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The DMSO molecule behaves as a zwitterion having a n electrostatic charge density on its oxygen atom comparable to that of the fluoride ion. Therefore the DMSO anion interacts with water to form an A-region having two water molecules, i.e., a DMSO.2H2O complex a t 66% DMSO. Studies on amylose and amylopectin show that DMSO.2H2O as well as anhydrous DMSO help to stabilize the helix structure of amylose and amylopectin. Because this helix structure is absent in dextran and hydroxyethyl cellulose, their properties in DMSO/water solutions are different from those of starch. The proposed model for the interaction of DMSO or hydrated DMSO with the starch helix shows how these molecules stabilize the helix by interacting with only one hydroxyl group of the C-2 and C'-3 hydrogen bonded hydroxyl groups. The a-helix of amylose and amylopectin is more stable at acid p H values of 90 and 100 yo DMSO solutions than alkaline values because of the formation of the (CH,),S+-OH cation. The hydroxyl group of this cation salts-out the hydrogen bonds just as the case of the hydrated A-regions of Li+ and Na+ cations. Optical rotation studies show that the addition of hydrated Na+ ions also stabilizes the a-helix just as a decrease in apparent pH. The greater stability of the helix in these DMSO solutions predicts that its average segment length will also increase. The decrease in the corrected specific rotation of am)lose in going from water to DMSO solutions is most likely due to an increase in the thermal motion of the amylose rather than any decrease in the helix stability. The DMSO disperses starch because, unlike the hydrogen bonds in the helix, both of the hydrox>l groups involved in intermolecular hydrogen bonds can become complexed to DMSO anions. The lower pK of such intermolecular hydrogen bonds also allows alkali in DMSO to increase the dispersion power of DMSO. Salt (NaCI) decreases the dispersion power of DMSO because of the formation of interchain linkages through the unhydrated C1-ion. The (CH,),S+-OH cation increases the dispersion power of DMSO by favoring the formation of those hydrogen bonds involved in the helix. ZUSAMMENFASSUNG:Das DMSO-Molekul verhalt si-h als Zwitterion und tragt am Sauerstoffatom eine elektrostatische Ladungsdichte, die mit der des Fluoridions vergleichbar ist. Daher reagiert das DMSO-Anion mit Wasser und bildet eine A-Region mit zwei Wassermolekiilen, d. h., einen DMSO ' Stability of the Helix of Amylose and Amylopectin in DMSO and H,O Solutions Helixstruktur von Amylose und Amylopektin stabilisieren. Da diese Helixstruktur in Dextran und in Hydroxyathylcellulose fehlt, sind die Eigenschaften dieser Verbindungen in DMSO/Wasser-Losungen von denen der Sttirke verschieden. Das vorgeschlagene Modell fii die Wechselwirkung von DMSO oder hydratisiertem DMSO mit der Starke-Helix zeigt, in welcher Art diese Molekiile die Helix stabilisieren; es tritt dabei nur eine der durchWasserstofiriicken verbundenen Hydroxylpppen am C-2 und C'-3 in Wechselwirkung.Die a-Helix von Amylose und Amylopektin ist bei s...

nisms produce a glycogen precursor and both are dependent upon ADPGlu pp. The initial higher radioactivity of amylose and the constant yield of amylose can be explained by a three or four day biosynthesis of this glycogen, followed by the removal of the glycogen's exterior branches by debranching enzymes to produce amylose and amylopectin. These removed branches are first degraded (using SSS I and II) to ADPGlu, which is the only source of ADPGlu for amylose synthesis. The retention of the polymodal behavior of debranched amylopectin in going from Bomi to shx barley amylopectins is most likely due to a change from phosphorylase to SSS II since both debranched amylopectins produce Poisson distributions.

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Amylopectin samples were obtained from mature and immature sweet, dent, and waxy varieties of corn starch samples by dispersing the starch samples with either 6 M LiBr or bufered amyl alcohol solutions. The degree of branching, molecular weights, and radii of gyration were obtained on these amylopectins. The results were explained assuming that Erlander's proposed mechanism for the synthesis of starch from glycogen is valid. The corn amylopectins and an immature sweet corn glycogen sample obtained from Schoch were hydrolyzed at a pH of 4.2 at the refluxing temperature. Samples were taken at various time intervals. The values of Mw obtained from these samples showed that glycogen and amylopectin behave as randomly formed polymers. The rates of hydrolysis obtained in these studies indicate that the large molecules in all corn endosperm amylopectins and glycogens exist in chemical aggregates of four. These chemical aggregates do not appreciably influence the statistical size distribution of the amylopectin and glycogen molecules. A comparison of the properties of a sweet corn glycogen sample and an immature sweet corn amylopectin sample indicates strongly that glycogen is a precursor to starch.