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M Marastoni

Publications and source records attributed to M Marastoni.

At least 37 records · Page 2Linked to original sources
PubMed1998

Synthesis and biological activity of chelator-peptide T conjugates.

The solid phase procedure was used to prepare two peptide T derivatives in which the 4-[(1,4,8,11-tetraazacyclotetradec-1-yl)methyl]benzoyl unit is linked to their N-terminus. In a human monocyte chemotaxis assay, both chelator-peptide conjugates showed a high binding property to the CD4 receptor, comparable to the parent H-D-Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr-NH2 and its pentapeptide fragment T(4-8)-NH2. These encouraging results make the above cyclam-oligopeptides candidates for the development of the CD4 receptor imaging agents.

Amino Acid Sequence↗
PubMed1997

Synthesis and pharmacological activity of deltorphin and dermorphin-related glycopeptides.

The solid phase procedure, based on the Fmoc chemistry, was used to prepare some opioid deltorphin (H-Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2, DEL C) and dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2, DER) analogues in which a D-glucopyranosyl moiety is beta-O-glycosidically linked to a Thr4 or Thr7 side chain. Their activities were determined in binding studies based on displacement of mu- and delta-receptor selective radiolabels from rat brain membrane synaptosomes, in guinea pig ileum and rabbit jejenum bioassays, and, in vivo, by a mouse tail-flick test after intracerebroventricular (icv) and subcutaneous (sc) administrations. The glyco analogues modified at position 4 displayed low opioid properties, while Thr7-glycosylated peptides retained high delta- or mu-selectivity and remarkable activity in vivo. In particular, as systemic antinociceptive agents, the latter glucoside-bearing compounds were more potent than the parent unglycosylated peptide counterparts, showing a high blood to brain rate of influx which may be due to the glucose transporter GLUT-1.

Amino Acid Sequence↗
PubMed1997

HIV-1 protease inhibitors containing a novel C2 symmetrical hydroxyalkylgem-diamino core structure.

Two series of peptidomimetics containing a novel C2 symmetrical hydroxyalkylgem-diamino core structure were prepared, from amino acid starting materials, and evaluated as inhibitors of HIV-1 protease (HIV-1 Pr). 1,1-Diamino-3-hydroxypropane (gHse) derivatives showed weak inhibitory potency (IC50 > 10 microM). In the 1,1-diamino-2-hydroxyethane (gSer) series, a compound containing P1/P1' benzyl and P2/P2'Fmoc substituents, displayed a significant HIV-1 Pr inhibition (IC50 = 440 nM).

Amino Acid Sequence↗
PubMed1996

Activation of epitope-specific memory cytotoxic T lymphocyte responses by synthetic peptides.

Cytotoxic T lymphocytes (CTL) recognize antigens as short peptides selected for presentation by their ability to bind to MHC class I molecules. Polyclonal Epstein-Barr virus (EBV)-specific memory CTL responses, reactivated from blood lymphocytes of HLA-A11-positive individuals by stimulation with the autologous EBV-transformed lymphoblastoid cell line (LCL), are often dominated by reactivites directed to the peptide epitope IVTDFSVIK (IVT), corresponding to amino acids 416-424 of EBV nuclear antigen-4 (EBNA4). We now report the selective activation of IVT-specific CTL by stimulation of lymphocytes with the corresponding synthetic peptide. A more than 10-fold increase in frequency of CTL clones with this specificity (from 8% to 96%) was obtained when the peptide was presented by HLA-A11-transfected T2 cells (T2/A11). Titration of synthetic peptide in cytotoxic assay demonstrated that clones activated under these conditions are as efficient as clones activated by conventional LCL stimulations. Induction of memory CTL responses required low surface density of MHC: peptide complexes, since reactivation was achieved by stimulation with T2/A11 cells pulsed with concentrations of peptide that are suboptimal for induction of target cell lysis. This protocol of activation revealed the presence of IVT-specific CTL precursors in a donor that failed to mount an IVT-specific response upon stimulation with the autologous B95.8 virus-transformed LCL. The results suggest that stimulation with synthetic peptide epitopes can be efficiently used for induction of memory CTL responses, and may be particularly helpful for the selective expansion of subdominant CTL specificities.

