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The model established at Orillia Soldiers Memorial Hospital involves family physicians as the most responsible physician. They act as "admission gatekeeper" for all unattached patients who are admitted to the psychiatry in-patient unit. A PubMed, EBSCO, OVID Medline, Embase, CINAHL, and Web of Science database review of the last 10 years (2006-2016) was undertaken. A satisfaction survey was undertaken. An intensive literature review found this model to be unique. The model has proved to be extremely efficient and cost-effective.
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Modelos Organizacionales , Servicio de Psiquiatría en Hospital/organización & administración , Análisis Costo-Beneficio , Médicos Hospitalarios/organización & administración , Humanos , Tiempo de Internación , Ontario , Satisfacción del Paciente , Servicio de Psiquiatría en Hospital/economía , Servicio de Psiquiatría en Hospital/normasRESUMEN
Zinc oxide (ZnO) nanostructures were produced using a novel pulsed laser ablation apparatus comprising in-situ analysis of the plume by reflection time-of-flight mass spectrometry. Various morphologies of nano and microstructures were obtained for laser wavelengths of 1064 and 355nm, and oxygen ambient pressures of 10(-6) and 10(-2)mbar, respectively. None of the produced structures exhibited a particular type of self-organisation whereas all of them showed low aspect ratios and good field emission properties. Optimum values of 5.2Vmicrom(-1) and 2060 were obtained for the turn-on field and Fowler-Nordheim enhancement factor, respectively, for deposited nano-tipped microstructures presenting a high coverage of the substrate. The experimental data showed that for a given laser wavelength, higher field enhancement factors were obtained for the samples grown at the lower pressure of 10(-6)mbar. In these conditions, the deposited materials showed distinct nanostructuring and comparison with existing data showed the corresponding ablation plumes to contain (ZnO)(n) clusters, up to n=13. This work also shows that the electronic properties of the nanostructured ZnO produced in our conditions, as determined by the oxygen concentration during deposition, have an influence on the field emission properties in addition to the nanostructure morphology.
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Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.
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BackgroundThe traditional treatment protocol for acute low back pain (ALBP) primarily used by healthcare professionals has in the past decade been strict bed rest; corsets; traction and `back schools'. However; current research has led to dramatic changes in the traditional treatment protocol. The literature suggests that the protocol should be replaced by parsimonious imaging; early return to normal activities and greater emphasis on exercise to prevent recurrences of ALBP and to treat chronic pain. The aim of this study was to investigate the guidelines prescribed by general practitioners (GPs) to patients with acute low back pain (ALBP) regarding `return to work'.MethodsA systematic sample of 212 GPs; selected from a list supplied by the Health Professions Council of South Africa (HPCSA); was selected to complete questionnaires. The highest qualifications of the GPs were MBChB or MFamMed; and all of them practise in the Bloemfontein area.ResultsSixty-three respondents stated that 40of ALBP patients returned for follow-up consultations. Of the 63 respondents; eight GPs had not consulted ALBP patients in the preceding two years; and thus were excluded from the final number of respondents. Bed rest is still prescribed by 67.27of GPs and; although 47.27of the GPs were aware of the change in protocol; only 9prescribe `return to work'. A total of 18.18are aware of evidence-based guidelines and 10of the GPs prescribe these. Among the guidelines defined by the GPs are lifestyle changes; rest and stabilisation. Only 18.18of ALBP patients are referred to occupational therapy for treatment.ConclusionOnly 47.27of the GPs knew about the new ALBP protocol; and even fewer had any knowledge of the content of the new protocol. Also; the guidelines prescribed by the GPs concerning `return to work' were indefinite. The researchers hypothesised that the reasons for this were a lack of awareness of the change in the acute low back pain protocol suggested by the Agency for Healthcare Research and Quality; as well as a lack of knowledge of the evidence-based guidelines suggested for their profession
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Dolor de Espalda , Protocolos Clínicos , Familia , Guía , Preparaciones Farmacéuticas , Médicos , PrescripcionesRESUMEN
