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Biomedical subjects

K Burger

Publications and source records attributed to K Burger.

51 records · Page 3Linked to original sources
PubMed1990

Acid-base properties and microspeciation of six angiotensin-type octapeptides.

The acid-base chemistry of six angiotensin II analogues (A II) was analyzed by determining two types of terms. Macroconstants were used to characterize the molecular proton-binding and dissociating ability of the octapeptides, and group constants to quantitate the submolecular basicity of each individual protonation site of the derivatives. The group constant values indicated that some sites (Arg-guanidino, Tyr-phenolate, C-terminal carboxylate) were of similar basicity in the different analogues, while others (His-imidazole, N-terminal amino) were significantly different. The group constant values are interpreted by taking into consideration the intramolecular effects of the adjoining moieties and are used for microspeciation.

Amino Acid Sequence↗
PubMed1988

7-Methylguanine nucleotides and their structural analogues; protolytic equilibria, complexing with magnesium (II) ion and kinetics for alkaline opening of the imidazole ring.

First-order rate constants for the alkaline opening of the imidazole ring of several 7-methylguanine nucleotides and their structural analogues were determined. The results obtained suggested that intramolecular interaction between the negatively charged 5'-phosphate group and the positively charged imidazole ring markedly retard the attack of hydroxide ion on the C8 atom of the 7-methylguanine ring. In contrast, hardly any influence on the acidities of the interacting base and phosphate moieties was detectable. No effect on the complexing of the phosphate group with magnesium(II) ion could be detected.

Chemical Phenomena↗
PubMed1987

Coordinative interactions in the separation of insulin and its derivatives by high-performance liquid chromatography.

The effects of various inorganic cations and anions on the chromatographic behaviour of insulin and its derivatives have been investigated. It was shown that on an octadecylsilica column at a given eluent composition the retention of insulins depends primarily on the nature of the anions. The cations have a secondary effect, depending on their size and coordination ability. The mechanism of the effect of the ions is complex. It includes the formation of ion pairs, their influence on dissociation processes, a silanophilic effect, coordination processes and changes in the structures of the insulins.

Animals↗
PubMed1985

Microcomputers enhance student health fairs.

To stimulate student interest in learning about health, faculty assigned students the task of planning and implementing a university health fair. Two questions were posed: (1) Could sophomore students effectively plan and implement a health fair as a learning opportunity? (2) Could microcomputers be used appropriately to influence client participation and to enhance the nurse-client interactions? Literature regarding the efficacy of the health fair as a mode of health care delivery and as a student learning opportunity and literature addressing the advantages of microcomputer use were reviewed. Two health fairs were piloted. Microcomputers were employed in three areas: nutrition, stress, and substance abuse. Students, with faculty guidance, developed educational materials using principles of teaching, learning, and health promotion. Clients rated the health fair as congruent with their health needs. Students identified learning gained from the experience. Students and clients were receptive to computer use. Future directions are discussed.

Community Participation↗
PubMed1983

Quantitative thin-layer chromatography of cobalamin complexes.

Quantitative thin-layer chromatography was used to study the hydroxo-, cyano- and dicyanocobalamin transformation equilibria. A new stereoisomer of cyanocobalamin was shown to be formed from dicyanocobalamin on the chromatographic plate. The formation, stability and UV spectrum of this compound (isocyanocobalamin) was studied.

Journal Article↗
PubMed1981

[Radiotherapy of the thymoma (author's transl)].

A report is given on 24 thymomas irradiated between 1971 and 1980. Ten patients were irradiated after a radical thymectomy, three after partial resection and eleven after histologic diagnosis alone The patients were treated by different irradiation methods, mostly with the photons of a Co60 unit and a 43 MeV betatron. The average focal dose was 45 Gy which were administered within five weeks. The observation period was five years on an average. The general five year survival probability was 54%; some partial collectives were evaluated individually. These studies show that by unique radiotherapy, too, a two-year survival rate of 100% and a five-year survival rate of 50% as sell as a local recurrence rate of about 20% can be reached. Patients under fourty years with epithelial thymomas and a dose of less than 40 Gy have a less favorable prognosis. Compared to other authors, a relatively high rate of remote metastases was observed which necessitated extensive follow-up measures and suggests an adjuvant chemotherapy.

Adolescent↗
PubMed1977

Coordination-chemistry study of polypeptides. III. protonation-deprotonation equilibrium study of synthetic alphaH -corticotropin1-32. Data on the pH-dependent conformation of corticotropin.

By potentiometric equilibrium measurements and the computer evaluation of experimental data, the protonation equilibrium constants of four fragments of corticotropin (ACTH), ACTH1-32. ACTH1-28, ACTH1-14 and ACTH1-4, were determined and assigned to the corresponding functional groups. From the dependence of the protonation constants on the length of the peptide chain, it was established which functional groups participate in the formation of intramolecular hydrogen-bonds in aqueous solutions at various pH. These results indicated a pH-dependent conformation of the molecule.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Proteolytically stable peptides by incorporation of alpha-Tfm amino acids.

A series of model peptides containing alpha-trifluoromethyl-substituted amino acids in five different positions relative to the predominant cleavage site of the serine protease alpha-chymotrypsin was synthesized by solution methods to investigate the influence of alpha-Tfm substitution on the proteolytic stability of peptides. Proteolysis studies demonstrated absolute stability of peptides substituted to the P1 position and still considerable proteolytic stability for peptides substituted at the P2 and P'2 positions compared with the corresponding unsubstituted model peptide. Comparison with peptides containing the fluorine-free disubstituted amino acid alpha-aminoisobutyric acid allowed to separate electronic from steric effects. Furthermore, the absolute configuration of the alpha-Tfm-substituted amino acid was found to exert considerable effects on the proteolytic stability, especially in P'1 substituted peptides. Investigations of this phenomenon using empirical force field calculations revealed that in the (S,R,S)-diasteromer the steric constraints exhibited by the alpha-Tfm group can be outweighed by an advantageous interaction of the flourine atoms with the serine side chain of the enzyme. In contrast, a favourable interaction between substrate and enzyme is impossible for the (S,S,S)-diastereomer.

Aminoisobutyric Acids↗
PubMedDate not supplied

[Positron lifetime studies of sodium- and zinc-hyaluronates].

The aim of this work was to test the positron lifetime technique (PLT) as a tool of the structure study of sodium- and zinc-hyaluronates. The information based on the PLT measurements (outlined as follows) proved that this method can be useful in this field as well. The lifetime of ortho-positronium (o-Ps) significantly increased and its intensity decreased in the samples containing Zn2+, comparing to Na-hyaluronates. It showed that the electronic orbitals are more closed in the case of Zn2+ cation that means the overlapping between the wave functions of the positron and of the electrons decreased. (See equation No 1.) The study of the effect of water content suggested that the hydrogen-bridge-bonds "localised" the free electron pairs. The increasing pressure increased the lifetime and it is an evidence that the effect of the cations (Na+ and Zn2+) can be explained rather with the change of the electronic structure than with the altering of the free volumes of the samples.

Adjuvants, Immunologic↗
PubMedDate not supplied

Prophage induction by alkylating ethyl methylaminosulfonate.

Treatment of the lysogenic strain M. lysodeikticus 53-40 (N5) with ethyl methylaminosulfonate results in a slight increase in infective center concentration of N5 phages which is only detectable once disturbing cells had been eliminated by lysozyme. After conversion of ethyl methylaminosulfonate with radioactive labelled guanosine at 37 degrees C, N7-ethyl-guanine could be ascertained. Therefore the biological activity of the drug may be due to an ethylation of DNA.

Alkylation↗