Amino Acid Sequence↗
PubMed1995

Calmodulin binding sites of the skeletal, cardiac, and brain ryanodine receptor Ca2+ channels: modulation by the catalytic subunit of cAMP-dependent protein kinase?

In this study, we define calmodulin binding sites of skeletal, cardiac, and brain ryanodine receptor (RYR) Ca2+ channels. Cardiac and brain RYR peptides corresponding to the calmodulin binding sites present in the skeletal RYR [Menegazzi, P., et al. (1994) Biochemistry 33, 9078-9084] were synthesized, and their interaction with calmodulin was monitored by fluorescent techniques. The central portions of the skeletal, cardiac, and brain RYR protomers display one high (CaM1; Kd ranging between 2.7 and 10.2 nM) and one low affinity (CaM2; Kd ranging between 116 and 142 nM) calmodulin binding site. Depending on the RYR model having 4 or 12 transmembrane segments, a third calmodulin binding site (CaM3) was identified a few residues upstream from the putative transmembrane segment M1 or M5. Its affinity for calmodulin varied between the RYR isoforms: the cardiac RYR CaM3 displays a high affinity (9.09 +/- 1.0 nM, n = 5), while the skeletal and brain RYR CaM3 have low affinity, the lowest affinity being displayed by the brain isoform (234 +/- 39 nM, n = 3). The RYRs calmodulin binding site CaM1 encompasses the sequence Arg-His-Arg-Val(Ile)-Ser-Leu, which is phosphorylated in vitro by the catalytic subunit of the cAMP-dependent protein kinase. Phosphorylation of RYR PM1 peptides occurs on the Ser, corresponding to amino acid number 2919, 3020, and 3055 of the brain, cardiac, and skeletal RYR protomers, respectively. We found that phosphorylation of the RYR PM1 peptides was inhibited by calmodulin binding and that the formation of the PM1 peptide-calmodulin complex was inhibited by peptide phosphorylation. These data indicate that the effect of calmodulin binding to RYR CaM1 may be regulated by the phosphorylation state of the Ser residue localized within the sequence Arg-His-Arg-Val(Ile)-Ser-Leu.

Amino Acid Sequence↗
PubMed1995

Effect of anchor residue modifications on the stability of HLA-A11/peptide complexes.

MHC class I antigens bind peptides derived from endogenous proteins and present them to cytotoxic T lymphocytes. This binding is selective and shows high allele specificity. Peptides binding to HLA-A11 contain a hydrophobic or a small polar amino acid at position 2 and a lysine at the carboxy terminus. Peptide analogues, derived from previously identified high affinity peptides and carrying amino acid substitutions in position 2, were used to determine the requirements for formation of stable HLA-A11/peptide complexes. By kinetic analysis we were able to discriminate among apparent and true binders. Only analogues carrying in position 2 the amino acids valine, threonine and isoleucine formed stable complexes with HLA-A11 with a half life > or = 72 hours.

Amino Acid Sequence↗
PubMed1995

Preparation of mono-radioiodinated tracers for study of the in vivo metabolism of atrial natriuretic peptide in humans.

In the present paper we evaluate the optimum chemical conditions for labelling atrial natriuretic peptide (ANP) and its metabolites and for preparing highly purified radiotracers which can be used for in vivo kinetic studies of ANP in humans. Synthetic alpha h1-28ANP and some hormone metabolites were iodinated with Na125I or Na131I by means of the lactoperoxidase (ANP) or the chloramine-T (ANP metabolites) technique. The biological activity of labelled ANP was tested by means of a binding study using mouse cardiac membranes. A high-performance liquid chromatography (HPLC) procedure was used to purify the labelled hormone and the principal labelled metabolites in venous plasma samples collected up to 50 min after the injection of 125I-labelled ANP from nine healthy men. The main ANP kinetic parameters were derived from the disappearance curves of the [125I]ANP, which were satisfactorily fitted by a biexponential function in all subjects. The main advantages of this tracer technique are: (1) high accuracy, allowing the identification of the metabolites produced in vivo under steady-state conditions after injection of the precursor (labelled hormone); (2) high sensitivity, allowing the detection of minimal quantities of metabolites (that cannot be identified on the basis of the integrated areas from the ultraviolet-absorbing peaks on HPLC); (3) high specificity, allowing the detection of possible in vitro artefactual generation of cleavage products of ANP using an internal labelled standard. Utilizing this tracer method, it was possible to estimate the principal parameters of ANP kinetics and also to plot the appearance curves of the labelled metabolites produced in vivo after the injection of the labelled precursor.

