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Biomedical subjects

J A Burton

Publications and source records attributed to J A Burton.

At least 19 recordsLinked to original sources
PubMed2005

Use of the excluded protecting group (EPG) method for peptide synthesis.

The excluded protecting group (EPG) method has been used for the solution synthesis of several peptides including Merrifield's Model Tetrapeptide, linear antamanide and an analogue of magainin-1, [Ala(19), Asn(22)]magainin-1. In the approach reported, the C-terminal amino acid is esterified to the 2-position of cholestane as the [2s,3s]iodohydrin ester and the penultimate amino acid added to the aminoacyl-steroid as the Fmoc-pentafluorophenyl-ester. The Fmoc group is removed with Et(2)NH/DMF ( approximately 15% v/v) and, after evaporation to approximately 10 mL, the solution chromatographed on Sephadex LH-20 in DMF. The dipeptidyl-steroid elutes as the free amine well separated from other reaction mixture components. Fractions containing the dipeptide, as determined by counting and TLC, are pooled and reacted with the next Fmoc-amino acid-pentafluorophenyl ester in the sequence. Repetition of the deprotection/purification/reaction cycle yields the fully protected peptide. On completion of the synthesis, the cholestane iodohydrin ester is selectively removed by treatment with Zn degrees /AcOH to yield the peptide with intact alpha-amino and side chain protecting groups. Global deprotection is achieved with HF. All intermediates from the syntheses reported were characterized. The magainin analogue was shown to have full biologic activity. The Fmoc iodohydrin esters of 16 of the 20 proteogenic amino acids have been prepared and characterized for use as the C-terminal amino acids in other EPG syntheses.

Amino Acid Substitution↗
PubMed1998

Peptide aldehyde inhibitors of the kallikreins: an investigation of subsite interactions with tripeptides containing structural variations at the amino terminus.

A series of tripeptide aldehyde derivatives containing variations at the P3 subsite and the amino terminus has been prepared and evaluated for trypsin-like serine protease inhibition. These compounds exhibit strong in vitro inhibition of human plasma kallikrein (HPK), porcine pancreatic kallikrein (PPK) and human plasmin (HP). As suspected from an examination of a related crystal structure, the presence of a hydrophobic residue (adamantyl) at the amino terminus dramatically improves the binding to PPK. The adamantyl group, however, represents a peak in binding; larger residues cause the binding to be reduced, and thus are less well accommodated in this subsite. Although both HP and HPK also can accept large molecular volume at the amino terminus, they do not exhibit the same preference for large residues at this subsite that is demonstrated by PPK. Selectivity differences also are observed with P3 subsite substitution; with PPK preferring a bulky, but compact side-chain (t-butyl) and HP and HPK preferring a more extended (e.g. benzyl) group.

Aldehydes↗
PubMed1989

Tinea incognito.

Explore the source record for details and available documents.

Face↗
PubMed1987

Isolation of mutants of Candida glabrata resistant to miconazole.

Elucidation of the mode of action of azole antifungals would be aided by studying resistant mutants. It is difficult to obtain mutants of Candida albicans in the laboratory, and there have only been a few studies on clinical isolates which seem to be resistant because of impaired drug uptake. C. glabrata, unlike C. albicans, is haploid and more likely to give rise to resistant variants. Over 30 mutants have been isolated by selection with miconazole on solid medium and have MICs of miconazole about ten times that of the parental strain. One such mutant has a reduced growth rate and final cell yield. In intact cells, ergosterol biosynthesis is tenfold less sensitive to miconazole than in the parent. However, uptake of [3H]miconazole by cells is identical in both strains. The significance of these observations is discussed.

Amino Acids↗
PubMed1983

Choosing an information system to meet specific needs.

Because of the increasing number of information systems on the market today, the user must select the system wisely according to the vendor's ability to solve specific company needs. An organization must know its filing and retrieval requirements, its potential for growth, etc., and must then contact only those vendors that fit specific company requirements. The vendor's reputation in the field, service history, "after-sales support," and ability to supply cost analyses should all be examined.

