An improved method for the separation of peptides and alpha-amino acids on copper-Sephadex

Hepatoprotective effects of Ganoderma lucidum peptides against D-galactosamine-induced liver injury in mice

Ganoderma lucidum (GL), a traditional Chinese medicinal mushroom, has been widely used for the treatment of chronic hepatopathy of various etiologies. The hepatoprotective activity of peptides from Ganoderma lucidum (GLP) was evaluated against d-galactosamine (d-GalN)-induced hepatic injury in mice. GLP was administered via gavage daily for 2 weeks at doses of 60, 120 and 180 mg/kg, respectively. Control groups were given the same amount of physiological saline synchronously. Then the mice from d-GalN control and GLP-treated groups were treated with d-GalN (750 mg/kg) suspended in normal saline by intraperitoneal injection. d-GalN-induced hepatic damage was manifested by a significant increase in the activities of marker enzymes (AST, ALT) in serum and MDA level in liver (P<0.01), and by a significant decrease in activity of SOD and GSH level in liver (P<0.01). Pretreatment of mice with GLP reversed these altered parameters to normal values. The biochemical results were supplemented by histopathological examination of liver sections. The best hepatoprotective effects of GLP were observed after treatment with the dose of 180 mg/kg as it was evidenced from biochemical parameters and liver histopathological characters which were similar to those of normal control group. Results of this study revealed that GLP could afford a significant protection in the alleviation of d-GalN-induced hepatocellular injury.

Chromatographic behavior of Bothrops erythromelas phospholipase and other venom constituents on Superdex 75

In a chromatographic method modification intended to preserve protease activity in Bothrops erythromelas venom, 2 mM CaCl2 was added to the gel filtration buffer [50mM Tris/HCl/150mM NaCl (pH 8.0)], in lieu of an equimolar portion of NaCl. This minor compositional change induced significant differences in the venom elution profile on Superdex 200. For this reason, the influence of buffer composition on chromatographic behavior was investigated using an analytical Superdex 75 HR 10/30 column. Phospholipase (PLA) was used as a marker because Naja atra PLA had previously been observed to interact hydrophobically with this resin. PLA elution volumes generally increased as buffer pH decreased. Addition of 20% acetonitrile to the Tris buffer with CaCl2, reduced hydrophobic interaction of the PLA so significantly that its elution was non-overlapping in the two buffers. Other venom constituents, including bradykinin-potentiating peptides and probable hemorrhagic metalloproteases, were similarly affected. Buffer calcium, bound by vicinal dextran hydroxyl groups, appears to retard elution of this acidic PLA.

Chromatographic separation of mixed peptides from amino acids in biological digests with volatile buffers

Two chromatographic methods, capable of separating mixed peptides from contaminating amino acids in biological digests, are described. Both methods involve separation on copper-Chelex resin, but each uses a different set of elution buffers. When separation method 1 was applied to a commercially available proteolytic digest of casein, the free amino acid content was reduced from 26.0% to 0.5%. With an enzymic digest of 14C-labelled proteins derived from plant biomass, separation method 2 decreased the contaminating free amino acids from 20.3% to 1.9%. Since the separated peptides are eluted with volatile buffers, they are suitable as substrates for biological experiments.

Effect of peptide chain length on absorption of egg protein hydrolysates in the normal human jejunum

The influence of the peptide chain length of partial enzymic hydrolysates of protein on nitrogen and amino acid absorption was studied in 12 subjects using a jejunal perfusion technique. Three hydrolysates of egg white and an equivalent amino acid mixture were perfused at 30 mmol/L and 100 mmol/L in two separate experiments. Two hydrolysates (OH1 and OH2) contained mainly dipeptides and tripeptides, whereas the third (OH3) comprised tripeptide to pentapeptides as judged chromatographically. Nitrogen absorption was significantly slower from the higher chain length mixture, OH3, than from the short chain mixtures, OH1 and OH2, at both concentrations. Similarly, several amino acid residues were absorbed less well from OH3 than from OH1 and OH2. These data demonstrate that the chain length of heterogeneous mixtures of peptides affects absorption of nitrogen and individual amino acid residues, and suggest that brush border hydrolysis of tetrapeptides and pentapeptides limits absorption from enzymic hydrolysates of protein which simulate the composition of the postprandial luminal contents.

Group separation of peptides by ligand-exchange chromatography with a Sephadex containing N-(2-pyridylmethyl)glycine

The synthesis of 2-hydroxy-3[N-(2-pyridylmethyl)glycine]propyl Sephadex ether--a new chelating resin--is described. This resin has been employed in the form of its Cu2+ complex to separate peptides, as a group, from alpha-amino acids and NaCl. Ninety-seven ligands of different structures were separated chromatographically at room temperature. It was shown that two structural parameters of the ligands control the separation process, namely, the presence of ligand donor groups and the possibility for them to form chelate rings of suitable size. Separation of peptides from alpha-, gamma-, delta-amino acids, N-acetyl derivatives of amino acids (except N-Ac-Trp), and NaCl is possible if the peptides fulfill the following structural requirements: the peptide molecule must have a free terminal amino group; a carbonyl group (of the peptide linkage) must be situated in the alpha- or beta-position of the free amino group; and the peptide may not contain an imidazole residue (except Gly-Gly-His). A relationship was found between the log k' and the corresponding pKHHL, log KCuCuL, and log KCuBipyCuBipyL values. Interpretation of the different K' values was possible based on the different basicities of the terminal amino groups and on the structures of the different side chains of the peptides.

Profiling of urinary medium-sized peptides in normal and uremic urine by high-performance liquid chromatography

This report describes the profiling of medium-sized peptides in both normal and uremic urine by ion-pair reversed-phase high-performance liquid chromatography using an acetonitrile--heptafluorobutyric acid solvent system as eluent. Several medium-sized peptide peaks could be detected in both normal and uremic urine at low picomole level by using post-column fluorescence derivatization with fluorescamine. Contrary to expectation, uremic urine contained slightly larger amounts of medium-sized peptides compared with normal urine.

Purification of peptides: an efficient procedure for the separation of peptides from amino acids and salt

A novel method for the separation of peptides from amino acids and salts has been developed. Separation is achieved by passage of the sample through a column of octadecasilyl-silica (ODS). Peptides, but not amino acids and salts, are strongly retained by ODS in an aqueous mobile phase and can be recovered by elution with an aqueous-alcoholic mobile phase. The method is applicable to most peptides and is fast and simple. Moreover, it is characterized by good recovery yields and high sample capacity.