, SCCs could affect multiple oncogenic signaling pathways in cells and tissues. We investigated the uptake, intracellular localization, and antitumor activity of two rhomboidal Pt(II)-based SCCs. Laser-scanning confocal microscopy in A549 and HeLa cells was used to determine the uptake and localization of the assemblies within cells and their effect on tumor growth was investigated in mouse s.c. tumor xenograft models. The SCCs are soluble in cell culture media within the entire range of studied concentrations (1 nM-5 µM), are nontoxic, and showed efficacy in reducing the rate of tumor growth in s.c. mouse tumor xenografts. These properties reveal the potential of Pt(II)-based SCCs for future biomedical applications as therapeutic agents.
Asunto(s)
Antineoplásicos , Neoplasias Experimentales/tratamiento farmacológico , Compuestos Organometálicos , Platino (Metal) , Transducción de Señal/efectos de los fármacos , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Células HeLa , Humanos , Ratones , Neoplasias Experimentales/metabolismo , Neoplasias Experimentales/patología , Compuestos Organometálicos/química , Compuestos Organometálicos/farmacología , Platino (Metal)/química , Platino (Metal)/farmacología , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Development of small-molecule inhibitors of protein-protein interactions is a fundamental challenge at the interface of chemistry and cancer biology. Successful methods for design of protein-protein interaction inhibitors include computational and experimental high-throughput and fragment-based screening strategies to locate small-molecule fragments that bind protein surfaces. An alternative rational design approach seeks to mimic the orientation and disposition of critical binding residues at protein interfaces. We describe the design, synthesis, biochemical, and in vivo evaluation of a small-molecule scaffold that captures the topography of α-helices. We designed mimics of a key α-helical domain at the interface of hypoxia-inducible factor 1α and p300 to develop inhibitors of hypoxia-inducible signaling. The hypoxia-inducible factor/p300 interaction regulates the transcription of key genes, whose expression contributes to angiogenesis, metastasis, and altered energy metabolism in cancer. The designed compounds target the desired protein with high affinity and in a predetermined manner, with the optimal ligand providing effective reduction of tumor burden in experimental animal models.
Asunto(s)
Biomimética/métodos , Descubrimiento de Drogas/métodos , Dominios y Motivos de Interacción de Proteínas/efectos de los fármacos , Bibliotecas de Moléculas Pequeñas/farmacología , Secuencia de Aminoácidos , Anaerobiosis , Animales , Western Blotting , Clonación Molecular , Perfilación de la Expresión Génica , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Luciferasas , Ratones , Datos de Secuencia Molecular , Estructura Molecular , Mutagénesis , Piperazina , Piperazinas/química , Factores de Transcripción p300-CBP/genética , Factores de Transcripción p300-CBP/metabolismoRESUMEN
Selective blockade of gene expression by designed small molecules is a fundamental challenge at the interface of chemistry, biology, and medicine. Transcription factors have been among the most elusive targets in genetics and drug discovery, but the fields of chemical biology and genetics have evolved to a point where this task can be addressed. Herein we report the design, synthesis, and in vivo efficacy evaluation of a protein domain mimetic targeting the interaction of the p300/CBP coactivator with the transcription factor hypoxia-inducible factor-1α. Our results indicate that disrupting this interaction results in a rapid down-regulation of hypoxia-inducible genes critical for cancer progression. The observed effects were compound-specific and dose-dependent. Gene expression profiling with oligonucleotide microarrays revealed effective inhibition of hypoxia-inducible genes with relatively minimal perturbation of nontargeted signaling pathways. We observed remarkable efficacy of the compound HBS 1 in suppressing tumor growth in the fully established murine xenograft models of renal cell carcinoma of the clear cell type. Our results suggest that rationally designed synthetic mimics of protein subdomains that target the transcription factor-coactivator interfaces represent a unique approach for in vivo modulation of oncogenic signaling and arresting tumor growth.