Adult↗
PubMed1995

In vivo measurement of ANP overall turnover and identification of its main metabolic pathways under steady state conditions in humans.

Using a tracer method, we evaluated, in vivo, the main turnover parameters and the main metabolic pathways of ANP in 10 normal subjects. HPLC was used to purify the labeled hormone and the principal labeled metabolites present in venous plasma samples collected at determined times after tracer injection. The main ANP kinetic parameters were derived from the disappearance curves of [125I] ANP, which were satisfactorily fitted by a biexponential function in all subjects. Newly produced ANP initially distributes in a large, plasma equivalent space (10.9 +/- 3.6 l/m2 body surface); the hormone rapidly leaves this space due to both degradation and to distribution in peripheral spaces. The mean residence time in the body (19.4 +/- 19.8 min) and the plasma equivalent total distribution volume (28.2 +/- 11.5 l/m2) indicate that ANP is also widely distributed outside the initial space in humans (circulating ANP is no more than 1/15 of the body pool). Metabolic clearance rate values were distributed across a wide range (from 740 ml/min/m2 to 2581 ml/min/m2, mean 1849 ml/min/m2), and were shown to strongly correlate (R = 0.962) with the daily urinary excretion of sodium. A complete separation of labeled ANP from its labeled metabolites was achieved by the HPLC technique; at least 3 different peaks due to labeled metabolites in vivo produced from the injected [125I]ANP1-28 were found. The first chromatographic peak eluted showed an identical elution time to monoiodotyrosine. At least two other peaks due to in vivo generated labeled metabolites were well identified in the chromatograms: one peak (coeluting with labeled COOH-terminal tripeptide, H-Phe-Arg-Tyr-OH) was eluted ahead and one (coeluting with labeled peptide fragments ANP7-28, ANP13-28, and ANP18-28) behind the elution peak of the labeled ANP. The peak of labeled tyrosine appearing in the plasma ranged between 3 and 5 min after tracer injection; the other two peaks of radioiodinated metabolites showed their highest activity in the first sample (1.5 min), suggesting an earlier occurrence of their peaks. These labeled metabolites seem to be intermediate peptides, between the intact circulating form of the hormone and the final labeled metabolite (tyrosine), which is the last amino acid of the peptide hormone, produced in vivo after injection of the tracer.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

Effects of peptide T derivatives on the proliferation of cultured human keratinocytes.

[D-Ala1]peptideT-amide, the linear hexapeptide H-Thr-Hse-Asn-Tyr-Thr-Asp-OH (LPT) and its cyclic analog, cyclo(-Thr-Hse-Asn-Tyr-Thr-Asp-) (CPT), were tested for their effects on the proliferation of cultured normal human keratinocytes (KTs) in comparison with vasoactive intestinal peptide (VIP). [D-Ala1]PT-NH2, LPT and VIP (all 0.1 mumol/l) increased the cell number in KT cultures, whereas CPT was ineffective. The VIP antagonist [N-Ac-Tyr1,D-Phe2]GRF (1-29)-NH2 significantly inhibited the VIP effects on KTs. On the other hand this antagonist did not affect the peptide T (PT) compounds-induced stimulation of KTs, providing indirect evidence that the mitogenic effects of VIP and PT peptides are probably mediated via different receptors.

Adenosine↗
PubMed1995

Synthesis and opioid activity of tyrosine sulfate containing dermorphin and deltorphin peptides.

To study the effect of the sulfate ester moiety on the opioid activity, we prepared two tyrosine sulfate-(Tyr(SO3H)-containing dermorphin and deltorphin peptides. Their activities were determined in binding studies based on displacement of mu- and delta-receptor selective radiolabels from rat brain membranes and in two bioassays, using guinea pig ileum and mouse vas deferens. In comparison to original peptides and morphine, the obtained data indicate that whereas H-Tyr(SO3H)-D-Ala-Phe-Gly-NH2 shows very minimal interaction with opioid receptors, H-Tyr(SO3H)-D-Ala-Phe-Asp-Val-Val-Gly-NH2 retains a significant activity.

