Gel filtration and disc gel electrophoresis of tomato pectic substances

Abstract

STEIN, BROWNcesses and eluent volume should be an important factor influencing its displacement.Increasing eluent volume from 25 to 50 ml significantly increased thiamine recovery (mean recovery increased from 90 to 97.5%) and decreased the standard deviation from 2.15 to 1.53 (Table V). Hence, eluent volume is an important factor affecting both the quantity and reproducibility of thiamine recovery from Decalso.Elution to 50 ml requires more reagent and time than for 25 ml. However, the acid-KC1 eluent is not expensive so time is the more important consideration. It averaged 15.9 min longer (about 29% longer) per column to elute to 50 ml than to 25 ml (Table VI). However, the additional time is not cumulative when 6-12 columns are run a t once.Hence, for maximum precision and accuracy in the thiochrome method the important effects of eluent temperature and volume on thiamine recovery from Decalso must be recognized and controlled. Both factors could cause inaccuracy when sample extracts are purified on Decalso by hot elutions on unthermostated columns to 25-ml eluent volume. The nearly quantitative recovery of thiamine possible on unthermostated columns by hot elution to 50 ml suggests a standard curve may now be used in the thiochrome method instead of standards run for every set of determinations as is now generally recommended.

Comparison of the Conformation of Tomato Pectins With Apple and Citrus Pectins

“…In that case the weight average molecular weights would range from approximately 7 x lo5 to 5 x lo6. These values would then be consistent with those obtained by Stein and Brown (1975).…”

“…In that case the weight average molecular weights would range from approximately 7 x lo5 to 5 x lo6. These values would then be consistent with those obtained by Stein and Brown (1975).Fishman et al. (1984) showed that the radii of gyration of pectin molecules were significantly affected by the degree of methylation, with 57% being an o p timal value where steric hindrance would prevent further aggregation.…”

“…The weight average molecular weights of tomato pectins in pH 4.6 citrate phosphate buffer were again relatively similar ranging in value from 3 x 106 to 5.5 x lo6. The measured molecular weights are somewhat larger than those reported in the literature earlier by Stein and Brown (1975) whose values were in the range of 2 X los. The difference could have occurred from the lack of use of the universal calibration curve by Stein and Brown (1975), which involves a semi-logarithmic plot of [q]Mw versus elution volume.…”

“…However, Thibault and Rinaudo (1986) found that monovalent cations caused a decrease in viscosity, the degree of which was greater with decreasing DE. Addition of salts of di-and tri-valent cations had the op posite effect.Tomato pectic substances extracted according to their solubility in water, 0.2% ammonium oxalate, 0.05N hydrochloric acid and 0.05N sodium hydroxide were found to be highly polydisperse, with the majority having a molecular weight of 2 X lo5 using gel filtration (Stein and Brown 1975) . Luh et af.…”

“…Tomato pectic substances extracted according to their solubility in water, 0.2% ammonium oxalate, 0.05N hydrochloric acid and 0.05N sodium hydroxide were found to be highly polydisperse, with the majority having a molecular weight of 2 X lo5 using gel filtration (Stein and Brown 1975) . Luh et af.…”