A method for the separation of nucleotides by concave gradient elution

The Accumulation of Nucleotides by Escherichia coli Strain 26-26

“…The other elution system was a modification of the concave chloride gradient described by Pontis & Blumsom (1958) using a column (0.9 x 50 cm.) of Dowex-1 x 2 (200-400 mesh).…”

“…were collected at a rate of 0.5 ml./min. The fractions containing each nucleotide peak were pooled, concentrated and the calcium chloride removed as described by Pontis & Blumsom (1958).…”

RADIOAUTOGRAPHIC LOCALIZATION OF DEOXYTHYMIDINE TRIPHOSPHATE IN TRADESCANTIA POLLEN GRAINS DURING DNA SYNTHESIS

“…This spreading was apparently due to leaching of dTTP-3H into the emulsion which contains some water and hence acts as an aqueous extractant. A number of attempts were made to reduce this spread of label: (1) evaporation of a carbon film onto the dried pollen grains on slides before dry-looping at room temperature, in order to interpose a thin hydrophobic layer of carbon between the pollen grains and the aqueous emulsion (Rossi and Baic, 1964); (2) treating the pollen grains with Ca + + in cold ethanol before drying them down on slides, in order to precipitate the dTTP-3H in situ as the calcium salt and thus reduce diffusion (Pontis and Blumson, 1958); (3) freezing the dry-looped emulsion on slides and then applying pollen grains in a xylene suspension onto this emulsion at -20'C, in the dark in a cryostat, with subsequent exposure at -100 0 C (Appleton, 1964); () exposure at -I 00°C after routine application of dry loops at room temperature onto the dried pollen grains on slides. The last two procedures were also intended to reduce diffusion.…”

The fractionation of phosphate esters on ion-exchange resin by a new system of pH-gradient elution

“…The separation of some of these nucleotides has been described by Hurlbert et al (1954) in a discontinuous form of gradient elution and also by Pontis & Blumson (1958). Eluent volume (1.)…”

“…The separation -of very dissimilar phosphates is greatly simplified bychnging the composition of the eluent continuously, e.g. Hurlbert, Schmitz, Brumm & Potter, 1954;Pontis & Blumson, 1958. A disadvantage of such systems is that the useful range of conditions is usually very limited and sometimes necessitates a discontinuous change in the elution programme (Hurlbert et al 1954).…”