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111.
Cell-free extracts ofAnacystis nidulans were fractionated by discontinuous sucrose density gradient centrifugation resulting in the separation of two distinct types of membranes, the heavier one containing the chlorophyll and the lighter one devoid of chlorophyll. Identity of the latter with plasma membrane was confirmed by labeling of intact cells with impermeant marker,35S-diazobenzenesulfonate, prior to cell disruption. Both membrane fractions were purified individually by repeated recentrifugation on identical gradients. Purified membranes were subjected to dissociating polyacrylamide gel electrophoresis, either type of membranes yielding a distinct polypeptide pattern. After transfer of the polypeptides to nitrocellulose by Western blotting, two of the proteins, with molecular weights of approximately 55,000 and 32,000, respectively, gave strong and specifically complementary cross-reactions with antibodies raised against subunits I and II of the aa3-type cytochrome oxidase fromParacoccus denitrificans. The findings will be discussed in terms of the presence of aa3-type cytochrome oxidase in both plasma and thylakoid membranes ofAnacystis nidulans. 相似文献
112.
113.
Matilde Jose Isabelle Tratner Maryse Poiret Jean-Louis Nahon Jean-Louis Danan Jose Maria Sala-Trepat 《Molecular & general genetics : MGG》1989,215(2):225-230
Summary The distribution of middle repetitive sequences in the genic and extragenic regions of the rat albumin and -fetoprotein genes was analyzed. Their presence was determined by probing Southern blots of restriction fragments of albumin and -fetoprotein genomic subclones with 32P-labeled total rat DNA. Repetitive sequences were detected in both genes. They were classified as weak, moderate and intense hybridizing elements according to the intensity of hybridization. Weak repetitive sequences were characterized as dG·dT repeats by using 32P-labeled poly-(dG·dT)(dC·dA) oligomer probe. They occurred in 5 and 3 extragenic regions of the two genes and in introns 4 and 5 of the albumin gene. The moderate repetitive sequence present in intron 6 of the albumin gene was identified as the rat SINES element, 4D12. The intense repetitive sequence, localized in the 3 non-coding region of the albumin gene, corresponded to the terminal segment of a rat high repeat long interspersed DNA family, L1Rn. 4D12 and L1Rn sequences were also scattered throughout the -fetoprotein locus as moderate and intense repetitive elements, respectively, but their distribution was different from that of the albumin genomic region. These results indicate that repetitive sequences invaded the two loci in a non-conservative manner. 相似文献
114.
De novo root formation in thin cell layers of tobacco: changes in free and bound polyamines 总被引:4,自引:0,他引:4
Patrizia Torrigiani Maria Maddalena Altamura Francesca Capitani Donatella Serafini-Fracassini Nello Bagni 《Physiologia plantarum》1989,77(3):294-301
Thin cell layers excised from tobacco ( Nicotiana tabacum L. cv. Samsun) stem internodes, with an appropriate exogenous hormonal balance, were able to form a greater number of roots, and in a larger percentage of the explants (93%) than when they were excised from pedicels (40%). The developmental sequence of root formation and explant growth were followed by histological analysis. Free and bound [trichloroacetic acid (TCA)-soluble and -insoluble] putrescine and spermidine increased in the explants, particularly when root meristemoids appeared. These meristemoids originated in the superficial (day 6 in culture) or deep (days 10–11) layers and inside the newly formed callus (day 25). At those times, TCA-soluble and, to a lesser extent, TCA-insoluble bound putrescine predominated over the other polyamines. Spermine was always present in trace amounts. Polyamines decreased again when root and callus formation was completed (day 30). The involvement of these three classes of polyamines (free, TCA-soluble and -insoluble) in morphogenic processes is discussed. 相似文献
115.
116.
Maria C. Nieto Elizabeth S. Song Denise McKinney Minnie McMillan Robert S. Goodenow 《Immunogenetics》1989,30(5):361-369
We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association
of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2Ld molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural
alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the
helical region of the alpha-1 domain. H-2Ld class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase
of 34-1-2 cross-reactivity following exchange with human B2m. The H-2Ld hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2Ld molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant
from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human
B2m with H-2Ld can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association
of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability
of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor. 相似文献
117.
118.
Hydrolysis of sunflower oil by means of hydrophobic membrane with lipolytic activity 总被引:3,自引:0,他引:3
Magdalena Rucka Bozena Turkiewicz Maria Tomaszewska Nikodem Chlubek 《Biotechnology letters》1989,11(3):167-172
Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m2 of the membrane area and the half-life time was calculated to be 7 days. 相似文献
119.
Douglas M. Templeton Anna Paudyn Andrew D. Baines 《Biological trace element research》1989,22(1):17-33
Interest in the biological behavior of a growing number of elements, along with increasing recognition of the importance of interactions among them, demands a versatile and reliable technique for multielement analysis of biological samples. Significant improvements over the sensitivity achieved with conventional inductively coupled plasma (ICP) optical emission spectrometries have been realized with the introduction of quadrupole mass spectrometry (MS) for detection of ions in the plasma. The hybrid technique of ICP-MS promises to be a method of rapid multielement analysis, at detection limits that approach or surpass those of other technologies. However, the application of ICP-MS to analyses of biological interest is truly in its infancy. Here we report the use of ICP-MS for the determination of more than 30 elements of biological interest in a tissue and a biological fluid (rat liver and serum, respectively). Experimental values of the elements serve as a basis for discussion of analytical protocols, performance criteria, and certain problems peculiar to ICP-MS. 相似文献
120.
Silvio De Flora Domizio Serra Anna Camoirano Patrizia Zanacchi 《Biological trace element research》1989,21(1):179-187
At variance with Cr(III), Cr(VI) compounds easily cross cell membranes and exert genotoxic effects. No metabolic oxidation of Cr(III) could be detected, whereas Cr(VI) reduction was observed in the presence of body fluids and subcellular fractions of various tissues from several animal species. The differential efficiency of this process may account for the selection of target tissues in Cr(VI) carcinogenesis. For instance, reduction by saliva and gastric juice may explain a lack of carcinogenicity by the oral route; reduction inside erythrocytes may explain a lack of carcinogenicity at a distance from administration sites; reduction by the epithelial-lining fluid of terminal airways and by alveolar macrophages may be consistent with the occurrence of thresholds in lung carcinogenesis. Liver preparations displayed the top efficiency in reducing Cr(VI), whereas skeletal muscle, i.e., a typical target in experimental Cr(VI) carcinogenesis, had no detectable activity. Bronchial tree and peripheral lung parenchyma preparations from almost 100 individuals reduced Cr(VI) to a variable extent. The efficiency of lung parenchyma and of isolated alveolar macrophages was enhanced in cigarette smokers. In rats, Cr(VI) reduction by lung preparations was significantly stimulated by the repeated i.t. instillation of Cr(VI) itself. Among the electron donors (chiefly GSH) and enzymatic mechanisms responsible for the intracellular Cr(VI) reduction, such as cytochrome P-450 reductase, glutathione redactase, and aldehyde oxidase, an important role can be ascribed to cytosolic DT diaphorase activity, usually catalyzing a 2-electron reduction. 相似文献