PubMed Health⌕ Search

Biomedical subjects

D Andreu

Publications and source records attributed to D Andreu.

101 records · Page 6Linked to original sources
PubMed1985

On the primary structures of lysozyme, cecropins and attacins from Hyalophora cecropia.

Diapausing pupae of Cecropia respond to a bacterial infection by the selective synthesis of RNA and 15-20 hemolymph proteins. Of these we have purified lysozyme and two classes of antibacterial proteins called cecropins and attacins. The primary structure has been determined for the lysozyme, one attacin and five cecropins. We have also prepared a cDNA bank, isolated and sequenced clones corresponding to the lysozyme, the two main attacins and one cecropin. The results of these structural studies are briefly summarized. Finally we review the solid phase synthesis of cecropin A and B and 9 analogs of cecropin A.

Amino Acid Sequence↗
PubMed1985

Molecular cloning, cDNA sequencing, and chemical synthesis of cecropin B from Hyalophora cecropia.

Two cDNA clones containing coding information for cecropin B from the Cecropia moth (Hyalophora cecropia) were identified by means of a synthetic probe. Sequencing of the two inserts showed that cecropin B is processed from a 62-amino acid residue precursor molecule including a 26-residue leader peptide and a COOH-terminal glycine residue. The latter presumably donates the nitrogen of the amide group present on the COOH-terminal leucine residue of the mature cecropin B. The sequence deduced for the mature cecropin B differed in the COOH-terminal region from the tentative structure previously determined by carboxypeptidase digestion. To settle the discrepancy, cecropin B was synthesized according to the cDNA sequence with an amidated COOH-terminal leucine. Natural and synthetic cecropin B were found to be indistinguishable with respect to electrophoretic mobility and antibacterial activity against seven different bacteria. The COOH-terminal tetrapeptides were isolated from both natural and synthetic cecropin B and found to be indistinguishable. The correct sequence for cecropin B is (formula; see text).

Amino Acid Sequence↗
PubMed1983

Solid-phase synthesis of cecropin A and related peptides.

Cecropin A, a 37-residue antibacterial peptide amide, was synthesized by the solid-phase method. It was shown to be homogeneous and totally indistinguishable from natural cecropin A by chemical and physical criteria, as well as by its antibacterial activity against several Gram-positive and Gram-negative organisms. The synthetic material was also used to establish unambiguously that the carboxyl-terminal blocking group of natural cecropin A is a primary amide as tentatively proposed earlier. The role of the amino terminus of cecropin A in antibacterial activity was investigated by the synthesis of two analogs.

Anti-Inflammatory Agents↗
PubMedDate not supplied

Native-like cyclic peptide models of a viral antigenic site: finding a balance between rigidity and flexibility.

Antigenic site A of foot-and-mouth disease virus (serotype C) has been reproduced by means of cyclic versions of peptide A15, YTASARGDLAHLTTT, corresponding to residues 136-150 of envelope protein VP1. A structural basis for the design of the cyclic peptides is provided by crystallographic data from complexes between the Fab fragments of anti-site A monoclonal antibodies and A15, in which the bound peptide is folded into a quasi-cyclic pattern. Head-to-tail cyclizations of A15 do not provide peptides of superior antigenicity. Internal disulfide cyclization, however, leads to analogs which are recognized as one to two orders of magnitude better than linear A15 in both ELISA and biosensor experiments. CD and NMR studies show that the best antigen, CTASARGDLAHLTT-Ahx-C (disulfide), is very insensitive to environment-induced conformational change, suggesting that cyclization helps to stabilize a bioactive-like structure.

Amino Acid Sequence↗
PubMedDate not supplied

Solution versus solid-phase cyclization strategies for large sidechain lactam-bridged peptides: a comparative study.

A 22-residue peptide with a sidechain lactam bridge involving 18 residues (60-atom cycle) has been synthesized. Three different protection schemes using Fmoc/tBu/cyclohexyl, Fmoc/tBu/allyl or Boc/Bzl/ fluorenylmethyl protecting group combinations have been explored for the solid phase of the linear precursors, which have been subsequently cyclized in solution or in the solid phase. Cyclization yields in solution have been consistently better than on solid phase; however, the solid-phase strategy requires fewer purification steps and therefore global yields are comparable.

Amino Acid Sequence↗
PubMedDate not supplied

Synthetic peptides as functional mimics of a viral discontinuous antigenic site.

Functional reproduction of discontinuous antigenic site D of foot-and-mouth disease virus (FMDV) has been achieved by means of synthetic peptide constructions that integrate into a single molecule each of the three protein loops that define the antigenic site. The site D mimics are designed on the basis of the X-ray structure of FMDV type C-S8c1 with the aid of molecular dynamics, so that the five residues assumed to be involved in antigenic recognition are located on the same face of the molecule, exposed to solvent and defining a set of native-like distances and angles. The designed site D mimics are disulphide-linked heterodimers that consist of a larger unit containing VP2(71-84), followed by a polyproline module and by VP3(52-62), and a smaller unit corresponding to VP1(188-194). Guinea pig antisera to the peptides recognize the viral particle and compete with site D-specific monoclonal antibodies, while inoculation with a simple (non-covalently bound) admixture of the three VP1-VP3 sequences yields no detectable virus-specific serum conversion. Similar results have been reproduced in two cattle. Antisera to the peptides are also moderately neutralizing of FMDV in cell culture and partially protective of guinea pigs against challenge with the virus. These results demonstrate functional mimicry of the discontinuous site D by the peptides, which are therefore obvious candidates for a multicomponent peptide-based vaccine against FMDV.