Amino Acid Sequence↗
PubMed1994

A bioactive fullerene peptide.

The highly hydrophobic C60 (buckminsterfullerene) was water solubilized by covalently linking the synthon 1,2-dihydro-1,2-methanofullerene [60]-61-carboxylic acid to the alpha-amino group of the hydrophilic 4-8 sequence of peptide T, known to display potent human monocyte chemotaxis. The resulting compound, characterized by a variety of analytical techniques, including a UV spectrum in aqueous solution, exhibits remarkable chemotactic potency, comparable to that of the parent pentapeptide. Furthermore, this fullerene-peptide conjugate inhibits, albeit weakly, HIV-1 protease.

Amino Acid Sequence↗
PubMed1994

Synthesis and biological activity of D-glucopyranosyl peptide T derivatives.

The solid phase procedure, based on the Fmoc (9-fluorenylmethyloxycarbonyl) chemistry, was used to prepare some peptide T analogues in which D-glucopyranosyl units are beta-O-glycosidically linked to Thr4 and/or Thr5 side chains. All glycopeptides showed significant human monocyte chemotaxis and high resistance to degradation by plasma or brain enzymes.

Amino Acid Sequence↗
PubMed1994

Synthesis and activity of new linear and cyclic peptide T derivatives.

Linear and head to tail cyclic hexapeptide analogs (Xaa-Thr-Thr-Asn-Tyr-Thr, Xaa = D-Asp or D-iso-Asp) of peptide T were prepared and tested for human monocyte chemotaxis. All new compounds showed significant bioactivity. In particular, the conformational restriction introduced into cyclo(-D-iso-Asp-Thr-Thr-Asn-Tyr-Thr-) was very suitable for CD4 receptor binding. The cyclic peptides also proved to be highly resistant to degradation by plasma or brain enzymes.

Amino Acid Sequence↗
PubMed1993

Structure-activity relationships of cyclic and linear peptide T analogues.

Using the potent cyclic peptide T analog [formula: see text] as parent compound, a series of analogues were synthesized and their potencies in a monocyte chemotaxis assay were compared with those of correspondingly modified linear peptides. Structure-activity relationships observed with cyclic compounds did not always parallel those determined with linear analogues. [formula: see text] showed the highest affinity to CD4 receptor of monocytes of any peptide thus far studied. It also proved to be highly resistant to degradation by plasma or brain enzymes.

Amino Acid Sequence↗
PubMed1993

Studies on the anti-phospholipase A2 and anti-inflammatory activities of a uteroglobin fragment and related peptides.

The nonapeptide antiflammin P1 (H-Met-Gln-Met-Lys-Lys-Val-Leu-Asp-Ser-OH), its isoAsp8 analogue and the corresponding aminosuccinyl peptide were prepared, characterized and tested for inhibition of phospholipase A2 (PLA2) in vitro and for anti-inflammatory activity in vivo under assay conditions recently recommended. All peptides are devoid of PLA2 inhibitory and anti-inflammatory activity.

Amino Acid Sequence↗
PubMed1991

New insights on mu/delta selectivity of opioid peptides: conformational analysis of deltorphin analogues.

The message domain of dermorphin (Tyr-D-Ala-Phe), a natural mu-opioid heptapeptide, has long been considered the main cause of the high mu selectivity of this peptide and of its analogues. The recent discovery, in the skin of Phyllomedusa sauvagei (i.e., the same natural source of dermorphin) and of Phyllomedusa bicolor of deltorphins, challenges this belief. Deltorphins, in fact, are three heptapeptides characterized by a message domain typical of mu-selective peptides, but endowed of an extremely high delta selectivity, the highest of all natural opioid peptides. A conformational analysis of dermorphin and deltorphins, based on nmr studies in DMSO and cryoprotective mixtures and internal energy calculations, showed that the enormous differences in receptor selectivity can be interpreted on the basis of receptor models for mu and delta opioids that recognize the same beta-turn in the N-terminal part, but discriminate for the conformation and polarity of the C-terminal part. Here we present the synthesis, biological activity, and conformational analysis in solution of three deltorphin analogues with very similar constitution, but with different net charge, different location of negative residues, or even without negative residues, which confirm these hypotheses and show that His4 can play a specific structural role.

Amino Acid Sequence↗