Polypeptides with known repeating sequences of amino acids. Comparison of several methods used for the synthesis of poly‐γ‐D‐ and L‐glutamylglycine and investigation of its serological reaction with antianthrax immune serum

Abstract

SynopsisTo make a comparison of some of the various polymerization methods, p0ly-y-Dand L-glutamylglycine were synthesized through the mixed anhydride, carbodiimide, and pentachlorophenyl active ester methods. This last method proved to be best, on the basis of weight-average molecular weights (ww). A detailed study was also carried oiit to determine the optimum conditions for this method. The M , values of the polymers were determined by the sedimentation equilibrium method; it was found that the pentachlorophenyl active ester gave Mw values of up to 11,500 but the mixed anhydride and carbodiimide methods gaveTests with rabbit antianthrax immune serum showed that neither D-nor L-isomer precipitated with the antiserum, but that both were able to inhibit the precipitation of the antiserum by anthrax polypeptide. In addition, the D-polymer gave more inhibition than the L, which would indicate a specificity of the antibody for D-glutamic acid residues.values of only about 1000.In order to compare the different polymerization methods and to demonstrate the general usefulness of the pentachlorophenyl (PCPOH) active ester for y-polypeptide synthesis, poly-y-glutamylglycine was prepared by several methods. This polypeptide was also of interest because of its similarity to native polyglutamic acid (poly-y-D-glutamic acid),2-6 which gives a precipitation reaction with antianthrax immune serum7-12 (For the synthesis of this polymer, see Bruckner et ~1 .~~9~~) .Derivatives of the repeating unit of this polymer, y-glutamylglycine, are suitable model compounds for the study of polymerization for the following reasons. Racemization was not expected since the C-activated amino acid is the optically inactive glycine. Formation of diketopiperazine was im-* This is the eleventh in a series of papers concerned with the use of pentachlorophenvl active esters. For the previous paper in this series, see Kovacs, Kisfaludy, and Ceprini.1

Synthesis of poly-γ-glutamyl-γ-aminobutyric acids and their reactivity with antiserum against Bacillus anthracis polypeptide

“…To investigate this problem further as well as to obtain data on the role of the carboxyl groups in the serological reaction, a series of sequential polypeptides were synthesized with glycyl, /3-alanyl, and 7-aminobutyryl residues separating the Y-glutamyl residues with a gradual increase in the distance of carboxyl groups. The synthesis of the l,d isomers of the first two members of this series, i.e., poly-Y-glutamylglycine and poly-7-glutamyl-/3-alanine were previously reported (Kovacs et al, 1968;Kovacs and Johnson, 1965). The serological reactions with antianthrax immune serum were also reported; this investigation showed that neither the d nor the l isomer of the above two polypeptides gave a precipitation reaction.…”

“…The scheme below indicates the synthetic route. The dipeptide methyl ester III was prepared by coupling V-benzyloxycarbonyl-a-zm-butylglutamic acid (I) (Kovacs et al, 1968) with methyl-y-aminobutyrate (II) through mixed anhydride coupling. The resulting /V-bcnzyloxycarbonylcx-rm-butylglutamyl-y-aminobutyric acid methyl ester (III) was saponified (4 min) to the dipeptide free acid IV, which was characterized through its dicylcohexylamine salt.…”

“…Polymerization was carried out starting with a highly concentrated solution of the hydrochloride salt VI in dimethylformamide in the presence of 2-2.5 equiv of triethylamine Kovacs et al, 1968). Extreme care was taken to use pure active ester hydrochloride VI as well as purified solvent and triethylamine to avoid undesired side reactions which would lower the degree of polymerization.…”

Review of the application of ε‐poly‐L‐lysine in improving food quality and preservation

“…α‐poly‐lysine (α‐PL) was synthesized in 1947 and is characterized by an amide bond between the α‐amino and α‐carboxylic residues (Kovacs, Schmit, & Ghatak, ). However, due to its toxicity, it is not suitable for food preservation.…”

Synthesis of two sequential polypeptides by dispersion in benzene and their circular dichroism spectra in aqueous solution: Poly(L‐Glu‐L‐Lys‐L‐Ala‐Gly) and Poly(L‐Ala‐D‐Glu‐L‐Lys‐D‐Ala‐Gly)

“…8 They determined the molecular weights of the L and D isomers of poly-7-glutamylglycine derived from the mixed anhydride, DCC, and pentachlorophenyl ester methods. I n addition, they compared dimethylformamide (DMF), dimethylsulfoxide, and hexafluoroacetone as solvents for polymerization.…”