The results of surveys to investigate the levels of 3-monochloropropane-1,2-diol (3-MCPD) and 1,3-dichloropropanol (1,3-DCP) in UK retail samples of soy sauces and similar products are reported. The products, sampled in 2000 and 2002, were analysed for 3-MCPD using an established solvent extraction technique with a reporting limit of 0.01 mg kg(-1), which also detected 2-monochloropropane-1,2-diol (2-MCPD), and for 1,3-DCP by an automated headspace method with a reporting limit of 0.005 mg kg(-1), which also detected 2,3-dichloropropanol (2,3-DCP). In the 2000 survey, 3-MCPD was quantified in 32 of 100 samples. After normalization to 40% dry matter, it was quantified at or above 0.02 mg kg(-1) in 25 of the samples and in excess of 1 mg kg(-1) in 16 samples, the highest containing 82.8 mg kg(-1). 2-MCPD was found in 26 samples, at up to 17.6 mg kg(-1) after normalization to 40% dry matter. The presence of 1,3-DCP was detected in 17 of the samples, at levels between 0.006 and 0.345 mg kg(-1). 1,3-DCP was only detected where 3-MCPD was present, but the levels of 1,3-DCP and 3-MCPD were not correlated. 2,3-DCP was detected in 11 samples at levels ranging from 0.006 to 0.043 mg kg(-1). In the 2002 survey, 3-MCPD was quantified (> 0.01 mg kg(-1)) in only eight of 99 samples and 2-MCPD in three samples. After normalization to 40% dry matter, 3-MCPD was present at or above 0.02 mg kg(-1) in seven of these, the maximum level being 35.9 mg kg(-1). 1,3-DCP was detected in this sample alone, at 0.017 mg kg(-1).
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Condimentos/análisis , Contaminación de Alimentos/análisis , Glycine max/química , alfa-Clorhidrina/análogos & derivados , alfa-Clorhidrina/análisis , Carcinógenos/análisis , Análisis de los Alimentos/métodos , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Garantía de la Calidad de Atención de Salud , Reino UnidoRESUMEN
A survey of the levels of 3-monochloropropane-1,2-diol (3-MCPD) in a range of selected food products available in the UK is reported. The survey was carried out on behalf of the Food Standards Agency (FSA) to identify the food groups that might provide a significant contribution to 3-MCPD exposure from the diet. Three hundred samples comprising meat, dairy, cereal, soup and miscellaneous products were purchased from retail outlets and analysed using a GC-MS procedure, which had been formally validated by an earlier collaborative trial. 3-MCPD was detected in 89 (30%) of the samples. Three samples, all crackers, contained levels of 3-MCPD > 0.1 mg kg(-1), the highest level being 0.134 mg kg(-1). Levels of 3-MCPD were generally slightly higher in foods after cooking. In all cases where 3-MCPD was detected in cooked foods, it was also present in the uncooked sample.
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Esterilizantes Químicos/análisis , Contaminación de Alimentos/análisis , alfa-Clorhidrina/análisis , Culinaria , Productos Lácteos/análisis , Grano Comestible/química , Análisis de los Alimentos/métodos , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Carne/análisis , Reino UnidoRESUMEN
A new potato tuber lipoxygenase full-length cDNA sequence (lox1:St:2) has been isolated from potato tubers and used to express in Escherichia coli and characterize a novel recombinant lipoxygenase (potato 13/9-lipoxygenase). Like most plant lipoxygenases it produced carbonyl compounds from linoleate (the preferred substrate) and was purified in the Fe(II) (ferrous) state. Typical of other potato tuber lipoxygenases, it produced 5-HPETE [5(S)-hydroperoxy-(6E, 8Z, 11Z, 14Z)-eicosatetraenoic acid] from arachidonate. In contrast to any other potato tuber lipoxygenase, it exhibited dual positional specificity and produced roughly equimolar amounts of 13- and 9-hydroperoxides (or only a slight molar excess of 9-hydroperoxides) from linoleate. We have used a homology model of pea 9/13-lipoxygenase to superimpose and compare the linoleate-binding pockets of different potato lipoxygenases of known positional specificity. We then tested this model by using site-directed mutagenesis to identify some primary determinants of linoleate binding to potato 13/9-lipoxygenase and concluded that the mechanism determining positional specificity described for a cucumber lipoxygenase does not apply to potato 13/9-lipoxygenase. This supports our previous studies on pea seed lipoxygenases for the role of pocket volume rather than inverse orientation as a determinant of dual positional specificity in plant lipoxygenases. We have also used deletion mutagenesis to identify a critical role in catalysis for a surface hydrophobic loop in potato 13/9-lipoxygenase and speculate that this may control substrate access. Although potato 13/9-lipoxygenase represents only a minor isoform in tubers, such evidence for a single lipoxygenase species with dual positional specificity in tubers has implications for the proposed role of potato lipoxygenases in the plant.