Asunto(s)
Factor 1 Inducible por Hipoxia/química , Factor 1 Inducible por Hipoxia/metabolismo , Péptidos/farmacología , Transducción de Señal/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Antineoplásicos/farmacología , Hipoxia de la Célula , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/genética , Femenino , Perfilación de la Expresión Génica , Células HeLa , Humanos , Factor 1 Inducible por Hipoxia/genética , Ligandos , Ratones , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Péptidos/química , Unión Proteica/efectos de los fármacos , Multimerización de Proteína , Estabilidad Proteica/efectos de los fármacos , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Elementos de Respuesta/genética , Transcripción Genética , Factor A de Crecimiento Endotelial Vascular/metabolismo , Ensayos Antitumor por Modelo de Xenoinjerto , Factores de Transcripción p300-CBP/metabolismoRESUMEN
Development of anti-cancer agents with high tumor-targeting specificity and efficacy is critical for modern multidisciplinary cancer research. Monoamine oxidase A (MAOA), a mitochondria-bound enzyme, degrades monoamine neurotransmitters and dietary monoamines. Recent evidence suggests a correlation between increased MAOA expression and prostate cancer (PCa) progression with poor outcomes for patients. MAOA induces epithelial-mesenchymal transition (EMT) and augments hypoxic effects by producing excess reactive oxygen species. Thus, development of MAOA inhibitors which selectively target tumors becomes an important goal in cancer pharmacology. Here we describe the design, synthesis, and in vitro and in vivo evaluation of NMI, a conjugate that combines a near-infrared dye for tumor targeting with the moiety derived from the MAOA inhibitor clorgyline. NMI inhibits MAOA with low micromolar IC50, suppresses PCa cell proliferation and colony formation, and reduces migration and invasion. In mouse PCa xenografts, NMI targets tumors with no detectable accumulation in normal tissues, providing effective reduction of the tumor burden. Analysis of tumor specimens shows reduction in Ki-67(+) and CD31(+) cells, suggesting a decrease of cell proliferation and angiogenesis and an increase in M30(+) cells, indicating increased apoptosis. Gene expression profiles of tumors treated with NMI demonstrate reduced expression of oncogenes FOS, JUN, NFKB, and MYC and cell cycle regulators CCND1, CCNE1, and CDK4/6, along with increases in the levels of tumor suppressor gene TP53, cell cycle inhibitors CDKN1A and CDKN2A, and MAOA-downstream genes that promote EMT, tumor hypoxia, cancer cell migration, and invasion. These data suggest that NMI exerts its effect through tumor-targeted delivery of a MAOA-inactivating group, making NMI a valuable anti-tumor agent.
Asunto(s)
Proliferación Celular/efectos de los fármacos , Colorantes/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/efectos de los fármacos , Neoplasias de la Próstata/patología , Animales , Masculino , Ratones , Ratones Desnudos , Espectroscopía Infrarroja CortaRESUMEN
We report in vitro and in vivo evaluation of a newly designed trifunctional theranostic agent for targeting solid tumors. This agent combines a dendritic wedge with high boron content for boron neutron capture therapy or boron MRI, a monomethine cyanine dye for visible-light fluorescent imaging, and an integrin ligand for efficient tumor targeting. We report photophysical properties of the new agent, its cellular uptake and in vitro targeting properties. Using live animal imaging and intravital microscopy (IVM) techniques, we observed a rapid accumulation of the agent and its retention for a prolonged period of time (up to 7 days) in fully established animal models of human melanoma and murine mammary adenocarcinoma. This macromolecular theranostic agent can be used for targeted delivery of high boron load into solid tumors for future applications in boron neutron capture therapy.
