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C Poulos

Publications and source records attributed to C Poulos.

11 recordsLinked to original sources
PubMed1992

Synthesis and biological activity of analogues of the C-terminal hexapeptide of substance P with modifications at glutaminyl and methioninyl residues. Structure-activity studies.

Analogues of [Orn6]-SP6-11 have been synthesized in which the methionyl residue is replaced by glutamine gamma-carboxamide substituted derivatives. These analogues where tested in three in vitro preparations representative of NK-1, NK-2 and NK-3 receptor types. Substitution of the SCH3 group of the Met11 side chain by CONHCH3, CON(CH3)2, CONHPh and CONCH3Ph groups results in analogues which are full agonists in NK-1 and NK-2 preparations with the exception of the Glu[N(CH3)2]11 and the Glu(NHCH3)11 analogues, which are partial agonists at NK-1 and NK-2 receptors respectively. The Glu(NHCH3)11 analogue shows selectivity for the NK-1 receptor type and is equipotent to the Glu(NCH3Ph)11 analogue in the same receptor type. The latter analogue is 2.84 times more potent than the parent hexapeptide in the NK-2 preparation. The Glu(NHPh)11 analogue is a full agonist in the NK-3 preparation and equipotent to the parent hexapeptide, in contrast to the other analogues in which Met has been replaced by glutamine gamma-carboxamide substituted residues. It is concluded that for NK-1 receptor type the lipophilic character of Met11 side chain is not a determining factor for activity but it is an important factor for activity in the NK-2 receptor type and has a stronger effect when a phenyl group is present, thus leading to analogues which are full agonists and more potent than the parent hexapeptide.

Amino Acid Sequence↗
PubMed1991

Application of carboxylic-phosphinic mixed anhydrides in the fragment peptide synthesis of protected analogues of substance P.

Mixed carboxylic-phosphinic anhydrides derived from peptide acids and 1-oxo-1-chlorophospholane have been applied in the synthesis of the protected [Leu11]-SP by the fragment coupling strategy. The yields from fragment couplings were ca. 75%, the products were of high purity while the conditions of formation and coupling of the corresponding mixed phosphinic anhydrides, for optimum yields, have been evaluated.

Amino Acid Sequence↗
PubMed1991

Synthesis of a potent agonist of substance P by modifying the methionyl and glutaminyl residues of the C-terminal hexapeptide of substance P. Structure-activity relationships.

Analogues of [Orn6]-SP6-11 have been synthesized in which the Met11 residue is replaced by glutamate gamma-alkylesters. These analogues were tested in three in vitro preparations representative of NK-1, NK-2, and NK-3 receptor types. Substitution of the SCH3 group of the Met11 side chain by a COOR (R = methyl, ethyl, n-propyl, n-butyl, cyclohexyl) group results in analogues which are full agonists in NK-1 and NK-2 preparations but show little agonist activity in the NK-3 preparation. When the SCH3 group is replaced by a t-butyl ester group and the resulting analogue is a full agonist in all the above preparations and more active than the parent hexapeptide and SP-OCH3 at NK-1 receptors. It is concluded that for activity at NK-1 receptors methionine can be replaced by gamma-t-butyl glutamate without loss of activity, whilst at NK-2 and NK-3 receptors the above substitution increases the activity of [Orn6]-SP6-11. Other gamma-alkyl esters of the glutamic acid reduce its biological activity.

Amino Acid Sequence↗
PubMed1991

Application of 2-chlorotrityl resin in solid phase synthesis of (Leu15)-gastrin I and unsulfated cholecystokinin octapeptide. Selective O-deprotection of tyrosine.

The carboxyl terminal dipeptide amide, Fmoc-Asp-Phe-NH2, of gastrin and cholecystokinin (CCK) has been attached in high yield through its free side chain carboxyl group to the acid labile 2-chlorotrityl resin. The obtained peptide resin ester has been applied in the solid phase synthesis of partially protected (Leu15)-gastrin I utilising Fmoc-amino acids. Quantitative cleavage of this peptide from resin, with the t-butyl type side chain protection intact is achieved using mixtures of acetic acid/trifluoroethanol/dichloromethane. Under the same conditions complete detritylation of the tyrosine phenoxy function occurs simultaneously. Thus, the solid-phase synthesis of peptides selectively deprotected at the side chain of tyrosine is rendered possible by the use of 2-chlorotrityl resin and Fmoc-Tyr(Trt)-OH. The efficiency of this approach has been proved by the subsequent high-yield synthesis of three model peptides and the CCK-octapeptide.

Amino Acid Sequence↗
PubMed1987

Structure-activity studies on the C-terminal hexapeptide of substance P with modifications at the glutaminyl and methioninyl residues.

Analogues of [Orn6]-SP6-11 have been synthesized in which the SCH3 group of the Met11 side chain is replaced by other functional groups, such as (CH2)2NH2, COOH, CONH2, and COOR, which have basic, acid, or neutral character and which may act as either H-bonding donors or H-bonding acceptors. These analogues were tested in guinea pig ileum and rat colon muscularis mucosae, in vitro. Substitution of Lys, Gln, or Glu at position 11 caused a marked reduction in biological activity in both tissues. In contrast, the glutamate benzyl ester analogue had only slightly reduced activity in the guinea pig ileum and an increased (4.7 times) activity in the rat colon. It is concluded that charged groups in the side chain at position 11 of SP6-11 reduce the biological activity of SP hexapeptide.

Amino Acid Sequence↗
PubMed1986

Synthesis and biological activity of substance P C-terminal hexapeptide analogues: structure-activity studies.

A series of analogues of the C-terminal hexapeptide of substance P, modified at the glutaminyl residue, was synthesized and their relative activities as spasmogens were determined in the guinea pig ileum and rat colon muscularis mucosae preparations in vitro. In general, when compared to SP6-11, the loss of the carboxamide group has little effect on activity in the colon and reduces activity on the ileum. The exception to this is the Orn6 analogue which retains activity on both preparations and is proposed as a useful tool for structure-activity studies. It is concluded that the hydrogen-bonding potential of the position 6 substituent may be an important determinant of biological activity.

Animals↗
PubMed1985

Conformationally restricted C-terminal peptides of substance P. Synthesis, mass spectral analysis and pharmacological properties.

Four cyclic analogues of the C-terminal hepta- or hexapeptide of substance P were prepared by the solution method. The cyclizations were obtained by substituting with cysteine the residues normally present in positions 5 or 6 or 11 of substance P and by subsequent disulfide bond formation. The final products were identified by ordinary analytical procedures and advanced mass spectroscopy. The biological activities were determined on three bioassays: the guinea pig ileum, the guinea pig trachea and the rabbit mesenteric vein. Results obtained with these assays indicate that all peptides with a disulfide bridgehead in position 11 are inactive and that a cycle between positions 5 and 6 already strongly reduces the biological activity. The acyclic precursors containing thiol protection groups display weak biological activities. These results further underline the importance of the side chain in position 11 of substance P and suggest that optimal biological activities may require a linear peptide sequence.

Animals↗