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Lipooxigenasa/metabolismo , Proteínas de Plantas/metabolismo , Solanum tuberosum/enzimología , Sitios de Unión , Clonación Molecular , Escherichia coli/metabolismo , Concentración de Iones de Hidrógeno , Lipooxigenasa/química , Lipooxigenasa/genética , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Filogenia , Especificidad por SustratoRESUMEN
A survey of the level of 3-monochloropropane-1,2-diol (3-MCPD) in soy sauces and similar products available in the UK is reported. The survey was carried out by the Joint Ministry of Agriculture, Fisheries and Food/Department of Health Food Safety and Standards Group (JFSSG) to check for compliance with the Food Advisory Committee's (FAC) recommended limit for 3-MCPD of 0.01 mg/kg following reports that soy sauces in several European countries had been found to contain high levels (up to 124 mg/kg) of 3-MCPD. Forty samples of soy sauce and similar products purchased from retail outlets were analysed using a GC-MS procedure which had been formally validated by an earlier collaborative trial. 3-MCPD was undetectable in 21 (52%) of samples analysed in the survey, with a further five samples containing very low levels of between 0.01 and 0.02 mg/kg. Five samples (13%) contained 3-MCPD at levels in the range 0.020-1 mg/kg while nine samples (23%) were found to contain 3-MCPD at levels greater than 1 mg/kg, with the highest level being 30.5 mg/kg.
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Carcinógenos/análisis , Esterilizantes Químicos/análisis , Condimentos/análisis , Glycine max/química , alfa-Clorhidrina/análisis , Cromatografía de Gases , Residuos de Medicamentos/análisis , Contaminación de Alimentos , Humanos , Espectrometría de Masas , Concentración Máxima AdmisibleRESUMEN
An automated system has been developed and validated for the analysis of liquid formulations (solution and suspension). The system comprises a multi-place magnetic stirrer, a diluter and a diode array UV spectrophotometer. The system can handle a wide range of drug formulation concentrations (> 200 mg ml-1) and gives excellent precision and accuracy with no detectable carryover. The analysis acceptance parameters are user-definable and the analysis process, including interpretation and reporting of the data, is fully automated.
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Preparaciones Farmacéuticas/análisis , Espectrofotometría Ultravioleta/métodos , Química Farmacéutica/métodos , Estudios de Evaluación como Asunto , Reproducibilidad de los Resultados , Soluciones , Espectrofotometría Ultravioleta/instrumentación , SuspensionesRESUMEN
The study's objective was to survey what and how psychiatry residents want to learn about ethics during residency. A 4-page questionnaire developed for this study was sent to 305 residents at 10 adult psychiatry programs in the United States. One-hundred and eighty-one (59%) of those surveyed responded. Seventy-six percent reported facing an ethical dilemma in residency for which they felt unprepared. Forty-six percent reported having received no ethics training during residency. More than 50% of the respondents requested that "more" curricular attention be paid to 19 specific ethics topics and more than 40% for 25 topics. Preferences with respect to learning methods are presented. This survey may provide guidance in structuring the content and process of ethics education for psychiatry residents. These findings should stimulate the efforts of faculty to commit time and attention to this important curricular area.