Asunto(s)
Dendrímeros/uso terapéutico , Neoplasias/diagnóstico , Neoplasias/terapia , Animales , Transporte Biológico , Línea Celular Tumoral , Supervivencia Celular , Dendrímeros/metabolismo , Dendrímeros/farmacocinética , Humanos , Integrinas/metabolismo , Ligandos , Ratones , Neoplasias/patología , Distribución TisularRESUMEN
Hypoxia is a hallmark of solid tumors, is associated with local invasion, metastatic spread, resistance to chemo- and radiotherapy, and is an independent, negative prognostic factor for a diverse range of malignant neoplasms. The cellular response to hypoxia is primarily mediated by a family of transcription factors, among which hypoxia-inducible factor 1 (HIF1) plays a major role. Under normoxia, the oxygen-sensitive α subunit of HIF1 is rapidly and constitutively degraded but is stabilized and accumulates under hypoxia. Upon nuclear translocation, HIF1 controls the expression of over 100 genes involved in angiogenesis, altered energy metabolism, antiapoptotic, and pro-proliferative mechanisms that promote tumor growth. A designed transcriptional antagonist, dimeric epidithiodiketopiperazine (ETP 2), selectively disrupts the interaction of HIF1α with p300/CBP coactivators and downregulates the expression of hypoxia-inducible genes. ETP 2 was synthesized via a novel homo-oxidative coupling of the aliphatic primary carbons of the dithioacetal precursor. It effectively inhibits HIF1-induced activation of VEGFA, LOX, Glut1, and c-Met genes in a panel of cell lines representing breast and lung cancers. We observed an outstanding antitumor efficacy of both (±)-ETP 2 and meso-ETP 2 in a fully established breast carcinoma model by intravital microscopy. Treatment with either form of ETP 2 (1 mg/kg) resulted in a rapid regression of tumor growth that lasted for up to 14 days. These results suggest that inhibition of HIF1 transcriptional activity by designed dimeric ETPs could offer an innovative approach to cancer therapy with the potential to overcome hypoxia-induced tumor growth and resistance.
Asunto(s)
Antineoplásicos/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Mama/efectos de los fármacos , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Neoplasias Pulmonares/tratamiento farmacológico , Pulmón/efectos de los fármacos , Piperazinas/uso terapéutico , Factores de Transcripción p300-CBP/metabolismo , Animales , Antineoplásicos/química , Mama/patología , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Línea Celular Tumoral , Dimerización , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Pulmón/patología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Ratones , Ratones Desnudos , Modelos Moleculares , Piperazinas/química , Mapas de Interacción de Proteínas/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/genética , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Although metallacycle-based photosensitizers have attracted increasing attention in biomedicine, their clinical application has been hindered by their inherent dark toxicity and unsatisfactory phototherapeutic efficiency. Herein, we employ a π-expansion strategy for ruthenium acceptors to develop a series of Ru(ii) metallacycles (Ru1-Ru4), while simultaneously reducing dark toxicity and enhancing phototoxicity, thus obtaining a high phototoxicity index (PI). These metallacycles enable deep-tissue (â¼7 mm) fluorescence imaging and reactive oxygen species (ROS) production and exhibit remarkable anti-tumor activity even under hypoxic conditions. Notably, Ru4 has the lowest dark toxicity, highest ROS generation ability and an optimal PI (â¼146). Theoretical calculations verify that Ru4 exhibits the largest steric bulk and the lowest singlet-triplet energy gap (ΔE ST, 0.62 eV). In vivo studies confirm that Ru4 allows for effective and safe phototherapy against A549 tumors. This work thus is expected to open a new avenue for the design of high-performance metal-based photosensitizers for potential clinical applications.
RESUMEN
The long-sought-after "magic bullet" in systemic therapy remains unrealized for disease targets existing inside most tissues, theoretically because vascular endothelium impedes passive tissue entry and full target engagement. We engineered the first "dual precision" bispecific antibody with one arm pair to precisely bind to lung endothelium and drive active delivery and the other to precisely block TGF-ß effector function inside lung tissue. Targeting caveolae for transendothelial pumping proved essential for delivering most of the injected intravenous dose precisely into lungs within one hour and for enhancing therapeutic potency by >1000-fold in a rat pneumonitis model. Ultra-low doses (µg/kg) inhibited inflammatory cell infiltration, edema, lung tissue damage, disease biomarker expression and TGF-ß signaling. The prodigious benefit of active vs passive transvascular delivery of a precision therapeutic unveils a new promising drug design, delivery and therapy paradigm ripe for expansion and clinical testing.
Asunto(s)
Anticuerpos Biespecíficos , Caveolas , Ratas , Animales , Caveolas/metabolismo , Factor de Crecimiento Transformador beta/metabolismo , Anticuerpos Biespecíficos/metabolismo , Pulmón/metabolismo , Endotelio Vascular/metabolismoRESUMEN
Designed ligands that inhibit hypoxia-inducible gene expression could offer new tools for genomic research and, potentially, drug discovery efforts for the treatment of neovascularization in cancers. We report a stabilized alpha-helix designed to target the binding interface between the C-terminal transactivation domain (C-TAD) of hypoxia-inducible factor 1alpha (HIF-1alpha) and cysteine-histidine rich region (CH1) of transcriptional coactivator CBP/p300. The synthetic helix disrupts the structure and function of this complex, resulting in a rapid downregulation of two hypoxia-inducible genes (VEGF and GLUT1) in cell culture.
