Transfer of Biologically Derived Nanometer-Scale Patterns to Smooth Substrates

Douglas, Kenneth T.; Devaud, Genevieve; Clark, Noel A.

doi:10.1126/science.257.5070.642

Cited by 99 publications

(54 citation statements)

References 6 publications

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“…Similarly, intact S-layer sacculi purified from S. acidocaldarius by detergent extraction spontaneously aggregate in suspension. This clumping, which can interfere with the use of S-layer fragments as nanometre-scale surface-patterning templates (see Douglas et al, 1992), can only be avoided through particular growth and purification conditions (J. Moore, personal communication). Our observation that 2 h Pronase treatment did not decrease fertility of S. acidocaldarius may also be significant, since S-layer subunits are the only externally exposed cell envelope proteins of S. acidocaldarius known to be completely resistant to Pronase digestion (Grogan, 1996b).…”

Section: Discussionmentioning

confidence: 99%

Chromosomal marker exchange in the thermophilic archaeon Sulfolobus acidocaldarius: physiological and cellular aspects

Ghane

Grogan

1998

Microbiology

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Exchange and recombination of chromosomal markers is an intrinsic genetic property of the thermoacidophilic archaeon Sulfolobus acidocaldarius that has not been thoroughly characterized. T o clarify the mechanism and experimental usefulness of this process, the frequency of 5. acidocaldarius prototrophs produced from mixtures of two pyrimidine auxotrophs under a variety of conditions was determined. The apparent efficiency of genetic exchange was essentially independent of the density of cells deposited on the surface of solid media. Furthermore, recombinant formation could initiate in liquid suspensions, as indieated by high recombinant frequencies resulting from mixtures plated at low cell densities, and the formation of recombinants a t equal or higher frequencies in liquid suspensions that were never plated. Apparent initiation of genetic exchange in liquid a t 22 "C was not prevented by DNase, prior digestion of parental cells with protease from Streptomyces griseus, or any other non-lethal chemical agent tested. The results support prior indications that chromosomal marker exchange in S. acidocaldarius proceeds via conjugation, and further indicate that this conjugation can initiate quickly in dilute liquid suspension. The mating system of S. acidocaldarius thus appears physiologically distinct from that of Haloferax volcanii but perhaps similar to conjugational transfer of Sulfolobus plasmid pNOB8. The frequency of recombinants formed in these assays (10'4-10'5 per c.f.u.) greatly exceeds the number of spontaneous forward mutational events per generation for biosynthetic genes in S. acidocaldarius. This suggests that chromosomal exchange has the potential to influence the genetic dynamics of natural Sulfolobus populations.

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Section: Discussionmentioning

confidence: 99%

Chromosomal marker exchange in the thermophilic archaeon Sulfolobus acidocaldarius: physiological and cellular aspects

Ghane

Grogan

1998

Microbiology

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“…Douglas e cols. 109 demonstraram que poros com diâmetros da ordem de nanômetros numa proteína derivada de bactérias, podem ser usados para transferir a imagem desses poros para outro substrato.…”

