917 resultados para Lac operons
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Includes bibliography.
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Letterpress accompanies the frontispiece.
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t. 1. Cyropaedia.--t. 2. Memorabilia Socratis.--t. 3. Anabasis.--t. 4. Historia graeca.--t. 5. Oeconomicus, Apologia Socratis, Convivium, Hiero, Agesilaus.--t. 6. Derrepublica lac. et Athen. De vectigalibus. De re equestri. De officio magistri equitum. De venatione LL.
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Engr. title pages; v. 1 has added t. p., printed.
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Based on Additional mss. 10292-4 in the British Museum.
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A collection of miscellaneous pamphlets.
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v. 2. Chanson à la lune -- Deux amants près du lac bleu -- Trois garçons -- L'arc-en-ciel -- Chant des canotiers -- La bise a soufflé -- L'oiselet -- Mon "chez-nous" -- Hardi, Jean-Louis -- Les mouettes -- Par le chemin grimpant -- J'ai descendu au verger -- Les bonnes dames de St. Gervais -- La chanson de blé -- Chantons comme les oiseaux -- Les garçons d'Yverdon.
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"A loose paraphrase of not quite fourteen folios of the first three volumes of the French romance of Lancelot du Lac."--Pref.
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Souvenirs du Vesuve -- Echos du Saleve -- Course au Niesen -- Fleurs d'Engadin -- Le Lac de St-Point -- Le Melchthal -- Le Monte-Moro -- Pillon et Jaman -- Echos des Gorges de l'Areuse.
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Mode of access: Internet.
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Salivary cortisol (C) and DHEA concentrations were measured in 9 elite swimmers (4 female and 5 male) over a 37-week period, 5 to 12 times per swimmer, before 68 competitions. For female and male swimmers, no significant relationship was found between C, DHEA and performance. For the whole group, C was negatively correlated with week number of training (r = -0.31, p < 0.01). The incorporation of the cumulated distance swum as a second variable in the regression increased r to 0.56 (p < 0.01). The higher the cumulated distance swum, the higher C. No significant relationship was found between DHEA and distance swum. For individual swimmers, 3 of 4 females showed a significant negative relationship between C and cumulated dry-land training. No equivalent relationship was found for DHEA. The 2 males practicing dry-land training showed a significant and negative relationship between DHEA and cumulated dry-land training. No equivalent relationship was found for C. Thus, C and DHEA were not good predictors of swimming performance. C for individual females, and DHEA for individual males were considered useful markers for dry-land training stress.
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Stx2d is a recently described Shiga toxin whose cytotoxicity is activated 10- to 1,000-fold by the elastase present in mouse or human intestinal mucus. We examined Shiga toxigenic Escherichia coli (STEC) strains isolated from food and livestock sources for the presence of activatable stx(2d). The stx(2) operons of STEC were first analyzed by PCR-restriction fragment length polymorphism (RFLP) analysis and categorized as stx(2), stx(2c) (vha), stx(2c) (vhb), or stx(2d) (EH250). Subsequently, the stx(2c) (vha) and stx(2c) (vhb) operons were screened for the absence of a PstI site in the stx(2a) subunit gene, a restriction site polymorphism which is a predictive indicator for the stx(2d) (activatable) genotype. Twelve STEC isolates carrying putative stx(2d) operons were identified, and nucleotide sequencing was used to confirm the identification of these operons as stx(2d). The complete nucleotide sequences of seven representative stx(2d) operons were determined. Shiga toxin expression in stx(2d) isolates was confirmed by immunoblotting. stx(2d) isolates were induced for the production of bacteriophages carrying stx. Two isolates were able to produce bacteriophages phi1662a and phi1720a carrying the stx(2d) operons. RFLP analysis of bacteriophage genomic DNA revealed that phi1662a and phi1720a were highly related to each other; however, the DNA sequences of these two stx(2d) operons were distinct. The STEC strains carrying these operons were isolated from retail ground beef. Surveillance for STEC strains expressing activatable stx(2d) Shiga toxin among clinical cases may indicate the significance of this toxin subtype to human health.
