elektrostatisch positiv geladene R eaktionskom po nente fu n g iert und eine H äm ag g lu tin atio n durch V irus dann zustande kom m t, w enn die folgenden V oraussetzungen erfüllt sin d :1. D er IE P des Virus ist so gelagert, daß in dem fü r die T iterbestim m ung üblichen pn-Bereich eine relativ hohe negative L ad u n g erw artet w erden kann.2 . D ie Lage des IE P s d er Erythrocyten bzw. Zellreceptoren g ara n tiert einen m öglichst geringen Ü berschuß an negativer L ad u n g im M eßbereich, der durch E lektrolyt-K ationen w eitgehend abgeschirm t w ird.3. D ie H A -hem m ende W irkung von In h ib ito ren ist ausgeschaltet, m öglicherweise durch V erd rän g u n g dieser Substanzen durch stärk er positiv geladene E rythrocyten, durch die W ahl eines günstigen pH-Wertes des R eaktionsm ilieus oder durch irre v er sible Inaktivierung.Es ist beabsichtigt, die Versuche u n te r diesen Ge sichtspunkten fortzusetzen und es soll zunächst auch besonders der 0 -D -Phasenw edisel im H inblick auf die physikalisch-chem ischen V oraussetzungen fü r das Z ustandekom m en d er H A untersucht w erden.
A nucleoprotein of a vitrous consistency was extracted from the gonads of the coalfish ( Gadus virens).The preparation of deoxyribonucleic acid (DNA) from this nucleoprotein and from staphylococci is described. Both of these different kinds of DNA have been mixed with bovine serum albumin or cytochrom c respectively to produce solutions which subsequently were spread onto the Langmuir trough under defined conditions. After transfer of aliquots from the surface monolayers to carbon support films the preparations were examined with the electron microscope. The micrographs show threads of various lengths, partly stretched, partly folded in loops, consisting of DNA molecules embedded in a protein envelope.Measurements and calculations of 5900 particles of the complex of Gadus w'rercs-DNA-Albumin, with relatively short threads show a distribution of discontinuous character. If length is plotted against number then it occurs that there are maxima of different lengths of threads. The abscissae of these maxima obey the ratio 1 : 2 : 4 : 8. This holds for longer threads too the maxima of which, however, have smaller ordinate values.Bei der C harak terisieru n g von D N S-M olekeln tritt die F rag e auf, wieweit bei einer E n tfern u n g von Begleitstoffen und kom plex gebundenen A nteilen im V erlauf der P rä p a ra tio n die In te g ritä t der M ak ro m oleküle gestört w ird. T reten Ä nderungen im p h y si kalisch-chemischen Z ustand auf. so w ird das m eist auch eine Ä nderung der F u nktion bedeuten. Dies hat Z a m e n h o f 1 am Beispiel des tran sfo rm ieren d en
Experiments were carried out to test the hypothesis that fibronectin is involved in reaggregation of dissociated sponge cells. Cells from the siliceous sponge Geodia cydonium were extracted with urea to solubilize fibronectin from cells of higher multicellular organisms. The crude extract was further fractionated by DNA, heparin, and collagen affinity chromatography; they were termed Geodia fibronectin like fractions. The fibronectin like fractions contained a series of proteins with molecular weights different from that of the genuine fibronectin. The Geodia fibronectin like fractions did not react with antiserum, produced against human fibronectin, under formation of a precipitin line. Using this antiserum the sponge cells could not be specifically labeled with FITC-anti-IgG antiserum. Radioimmunoprecipitation experiments revealed that the Geodia fractions contain--if at all--0.1% fibronectin or fibronectin like protein at the most. In the crucial experiments it was shown that the Geodia fibronectinlike fractions, human fibronectin, and antifibronectin antiserum exerted no influence on adhesion of Geodia cells either in the absence or in the presence of the soluble aggregation factor. Based on these findings, we conclude that fibronectin is apparently not present on Geodia cells and does not play a role in aggregation of this biological system.
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