Section: Matrizes Hospedeiras Unidimensionaisunclassified

Síntese de polímeros condutores em matrizes sólidas hospedeiras

Maia¹,

Paoli²,

Alves³

et al. 2000

Quím. Nova

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Recebido em 7/12/98; aceito em 8/6/99 CONDUCTIVE POLYMER SYNTHESIS IN SOLID HOST MATRICES. This review discusses the methods used to prepare conductive polymers in confined environments. This spatial restriction causes formation of defect-free polymer chains in the interlayer as porous cavities of inorganic hosts. The properties of the different composites obtained are a synergist combination of the characteristics of the inorganic host and the polymer. This opens new perspectives for the preparation of these materials and widens its potential applications.Keywords: conductive polymers; inorganic matrices; composites. REVISÃO INTRODUÇÃOUm histórico sobre tecnologia de polímeros evidenciaria, sem dúvida alguma, que uma das propriedades mais importantes destes materiais sintéticos é a capacidade de comportar-se como excelentes isolantes elétricos, tanto para altas freqüências quanto para voltagens. No entanto, nos últimos anos uma nova classe de polímeros orgânicos tem sido desenvolvida, cuja importância está relacionada à possibilidade de conduzir eletricidade 1 . Os membros desta nova classe de materiais, chamados de "metais sintéticos", possuem uma característica em comum: longos sistemas π conjugados, ou seja, uma alternância de ligações simples e duplas ao longo da cadeia. O interesse evidente é combinar em um mesmo material as propriedades elétricas de um semicondutor ou metal com as vantagens de um polímero.Desde a década de 60, é conhecido que moléculas orgânicas que apresentam duplas ligações conjugadas podem exibir propriedades semicondutoras. O desenvolvimento inicial foi inibido pelo fato que as cadeias rígidas, em uma estrutura conjugada, também produzem uma intratabilidade extrema, tal que a maioria dos primeiros exemplos de polímeros condutores eram infusíveis, insolúveis e, portanto, de pouco valor tecnológico. No começo dos anos 70 Shirakawa e Ikeda 2,3 demonstraram a possibilidade de preparar filmes auto-suportados de poliacetileno pela polimerização direta do acetileno. O polímero produzido apresentou propriedades semicondutoras que atraiu pouco interesse até 1977, quando MacDiarmid e cols.4 descobriram que, tratando o poliacetileno com ácido ou base de Lewis, era possí-vel aumentar a condutividade em até 13 ordens de grandeza. Este processo envolve a remoção ou adição de elétrons da cadeia polimérica, sendo denominado "dopagem". O termo dopagem é utilizado em analogia com os semicondutores inorgânicos cristalinos, sugerindo semelhanças com os polímeros intrinsecamente condutores (PICs). Em ambos os casos a dopagem é aleatória e não altera a estrutura do material. No entanto, na dopagem de um polímero as impurezas não são introduzidas nas cadeias, mas sim nas suas "vizinhanças". A interação impureza-cadeia gera deformações e "defeitos carregados" localizados, responsáveis pelo aumento na condutividade 5 . Outra diferença significativa está na quantidade de dopante utilizada. Enquanto os semicondutores apresentam "impurezas" que atuam como dopantes, da ordem de ppm, os PICs chegam a ter 50% em ma...

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“…Patterns in the nanometer range were prepared by transferring biological protein assemblies onto suitable substrates [17]. The development of nanometer size patterns has also been demonstrated by using scanning probe microscopy [18].…”

Section: Introductionmentioning

confidence: 99%

Chemical pattern on silica surface prepared by UV irradiation of 3-mercaptopropyltriethoxy silane layer: surface characterization and fibrinogen adsorption

Liu¹,

Hlady²

1996

Colloids and Surfaces B: Biointerfaces

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A flat silica surface modified with 3-mercaptopropyltriethoxy silane (MTS) was patterned using UV irradiation and a custom-designed mask. The irradiated surface was characterized by X-ray photoelectron spectroscopy (XPS), scanning force microscopy (SFM) and water contact angle measurements. The XPS S2p spectra indicated that the UV treatment resulted in the oxidation of MTS sulfur. The optimal UV irradiation dose for patterning, estimated from the XPS S2p binding energy shifts and water contact angles of irradiated surfaces, was 4.8 J cm −2 at 270 nm. The surface patterns were visualized by total internal reflection fluorescence microscopy, while exposing the pattern to a solution of acridine orange, by water vapor condensation, and by SFM lateral force imaging in dilute electrolyte solution. The adhesion SFM measurements revealed the adhesion force only on the areas which were not UV-irradiated. The adsorption of fluoresceinlabeled fibrinogen (FITC-Fgn) from dilute buffer solution also produced visual information on the pattern. The kinetics of FITC-Fgn adsorption onto the oxidized and unoxidized MTS-silica surfaces from dilute protein solution proceeded with identical initial adsorption rates. The steadystate FITC-Fgn adsorption was twice as large on the unoxidized MTS-silica than on the oxidized MTS-silica surface.

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Transfer of Biologically Derived Nanometer-Scale Patterns to Smooth Substrates

Cited by 99 publications

References 6 publications

Chromosomal marker exchange in the thermophilic archaeon Sulfolobus acidocaldarius: physiological and cellular aspects

Chromosomal marker exchange in the thermophilic archaeon Sulfolobus acidocaldarius: physiological and cellular aspects

Síntese de polímeros condutores em matrizes sólidas hospedeiras

Chemical pattern on silica surface prepared by UV irradiation of 3-mercaptopropyltriethoxy silane layer: surface characterization and fibrinogen adsorption

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