Biological Consequences of the Incorporation of Amphiphilic Amino Acids into Opioid Peptide Sequences

Summary Hydrophobic and aromatic interactions are most critical for membrane peptide receptor-ligand complex stability. We have hypothesized that proper location of hydrophilic counterparts to lipophilic and/or aromatic residues may stabilize complexation with the receptor pocket. In this work, we are presenting the biological consequences of introduction of a hydroxymethyl group into the α-position of phenylalanine or tyrosine residues of enkephalin or deltorphin analogues. The consequences of such a modification are strongly dependent on the position of the primary amino acid in the peptide chain.     

Biological Consequences of the Incorporation of Amphiphilic Amino Acids into Opioid Peptide Sequences

Hydrophobic and aromatic interactions are most critical for membrane peptide receptor-ligand complex stability. We have hypothesized that proper location of hydrophilic counterparts to lipophilic and/or aromatic residues may stabilize complexation with the receptor pocket. In this work, we are presenting the biological consequences of introduction of a hydroxymethyl group into the -position of phenylalanine or tyrosine residues of enkephalin or deltorphin analogues. The consequences of such a modification are strongly dependent on the position of the primary amino acid in the peptide chain.     

促黄体生成激素释放激素类似物的研究进展

促黄体生成激素释放激素(LHRH)激动剂药物已商品化,用于治疗性激素依赖的癌症,LHRH拮抗剂的研究还处于试验阶段.近几年,在寻找高活性,低组胺释放,水溶性好,稳定性高的拮抗剂研究方面,已取得明显进展.一些较小的环肽及肽模拟物也表现出较好的生物活性.在十肽拮抗剂分子内,中间四肽的βⅡ-turn及N端的三肽对活性影响很大.     

New analogues of leucine-methionine-enkephalin

Nine analogues of the opioid pentapeptides leucine-/ methionine-enkephalinamide, involving replacement of amino acid at position 5 or amino acids at positions 2 and 5, have been synthesized by the solid phase method using mainly 9-fluorenylmethyloxycarbonyl amino acid trichlorophenyl esters in the presence of 1-hydroxybenzotriazole, the solid support being the Merrifield resin. All the analogues were effective in inhibiting the electri cally stimulated contractions of the guinea pig ileum (in vitro) and one of them, tyrosyl-Dnorvalyl-glycyl-phenylalanyl-methioninamide was found to be about 82 times more active than morphine. They also exhibited analgesic activity as well as antidiarrhoeal activity in mice (in vivo). Presented at the 3rd National Symposium on Bioorganic Chemistry, 1987, Hyderabad.     

Thermostabilization of ovalbumin by alkaline treatment: Examination of the possible roles of d-serine residues

It was revealed from the crystal structure analysis of S-ovalbumin (S-OVA) formed by alkaline treatment that Ser164, Ser236, and Ser320 take the d-amino acid residue configuration (Yamasaki et al., J Biol Chem 2003; 278:35524–35530). To address the implications of a d-configuration for these Ser residues in S-OVA formation, three mutant OVAs (S164A, S236A, and S320A) were generated to compare their thermostabilities before and after alkaline treatment. Following alkaline treatment, S236A showed a marked increase in melting temperature similar to the wild type (ΔT_m, +9°C) which corresponded to the formation of S-OVA, whereas the increment in T_m for both S164A and S320A was only 4.5°C. Furthermore, the T_m value of the double mutant S164/320A remained unchanged after alkaline treatment, supporting the relevance of Ser164 and Ser320 for thermostabilization of OVA. As Arg142 was predicted to interact with D-Ser164 upon S-OVA formation, it was substituted to Ala to generate R142A. The resulting increment in T_m of mutant R142A after alkaline treatment was 5.8°C. The double mutant R142/S320A was therefore prepared to eliminate the participation of Ser320 in thermostabilization, and its T_m value was compared before and after alkaline treatment. As expected, the increase in T_m for the double mutant was only 1.2°C. Taken together, the data suggest that d-configuration of Ser164 caused by alkaline treatment favors interaction with Arg142 through conformational changes of the side chain. These results strongly supported the participation of the configurational inversion of both Ser164 and Ser320 residues in the formation of S-OVA.     

