For many years the chemical literature has contained references to starch fractionation. The methods employed have been numerous and the products obtained by different methods have generally been at variance in their chemical and physical properties.2Recently, however, three methods of fractionation have been developed which appear to give nearly identical results. The methods are (a) hot water extraction of one component,* (b) selective adsorption of this same component on cellulose,4 and (c) the selective precipitation of this component by butanol and other alcohols.6In each case one fraction stains blue with iodine, is converted almost completely to maltose by /3-amylase, retrogrades easily, and furnishes good quality X-ray diffraction patterns in "A," " " and "V" modifications. The other fraction stains purple to red with iodine, is only partially converted to maltose by (3-amylase, retrogrades with difficulty or not at all, and yields poor or even amorphous diffraction patterns regardless of treatment.Meyer has made a thorough study of the two components of his fractionation,6 and has concluded that the hot-water extracted fraction is straight-chain starch, i. e,, glucose residues united exclusively by a-l,4-glucosidic linkages, the other fraction is similar but highly branched, probably through a-l,6-glucosidic linkages.7 He has used the term, "amylose" to designate the straightchain fraction, and "amylopectin," the branchedchain fraction.* At the present time the proof of the structure of the two starch components is based almost entirely upon quantitative methylation studies. These are executed only with difficulty and can

The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI UMI Microform DP12570