Reversed-phase chromatography of pentosidine-containing CNBr peptides from collagen

Investigation of the pyrolysis products of methionine-enkephalin-Arg-Gly-Leu using liquid chromatography-tandem mass spectrometry

Low-temperature pyrolysis of methionine-enkephalin-Arg-Gly-Leu has been carried out and the non-volatile residues have been analyzed. The fragments were separated and characterized by LC-UV/Vis-MS/MS. Two major types of pyrolysis products were identified by matching the experimental results with a theoretical list that contains the expected fragments. These products were mainly composed of cyclic oligopeptides and linear fragments produced from the peptide backbone. These fragments have preserved the sequence of amino acids in the peptide. In some cases, a complete or partial loss of an amino-acid side group was observed. Tandem mass spectrometry and cyanogen bromide cleavage experiments were used to confirm the nature of the cyclic and linear pyrolysates, in addition to chromatographic and mass spectrometric data of actual standard synthetic cyclic peptides.

Application of Pluronic copolymer liquid crystals for the capillary electrophoretic separation of collagen type I cyanogen bromide fragments

A capillary electrophoretic method exploiting the properties of Pluronic copolymer liquid crystals (F127) was developed for the separation of collagen cyanogen bromide (CNBr) fragments. The separations obtained were at least comparable (if not better) to those obtained by other methods applicable to this category of compounds. In the optimized version a bare silica capillary [47 cm (40 cm to the detector) x 75 microm I.D.] was used with 10 mM Tris and 75 mM phosphate buffer (pH 2.5) containing 7.5% Pluronic F127 copolymer. The separation mechanism which involves both the molecular sieving and surfactant properties of the Pluronic F127 gel phase is discussed.

Separation of proteins and peptides by capillary electrophoresis in acid buffers containing high concentrations of surfactants

Separations of proteins at acid pH in the presence of a high concentration of surfactant [sodium laurylsulfate (SDS), 50 mmol/l] was investigated. The purpose of using high concentrations of SDS as background electrolyte modifier was threefold: First, the surfactant exerts a washing effect upon the capillary wall thus preventing binding of analytes and possible clogging of the capillary. Second, it was revealed that even under very acid conditions (below pH 3) the surfactant is capable of forming associates with protein analytes which still bear considerable negative charge and can be separated on this basis. Third, the system can be applied not only for protein mixtures sufficiently soluble in neutral to alkaline media (leukocyte lysates, standard proteins), but it can be used also with proteins, that are under such conditions virtually insoluble and their solubilization is possible in acid buffers only (eggshell proteins or collagen CNBr fragments). The result was that adsorption to the capillary wall was minimized and the analytes were separated as negatively charged associates with high efficiency. With collagen fragments partition was possible on the affinity differences of the peptides to the surfactant micelles and inner wall of the capillary. Theoretical plate counts approaching 100,000 were easily achieved even with proteins which under the more conventional operation conditions exhibit considerable sticking to the capillary wall. The other feature of this system is that the associates move very rapidly to the anode. Owing to the low pH, endoosmotic flow is negligible, and therefore the system has to be operated at reversed polarity.

Binding of lead to collagen type I and V and alpha2(I) CNBr (3,5) fragment by a modified Hummel-Dreyer method

Binding of lead (as lead acetate) to collagen type I alpha, and alpha2 chains, collagen type V and a large cyanogen bromide fragment of type I collagen [alpha2(I)CB(3,5)] was investigated by the large-zone Hummel-Dreyer method. It was demonstrated that two categories of binding sites exist in the collagen molecule, the number of which correlates rather well with the available aspartic and glutamic acid residues. Similar results were obtained for all collagen chains (fragments) used. The number of sites thus obtained was compared with the cross-striation pattern (reflecting areas where lead is bound) of the SLS form of collagen type I (alpha1 chain); it is suggested that the number of bands seen in the SLS form reflects primarily the number of available aspartic acid residues in the molecule. The association constants obtained are comparable with the low affinity interactions seen e.g., between Cu and bovine serum albumin.

Multicomponent analysis by off-line combination of synchronous fluorescence spectroscopy and capillary electrophoresis of collagen glycation adducts

Capillary electrophoresis separation and synchronous fluorescence spectral detection was used off-line to reveal the nature of fluorescent adducts formed in vivo in the collagen molecule and their distribution in the molecule. It was shown that by using the delta lamda in the area of the Stokes shift for the analyzed entities (approximately 10 nm for pentosidine, 4,5(E)-epoxy-2(E)-heptenal and 4,5(E)-epoxy-2(E)-decenal lysine adducts) a distinct profile of spectral bands can be obtained allowing for differentiation of the several entities involved. In combination with capillary electrophoretic separation of the CNBr peptides the location of individual adducts was possible: while pentosidine (and, perhaps, pentosidine related compounds K1-K4) is found in the large alpha 1(I)CB6 and alpha 2(I)CB3.5 peptides along with a complete set of the other fluorescent adducts, low-molecular-mass peptides originating from the terminal region of the molecule are devoid of any fluorescence. All other parts of the molecule possess synchronous fluorescence profiles corresponding to the intact molecule except that they are devoid of pentosidine. The results indicate random distribution of fluorescent adducts in the collagen molecule and, in a broader context, indicate the usefulness of multicomponent analysis by means of combining synchronous luminescence spectra and capillary electrophoresis.