Sedimentation analysis of the ionic strength dependence of the tertiary structure of native DNA in solution

Abstract

SynopsisSedinieiittttioii experiments have been performed on a polydisperse bactcrid l)XAl sample over a wide range of ionic strength (8 X 10-4LV to 2.11 Ka+), at very low I1X-l coiicerit rat ions (.5-30 pglml). True sedimentat ioii const ail t disti,ibut ions were ob taiiied by careftil aiialysis of experimental data and extrapolation to iiifiuite dilution. 111 order to give a qunnt itntive description of macromolecular shape, the chaiiges of the expoiieiil. a, iii the geiierd equation, so = k,31as, have been determiiied by compitriiig aedimeiit:itioii coiistaiit distributioiis obtained at ditrereiit ioiiic strengths. a, has beeii fouiid to vary from 0.41,, at 2.lJ Kit+ to 0.200 at S X lO-4dL N:t+. ils well :is the decrease of the nieaii sedimeiitatioii constant, this result indicates a pronoiinced espaiisioii of IIPi-4 molecules with decreasing ioiiic strength. h discussion of the distiiict niechaiiisni re>poilsible for the erpaiisioii behavior of UX-4 is giveii. Furthermore, the depeiideiice of the 1Iaiidelkerir-Flory parameter p o i l ionic. strength has beeii calcrilated by cwrnbiiiiiig the ,so data with the c*ori,espoiidiiig 171 values of the sample.

Opticohydrodynamic properties of high‐molecular‐weight DNA. III. The effects of NaCl concentration

“…In any event, a saturation effect at high salt concentrations is qualitatively in accord with both theoretical expectation2 and other hydrodynamic property data. 2,31,32 Of the various theories currently available to explain polyelectrolyte chain-expansion effects,2 the thermodynamic treatment of F l 0 r 9~ agrees most closely with the data between 0.005 and 0.6M NaCl presented here. This theory predicts that the mean-square end-to-end distance (h2) = kM;0,4, where k is a constant of proportionality.…”

Neutron‐Scattering Studies of Accurately Reconstituted Nucleosome Core particles and the Effect of Ionic Strength on Core Particle Structure

“…The transition in sedimentation coefficient at this ionic strength [33] indicates a change in core particle shape which should have been detected by neutron scattering. It is known, however, that DNA itself shows a pronounced expansion on decreasing ionic strength [35] and it could be that the transition involves the core particle DNA within the 9 "/, radius of gyration change or a transition in the DNA in excess of 146 base pairs which was present in the core particles studied by Gordon et al [33]. The hydrodynamic data are influenced by changes of hydration whereas the neutron data refer to the 'dry' particle because water associated with the particle is always approximately contrast-matched : this is a second effect which might explain the fact that the higher-ionic-strength transition cannot be detected by neutron scattering.…”

Mittelwerte des Molekulargewichtes und anderer Eigenschaften

“…F fir a, # I wurde sie unabh~ingig voneinander von Kuhn (1934), Mark (1937), Sakurada (1940) (Crothers u. Zimm, 1965;Sharp u. Bloomfield, 1968). Da bei DNS f'tir kleine Molekulargewichte experimentell b,/[tI] > t gefunden wird (Crothers u. Zimm, 1965;Reinert et al, 1971), muB b~ noch eine Funktion des Molekulargewichtes sein (Sharp u. Bloomfield, 1968). Folglich mug auch gelten (Reinert, 1970) Flory (1943) (Lansing u. Kraemer, 1935), ftir a~ = -1 mit dem Zahlenmittel (Mark u. Tobolsky, 1950).…”

“…Experimentell wurden dagegen Werte von 2,27.106 (Crothers u. Zimm, 1965) und 2,39.10 6 (Reinert et al, 1971) gefunden. Der EinfluB der Ionenstarke auf den Exponenten a, bei einer polymolekularen DNS-Probe und der resultierende EinfluB auf die Konstante/3 wurde ktirzlich von Triebel und Reinert (1971) Interessant ist, dab die Kombination des Gewichtsmittels des Sedimentationskoeffizienten mit dem Staudinger-Index im Theta-Zustand (a n = 0.5) unabh~ingig vom Typ der Verteilu ng immer das Viscosiffitsmittel des Motekulargewichtes liefert (Elias und Bareiss 1967b) Wert von 3~ aus dem Exponenten a n und dem Kopplungsgrad k berechnet werden.…”