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