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Biomedical subjects

F Naider

Publications and source records attributed to F Naider.

132 records · Page 8Linked to original sources
PubMed1971

Conformation of cyclolinopeptide a observed by circular dichroism.

A stereochemical investigation, by circular dichroism, of a synthetic nonapeptide (cyclolinopeptide A) in several organic and organic-sulfuric acid solvents is presented. From this examination, and results found for a conformationally rigid model compound, 1,7,7-trimethyl-3-azabicyclo [2.2.1] heptan-2-one(camphorolactam), it is concluded that cyclolinopeptide A may exist in several conformations in solution. None of these conformations is believed to be stabilized by intramolecular hydrogen bonds. Some details on an x-ray analysis of the cyclic nonapeptide are also presented.

Journal Article↗
PubMedDate not supplied

Conformational studies of nikkomycin X in aqueous solution.

Nikkomycin X is a peptidyl-nucleoside antibiotic that inhibits chitin synthesis in fungi. Information on its conformation in aqueous solution was obtained from pH titration studies in which the nmr shifts of exchangeable and nonexchangeable protons were monitored. These studies and nuclear Overhauser effects support an unfolded or conformationally flexible structure for the antibiotic, and the syn and anti conformations of the nucleoside moiety were found to coexist. The conformation of the ribose ring was determined using a two-state model; a slight shift from type N to type S conformers occurred as the pH was raised from 1 to 6.

Aminoglycosides↗
PubMedDate not supplied

Hydrolysis of oligopeptides by sera used in cell and tissue culture.

Sera commonly used in cell and tissue culture as medium supplements possess high peptidase activity. Pligopeptides incubated with 1% serum are rapidly hydrolyzed to intermediate length peptides and the constituent amino acids. Hydrolysis of lysine peptides is difficult to verify by a quantitative ninhydrin procedure because of reaction of the lysine epsi-lon-amino group and serum components with ninhydrin. Attempts to evaluate oligopeptides as sole sources of indispensable amino acids for cultured mammalian cells are of doubtful value when serum is used as a medium supplement.

Blood↗
PubMedDate not supplied

Multiplicity and regulation of genes encoding peptide transporters in Saccharomyces cerevisiae.

The model eukaryote Saccharomyces cerevisiae has two distinct peptide transport mechanisms, one for di-/tripeptides (the PTR system) and another for tetra-/pentapeptides (the OPT system). The PTR system consists of three genes, PTR1, PTR2 and PTR3. The transporter (Ptr2p), encoded by the gene PTR2, is a 12 transmembrane domain (TMD) integral membrane protein that translocates di-/tripeptides. Homologues to Ptr2p have been identified in virtually all organisms examined to date and comprise the PTR family of transport proteins. In S. cerevisiae, the expression of PTR2 is highly regulated at the cellular level by complex interactions of many genes, including PTR1, PTR3, CUP9 and SSY1. Oligopeptides, consisting of four to five amino acids, are transported by the 12-14 TMD integral membrane protein Opt1p. Unlike Ptr2p, distribution of this protein appears limited to fungi and plants, and there appears to be three paralogues in S. cerevisiae. This transporter has an affinity for enkephalin, an endogenous mammalian pentapeptide, as well as for glutathione. Although it is known that OPT1 is normally expressed only during sporulation, to date little is known about the genes and proteins involved in the regulation of OPT1 expression.

Amino Acid Sequence↗