The chemical structure of amylose and amylopectin fractions of starch from tobacco leaves during development and diurnally-nocturnally.

Starches, isolated from rapidly expanding tobacco leaves four times during the day and night and once from fully expanded leaves, were fractionated with concanavalin A. From an examination of the amounts and properties of amylose, the diurnal decrease in iodine absorption of the starches on illumination appeared to be due to an increase in its branched character, and possibly the presence of unbranched polymer of low dp, combined with a decrease in the proportion of amylose fraction. The increase in apparent amylose content with age was due to an increase in the proportion of amylose. The amylose fractions at different times had only small differences in average mol size in solution and relative mol wt (M(r) near 4 x 10(5)) which were lower than those of storage organs. The average mol size in solution and relative mol wt of the amylopectins decreased during illumination, increased in darkness, and were lower (M(r) 2-2.7 x 10(6)) at all times than those from storage organs. Debranching followed by size-exclusion chromatography [on Fractogel TSK 50(S)] gave similar proportions of long, medium, and short chains for all amylopectin samples, and these proportions differed from those for debranched amylopectin from n-maize seed starch. On debranching and chromatography of the amylopectin beta-limit dextrins (which gives an estimate of the proportions of core chains) differences persisted. Structural characteristics of amylopectin from tobacco leaf starch were similar to those of normal genotypes from storage organs. The proportion of glucosyl units in core chains, the external-to-core chain ratio, and indices of compactness were calculated for a number of (1-->4)(1-->6) alpha-glucans. A plot of the index of compactness for glycogens and amylopectins showed that the decrease in compactness and the increase in total average chain length that occurs from glycogen to normal and then to amylose extender amylopectins involves a proportionate increase in average internal, external, and core chain lengths and not a selective increase in one type of chain.

Hexose-6-kinases in germinating honey locust cotyledons: substrate specificity of D-fructo-6-kinase.

Extracts of the cotyledons of germinated honey locust (Gleditsia triacanthos) seeds, which contain galactomannan as a reserve polysaccharide in the endosperm, were fractionated by chromatography and the fractions examined for the presence of a specific manno-6-kinase which could phosphorylate the D-mannose released by hydrolysis of galactomannan. One particulate hexokinase (the major hexose-6-kinase fraction) and two soluble hexokinase fractions (the minor portion), as well as a soluble fructo-6-kinase fraction, were initially separated. From chromatography, electrophoresis and kinetic studies, no evidence for a specific manno-kinase was obtained. This and the level and kinetic behaviour of the particulate hexokinase implicated it as the enzyme catalysing the phosphorylation of released D-mannose. The fructo-kinase activity was further separated into three fractions. Kinetic studies on one of these with native and synthetic substrates indicated that the structural requirements for the monosaccharide substrate were a beta-D-anomeric 2-OH in the furanose ring, a 4-OH trans to the D-5-CH2OH and a -CH2OH substituent on C2 (trans to the 5-CH2OH) which could be modified. The orientation of the hydroxyl on C-3 had only a limited effect.

Structures of the amylopectins of waxy, normal, amylose-extender, and wx:ae genotypes and of the phytoglycogen of maize.

Average chain lengths and beta-amylolysis limits have been determined for the waxy and ae/wx genotypes of mature maize starch, and for the amylopectin fractions of normal and amylose-extender starches (prepared by precipitation with concanavalin A), rabbit-liver glycogen, phytoglycogen, and waxy rice starch. All amylopectin samples had similar A:B chain ratios of > 1 and the two glycogens had ratios of < 1. This finding led to average frequencies of substitution of B chains over the whole molecule of > 2 for the amylopectins and < 2 for the glycogens. An equation for the number of tiers for a molecule with various frequencies of substitution of B chains and chain lengths has been used to determine the effect of variation in average frequency of branching and average chain length on structure.

Lateralization differences for color-naming and color-matching in men and women.

The relationship between accuracy of color-naming and color-matching in both visual fields (LVF and RVF) as a function of sex was investigated. Subjects were 19 men and 15 women who ranged in age from 18 to 32 yr. Each subject was tested on both a color-naming task and a color-matching task presented tachistoscopically. Accuracy measures for each task were obtained separately for both left and right visual fields. A two-factor analysis of variance with repeated measures on one factor followed by a t test for simple main effects showed significant right visual-field advantage for the color-naming task, a significant sex main effect for the color-matching task (in the left visual field only), and a significant interaction of sex by visual field for the matching task. Men performed in a more strongly lateralized fashion on the color-matching task than did women, supporting the notion of greater lateralization among males.

Beta-D-mannanases in germinating lucerne (alfalfa) seeds.

Extraction and fractionation of the beta-D-mannanases in germinating lucerne produced four fractions if extracts were stored prior to chromatography. However, when extracts were applied rapidly to DEAE-cellulose, one of the fractions of high molecular weight (separated subsequently by gel chromatography) was not detected, indicating that it was formed after maceration. On storage, the amount of the lower-molecular-weight, unbound fraction from chromatography on DEAE-cellulose did not increase relative to that bound. During germination, the bound and unbound fractions both increased initially and then decreased, with only small changes in the ratio of each. The results suggest that three of the beta-D-mannanase fractions are formed in vivo prior to maceration.

alpha-L-Arabinofuranosidases and beta-D-galactosidases in germinating-lupin cotyledons.

Extraction of germinating-lupin cocyledons, followed by ion-exchange and gel chromatography, gave two alpha-L-arabinofuranosidases and three beta-D-galactopyranosidases. Some fractions were further purified by using Concanavalin A-Sepharose. The changes in the activities of the enzymes during germination have been determined. Some kinetic and physical properties of these enzymes are described, and their role in the modification of cell-wall polysaccharides is discussed.