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  • 1
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    Reprogramming control of an allosteric signaling switch through modular recombination (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-09-27
    Description: Many eukaryotic signaling proteins are composed of simple modular binding domains, yet they can display sophisticated behaviors such as allosteric gating and multi-input signal integration, properties essential for complex cellular circuits. To understand how such behavior can emerge from combinations of simple domains, we engineered variants of the actin regulatory protein N-WASP (neuronal Wiskott-Aldrich syndrome protein) in which the "output" domain of N-WASP was recombined with heterologous autoinhibitory "input" domains. Synthetic switch proteins were created with diverse gating behaviors in response to nonphysiological inputs. Thus, this type of modular framework can facilitate the evolution or engineering of cellular signaling circuits.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dueber, John E -- Yeh, Brian J -- Chak, Kayam -- Lim, Wendell A -- New York, N.Y. -- Science. 2003 Sep 26;301(5641):1904-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Program in Biological Sciences, University of California, San Francisco, CA 94143-2240, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14512628" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/metabolism ; Allosteric Regulation ; Amino Acid Motifs ; Animals ; Combinatorial Chemistry Techniques ; Evolution, Molecular ; Ligands ; Male ; Nerve Tissue Proteins/*chemistry/genetics/*metabolism ; Oocytes/metabolism ; Peptide Library ; Protein Engineering ; Protein Structure, Tertiary ; Recombinant Fusion Proteins/chemistry/metabolism ; Recombination, Genetic ; *Signal Transduction ; Wiskott-Aldrich Syndrome Protein, Neuronal ; Xenopus ; cdc42 GTP-Binding Protein/metabolism ; src Homology Domains
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
    Electronic Resource
    Electronic Resource
    In Situ Study of Single Aqueous Droplet Solidification of Ceramic Precursors Used for Spray Pyrolysis (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The electrodynamic balance (EDB) is demonstrated to be useful for the in situ study of aqueous droplet solidification. We have used an EDB to study the solidification of solution droplets used for ceramic powder synthesis by spray pyrolysis. The mass change and the elastic light scattering of the drying 20 μm solution droplets were monitored. We found that aqueous MgCl2 droplets crystallize but Mg(COOCH3)2, MgSO4, ZrO(OH)Cl, and Zr(COOCH3)4 droplets appear to form gels at high concentrations. As a result of the gel formation, the rate of loss of water from the droplets can be reduced by approximately 150 times and drying is limited by solute diffusion in the gel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02384.x
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  • 3
    Electronic Resource
    Electronic Resource
    Thermodynamic Properties of Aqueous (NH4)2SO4 to High Supersaturation as a Function of Temperature (1995)
    s.l. : American Chemical Society
    Journal of chemical & engineering data 40 (1995), S. 1079-1090 
    Details
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/je00021a011
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Calcination on the Microstructures and Photocatalytic Properties of Nanosized Titanium Dioxide Powders Prepared by Vapor Hydrolysis (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ultrafine titanium dioxide powders are produced in an aerosol reactor using vapor hydrolysis of titanium tetraisopropoxide (TTIP) at 260°C and higher temperatures (600°, 700°, 800°, and 900°C). The effect of calcination on the microstructure characteristics and the photoactivity is studied. The powders are characterized using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses. The photocatalytic activity of the powders is also studied using degradation of phenol in water as a test reaction. The powder produced at 260°C is calcined at 500° to 900°C while those produced at higher temperatures are calcined at 600°C for 3 h. Raw powder produced at 260°C is amorphous but becomes crystalline after calcination. As the calcination temperature increases, the surface area decreases but the rutile-to-anatase ratio and the anatase and rutile crystallite sizes increase. The photoactivity increases as calcination temperature increases to 900°C, when the powder becomes densified and the surface area drops significantly because of sintering. Powders produced at higher temperatures are predominantly anatase and are generally more photoactive. Calcination of the powders at 600°C for 3 h results in little loss of surface areas and enhances the photoactivity. Among the factors examined, large surface area and good dispersion of the powders in the reaction mixture are favorable to photoactivity. Conversely, prolonged calcination at high temperatures is detrimental to photoactivity. However, surface area, crystallite size, anatase-to-rutile ratio, and dispersity of the powders alone cannot account for the observed trend of photoactivity. The role of crystallinity needs to be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01802.x
