Biomedical subjects

T F Gabriel

Publications and source records attributed to T F Gabriel.

14 recordsLinked to original sources

PubMed1991

Identification of 11,13-dihydroxy-14-octadecaenoic acid as a circulating Na+/K(+)-ATPase inhibitor.

Two digitalis-like compounds (DLC) were purified to homogeneity from bovine plasma. The purification procedure consisted of organic extractions and batch chromatography followed by three subsequent separations using reverse-phase high-performance liquid chromatography. The presence of a DLC in the different fractions was monitored by their ability to inhibit (a) [3H]ouabain binding to rat brain synaptosomes, and (b) microsomal Na+/K(+)-ATPase activity. Using mass spectrometry and nuclear magnetic resonance spectroscopy the structure of one of the DLCs was identified as 11,13-dihydroxy-14-octadecaenoic acid. It is suggested that this new hydroxy, unsaturated, fatty acid derivative may regulate Na+/K(+)-ATPase activity under some physiological and pathological conditions.

Animals↗

PubMed1987

Simple, rapid method for converting a peptide from one salt form to another.

A method for converting peptide trifluoroacetate salts to the corresponding acetate salts has been developed. The procedure involves reversed phase HPLC with a volatile buffer system. The method is exemplified by the conversion of Growth Hormone-Release Factor, GRF(1-44)-NH2 trifluoroacetate to the acetate which was achieved in greater than 95% recovery. Extensive analytical studies of the product confirmed the absence of trifluoroacetate and that the acetate salt was obtained without degradation. This procedure is expected to be generally applicable to other peptides and to other salt form conversions.

Chromatography, High Pressure Liquid↗

PubMed1984

Intramolecular dislocation of the COOH terminus of the lac carrier protein in reconstituted proteoliposomes.

A dodecapeptide corresponding to the carboxyl terminus of the lac carrier of Escherichia coli was synthesized, coupled to thyroglobulin, and the conjugate was used to generate site-directed polyclonal antibodies. The antibodies react with the carboxyl-terminal peptide and with the lac carrier protein, while monoclonal antibody 4B1 reacts with intact lac carrier protein, but not with the carboxyl-terminal peptide. Antibody 4B1 binds preferentially to right-side-out membrane vesicles relative to inside-out vesicles, confirming the presence of the 4B1 epitope on the periplasmic surface of the membrane. Alternatively, anti-carboxyl-terminal antibody binds preferentially to inside-out vesicles, demonstrating that the carboxyl terminus of the lac carrier protein is on the cytoplasmic surface. Surprisingly, both antibodies bind to proteoliposomes reconstituted with purified lac carrier protein, and quantitative binding assays indicate that the epitopes are equally accessible. When proteoliposomes containing purified lac carrier protein are digested with carboxypeptidases A and B, binding of anti-carboxyl-terminal antibodies decreases by greater than 80%, while binding of antibody 4B1 and various transport activities remain essentially unchanged. It is suggested that during reconstitution, the lac carrier protein undergoes intramolecular dislocation of the carboxyl terminus with no significant effect on its catalytic activity.

Amino Acid Sequence↗

PubMed1984

Isolation and identification of thymosin alpha 1 from calf spleen using high performance liquid chromatography.

A peptide isolated from calf spleen has been identified as thymosin alpha 1. The isolation involved defatting of the desiccated glands with acetone, extraction of the acetone power with pyridine acetate pH 5.5, heat denaturation, reverse phase chromatography on an RP-8 column, anion exchange chromatography on a Partisil SAX column and, finally, reverse phase purification on a microBondapak C18 column. The identification was based on: 1) amino acid analysis; 2) thermolysin digest; and 3) retention time in two different HPLC systems. The amount isolated from the spleen was 10-20% of that isolated from calf thymus glands.

Animals↗

PubMed1983

Confirmation of the primary structure of thymosin alpha1 by microsequence analysis of limited acid and enzymatic hydrolysis fragments.

The primary structure of the 28-peptide thymosin alpha 1 as determined by Goldstein et al. (1) has been confirmed by independent procedures. Limited dilute acid digestion generated a 26-peptide and a 22-peptide both extending to the C-terminal and lacking the N-terminal blocking group. A combination of Edman microsequencing, carboxypeptidase Y and thermolysin digestion, and fast atom bombardment mass spectrometry was used.

Amino Acid Sequence↗

PubMed1980

Synthesis of human beta-endorphin in solution using benzyl-type side chain protective groups.

A solution synthesis of human beta-endorphin (beta-EP) was carried out by condensation of protected peptide segments bearing N alpha-tert.-butyloxycarbonyl groups and benzyl-derived groups for the protection of functionalities in amino acid side chains. Five intermediate segments were assembled in a stepwise manner starting at the carboxyl terminus. Thus, the segment of sequence region (27-31) was coupled to segment (22-26) by the azide method. Segment (19-21) was incorporated into the growing chain by azide coupling, and segment (10-18) by dicyclohexylcarbodiimide coupling in the presence of 1-hydroxybenzotriazole (DDC-HOBt). Solubility problems in condensing the ensuing 22-peptide with segment (1-9) by DDC-HOBt were overcome by using a dimethylformamidephenol mixture as a solvent. Protecting group cleavage by Na in liquid NH3 was much superior to liquid HF which gave rise to many decomposition products. Homogeneous betah-EP indistinguishable from authentic material in physiochemical and biological properties, was obtained in a single preparative reversed phase liquid chromatographic step after protecting group cleavage.

Amino Acid Sequence↗

PubMed1977

Purification of protected syntheic peptides by preparative high performance liquid chromatography on silica gel 60.

A simple preparative system is described for rapid and efficient purification of protected synthetic peptides on a gram scale by high performance liquid chromatography on prepacked silica gel 60 columns. A variety of protected peptides up to tetradecapeptides have been chromatographed at pressures of 50 to 150 psi and obtained in analytically pure from within 2 to 4 h. With such commonly used protecting groups as N-benzyloxycarbonyl (Z), N-2-(p-biphenylyl)-2-propyloxycarbonyl (Bpoc), N-t-butyloxycarbonyl (Boc), O- and S-t-butyl (But), and S-acetamidomethyl (Acm), compounds were sufficiently soluble in chloroform, alcohols, acetic acid, or mixtures of these solvents for column loading. Dimethylformamide was also used as a solvent for loading. Solvent systems for column elution in isocratic, stepwise, or gradient modes were composed of chloroform, isopropanol, ethanol, or methanol and acetic acid in ratios that differed for each protected peptide depending on Rf values on t.l.c. plates. A simple chromatography is described which was self-assembled using standard instruments commonly in use in most laboratories. A shut-off valve was designed to prevent loss of material between fractions.

Chromatography, Liquid↗

PubMed1976

Preparative high-performance liquid chromatography applied to peptide synthesis.

A variety of protected synthetic peptides were purified by high-performance liquid chromatography on pre-packed silica gel columns. The compounds varied in protecting groups, amino acid composition and molecular weight. Flow-rates of two to four column volumes per hour were employed, with resultant back pressure of less than 150 p.s.i. A typical column load of 0.2-5 g was purified in 2-5 h.

Amino Acid Sequence↗

PubMed1973