STRUCTURE AND PROPERTIES OF A PTERIN-CONTAINING TERNARY COPPER(II) COMPLEX, [CU(BPY)(PC)(H2O)].3H2O (BPY = 2,2'-BIPYRIDINE, PC = PTERIN-6-CARBOXYLATE) - IMPLICATIONS FOR THE ACTIVE-SITE COPPER-COFACTOR BONDING IN CHROMOBACTERIUM-VIOLACEUM PHENYLALANINE-HYDROXYLASE