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Synthetic luteinizing hormone-releasing hormone (LH-RH) lost both its immunore-activity and hormonal activity on incubation with hypothalamic or cerebrocortical slices or homogenates. This inactivation was shown to be due to degradation of the decapeptide by soluble enzyme(s) present in the 100,000 × g supernatant fraction of the homogenates. The supernatant derived from one rat hypothalamus was capable of destroying 1 μg of exogenous LH-RH within 5 min. The hexapeptide pGlu-His-Trp-Ser-Tyr-Gly was identified as the major radioactive breakdown product of [pGlu-3-3H] LH-RH, and tentative evidence for the formation of the tetrapeptide Leu-Arg-Pro-Gly-NH2 was obtained by sequential electrophoresis and paper chromatography. These findings suggest that the Gly-Leu bond may be the preferred site of cleavage.

The advantages applying NMR techniques to the study of racemization is illustrated and discussed. Using NMR it is possible to measure the rate of racemization of each individual amino acid residue in a peptide. It was found that the rate of racemization depends on the nature of the side chain of the amino acid residue, and on the location of the amino acid in the peptide chain.

A new route for the synthesis of polyamino acids containing histidine is described and illustrated in the preparation of poly l -histidine. This method involves the use of the 2,4-dinitrophenyl group for the protection of the imidazole imino-nitrogen during polymerization. The N -carboxy anhydride of N Im -DNP- l -histidine was polymerized to yield poly (DNP- l -histidine) with an average molecular weight of 29,400. After polymerization, the protecting groups were removed under very mild reaction conditions by thiolysis with mercaptans in N,N′ -dimethylformamide (22 °). The mildness of the conditions for deblockage allows the preparation of histidine-containing polyamino acids and polypeptidyl proteins which could not be prepared by the previously available methods.

Poly-β-N-diphenylmethyl-L-asparagine and poly-γ-N-diphenylmethyl-L-glutamine were prepared from the corresponding N-carboxyanhydrides. Poly-L-aspuragine and poly-L-glutamine were obtained by removal of the diphenylmethyl protecting groups with liquid anhydrous hydrofluoric acid.

Administration of an antiserum (0.10–0.25 ml/rat) to the synthetic decapeptide “luteinizing hormone releasing hormone” (LH-RH) suppressed the cyclic surge of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in proestrous rats and prevented ovulation; exogenous LH reversed the block of ovulation. Serum prolactin levels remained unaffected. In ovariectomized rats, the antiserum suppressed the elevated serum levels of both gonadotropins. These findings are compatible with the view that the synthetic decapeptide is identical with the natural hypothalamic hormone that regulates the secretion of both LH and FSH.

α-Trimethylsilyl acrylic acid and its methyl ester were prepared in good yield starting from 1,2-dibromoethyltrimethylsilane. These monomers were polymerized with difficulty by free radicals to viscous polymers, but gave solid copolymers with styrene. The methyl ester was also a weak monomer in anionic polymerization. This non-reactivity is due to the steric effect of the α-trimethylsilyl group adjacent to the double bond.

A new method for the detection of the aromatic residues in aromatic amino acids and peptides on thin-layer chromatography by the apparent colour of their charge-transfer complexes with various electron acceptors, is described. The method was found most suitable for the detection of tryptophan- and tyrosine-containing peptides where amounts of 1–2 μg of the peptide could be detected. The intact amino acids and peptides can be released by treatment of the coloured spots with suitable aqueous solvents.

Tritiated poly-L-lysine (γ, δ-T2) (IX) was prepared according to the following procedure: Tritiated DL-lysine (γ, δ-T2) (III) was derived from acetamino-(-4-amino-Δ2-butenyl)-diethylmalonate (I) by tritiation followed by acid hydrolysis. The racemic tritiated lysine was converted to its e, N-trifluoroacetyl derivative IV, and the latter resolved via its chloroacetyl derivative by means of hog kidney acylase. The optically active tritiated e, N-trifluoroacetyl-L-lysine (VI) was converted into the corresponding N-carboxyanhydride VII with phosgene, and polymerization carried out in dioxane using triethylamine as initiator. The required tritiated poly-L-lysine (IX, n = 250) was obtained from the blocked polymer VIII after removal of the protecting groups with piperidine. The tritiated polypeptide possessed an activity of 250 mC. per mmole lysine residue. The procedure described enables, however, the preparation of poly-L-lysine with up to 25 times higher specific activity.