Synthesis of 6- or 7-substituted 1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acids

A straightforward approach for the synthesis of several new, aryl-substituted derivatives of the conformationally constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) is described. Tic, nitro-substituted at the 6 or 7 position, was prepared by base-catalyzed cyclization of diethyl acetamidomalonate with ,-dibromo-4-nitro-o- xylene followed by decarboxylation and deacylation under refluxing conditions in aqueous HCl. Catalytic hydrogenation of nitro-Tic in the presence of 10% Pd/C afforded amino-Tic, which was then converted to iodo-Tic by a modified Sandmeyer reaction. Both amino- Tic and iodo-Tic can easily be transformed to other substituents.     

Synthesis of 6- or 7-substituted 1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acids

Summary A straightforward approach for the synthesis of several new, aryl-substituted derivatives of the conformationally constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) is described. Tic, nitrosubstituted at the 6 or 7 position, was prepared by base-catalyzed cyclization of diethyl acetamidomalonate with α,α-dibromo-4-nitro-o-xylene followed by decarboxylation and deacylation under refluxing conditions in aqueous HCl. Catalytic hydrogenation of nitro-Tic in the presence of 10% Pd/C afforded amino-Tic, which was then converted to iodo-Tic by a modified Sandmeyer reaction. Both amino-Tic and iodo-Tic can easily be transformed to other substituents.     

Improved solid phase synthesis of luteinizing hormone releasing hormone analogues using 9-fluorenylmethyloxycarbonyl amino acid active esters and catalytic transfer hydrogenation with minimal side-chain protection and their biological activities

Using mainly 9-fluorenylmethyloxycarbonyl amino acid 2, 4, 5-trichlorophenyl esters in the presence of 1-hydroxybenzotriazole and the solid supportp-alkoxybenzyl alcohol resin, synthesis of luteinizing hormone releasing hormone analogues was carried out with minimal side-chain protection. Catalytic transfer hydrogenation was employed for removal of NO₂ and Z-groups from Arg and < Glu respectively avoiding the use of HF and this led to good yields. An aromatic, hydrophilic amino acid, D-(p-hydroxyphenyl) glycine was incorporated into luteinizing hormone releasing hormone molecule along with other modifications. The agonistic as well as antagonistic activities of all the peptides have been studied     

Agonistic action of synthetic analogues of quisqualic acid at the insect neuromuscular junction

One hundred twenty analogues of quisqualic acid were synthesized and assayed on the neuromuscular junction of larva of the mealworm, Tenebrio molitor. Two new agonists for amino acid receptors, L-glutamic acid N-thiocarboxyanhydride (L-GANTA) and DL-hydantoinpropionic acid (DL-HPA), were discovered in this study. L-GANTA and DL-HPA produced muscle membrane depolarization, accompanied by a reduction of the muscle input resistance. The amplitude of excitatory postsynaptic potentials was decreased in the presence of L-GANTA and DL-HPA. The apparent dissociation constants obtained from dose-depolarization plots were 7 x 10^?4 M for L-GANTA and 9 x 10^?4 M for DL-HPA. Some structural constraints imposed on agonists at amino acid receptors on insect muscle were discussed.     

Full-genome sequences of hepatitis B virus subgenotype D3 isolates from the Brazilian Amazon Region

The Brazilian Amazon Region is a highly endemic area for hepatitis B virus (HBV). However, little is known regarding the genetic variability of the strains circulating in this geographical region. Here, we describe the first full-length genomes of HBV isolated in the Brazilian Amazon Region; these genomes are also the first complete HBV subgenotype D3 genomes reported for Brazil. The genomes of the five Brazilian isolates were all 3,182 base pairs in length and the isolates were classified as belonging to subgenotype D3, subtypes ayw2 (n = 3) and ayw3 (n = 2). Phylogenetic analysis suggested that the Brazilian sequences are not likely to be closely related to European D3 sequences. Such results will contribute to further epidemiological and evolutionary studies of HBV.