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Biomedical subjects

H Eckstein

Publications and source records attributed to H Eckstein.

At least 19 recordsLinked to original sources
PubMed2006

Protease-catalyzed synthesis of the tripeptide CCK(26-28), a fragment of CCK-8.

Two enzymatically synthetic strategies of the tripeptide derivative PhAc-Asp(OMe)-Tyr-Met-OAl are reported. The second strategy gains the advantage of more economical starting materials, less reaction steps and a higher overall isolated yield of this tripeptide fragment over the first strategy. The effect of the acyl-donor ester concentration and structure, the C-alpha protecting group of the nucleophile, reaction media, enzyme and the carrier on the tripeptide derivative synthesis were studied. This tripeptide selected is a fragment of the cholecystokinin C-terminal octapeptide (CCK-8), a potential therapeutic agent in the control of gastrointestinal function and also a drug candidate for the treatment of epilepsy.

Chymotrypsin↗
PubMed2004

Total enzymatic synthesis of cholecystokinin CCK-5.

This paper describes the enzymatic synthesis of the C-terminal fragment H-Gly-Trp-Met-Asp-Phe-NH2 of cholecystokinin. Immobilized enzymes were used for the formation of all peptide bonds except thermolysin. Beginning the synthesis with phenylacetyl (PhAc) glycine carboxamidomethyl ester (OCam) and H-Trp-OMe by using immobilized papain as biocatalyst in buffered ethyl acetate, the dipeptide methyl ester was then coupled directly with Met-OEt.HCl by alpha-chymotrypsin/Celite 545 in a solvent free system. For the 3+2 coupling PhAc-Gly-Trp-Met-OEt had to be converted into its OCam ester. The other fragment H-Asp(OMe)-Phe-NH2 resulted from the coupling of Cbo-Asp(OMe)-OH with H-Phe-NH2.HCl and thermolysin as catalyst, followed by catalytic hydrogenation. Finally PhAc-Gly-Trp-Met-Asp-Phe-NH2 was obtained in a smooth reaction from PhAc-Gly-Trp-Met-OCam and H-Asp(OMe)-Phe-NH2 with alpha-chymotrypsin/Celite 545 in acetonitrile, followed by basic hydrolysis of the beta-methyl ester. The PhAc-group is removed with penicillin G amidase and CCK-5 is obtained in an overall isolated yield of 19.6%.

Acetates↗
PubMed1998

Neutrophil function in peripheral arterial occlusive disease: the effects of prostaglandin E1.

The role of polymorph nuclear neutrophils (PMN) in limb ischemia and reperfusion has been recognized only in recent years. The present study aimed to investigate the systemic and local (in femoral venous blood) effects of intra-arterially or intravenously applied prostaglandin E1 (PGE1) on systemic and ischemia-induced local changes in neutrophil function. Thirty patients with intermittent claudication were randomly assigned to intra-arterial or intravenous infusion of prostaglandin E1 (10 microg i.a. or 15 microg i.v. over 30 min). Prior to infusion femoral arterial and venous blood samples were obtained from the predominantly affected leg under resting conditions and immediately after a 3-min period of ischemia induced by suprasystolic thigh compression. After 24 h additional blood samples were obtained at baseline, following infusion of prostaglandin E1, and again after another 3-min period of ischemia following the prostaglandin E1 infusion. Intra-arterially administered prostaglandin E1 caused an increase in the PMN count by 3.5 +/- 2% (p<0.05) and a decrease in free oxygen radical production by 13 +/- 8% (p<0.05) measured by whole blood chemiluminescence. Additionally, a trend for lower PMN filterabilities (9 +/- 12%, NS) was observed. Intra-arterially infused prostaglandin E1 significantly reduced the ischemia-induced decrease in neutrophil filterability (arterial and venous blood difference after ischemia -- control: 22 +/- 17% (p<0.05); IA PGE1: 8 +/- 11% (NS), each compared to baseline). Intravenously administered prostaglandin E1 showed similar systemic effects as the intra-arterial application, but did not affect the ischemia-induced changes in neutrophil filterability. In conclusion, prostaglandin E1 reduces PMN activation in patients with peripheral arterial occlusive disease.

Aged↗
PubMed1995

A dodecapeptide comprising the extended chain-alpha 4 region of the restriction endonuclease EcoRI specifically binds to the EcoRI recognition site.