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We examined the role of p53 oligomerization in DNA binding and in transactivation. By conventional electron microscopy (EM) and scanning transmission EM, we find that wild-type tetramers contact 18-20 bp at single or tandem 19 bp consensus sequences and also stack in apparent register, tetramer on top of tetramer. Stacked tetramers link separated DNA binding sites with DNA loops. Interestingly, the p53(1-320) segment, which lacks the C-terminal tetramerization domain, binds DNA consensus sites as stacked oligomers. Although the truncated protein binds DNA with reduced efficiency, it nevertheless induces DNA looping by self-association. p53, therefore, has a C-terminal tetramerization domain that enhances DNA binding and a non-tetrameric oligomerization domain that stacks p53 at consensus sites and loops separated consensus sites via protein-protein interactions. Using model promoters, we demonstrate that wild-type and tetramerization-deficient p53s activate transcription well when tandem consensus sites are proximal to TATA sequences and poorly when tandem sites are distal. In the presence of proximal sites, however, stimulation by distal sites increases 25-fold. Tetramerization and stacking of tetramers, therefore, provide dual mechanisms to augment the number of p53 molecules available for activation through p53 response elements. DNA looping between separated response elements further increases the concentration of local p53 by translocating distally bound protein to the promoter.
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ADN/ultraestructura , Conformación de Ácido Nucleico , Activación Transcripcional , Proteína p53 Supresora de Tumor/ultraestructura , Animales , Secuencia de Bases , Sitios de Unión , Secuencia de Consenso , ADN/metabolismo , Ratones , Microscopía Electrónica de Transmisión de Rastreo , Modelos Moleculares , Datos de Secuencia Molecular , Peso Molecular , Regiones Promotoras Genéticas , Unión Proteica , Conformación Proteica , Secuencias Reguladoras de Ácidos Nucleicos , Transcripción Genética , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
For inorganic crystals such as calcite (CaCO3), Atomic Force Microscopy (AFM) has provided surface structure at atomic resolution (Ohnesorge and Binnig, 1993). As part of a broad effort to obtain high resolution for an individual protein or protein assembly (Binnig et al., 1986; Rugar and Hansma, 1990; Radmacher et al., 1992), we applied AFM to study the ATP-dependent double hexamer of SV40 large T antigen, which assembles around the viral origin of DNA replication. Multimeric mass has been determined in two-dimensional projected images by Scanning Transmission Electron Microscopy (STEM) (Mastrangelo et al., 1989). By AFM, if the DNA-protein preparation has been stained positively by uranyl acetate, the contour at the junction between hexamers is visible as a cleft, 2-4 nm deep. The cleft, whether determined as a fraction of height by AFM or as a fraction of mass thickness by STEM, is of comparable magnitude. On either side of the cleft, hexamers attain a maximum height of 13-16 nm. Monomers found in the absence of ATP show heights of 5-7 nm. Taken together, the z coordinates provide a surface profile of complete and partial replication assemblies consistent with the spatial distribution of recognition pentanucleotides on the DNA, and they contribute direct geometrical evidence for a ring-like hexamer structure.
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Antígenos Virales de Tumores/química , Virus 40 de los Simios/inmunología , Antígenos Virales de Tumores/ultraestructura , Fenómenos Biofísicos , Biofisica , Replicación del ADN , Microscopía/métodos , Microscopía Electrónica de Transmisión de Rastreo , Estructura Molecular , Conformación Proteica , Virus 40 de los Simios/químicaRESUMEN
Three advances involving DNA in atomic force microscopy (AFM) are reported here. First a HEPES-Mg buffer has been used that improves the spreading of DNA and provides good DNA coverage with as little as 200-500 picograms per sample. Second, the new "tapping" mode has been used to improve the ease and resolution of AFM-imaging of DNA in air. Finally, AFM images are presented of single-stranded phi X-174 virion DNA with the gene 32 single-stranded binding protein. A summary of the current state of the field and of the methods for preparing and imaging DNA in the AFM is also presented.
