PubMed Health⌕ Search

Biomedical subjects

J DiMaio

Publications and source records attributed to J DiMaio.

28 records · Page 2Linked to original sources
PubMed1990

Bifunctional thrombin inhibitors based on the sequence of hirudin45-65.

The interaction of alpha-thrombin with the hirudin (HV1) fragment N alpha-acetyl desulfo hirudin45-65 (P51) was investigated. Kinetic analysis revealed that P51 inhibits the proteolysis of a tripeptidyl substrate with Ki = 0.72 +/- 0.13 and 0.11 +/- 0.03 microM for bovine and human alpha-thrombins, respectively. The inhibition was partially competitive, affecting substrate binding to the enzyme-inhibitor complex by a factor alpha = 2 (bovine) and alpha = 4 (human) characteristic of hyperbolic inhibitors. P51 also inhibited thrombin-induced fibrin clot formation with IC50 values of 0.94 +/- 0.20 and 0.058 +/- 0.006 microM for bovine and human alpha-thrombins, respectively. The enhanced antithrombin activity for human thrombin could be attributed to species variations in the putative auxiliary "anion" exosite since N alpha-acetyl desulfo hirudin55-65 displayed the same rank order of potency shift in a clotting assay without inhibiting the amidolytic activity of either enzyme. From these observations, a potent thrombin inhibitor was designed having modified residues corresponding to the P1 and P3 recognition sites. N alpha-Acetyl[D-Phe45, Arg47] hirudin45-65 (P53) emerged as a pure competitive inhibitor with a Ki = 2.8 +/- 0.9 nM and IC50 = 4.0 +/- 0.8 nM (human alpha-thrombin) and is designated as a "bifunctional" inhibitor. Its enhanced potency could be explained by a cooperative intramolecular interaction between the COOH-terminal domain of the inhibitor and the auxiliary exosite of thrombin on the one hand, and the modified NH2-terminal residues with the catalytic site on the other.

Amino Acid Sequence↗
PubMed1990

Synthesis and biological activity of atrial natriuretic factor analogues: effect of modifications to the disulfide bridge.

A series of atrial natriuretic factor (ANF) analogues with modifications to the disulfide bridge and lacking the exocyclic N-terminal sequence was synthesized. The native cystine residue was substituted by isofunctional deamino carba, beta,beta-dimethyl carba and dehydro dicarba spanners that bridge residues 106 and 120. The compounds were prepared by segment condensation coupling using the base-labile (9-fluorenylmethyl)carboxyl protecting group. Biological evaluation revealed that the exocyclic N-terminal segment of ANF is not necessary for expression of high biological activity. The compounds retained high affinity for ANF receptors in bovine adrenal zona glomerulosa cells and were found to be potent antihypertensive and diuretic agents, indicating that the native disulfide bridge can be mimicked by isosteric spanning residues. It was noted that the reported analogues, unlike the endogenous hormone, show marked reduced inhibitory activity on PGE1-stimulated aldosterone secretion from adrenal zona glomerulosa cells. This lack of inhibition may be a contributing element to the low saluresis in spite of the high level of diuresis observed with some analogues.

Amino Acid Sequence↗
PubMed1986

Topological similarities between a cyclic enkephalin analogue and a potent opiate alkaloid: a computer-modeling approach.

The cyclic enkephalin analogue H-Tyr-cyclo[-D-N delta-Orn-Gly-Phe-Leu-] (1-c) and the rigid narcotic alkaloid 7 alpha-[(1R)-1-hydroxy-1-methyl-3-phenylpropyl]-6,14- endo-ethenotetrahydrooripavine (PEO) were studied by using computer graphics methods to investigate potential geometrical congruencies of their respective pharmacophoric elements. Particular emphasis was placed on the relative spatial disposition of the tyramine moiety and the additional aromatic ring that occurs in both molecules. A three-dimensional vector map was generated defining the locus of the C21 aromatic ring for all those conformers of PEO having up to 10 kcal above the minimum energy conformer. A systematic conformational search on the cyclic peptide afforded four allowable sets of conformers whose side chain of the phenylalanine residue coincided with the vector map of PEO. Local energy minima for the peptide within the revised mutual vector space were found and subjected to bimolecular energy refinement with correspondingly local energy minima for the opiate alkaloid. Several low-energy conformers of the cyclic peptide were identified that permitted a good fit with the alkaloid provided that the tyramine moiety of the respective molecules does not coincide. In the designated conformations the basic nitrogen of the former occupies a distinct geometrical locus, and the side chain of the leucine residue has no structural correlate in the alkaloid.

Chemical Phenomena↗
PubMed1983

Comparison of mu-, delta- and kappa-receptor binding sites through pharmacologic evaluation of p-nitrophenylalanine analogs of opioid peptides.

For the purpose of comparing the structural requirements of opioid receptor subsites interacting with phenylalanine residues of opioid peptides, analogs containing p-nitrophenylalanine (Phe(pNO2) ) were synthesized and tested in the guinea pig ileum (GPI) and mouse vas deferens (MVD) assay as well as in mu- and delta-receptor selective binding assays. Whereas substitution of Phe(pNO2) in position 4 of the mu-selective analog H-Tyr-c[-N epsilon-D-Lys-Gly-Phe-Leu-] and of the delta-selective analog H-Tyr-D-Ser-Gly-Phe-Leu-Thr-OH produced a significant potency increase in all assays, the corresponding substitution in the kappa-selective dynorphin-(1-13) fragment resulted in a decreased potency in the GPI-assay. These findings suggest that the electronic requirements of the Phe4 binding site at the mu- and delta-receptor are identical, but different from those of the corresponding site at the kappa-receptor. The observation that Phe(pNO2) substitution in position 3 of morphiceptin and dermorphin also produces a drastic potency drop indicates that the Phe3 side-chain of the latter peptides at the mu- and delta-receptor may bind to a site different from that interacting with the Phe4 side-chain of enkephalins.

