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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of radiation damage to biological specimens at water window wavelengths : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 599-600 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article reports the continuation of a series of experiments investigating the effects of soft x-ray radiation damage on the contractile elements of mammalian striated muscle (myofibrils), using their ability to contract as a functional assay. The myofibrils were exposed to 385 eV x rays. This energy is within the "water window'' between the oxygen and carbon K edges, where the x-ray absorption coefficient of biological materials, such as protein, is about an order of magnitude greater than that for water. An exposure of 8×105 photons μm−1 was found to prevent contraction in the majority of myofibrils. Preliminary results indicate that it is possible to increase this exposure level by approximately 25% by adding the radioprotective dimethyl sulphoxide (DMSO), an OH radical scavenger to the myofibril buffer during irradiation. This suggests that OH radicals are important in the inactivation of myofibrils through irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143802
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  • 2
    Electronic Resource
    Electronic Resource
    In vitro formation of a complex between cytoskeletal proteins of the human erythrocyte (1979)
    [s.l.] : Nature Publishing Group
    Nature 280 (1979), S. 811-814 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The formation of a high-molecular weight complex between spectrin and F-actin depends on the presence of a third cytoskeletal constituent, protein 4.1. Electron microscopy shows that in this ternary complex the actin filaments are linked by bridges, which have the appearance of spectrin. The ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/280811a0
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of magnesium ions on red cell membrane properties (1990)
    Springer
    The journal of membrane biology 118 (1990), S. 251-257 
    Details
    ISSN: 1432-1424
    Keywords: erythrocytes ; membrane elasticity ; micropipette ; membrane skeleton ; spectrin ; magnesium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Spectrin forms aggregates in solution when incubated at relatively high concentrations (several millimolar) of divalent cations. According to the evidence of electron microscopy, aggregates of globular appearance and, rather uniform size are cooperatively formed from spectrin dimers, no intermediate structures being seen. Inter-dimer chemical cross-linking of spectrin in intact red cell membranes is enhanced if magnesium ions at a concentration of 0.5mm or more are present. On the other hand, the elimination of magnesium from the interior of intact cells causes no significant change in shear elastic modulus, measured by micropipette assays, nor is there any dependence of membrane filtration rate on intracellular free magnesium concentration in the range 0–1mm. Magnesium-depleted cells are, however, converted into echinocytes within a short period, in which, control cells, exposed to ionophore and external magnesium ions, remain completely discoid. Magnesium-depleted cells also undergo structural, changes on heating below the temperature at which vesiculation sets in. These reveal themselves by the transformation of the cells to a unique characteristic shape, by grossly reduced filtrability, and by extensive agglutination of the cells when treated with a bifunctional reagent. Magnesium ions thus regulate the stability, but not to any measurable extent the gross elasticity, of the red cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868609
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  • 4
    Electronic Resource
    Electronic Resource
    Cointegrates are not obligatory intermediates in transposition of Tn 3 and Tn 21 (1983)
    [s.l.] : Nature Publishing Group
    Nature 305 (1983), S. 743-744 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The tnpR derivative of Tn3 that was used (Tn3.E5) was generated by insertion of an EcoRl linker into the tnpR gene3'5. Transposition was from pACYC184::Tn3.E5 recombinants to pUB307 in a recA strain. Plasmid pUB307 is transfer-proficient, while pACYC184 is not, and is not mobilized by pUB307 (see ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/305743a0
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  • 5
    Electronic Resource
    Electronic Resource
    Duplex microtubule is a new form of tubulin assembly induced by polycations (1975)
    [s.l.] : Nature Publishing Group
    Nature 257 (1975), S. 707-709 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Highly purified tubulin prepared from pig brain4 was polymerised at 37 C to form microtubules. Protamine was added at a twofold molar excess over protein, and there was an immediate increase in turbidity. The microtubules, which had the characteristic 40 A axial periodicity and 250 A diameter, were ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/257707a0
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  • 6
    Electronic Resource
    Electronic Resource
    A molecular analysis of transductional marker rescue involving P-group plasmids in Pseudomonas aeruginosa (1976)
    Springer
    Molecular genetics and genomics 143 (1976), S. 333-337 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The molecular properties of the P-group plasmids R26, R527 and R18-18 (a carbenicillin-sensitive derivative of R18) have been compared with those of RP1. R18-18 and RP1 have a MW about 38×106 daltons, and R26 and R527 of 52×106 daltons (determined from contour lengths). All three plasmids have a buoyant density similar to that of RP1 (1.719 g/cm3, 60% G+C). From their molecular and phenotypic similarities, these plasmids probably represent two pairs of identical or closely similar elements. Resistant bacteria are not recovered following F116L-mediated transduction of R26 (or R527), and this correlates with the plasmids' larger size (phage genome=40×106 daltons). Fragments of R26 are, however, transduced and their resistance determinants may be “rescued” by recombination if the recipient harbours R18-18. Such events are accompanied by an increase in the size of the recipient plasmid from 38×106 to 52×106 daltons following inheritance of the resistance determinants Sm Su Gm Hg, but not Cb. Thus, Sm Su Gm Hg are encoded in a DNA segment of MW about 14×106 daltons which apparently has no homologous region on R18-18. Since a piece of DNA of this MW also corresponds to the difference in size between R26 and R18-18, it is possible that the former is derived from an RP1-like element which has acquired these additional resistance determinants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269412