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ADN de Cadena Simple/ultraestructura , ADN Viral/ultraestructura , Microscopía de Túnel de Rastreo , Bacteriófago T4/metabolismo , Bacteriófago phi X 174/genética , Bacteriófago phi X 174/ultraestructura , Tampones (Química) , ADN de Cadena Simple/metabolismo , ADN Viral/metabolismo , Proteínas de Unión al ADN/metabolismo , HEPES , Microscopía de Túnel de Rastreo/métodos , Unión Proteica , Proteínas Virales/metabolismoRESUMEN
We show assembly of low and high multimers of HeLa cell nuclear protein, RIP60, at the origin of bidirectional replication (OBR) identified by Burhans, Vassilev, Caddle, Heintz and DePamphilis in Chinese hamster ovary cells. RIP60 binds a 5'-ATT-3' reiterated sequence downstream of the OBR and a second, homologous ATT sequence of opposite orientation situated within the OBR zone. Specifically bound structures were studied by conventional electron microscopy (EM) and quantitative scanning transmission electron microscopy (STEM). Dimers and multiples of dimers link the downstream binding site that overlaps a bent DNA sequence and the homologous upstream OBR sequence, looping out 700 bp of intervening DNA. Superposed dimers are found at individual unlinked sites, stabilized presumably through protein-protein interaction, and such superposition appears to occur also in the basic link structure. Along the loop, single crossovers and extended twists are observed by conventional EM. By STEM, loop DNA is laterally compacted, with diameter and mass equivalent to double-duplex DNA strands. Supercoiled 736 bp and 5243 bp circular DNAs assume similar laterally compacted geometries that are mostly absent from relaxed forms. These observations parallel the compacted, interwound superhelices viewed by cryo-electron microscopy in vitrified solutions containing magnesium ions, and provide structural evidence in agreement with that from conventional EM for superhelical tension in RIP60 loop DNA. Loop superhelicity could arise as a topological response to linking and suggests a functional role for link formation.
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Replicación del ADN/fisiología , Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Proteínas Nucleares/metabolismo , Tetrahidrofolato Deshidrogenasa/genética , Animales , Sitios de Unión , Biopolímeros , Células CHO , Cricetinae , ADN/ultraestructura , Proteínas de Unión al ADN/ultraestructura , Células HeLa , Humanos , Microscopía Electrónica , Microscopía Electrónica de Transmisión de Rastreo , Proteínas Nucleares/ultraestructura , Conformación de Ácido Nucleico , Conformación ProteicaRESUMEN
Using conventional and scanning transmission electron microscopy, we have examined the physical basis of long-range enhancer effects between distal and proximal elements in a eukaryotic promoter. Specifically, we have studied binding of human transcription factor Sp1 to 10-base-pair G+C-rich elements ("GC boxes") located at -100 and +1700 relative to the RNA start site. It was previously observed that the distantly located site functions in synergism with the promoter-proximal site to strongly activate transcription in vivo. Here we demonstrate that this synergism is likely to be a direct consequence of interactions between remote and local Sp1, the remote Sp1 translocated to the promoter by a DNA loop. Scanning transmission electron microscopy shows that Sp1 initially forms a tetramer and subsequently assembles multiple tetramers stacked in register at the DNA loop juncture. This unexpected finding not only provides the physical basis for loop formation but also defines a biological process leading to strongly increased concentration of activator protein at the promoter. The mechanism may unify the problem of transcriptional activation by removing enhancer action as a separate class of regulatory activity.
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ADN/metabolismo , Elementos de Facilitación Genéticos , Regulación de la Expresión Génica , Regiones Promotoras Genéticas , Factor de Transcripción Sp1/fisiología , Transcripción Genética , ADN/ultraestructura , Técnicas In Vitro , Sustancias Macromoleculares , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Plásmidos , Unión Proteica , Secuencias Reguladoras de Ácidos NucleicosRESUMEN
Simian virus 40 (SV40) replicates in nuclei of human and monkey cells. One viral protein, large tumour (T) antigen, is required for the initiation of DNA replication. The development of in vitro replication systems which retain this property has facilitated the identification of the cellular components required for replication. T antigen recognizes the pentanucleotide 5'-GAGGC-3' which is present in four copies within the 64 base-pairs (bp) of the core origin. In the presence of ATP it binds with increased affinity forming a distinctive, bilobed structure visible in electron micrographs. As a helicase, it unwinds SV40 DNA bidirectionally from the origin. We report here that in vitro and in the presence of ATP, T antigen assembles a double hexamer, centred on the core origin and extending beyond it by 12 bp in each direction. The assembly of this dodecamer initiates an untwisting of the duplex by 2-3 turns. In the absence of ATP, a tetrameric structure is the largest found at the core origin. In the absence of DNA, but in the presence of ATP or its non-hydrolysable analogues, T antigen assembles into hexamers. This suggests that ATP effects an allosteric change in the monomer. The change alters protein-protein interactions and allows the assembly of a double hexamer, which initiates replication at the core origin.
