Complexes of Lysine, Histidine, and Arginine with Sulfonated Azo Dyes:  Model Systems for Understanding the Biomolecular Recognition of Glycosaminoglycans by Proteins

Abstract

The X-ray crystal structures of six salts composed of amino acids and sulfonated azo dyes have been determined, four of them at low temperature (173 K). The compounds are dl-lysine/4-[(4-hydroxyphenyl)azo]benzenesulfonate (HABS) monohydrate (1), dl-lysine/7-hydroxy-8-(phenylazo)-1,3-naphthalenedisulfonate (Orange G) dihydrate (2), l-lysine/Orange G 1.5-hydrate (3), dl-histidine/Orange G trihydrate (4), l-histidine/Orange G trihydrate (5), and tosylarginine methyl ester (TAME)/4-[(2-hydroxy-6-tert-butyl-1-naphthalenyl)azo]benzenesulfonate (“Little Rock Orange,” LRO) (6). By virtue of their basic side chains, these amino acids are the ones most important in the binding interactions between proteins and sulfated macromolecules such as glycosaminoglycans in living systems. The sulfonate salts described here serve as model systems for these interactions. Close intermolecular approaches between the dye sulfonate groups and neighboring amino acids and water molecules are examined, and the graph-set formalism is used to describe packing patterns and to identify corresponding interactions in different crystal structures. The recurrence of certain interactions between sulfonate groups and amino acid functional groups in these small-molecule crystal structures, including numerous interactions mediated by water molecules, suggests specificity that may also be a feature of the interactions between proteins and sulfated biological macromolecules.

Interaction of 7-Hydroxy-8-(phenylazo)1,3-naphthalenedisulfonate with Bovine Plasma Albumin

“…The spectrum shows several cross-peaks between the proton pairs of OG including those between protons of ring A and ring B. It is clear that the conformation of bound OG is significantly different from that found in x-ray crystal structure (11). In fact, if the crystal structure was maintained in the bound OG then none of the nuclear Overhauser effects between protons in ring A and ring B should have been observed.…”

“…It is known that the sulfonated compounds interact with amino acids such as Arg, Lys, His, etc., via sulfonate oxygen and make direct or indirect hydrogen bonds with the side chain NH (11). A closer inspection of BPA sequence reveals the presence of such charged residues near Trp-135.…”

“…1B) with amino acids such as Arg, Lys, and His has been reported (11). To the best of our knowledge, there is no report on the interaction of OG with any protein.…”

Femtochemistry of orange II in solution and in chemical and biological nanocavities

“…A previous x-ray crystal study of structures of salts composed of amino acids (like those of HSA) and sulfonated AZO dyes (like OII) has shown that short (Ͻ3 Å) intermolecular H-bonds between the dye sulfonate groups and neighboring amino acids (48). For OII:HSA complexes, we cannot provide in this work an x-ray structure; however, if such kinds of interactions between the SO 3 Ϫ group of OII and the amino acids of the protein happen as it does in comparable systems (48), it makes robust the complex avoiding its dissociation. In a previous study, using a smaller molecular probe, we found a very large docking of the guest within Table 2.…”

Crystal Chemistry and Prototropic Tautomerism in 2-(1-Iminoalkyl)- phenols (or naphthols) and 2-Diazenyl-phenols (or naphthols)

“…A rather homogeneous group is given by the sulfonate azo-dyes. Although no diffraction data at variable temperature are available, all the 11 structures retrieved [100][101][102] were interpreted and discussed as being N-H…O tautomers, a conclusion justified by the fact that their average structural data of C-O = 1.271 [7], N-N = 1.298 [6] and O…N = 2.51 [2] Å are typical of an equilibrium strongly shifted towards the N-H tautomeric form. As an example, bis(adenine)-7-hydroxy-8-(phenylazo)-1,3-naphtalene-disulfonate pentahydrate (LEZHIH) [100] is reported in Fig.…”