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Bistability arises within a wide range of biological systems from the A phage switch in bacteria to cellular signal transduction pathways in mammalian cells. Changes in regulatory mechanisms may result in genetic switching in a bistable system. Recently, more and more experimental evidence in the form of bimodal population distributions indicates that noise plays a very important role in the switching of bistable systems. Although deterministic models have been used for studying the existence of bistability properties under various system conditions, these models cannot realize cell-to-cell fluctuations in genetic switching. However, there is a lag in the development of stochastic models for studying the impact of noise in bistable systems because of the lack of detailed knowledge of biochemical reactions, kinetic rates, and molecular numbers. in this work, we develop a previously undescribed general technique for developing quantitative stochastic models for large-scale genetic regulatory networks by introducing Poisson random variables into deterministic models described by ordinary differential equations. Two stochastic models have been proposed for the genetic toggle switch interfaced with either the SOS signaling pathway or a quorum-sensing signaling pathway, and we have successfully realized experimental results showing bimodal population distributions. Because the introduced stochastic models are based on widely used ordinary differential equation models, the success of this work suggests that this approach is a very promising one for studying noise in large-scale genetic regulatory networks.
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Recently identified genes located downstream (3') of the msmEF (transport encoding) gene cluster, msmGH, and located 5' of the structural genes for methanesulfonate monooxygenase (MSAMO) are described from Methylosulfonomonas methylovora. Sequence analysis of the derived polypeptide sequences encoded by these genes revealed a high degree of identity to ABC-type transporters. MsmE showed similarity to a putative periplasmic substrate binding protein, MsmF resembled an integral membraneassociated protein, and MsmG was a putative ATP-binding enzyme. MsmH was thought to be the cognate permease component of the sulfonate transport system. The close association of these putative transport genes to the MSAMO structural genes msmABCD suggested a role for these genes in transport of methanesulfonic acid (MSA) into M. methylovora. msmEFGH and msmABCD constituted two operons for the coordinated expression of MSAMO and the MSA transporter systems. Reverse-transcription-PCR analysis of msmABCD and msmEFGH revealed differential expression of these genes during growth on MSA and methanol. The msmEFGH operon was constitutively expressed, whereas MSA induced expression of msmABCD. A mutant defective in msmE had considerably slower growth rates than the wild type, thus supporting the proposed role of MsmE in the transport of MSA into M. methylovora.
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Current approaches for purifying plasmids from bacterial production systems exploit the physiochemical properties of nucleic acids in non-specific capture systems. In this study, an affinity system for plasmid DNA (pDNA) purification has been developed utilizing the interaction between the lac operon (lacO) sequence contained in the pDNA and a 64mer synthetic peptide representing the DNA-binding domain of the lac repressor protein, LacI. Two plasmids were evaluated, the native pUC19 and pUC19 with dual lacO3/lacOs operators (pUC19lacO3/lacOs), where the lacOs operator is perfectly symmetrical. The DNA-protein affinity interaction was evaluated by surface plasmon resonance using a Biacore system. The affinity capture of DNA in a chromatography system was evaluated using LacI peptide that had been immobilized to Streamline™ adsorbent. The KD-values for double stranded DNA (dsDNA) fragments containing lacO1 and lacO3 and lacOs and lacO3 were 5.7 ± 0.3 × 10 -11 M and 4.1 ± 0.2 × 10-11 M respectively, which compare favorably with literature reports of 5 × 10-10 - 1 × 10-9 M for native laCO1 and 1-1.2 × 10-10 M for lacO1 in a saline buffer. Densitometric analysis of the gel bands from the affinity chromatography run clearly showed a significant preference for capture of the supercoiled fraction from the feed pDNA sample. The results indicate the feasibility of the affinity approach for pDNA capture and purification using native protein-DNA interaction. © 2006 Wiley Periodicals, Inc.