Insoluble (4-hydroxy-3-nitro)benzylated polystyrene (PHNB) was prepared by reacting 4-hydroxy-3-nitrobenzyl chloride with copolystyrene-2%-divinylbenzene in the presence of aluminium trichloride. PHNB-active esters of many N-blocked amino acids were prepared using dicyclohexylcarbodiimide as a coupling agent, and used for the preparation of di, tri and tetra-peptides. The synthesis of the tetra-peptide Boc-l-Leu-l-Leu-l-Val-OBzl-l-Tyr-OBzl, was effected by means of the polymeric active esters of Boc-l-Val and Boc-l-Leu. The synthesis was initiated by reacting O-benzyl-l-tyrosine benzyl ester with Boc-Val-PHNB in dichloromethane to yield N-tert-butyloxycarbonyl-l-valyl-O-benzyl-l- tyrosine benzyl ester. Removal of the tert-butyloxycarbonyl group yielded a dipeptide ester which was coupled with the corresponding polymeric active ester to yield an N-blocked tripeptide ester. Repetition of this set of reactions led to the formation of the pure blocked tetrapeptide in 82% over-all yield.

Nous avons determine par titrage volumetrique une serie d'hydrazides peptidiques et teste les titrages acides, basiques et oxidants. Un tableau condense les resultats obtenus avec les trois meilleurs reactifs de titrage (acide perchlorique dans l'acide acetique glacial, l'hypobromite de sodium et le permanganate de potassium) qui sont tous utilisables a cet effet.

The synthetic decapeptide “luteinizing hormone-releasing hormone” (LH-RH) was rendered antigenic by reaction of its histidine or tyrosine residues (7 : 3 approx.) with p-diazonium phenylacetic acid and coupling of the azo-derivatives formed to bovine serum albumin (BSA). Immunization of rabbits yielded antisera that bound 125 I-labeled LH-RH (approx. 50 pg) at dilutions up to 1:200, 000 and showed no cross-reaction with unrelated hypothalamic and pituitary hormones, extracts from rat cerebral cortex, and with small fragments of LH-RH. Cross-reaction was minimal (0.2%) with the free acid analogue of LH-RH, and moderate with des -pGlu LH-RH (20%), des -pGlu-His-LH-RH (2.4%) and with LH-RH analogues in which a single residue (No. 4–6 or No. 8) was exchanged by an amino-acid of similar character (1.2–12%). Biologically active hypothalamic extract and LH-RH produced parallel 125 I-LH-RH-binding inhibition curves, providing immunochemical support for the identity of the native releasing hormone with synthetic LH-RH.

The synthesis of poly(L-leucyl-L-ornithyl-L-leucine) and of poly(L-leucyl-L-arginyl-L-leucine) is reported. The antibacterial action of the two copolymers was checked by growth inhibition experiments on Staphylococcus aureus. The activity was found to be identical with that of a disordered 1:1 copolymer of L-ornithine and L-leucine. Conversion of 75% of the ornithine residues to arginine had no effect on the antibacterial activity.

New methods of peptide synthesis have yielded impressive successes in recent years in the preparation of many naturally occurring polypeptides. ACTH (Schwyzer and Sieber, 1963), glucagon (Wunsch, 1967), calcitonin (Sieber et al., 1968; Guttman et al., 1968), ferredoxin (Bayer et al., 1968), ribonuclease A (Denkewalter et al., 1969 ; Gutte and Merrifield, 1969), and human pituitary growth hormone (Li and Yamashiro, 1970) are representative of a large number of polypeptides which have been prepared chemically.