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  • 5
    Electronic Resource
    Electronic Resource
    Study of the Hygroscopic Properties of Selected Pharmaceutical Aerosols Using Single Particle Levitation (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 1104-1109 
    Details
    ISSN: 1573-904X
    Keywords: hygroscopic property ; water activity ; particle growth ; atropine sulfate ; isoproterenol hydrochloride ; isoproterenol hemisulfate ; disodium cromoglycate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To use a single particle levitation technique to investigate the equilibrium water sorption characteristics in both the evaporation and growth of four respiratory drugs at 37°C: atropine sulfate (AS), isoproterenol hydrochloride (IPHC) and isoproterenol hemisulfate (IPHS) and disodium cromoglycate (DSCG). Methods. The equilibrium water content was measured as a function of relative humidity (RH) by a single particle levitation technique using an electrodynamic balance (EDB). The change of water content was determined by the voltage required to balance the weight of the levitated particle electrostatically. The water activities of bulk samples were also measured. Growth ratios were determined and compared with values in the literature. Results. Crystallization or deliquescence was not observed for AS, IPHC and IPHS. The hysteresis in the water cycle was not observed for any of the drugs. At RH ∼ 0%, AS particles still contain about 5% water but IPHC and IPHS particles do not contain any residual water. The aerodynamic growth ratio from RH 0% to 99.5% is 2.60, 2.86, 2.42 and 1.26 for AS, IPHC, IPHS and DSCG, respectively. Super- saturated droplets of IPHC and IPHS are expected to exist in the am- bient conditions. DSCG is in a solid state in the RH range of 10-90%. Conclusions. It is expected that some aerosolized drugs of low solubility may experience supersaturation before they enter the human body and this could exert a significant influence both on particle loss before inhalation and on the deposition of the drugs in the lungs. The EDB is a convenient and reliable tool for studying the hygroscopic properties of pharmaceutical aerosols, especially for supersaturated solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026409813779
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  • 6
    Electronic Resource
    Electronic Resource
    Study of Hygroscopic Properties of Aqueous Mixtures of Disodium Fluorescein and Sodium Chloride Using an Electrodynamic Balance (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 1171-1175 
    Details
    ISSN: 1573-904X
    Keywords: electrodynamic balance ; single particle levitation ; water activity ; hygroscopic aerosol growth ; disodium fluorescein ; sodium chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purposes of this study are: a) to demonstrate the use of an Electrodynamic Balance (EDB) to investigate the hygroscopic properties of pharmaceutical aerosols; and b) to evaluate the applicability of the Zdanovskii-Stokes-Robinson model (ZSR) in the associated data analysis with multicomponent pharmaceutical aerosols. Methods. The compositional dependence of the water activity of two model materials commonly employed in the study of pharmaceutical aerosols, namely, NaCl and Disodium Fluorescein(DF), was investigated using an EDB. The water contents of single levitated droplets of NaCl and DF and their mixtures at mass ratios of 1:3, 1:1, 3:1, and 6:1 from dilute concentration to high supersaturation were determined as a function of relative humidity (RH). Results. At decreasing ambient RH, supersaturated aqueous NaCl droplets lose water and crystallize to form dry solid particles at an RH of ~50%. Aqueous DF droplet continues to lose water until it reaches a final state containing about 20% by mass of residual water. Mixed solutions of DF and NaCl crystallize at an RH of ~50% and then continue to lose water at lower RHs. The resulting 'dried' particle still contains water whose amount depends on the mass ratios of DF and NaCl in the mixture. Good prediction of water activity of the DF-NaCl mixture can be achieved with the ZSR model. Collection of a full set of water activity-composition data at each mass ratio of DF-NaCl requires only a few hours. Conclusions. The EDB, together with the application of the ZSR model in data treatment, appears to be a valuable tool for studying the hygroscopic properties of pharmaceutical aerosols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012146621821
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  • 7
    Electronic Resource
    Electronic Resource
    Two overlapping SOS-boxes in ColE operons are responsible for the viability of cells harboring the Col plasmid (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 407-411 
    Details
    ISSN: 1617-4623
