th" o."ng" "lb"do "t.ofrJinsotUlte iolias 1ats1 *att pieparatlon, *"reri"t prepa."a frorn tfr" ll"ao tissue of nrarure orange fruit, contained 55 mol% pectic polysaccharides, including homogalacturonan (HC). rhamnogalacruronan 1 (RG I) and rhamnogalacturonan Il (RC II) together with Type I arabinoga)actan (AC) and arabinan. lt also contained ceUulose (22mol%) and other non-cellulosic polysa(charides (14molz), including xyloglucans (XCs)(l0mol%), heteromannans (2rnol%)and heteroxylans (2molZ)- Sequential exiradion ofthe AIS pedornred with NaOAc, CDTA, Na2COr, 1 M KOH and 4 M KOH produced soluble h'acrions (Frs.) wirh different relative proportions ofthese polysaccharides. The NaOAc and CDTA Frs. were composed predominantly of pectic polysaccharides (89 and 97 molx, respectively) with only very low proportions of other non-cellulosic polysaccharides. NarCOr (50mM) released highly rami- 6ed pectic polysaccharides. whereas stronger alkali (1 M and 4M KoH) liberated mosdy non-cellulosic polysaccharide, romprised predominantly of XG. The NaOAc, CDTA and Na2COt Frs. contain low levels of2-O-methvlFuc and 2 O-mcthvl-Xvl, s(ggesiing the presence of RC Il. To obtain the RC II for structural characlerization. the NaOAc liaclioD was digested with a combination ol endo-polygalacturonase (endo-PC; PC I and PC II) and exo-Pc, and rh€ degrddatioD product was fra.tionated by anion exchange and size exclusion chromatography. The isolated product (approx. 0.5% oforange albedo AIS) contained all six diagnostic sugars and has a glycosyl Iinkage composition consistent with the structural model of RC II,