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Adenosina Trifosfato/farmacología , Antígenos Transformadores de Poliomavirus , Replicación del ADN , Centrifugación por Gradiente de Densidad , Simulación por Computador , ADN Helicasas/metabolismo , ADN Viral/metabolismo , Sustancias Macromoleculares , Microscopía Electrónica , Peso Molecular , Virus 40 de los Simios/genética , Virus 40 de los Simios/inmunologíaRESUMEN
The gene-specific transcription initiation factor USF (upstream stimulatory factor) binds at a palindromic sequence that extends from -52 to -63 relative to the start site of the adenovirus type 2 major late promoter; USF enhances in vitro transcription 10- to 20-fold. By analysis of digital micrographs from the Brookhaven scanning transmission electron microscope, we have identified a sample of 29 proteins (mass, 55 +/- 5 kDa) specifically bound at the palindrome. The individual protein digital images show extensive homology, which permits modeling a three-dimensional structure at a relatively low resolution, which is nonetheless significant for the study of protein-protein interactions in initiation. Non-sequence-specific competitor DNA at high mass excess can be used in reactions for microscopy, enabling characterization of specific binding for proteins present at 1% of total protein or less.
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Adenoviridae/análisis , Proteínas de Unión al ADN/metabolismo , Genes Virales , Regiones Promotoras Genéticas , Factores de Transcripción/metabolismo , Secuencia de Bases , ADN Viral/metabolismo , ADN Viral/ultraestructura , Microscopía Electrónica de Rastreo , Modelos Moleculares , Peso Molecular , Conformación de Ácido Nucleico , Conformación Proteica , Proteínas ViralesRESUMEN
Three sequence components direct high affinity binding of dimeric SV40 T antigen to SV40 origin region I. Two signals are encoded by two directly repeated 5'-GAGGC-3' pentanucleotides. Approximately equal contributions to binding stability are made by each pentanucleotide, and both spacing and orientation of the pentanucleotides are important for binding affinity. The third vital component is contained in a 5'-TTTTTTG-3' spacer sequence that separates the pentanucleotides. Sequence-specific features of the spacer stabilize binding to the adjacent pentanucleotides. The asymmetry of the spacer suggests that a novel binding mechanism is involved. Because the alignment of T antigen on mutant and wild-type DNAs is similar, we propose that any two of the three sequence signals are sufficient to determine the unique arrangement of a bound protein dimer.
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Antígenos Virales de Tumores/metabolismo , ADN Viral/metabolismo , Genes Virales , Virus 40 de los Simios/genética , Proteínas Virales/metabolismo , Antígenos Transformadores de Poliomavirus , Secuencia de Bases , Sitios de Unión , Clonación Molecular , Replicación del ADN , ADN Viral/genética , Etilnitrosourea , Mutación , Oligodesoxirribonucleótidos/metabolismo , Secuencias Repetitivas de Ácidos Nucleicos , Virus 40 de los Simios/inmunología , Virus 40 de los Simios/metabolismoRESUMEN
Large tumor (T) antigen and its bound multimeric states are positioned by scanning transmission electron microscopy (STEM) within a few base pairs at control sequences of the simian virus 40 DNA origin of replication region. Proximal and distal edge positions for each multimer group match the end positions of previously mapped fragments protected from DNase cleavage. Since chance correspondence is shown to be extremely unlikely, STEM mass measurements, obtained concurrently with STEM map positions, indicate that the DNase fragments arise from bound monomers, dimers, trimers, and tetramers in binding region II and monomers, dimers, and trimers in binding region I. Simultaneous binding of seven monomer-equivalent masses is observed, three in region I and four in region II, with an ordered and interpretable mass distribution in the plane of the foil. Although this observation does not prove that the six G-A-G-G-C and one T-A-G-G-C sequences, similarly distributed, function as recognition sequences for T-antigen monomer, it provides strong support for such a model. The stable existence in solution of low-and intermediate-mass structures, observed at lower T-antigen concentrations, suggests a role as assembly intermediates.