Animals↗
PubMed1983

The effect of phenylalanine derivatives on the solubility of deoxyhemoglobin S. A model class of gelation inhibitors.

Among the class of non-covalent inhibitors of deoxyhemoglobin S gelation, the aromatic amino acids have been shown to be the most effective. We have examined several synthetic chemical modifications of phenylalanine in order to determine the stereospecific constraints for inhibition of gelation by this class of compounds. The phenylalanine derivatives with ring modification by electron-donating groups (NH2, CH3, or OH) inhibited gelation to the same order of magnitude as phenylalanine (10-20% increase in deoxyhemoglobin S solubility at 32 mM). The phenylalanine derivative with the electron-withdrawing group NO2 in the p-position behaved similarly, but the inhibitory effect was eliminated by NO2 in the m- and possibly o-positions. Furthermore, side-chain modifications also eliminated the inhibitory effect. These studies, in conjunction with crystallographic analyses of the binding sites of gelation inhibitors, may provide a rational strategy for finding suitable compounds (whether covalent or non-covalent inhibitors) with appropriate physicochemical and biological properties to pursue as potential therapies with sickle cell disease.

Anemia, Sickle Cell↗
PubMed1982

Synthesis and pharmacological characterization in vitro of cyclic enkephalin analogues: effect of conformational constraints on opiate receptor selectivity.

Using a combination of solid-phase and solution methods, we synthesized a series of cyclic [Leu5]enkephalin analogues by substitution of D-alpha, omega-diamino acids in position 2 of the enkephalin sequence and cyclization of the omega-amino group to the C-terminal carboxy group of leucine. Cyclic analogues containing D-alpha, beta-diaminopropionic acid (1), D-alpha, gamma-diaminobutyric acid (2), D-ornithine (3), or D-lysine (4) in position 2 and the [D-Leu5] and [des-Leu5] analogues of 4 (5 and 6) showed, in general, high potency in the guinea pig ileum (GPI) assay and low potency in the mouse vas deferens (MVD) assay. IC50 (MVD)/IC50 (GPI) ratios ranging from 3.1 to 29.4 were obtained, indicating the preference of the cyclic analogues for mu receptors over delta receptors. With two exceptions, preferential affinity for mu receptors is reflected in the Ki ratios determined in parallel binding assays using [3H]naloxone and [3H] [D-Ala2, D-Leu5]enkephalin as mu and delta receptor selective radioligands, respectively. Comparison of the pharmacological profiles of the cyclic analogues 1-4 with those of their corresponding open-chain analogues, [D-Ala2, Leu5]enkephalinamide (1a), [D-Abu2, Leu5]enkephalinamide (2a), [D-Nva2, Leu5]enkephalinamide (3a), and [D-Nle2, Leu5]enkephalinamide (4a), revealed that the pronounced mu character of compounds 1-4 is a direct consequence of the conformational constraints introduced by cyclization. This finding is in agreement with the concept of different conformational requirements of mu- and delta-opiate receptors and raises the possibility of manipulating opiate receptor selectivity by varying the type and degree of conformational restriction.

Animals↗
PubMed1980

A cyclic enkephalin analog with high in vitro opiate activity.

A conformationally restricted analog of [Leu5]enkephalin was synthesized by cyclization of the COOH-terminal carboxyl group of leucine to the gamma-amino moiety of alpha, gamma-diaminobutyric acid (A2bu) substituted in position 2 of the peptide. Relative to [Leu5]enkephalin, the cyclic analog with D configuration in position 2, H-Tyr-cyclo(-N gamma-D-A2bu-Gly-Phe-Leu-), was 17.5 times more potent in the guinea pig ileum assay and twice as potent in the rat brain receptor binding assay, whereas its diastereomer H-Tyr-cyclo(-N gamma-L-A2bu-Gly-Phe-Leu-) showed low activity. The cyclic D isomer was also slightly more active than the open-chain reference compound [D-Nva2, Leu5]enkephalinamide in both assays, and it proved to be highly resistant to degradation by brain "enkephalinases." The steric constraints introduced in H-Tyr-cyclo(-N gamma-D-A2bu-Gly-Phe-Leu-) were shown to prevent the realization of most of the conformational features ascribed to linear enkephalin in solution or in the crystalline state and permitted an assessment of proposed models of the conformation of enkephalin when it is bound to the receptor.

Animals↗
PubMedDate not supplied

Regulation of a hevein-like gene in Arabidopsis.

An Arabidopisis cDNA clone was isolated that encodes a protein similar to the antifungal chitin-binding protein hevein from rubber tree latex. This hevein-like (HEL) mRNA was inducible by either turnip crinkle virus infection or ethylene treatment. In addition, expression was moderately inducible by treatment with the resistance-inducing compounds salicylic acid and 2,6-dichlorisonicotinic acid. The 786-bp cDNA contains an open reading frame of 212 codons. The deduced amino acid sequence contains a putative signal sequence of 21 amino acids followed by a 43-amino-acid cysteine-rich lectin domain and a 129-amino-acid carboxy-terminal domain. The predicted protein is approximately 70% identical to hevein, to the wound-inducible WIN1 and WIN2 proteins from potato, and to PR-4, a pathogenesis-related protein from tobacco.

Amino Acid Sequence↗