Commerce↗
PubMed1977

Enhancement of pulmonary drug absorption in the rat by bromphenol blue and related dyes.

1. Pulmonary absorption studies in the rat showed that intratracheally administered 5-10 mM bromphenol blue, bromcresol green and bromthymol blue markedly increased the absorption rate of 0.1 mM phenol red. 2. Similarly, 1-10 mM bromphenol blue increased the absorption rate of 0.1 mP p-,minohippuric acid, tetraethylammonium and mannitol by 2- to 18-fold in a concentration-dependnet manner. 3. Mannitol absorption was enhanced more by bromthymol blue, sulphobromophthalein, bromcresol purple, thymol blue and bromcresol green than by bromphenol blue or m-cresol purple. Chlorphenol red and phenol red had no effect on mannitol absorption. 4. The results indicated that certain sulphonic acid dyes increase the permeability of the respiratory tract epithelium, perhaps by increasing its porosity.

Aminohippuric Acids↗
PubMed1976

The renin-angiotensin-aldosterone system in congestive failure in conscious dogs.

The role of the renin-angiotensin-aldosterone system in the development of congestive failure has been assessed in the conscious dog by use of the nonapeptide converting enzyme inhibitor. Constriction of the pulmonary artery or thoracic inferior vena cava was maintained for 2 wk while daily measurements were made of plasma renin activity, plasma aldosterone, plasma volume, hematocrit, serum sodium and potassium concentrations, sodium and water balance, body weight, and arterial, caval, and atrial pressures. The initial response to constriction was a reduction in blood pressure, a rise in plasma renin activity, plasma aldosterone, and water intake, and nearly complete sodium retention. In the days after moderate constriction plasma volume and body weight increased (with development of ascites and edema); blood pressure, sodium excretion, plasma renin acvitity, and plasma aldosterone returned to normal. In animals in which blood pressure was not restored, plasma renin activity and plasma aldosterone remained elevated throughout the period of constriction. Single injections of converting enzyme inhibitor reduced blood pressure when plasma renin activity was elevated. Chronic infusion of the inhibitor in dogs with thoracic inferior vena caval constriction prevented the restoration of blood pressure and suppressed the rise in plasma aldosterone; sodium retention and volume expansion were less than in control experiments. Thus the renin-angiotensin-aldosterone system plays an essential role in the maintenance of blood pressure during the genesis of congestive failure. Initially, the restoration of blood pressure is dependent upon circulating angiotensin II; in the later stages, blood pressure is dependent upon the increase in plasma volume.

Aldosterone↗
PubMed1974

Tuberculosis as a continuing cause of renal amyloidosis.

In 40 patients with renal amyloidosis seen in a ten-year period tuberculosis was the major preceding disease in 20, though it was active in only two at diagnosis. Most patients presented with renal failure, and only two survived for five years. This experience (at least, in the west of Scotland) conflicts with the generally accepted view that rheumatoid arthritis is the commonest cause of renal amyloidosis.

Acute Kidney Injury↗
PubMed1974

The measurement of response force during a lever-press shock-escape procedure in rats.

Three albino rats were given extensive exposure to an escape procedure in which shocks were scheduled to occur 30 sec apart. The amount of downward force exerted on the lever was continuously recorded and compared with traditional discrete measurement in which only responses above an arbitrary force threshold were recorded. Subjects typically remained in contact with the lever throughout the shock-free intertrial interval. Shock onset reliably occasioned a brief lurch from and return to the lever, which resulted in a lever-press escape response being recorded. Lever contact, which occupied an average of 90% of session time, showed great stability in force after a brief (e.g., 5-sec) period of instability after each shock terminated. In general, continuous measurement revealed considerably different results than discrete measurements of on-lever behavior. For example, continuous lever contact fluctuating near response threshold was often recorded as discrete responding, and sustained lever contact occurring below response threshold was omitted from discrete measurement.

Animals↗