    Keywords: Key words Colicin E7 ; SOS box ; Oligonucleotide-directed site specific mutagenesis ; LexA binding motif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In this study, oligonucleotide-directed site-specific mutagenesis was used to change the consensus sequences of the LexA binding motifs in either one of the two SOS-boxes of the ColE7 operon. The results indicated that both mutants produced larger amounts of colicin than cells harboring the wild-type ColE7 plasmid. This finding would imply that two biologically functional SOS boxes exist in the ColE7 operon. In the non-induced state, no lysis of cells harboring wild-type plasmids occurred at 37° C, whereas, cells harboring recombinant plasmids containing either one of the mutated SOS boxes underwent lysis within 100 min under the same conditions. This result indicated that adaptation of two SOS boxes of the ColE operon would obviously tightly control the expression of ColE operons. In such a way that it may prevent excessive expression of the lysis (cel) gene, thus safeguard the host cells from being lysed in ordinary living conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172368
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  • 8
    Electronic Resource
    Electronic Resource
    Mapping of transcriptional start sites of the cea and cei genes of the ColE7 operon (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 477-481 
    Details
    ISSN: 1617-4623
    Keywords: Colicin E7 ; cea gene ; cei gene ; Promoter ; Transcriptional start site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two transcriptional start sites were identified 77 and 78 nucleotides upstream of the translation initiation codon of the colicin E7 gene (ceaE7). The guanosine nucleotide located at the fifth position of the SOS box is probably a universal transcriptional start site of all E group colicins. Major and minor transcripts of the immunity gene (cei) are initiated at the 3′ end of the cea gene. Relative to the −10 sequence, CAAAAT, of the major ceiE7 promoter, the corresponding region of the cei gene of other E group colicins has an increased content of guanosine nucleotides. However the −10 sequence of the minor ceiE7 promoter, TATGAT, was found to be conserved in other colicin promoters. The results indicate that the structure of the major promoter of the ceiE7 gene is unique among the E group colicins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280479
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  • 9
    Electronic Resource
    Electronic Resource
    Two overlapping SOS-boxes in ColE operons are responsible for the viability of cells harboring the Col plasmid (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 407-411 
    Details
    ISSN: 1617-4623
    Keywords: Colicin E7 ; SOS box ; Oligonucleotide-directed site specific mutagenesis ; LexA binding motif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study, oligonucleotide-directed site-specific mutagenesis was used to change the consensus sequences of the LexA binding motifs in either one of the two SOS-boxes of the ColE7 operon. The results indicated that both mutants produced larger amounts of colicin than cells harboring the wild-type ColE7 plasmid. This finding would imply that two biologically functional SOS boxes exist in the ColE7 operon. In the non-induced state, no lysis of cells harboring wild-type plasmids occurred at 37°C, whereas, cells harboring recombinant plasmids containing either one of the mutated SOS boxes underwent lysis within 100 min under the same conditions. This result indicated that adaptation of two SOS boxes of the ColE operon would obviously tightly control the expression of ColE operons. In such a way that it may prevent excessive expression of the lysis (cel) gene, thus safeguard the host cells from being lysed in ordinary living conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172368
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of calcination on the microstructural characteristics and photoreactivity of Degussa P-25 TiO2 (1999)
    Springer
    Journal of materials science 34 (1999), S. 1523-1531 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Changes in the microstructural characteristics of Degussa P-25 titania as a result of calcination have been studied using XRD, BET and TEM. The photocatalytic activities of the samples were also examined using the degradation of phenol as a model reaction. The results indicate firstly that calcination significantly affects both microstructural characteristics and photoactivity and secondly that there is an apparent relationship between photocatalytic activity and certain microstructural characteristics. Over the range of calcination temperatures and durations studied, the sample calcined at 923 K for 3 hours revealed the highest photoreactivity, which can be ascribed to an improvement in crystallinity on calcination. The increase in the rutile content and grain growth caused by the calcination at higher temperatures were observed to decrease the photocatalytic activities of the TiO2 samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004560129347
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