Asunto(s)
Disulfuros/farmacología , Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Alcaloides Indólicos/farmacología , Transactivadores/antagonistas & inhibidores , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Células HeLa , Humanos , Enlace de Hidrógeno , Factor 1 Inducible por Hipoxia/química , Factor 1 Inducible por Hipoxia/metabolismo , Estructura Secundaria de Proteína , Transactivadores/química , Transactivadores/metabolismoRESUMEN
The indole-diketopiperazine bridge is an important structural feature of many bispyrrolidinoindoline and epipolythiodiketopiperazine fungal metabolites. Organocatalytic conjugate addition of diketopiperazines to indoles was achieved in good to excellent yields through electrophilic indolenine intermediates generated under mild conditions. Screening of catalysts and solvents at different temperatures was performed in order to achieve high product yields.
RESUMEN
Selective blockade of hypoxia-inducible gene expression by designed small molecules would prove valuable in suppressing tumor angiogenesis, metastasis and altered energy metabolism. We report the design, synthesis, and biological evaluation of a dimeric epidithiodiketopiperazine (ETP) small molecule transcriptional antagonist targeting the interaction of the p300/CBP coactivator with the transcription factor HIF-1alpha. Our results indicate that disrupting this interaction results in rapid downregulation of hypoxia-inducible genes critical for cancer progression. The observed effects are compound-specific and dose-dependent. Controlling gene expression with designed small molecules targeting the transcription factor-coactivator interface may represent a new approach for arresting tumor growth.
Asunto(s)
Inhibidores de la Angiogénesis/farmacología , Dicetopiperazinas/farmacología , Disulfuros/farmacología , Subunidad alfa del Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Factores de Transcripción p300-CBP/antagonistas & inhibidores , Inhibidores de la Angiogénesis/síntesis química , Inhibidores de la Angiogénesis/química , Inhibidores de la Angiogénesis/toxicidad , Unión Competitiva , Hipoxia de la Célula , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Dicetopiperazinas/síntesis química , Dicetopiperazinas/química , Dicetopiperazinas/toxicidad , Disulfuros/síntesis química , Disulfuros/química , Disulfuros/toxicidad , Relación Dosis-Respuesta a Droga , Expresión Génica/efectos de los fármacos , Perfilación de la Expresión Génica , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Luciferasas/genética , Modelos Moleculares , Estructura Molecular , Neovascularización Patológica/metabolismo , Neovascularización Patológica/prevención & control , Análisis de Secuencia por Matrices de Oligonucleótidos , Unión Proteica , Factor A de Crecimiento Endotelial Vascular/biosíntesis , Factores de Transcripción p300-CBP/metabolismoRESUMEN
Organocatalytic alpha-sulfenylation of substituted piperazine-2,5-diones is reported through the use of cinchona alkaloids as Lewis bases and electrophilic sulfur transfer reagents. 1-Phenylsulfanyl[1,2,4]triazole, a novel sulfur transfer reagent, gave excellent product yields with a number of substituted piperazine-2,5-diones under mild conditions. Catalyst loading, stoichiometry of sulfur electrophile, temperature and solvent were optimized to achieve high product yields.
RESUMEN
A crystallographic investigation of the title compound, C22H28Cl2N4O4, using crystals obtained under different crystallization conditions, revealed the presence of two distinct polymorphic forms. The molecular conformation in the two polymorphs is very different: one adopts a 'C' shape, whereas the other adopts an 'S' shape. In the latter, the molecule lies across a crystallographic twofold axis. The 'S'-shaped polymorph undergoes a reversible orthorhombic-to-monoclinic phase transition on cooling, whereas the structure of the 'C'-shaped polymorph is temperature insensitive.
