The degree of starch phosphorylation is related to the chain length distribution of the neutral and the phosphorylated chains of amylopectin Andreas Blennow a, *, Anne Mette Bay-Smidt a , Bente Wischmann a , Carl Erik Olsen b , Birger Lindberg Mùller a a The Royal Veterinary and Agricultural University, Department of Plant Biology, Plant Biochemistry Laboratory, 40 Thorvaldsensvej, DK-1871 Fredriksberg C, Copenhagen, Denmark b The Royal Veterinary and Agricultural University, Chemistry Department, 40 Thorvaldsensvej, DK-1871 Fredriksberg C, Copenhagen, Denmark Received 1 September 1997; accepted 10 December 1997 Abstract The chain length distribution of the amylopectin neutral and phosphorylated -glucan chains of isoamylase (EC 3.2.1.68)-debranched starch in dependence of starch phosphorylation has been analyzed using high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Neutral chains of moderately phosphorylated starches showed poly- modal distributions with main peaks at dp (degree of polymerisation) 14±15 and 50, respectively. Highly phosphorylated starches speci®cally showed an increasing proportion of chains with mean dp 19. In the extremely highly phosphorylated curcuma (Curcuma spp.) starch, this chain popu- lation dominated the chain length pro®le. The sub-population of the corresponding phosphory- lated chains from highly phosphorylated starches showed longer retention times than moderately phosphorylated starches on HPAEC. Separation of the phosphorylated chains using anion- exchange chromatography at neutral pH demonstrated a partial separation of chains containing Glc3P residues and Glc6P residues, respectively, as well as a separation of chains containing one or several phosphate groups. Major determinants for the observed elution characteristics of phosphorylated chains using HPAEC are suggested to be a combination of chain length (as determined by gel-permeation chromatography), multiple phosphorylation of the chains (as determined from their content of Glc6P and reducing ends) and ®nally, the presence of the phos- phate group on either the C-3 or the C-6 position on the glucose moieties (as determined by 31 P NMR). The results demonstrate that general rules exist in the relationship between starch phos- phorylation and chain length distribution of starches. # 1998 Elsevier Science Ltd. All rights reserved Keywords: Amylopectin; Chain length distribution; Starch phosphorylation; Starch structure 0008-6215/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved PII S0008-6215(98)00015-9 Carbohydrate Research 307 (1998) 45±54 * Corresponding author. Fax: 45 35 28 3333.