Amino Acid Sequence↗
PubMedDate not supplied

Conjugation of epitope peptides with SH group to branched chain polymeric polypeptides via Cys(Npys).

Since bioconjugates may play an important role as therapeutics in the future, the development of new and effective conjugation strategies is necessary. For the attachment of peptide-like molecules to carriers, there are two main coupling methods involving amide or disulfide bonds. Conjugation through an amide bond can be achieved in several well-defined ways known from peptide chemistry. However, the formation of disulfide bridges between cysteine-containing peptides and carrier molecules still has some problems. In this paper, we describe a novel approach in which the carrier polypeptide is modified by 3-nitro-2-pyridinesulfenyl (Npys)-protected cysteine and this derivative has been applied for conjugation of Cys-containing epitope peptides with poly(L-lysine)-based branched polypeptides. Considering the stability of Npys group in the presence of pentafluorophenol, Boc-Cys(Npys)-OPfp dervivative was selected for introduction to the N-terminal of branches of polypeptides backbone. The branches of the polymers were built up from oligo(DL-alanine) (poly[Lys(DL-Ala(m))], AK) and elongated by an optically active amino acid [poly[Lys(X(i)-DL-Ala(m))], XAK]. We found that the nature of X (Glu, Ser, Thr) has great influence on the incorporation of the protected cysteine residue. Herpes simplex virus and adenovirus epitope peptides were conjugated to Boc-Cys(Npys)-modified polypeptides. Results indicate that the incorporation of epitope peptides depends on the number of Npys group on the polymers as well as on the presence/absence of Boc-protecting group on the Cys residue. This new class of Cys(Npys)-derivatized branched polypeptides is stable for a couple of months and suitable for effective preparation of epitope peptide conjugates possessing increased water solubility.

Affinity Labels↗
PubMedDate not supplied

D-enantiomers of 15-residue cecropin A-melittin hybrids.

The all-D enantiomers of six 15-residue hybrids of cecropin A and melittin were synthesized. They contained the seven N-terminal residues of cecropin A, followed by eight residues from the N-terminal region of melittin. They were pure and of the correct composition and structure. The peptides were compared with their all-L enantiomers. The L and D isomer pairs were each exact mirror images by circular dichroism at several concentrations of hexafluoroisopropanol, and at 12 or 20% were highly helical. The L analogs were rapidly hydrolyzed by trypsin but the D analogs were very resistant, making them suitable candidates for orally active drugs. These 15-mers did not form ion channels in normal lipid bilayers made in decane, but those bilayers made in squalene were thinner and the peptides did form ion-conducting channels. The D/L pairs of peptides were very active antibiotics against five representative Gram-negative and Gram-positive bacteria. In each case the D and L isomers were essentially equally active within experimental error. This is interpreted to mean that the peptides do not act by tight interactions with chiral receptors, enzymes or lipids. The action of these peptides against these organisms is best explained by self-aggregation and the formation of ion-conducting pores across bacterial membranes.

Anti-Bacterial Agents↗
PubMedDate not supplied

Compatibility of the S-(3-nitro-2-pyridinesulfenyl) protecting group with DCC/HOBt coupling chemistry.

Two recent reports on the partial lability of the 3-nitro-2-pyridinesulfenyl (Npys) thiol protecting group towards 1-hydroxy-benzotriazole (HOBt) have prompted a rechecking of the chemical behavior of this group. Using both soluble and polymer-bound forms of Cys(Npys) as test materials, the complete stability of this protection against HOBt has now been definitively established, and its compatibility with Boc-benzyl-based solid-phase synthesis strategies has been clearly confirmed by stability assays against a wide range of reagents, as well as by the successful synthesis of several Cys(Npys)-containing peptides.

Amino Acid Sequence↗
PubMedDate not supplied

Peptide ionophores: synthesis and cation-binding properties of a bicyclic peptide containing glycine and lysine residues.

Peptide 1, cyclo(1,5-epsilon-succinoyl) (Lys-Gly-Gly-Gly)2, is a representative member of a family of polycyclic peptide ionophores characterized by C2 symmetry and a relatively flexible structure resulting from its high Gly content. Peptide 1 has been synthesized by two different solid-phase protocols from its linear precursors, H-Gly-Gly-Lys(Fmoc)-Gly-Gly-Gly-Lys(Fmoc)-Gly-OH and H-Gly-Gly-Lys(Z)-Gly-Gly-Gly-Lys(Z)-Gly-OH), and satisfactorily characterized by chemical means. The CD spectrum of 1 is compatible with a beta-folded structure, stabilized by two internal hydrogen bonds. The complexation behavior of 1 toward alkaline and alkaline-earth cations can be envisaged as an equilibrium between inclusion (1:1) and sandwich (2:1) complex models, with affinities in the 10(6) M-1 and 10(11) M-2 range, respectively. A slight preference of 1 for Sr2+ over other cations has been found.

Amino Acid Sequence↗