Asunto(s)
Dicetopiperazinas/química , Cristalización , Cristalografía por Rayos X , Modelos Moleculares , Transición de Fase , TemperaturaRESUMEN
The title compound, C(28)H(34)N(2)O(8)S(2), was synthesized as part of a project to develop synthetic routes to analogues of sporidesmins, a class of secondary metabolite produced by the filamentous fungi Chaetomium and Pithomyces sp. The complete molecule is generated by crystallographic inversion symmetry: the methoxy group is essentially coplanar with the benzene ring to which it is bonded, a mean plane fitted through the non-H atoms of the aromatic ring and the meth-oxy group having an r.m.s. deviation of 0.0140â Å. Similarly, the ester group is also essentially planar (r.m.s. deviation of a plane fitted through all non-H atoms is 0.0101â Å). There is only one independent C-Hâ¯O inter-action, which links together adjacent mol-ecules into a two-dimensional sheet in the bc plane.
RESUMEN
A high-performance liquid chromatography-electrospray ionization tandem mass spectrometric (HPLC-ESI-MS/MS) method was developed for the quantification of MHI148-clorgyline amide (NMI-amide), a novel tumor-targeting monoamine oxidase A inhibitor, in mouse plasma. The method was validated in terms of sensitivity, precision, accuracy, recovery and stability and then applied to a pharmacokinetic study of NMI-amide in mice following intravenous administration. NMI-amide together with the internal standard (IS), MHI-148, was extracted by protein precipitation using acetonitrile. Multiple reaction monitoring was used for quantification of NMI-amide by detecting m/z transition of 491.2-361.9, and 685.3-258.2 for NMI-amide and the IS, respectively. The lower limit of quantification (LLOQ) of the HPLC-MS/MS method for NMI-amide was 0.005 µg/mL and the linear calibration curve was acquired with R2 > 0.99 in the concentration range of 0.005-2 µg/mL. The intra- and inter-day precisions of the assay were assessed by percentage of the coefficient of variations, which was within 9.8% at LLOQ and 14.0% for other quality control samples, whereas the mean accuracy ranged from 86.8% to 113.2%. The samples were stable under storage and experimental conditions. This method was successfully applied to a pharmacokinetic study in mice following intravenous administration of 5 mg/kg NMI-amide.
RESUMEN
Hairpin pyrrole-imidazole (Py-Im) polyamides are programmable oligomers that bind the DNA minor groove in a sequence-specific manner with affinities comparable to those of natural DNA-binding proteins. These cell-permeable small molecules have been shown to enter the nuclei of live cells and downregulate endogenous gene expression. We complete here a library of 27 hairpin Py-Im polyamides which bind 7-base-pair sequences of the general form 5'-WWGNNNW-3' (where W = A or T, N = W, G, or C). Their equilibrium association constants (K(a)) range from K(a) = 1×10(8) M(-1) to 4×10(10) M(-1) with good sequence specificity. A table of binding affinities and sequence contexts for this completed 27-member library has been assembled for the benefit of the chemical biology community interested in molecular control of transcription.
RESUMEN
A pivotal step forward in chemical approaches to controlling gene expression is the development of sequence-specific DNA-binding molecules that can enter live cells and traffic to nuclei unaided. DNA-binding polyamides are a class of programmable, sequence-specific small molecules that have been shown to influence a wide variety of protein-DNA interactions. We have synthesized over 100 polyamide-fluorophore conjugates and assayed their nuclear uptake profiles in 13 mammalian cell lines. The compiled dataset, comprising 1300 entries, establishes a benchmark for the nuclear localization of polyamide-dye conjugates. Compounds in this series were chosen to provide systematic variation in several structural variables, including dye composition and placement, molecular weight, charge, ordering of the aromatic and aliphatic amino-acid building blocks and overall shape. Nuclear uptake does not appear to be correlated with polyamide molecular weight or with the number of imidazole residues, although the positions of imidazole residues affect nuclear access properties significantly. Generally negative determinants for nuclear access include the presence of a beta-Ala-tail residue and the lack of a cationic alkyl amine moiety, whereas the presence of an acetylated 2,4-diaminobutyric acid-turn is a positive factor for nuclear localization. We discuss implications of these data on the design of polyamide-dye conjugates for use in biological systems.