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  • 7
    Electronic Resource
    Electronic Resource
    The stable carriage of two TnA units on a single replicon (1978)
    Springer
    Molecular genetics and genomics 160 (1978), S. 339-346 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Bacterial plasmids which contain a copy of TnA are refractory to the uptake of a second by transposition. However plasmids containing two such copies can be constructed by in vitro recombination techniques. Some plasmids containing two copies of TnA have been obtained by conventional transposition, but in all cases they arose by the virtually simultaneous insertion of both units into a replicon that carried no TnA. All stable plasmids containing two copies of TnA carried the transposons in opposite orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332978
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  • 8
    Electronic Resource
    Electronic Resource
    Isolation and characterisation of deletion mutants involving the transfer genes of P-group plasmids in Pseudomonas aeruginosa (1976)
    Springer
    Molecular genetics and genomics 149 (1976), S. 211-216 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The P-group plasmids RP1 and R26 are recovered at low frequency following conjugal transfer to B3-lysogens of P. aeruginosa PAO. The rare carbenicillin-resistant transcipients that do arise are usually transfer-defective (Tra-) and may show the loss of other plasmid borne functions, namely kanamycin-resistance (Kmr) and reduced plating of phage GlOl (Spp+). The four phenotypic classes that occur among the Tra- derivatives are respectively, Tra- (69–81%), Tra- Spp- (12–30%), Tra- Kms and Tra- Kms Spp- (0.2–1%), of which the latter three are due to plasmid deletions. This is seen from the sizes of the plasmids carried by these bacteria and from the transductional analysis of the R26-derivatives. Thus, although R26 (MW=52×106 daltons) is too large to be transduced by phage F116L (MW=40×106), this is possible for its Tra- Kms and Tra- Kms Spp- derivatives. The phenotypes and frequencies of the various transcipient classes suggests that the gene order Km..Tra..Spp occurs in both RP1 and R26, and that Spp is more closely linked to Tra than is Km. These conclusions are supported by the sizes of the plasmid mutants since deletions spanning the loci Km Tra Spp, Km Tra, and Tra Spp involve the loss of DNA of MW 8-17×106, 5-13×106 and 1-9×106 daltons respectively. Whilst all the transcipients displayed the incompatibility properties of the parent plasmids (Inc+), only some retained plasmid surface exclusion (Sfx+). Moreover, a strict correlation existed between the Sfx and Spp phenotypes such that the transcipients were either wild type, Sfx- Spp-, or displayed an intermediate phenotype for both characters. This suggests that these phenotypes are controlled by closely linked genes or are different manifestations of the same gene function. The deletion map of these various markers in both RP1 and R26 therefore seems to be Km..Tra..Sfx/Spp..Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332891
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  • 9
    Electronic Resource
    Electronic Resource
    The properties of hybrids formed between the P-group plasmid RP1 and various plasmids from Pseudomonas aeruginosa (1976)
    Springer
    Molecular genetics and genomics 149 (1976), S. 217-223 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary R38, R931-1, and R933 are conjugative plasmids derived from strains of Pseudomonas aeruginosa. They confer resistance to mercuric ions (Hg-r), and do not transfer from P. aeruginosa to Escherichia coli at detectable frequencies. Hybrids between each of these plasmids and the P-group plasmid, RP1, have been detected among the rare Hg-r transconjugants arising from matings of P. aeruginosa PAO donors (RP1+ R+) and E. coli K12 recipients. Two independently isolated hybrid plasmids from each of the three mating combinations have been studied. All were found to confer the entire marker phenotype of RP1, but only the Hg-r phenotype of their second parent. Moreover, all were larger than RP1 but comprised only two groups of sizes; those increased by about 14×106 daltons (the RP1/R38 hybrids), and those increased by about 30×106 daltons (the RP1/R931-1 and RP1/R933 hybrids). The hybrid plasmids were all too large to be transduced intact by phage F116L, but transduction of fragments was possible. Thus, the determinants for both carbenicillin-resistance (Cb-r) (from RP1) and mercuric-ion-resistance could be “rescued” by recipients that already carried an RP1-like plasmid and were recombination-proficient. A molecular analysis of the plasmids recovered from such transductants suggested that each of the parental hybrids was comprised of an entire RP1 genome into which a fragment of heterologous DNA had been inserted. In similar experiments in which the recipient carried a derivative of R931-1, the Hg-r but not the Cb-r determinant could be rescued. This suggested that R38, R931-1, and R933 shared sufficient homology in the region of the mer gene for recombination to occur between them. The reason for the inability to rescue the Cb-r determinant was also investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332892
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  • 10
    Electronic Resource
    Electronic Resource
    Characterisation of Tn501, a transposon determining resistance to mercuric ions (1978)
    Springer
    Molecular genetics and genomics 159 (1978), S. 101-106 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The transposon encoding resistance to mercuric ions, Tn501, is 5.2 (±0.1)×106 daltons and is bounded by small inverted repeats. The restriction sites for the restriction endonucleases EcoRI, HindIII and SalGI have been mapped on the element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401753
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