beta-D-Ribf-(1->5)-D-Rib-(?->3)-beta-D-Ribf-(1->5)-D-Rib-(?->3)-beta-D-Ribf-(1->5)-D-Rib-(?->3)-beta-D-Ribf-(1->5)-D-Rib-(?->3)-beta-D-Ribf-(1->5)-D-Rib-(?->3)-beta-D-Ribf(1->