Biomedical subjects

F Kaddari

Publications and source records attributed to F Kaddari.

5 recordsLinked to original sources

PubMed1989

Ionic pores formed by cyclic peptides.

It is shown that 2 cyclic tetrapeptides, namely tentoxin and HC toxin, are able to induce the formation of transmembrane ionic channels, although a carrier mechanism could be expected on the basis of their chemical structure (presence of proline or N-methylated residues). Since other cyclic peptides but of larger size, i.e., tyrocidines, gramicidin S (decapeptides) and an octapeptide with a sequence similar to that of HC toxin, are also able to form pores, it appears that this property can be extended to a large number of cyclic peptides. A pore structure based on aggregates is proposed.

Circular Dichroism↗

PubMed1989

Conformations, cation binding, and transmembrane ion transfer properties of a cyclooctapeptide built by an alternation of D and L residues.

The conformations of a cyclic octapeptide built with an alternation of D and L residues are investigated on the basis of 1H n.m.r. and CD data. The cyclooctapeptide can form structures which are specific to the alternating D-L sequence. This peptide can form two types of complexes with cations (peptide 2-cation and peptide-cation complexes) and the binding with monovalent cation is weak. This peptide is able to induce transmembrane ion transfer through both a carrier mechanism and pore formation.

Acetonitriles↗

PubMed1987

Cyclic tetrapeptides with sequences related to HC toxin. Conformations and cation binding.

Peptides with sequences related to HC toxin (cyclo(LAla-DAla-L-Aoe-DPro] can adopt a conformation locked by three gamma turns. A "structure--spectroscopy characteristics" relationship is proposed. These peptides can complex Mg++ cations and the binding is accompanied by a transconformation of the peptide backbone. The relevance with the biological activity of the toxin is discussed.

Amino Acid Sequence↗

PubMed1986

Aggregation and ion transfer induced by tentoxin.

It is shown that tentoxin, a cyclic tetrapeptide with two N-methylated residues, is able, when added to lipid bilayers, to increase the transmembrane current through discrete events. Conformational investigations involving 1H-NMR, infrared and circular dichroism studies show that, at concentrations above 7 X 10(-5) M, the cyclic tetrapeptide aggregates in chloroform. We suggest that the aggregates could form a pore through a stacking of cycles.

Circular Dichroism↗

PubMedDate not supplied

[Neonatal screening of glucose-6-phosphate dehydrogenase deficiency in umbilical cord blood].

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most frequent enzyme deficiency. It is a sex-linked genetic disease concerning mostly african, mediterranean and far-eastern populations. The main clinical expression is a hemolytic anemia which can be acute or chronic. During the neonatal period the disease may manifest as neonatal jaundice. We have been asked by the neonate department to set up a blood screening test for this deficiency. We have therefore developed a test using umbilical cord blood. The assay of G6PD has been automatised and red blood cell aspartate-amino-transferase (ASAT) chosen as a reference enzyme to evaluate the age of red blood cells. Normal values of G6PD, ASAT and G6PD/ASAT ratio have been calculated from 235 cord samples. Genetic frequency of this deficiency in 2002 was 6% in male and 1% in female newborns.

Acute Disease↗