The restriction endonuclease EcoRI binds and cleaves DNA containing GAATTC sequences with high specificity. According to the crystal structure, most of the specific contacts of the enzyme to the DNA are formed by the extended chain region and the first turn of alpha-helix alpha 4 (amino acids 137-145). Here, we demonstrate that a dodecapeptide (WDGMAAGNAIER), which is identical in the underlined parts of its sequence to EcoRI amino acids 137-145, specifically binds to GAATTC sequences. The peptide inhibits DNA cleavage by EcoRI but not by BamHI, BclI, EcoRV, HindIII, PacI, and XbaI. DNA cleavage by XbaI is slowed down at sites that partially overlap with EcoRI sites. The peptide inhibits cleavage of GAATTC sites by ApoI, which recognizes the sequence RAATTY. It interferes with DNA methylation by the EcoRI methyltransferase but not by the BamHI methyltransferase. It competes with EcoRI for DNA binding. Based on these results, the DNA binding constant of the peptide to GAATTC sequences was calculated to be 3 x 10(4) M-1. DNA binding is not temperature-dependent, suggesting that binding of the peptide is entropy-driven. As the peptide does not show any nonspecific binding to DNA, its DNA binding specificity is similar to that of EcoRI, in spite of the fact that the affinity is much smaller. These results suggest that contacts to the phosphate groups in EcoRI mainly provide binding affinity, whereas the specificity of EcoRI is based to a large extent on sequence-specific base contacts.

Amino Acid Sequence↗
PubMed1991

Immobilization of papain on epoxy-polymers for papain-catalyzed peptide synthesis.

In this paper we describe the immobilization of papain on two commercially available carriers, VA Biosynth and Eupergit C, both in their epoxidized form. Papain can be immobilized on both polymers and shows high activity. The stability (lyophilization, storage) of the papain-VA Biosynth is very good. Even after prolonged storage (-20 degrees C) it can be reactivated to its full activity.

Catalysis↗
PubMed1988

3':5'-cyclic GMP in the yeast Saccharomyces cerevisiae at different metabolic conditions.

cGMP is characterized as undetectable in yeast [(1986) Yeast Cell Biology, UCLA Symp. Mol. Cell Biol. (Hicks, J. ed.) p. 495], though in many organisms it contributes specifically to the regulation of metabolism. Here, we detected cGMP, using radioactive labeling and RIA techniques, after extraction of the cells with 1 mol/1 HClO4 at 37 degrees C. The cGMP 0.015-fold cAMP, about 3-times higher with exponentially growing cells than with pressed baker's yeast, and depends on glucose and O2 supply. The PDE inhibitors DMX and IBMX induce in growing cells an additional increase of the cGMP level, without similar effects on cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1986

[Prognosis of cardiogenic cerebral embolism].

In a retrospective study the reports of 211 cases of cardiogenic cerebral embolism--diagnosed on the base of neurological and cardiological findings--were analyzed in view of signs and findings of prognostic value. There were 21 patients with TIA, 39 cases of RIND and 151 patients with cerebral infarction, 60 of which showed mild and 91 severe neurological symptoms. 38 patients died during the period of hospitalization. While sex of the patients as well as vascular risk factors (hypertension, diabetes mellitus, cigarette smoking) did not influence the clinical course of the disease, patients with TIA or RIND in general were younger (about 5 years) than those with severe stroke. Prognosis of cardiogenic cerebral embolism depended to a great degree on the underlying heart disease. Cerebral embolism after myocardial infarction showed a better remission of symptoms than embolism in atrial fibrillation. In the group of valvular diseases the course of embolic strokes in mitral lesions was worse than in aortal valve disease. Prognosis was worst in endocarditis, both in view of neurological deficit and of mortality. Mostly, the cardiogenic emboli lead to infarctions of the middle cerebral artery territory (78 per cent) with a predilection for the left hemisphere. In media-syndromes the clinical course was significantly worse in patients with additional homonymous visual defect compared to incomplete infarctions. Initial disturbance of conscience reduced prognosis quoad vitam et restitutionem significantly. Of the neuroradiological findings, the detection of arterial occlusion or circulatory disturbance in angiography as well as the finding of an ischemic lesion in computed axial tomography (CAT) was correlated with a severe course of the embolic stroke. While 7 patients with hemorrhagic infarction in CAT-Scan showed no differences in the clinical course, the 14 patients with pathological cerebral spinal fluid findings in embolism had an unfavourable prognosis. The development of epileptic seizures did not influence the further course of the infarction to a significant extent. Results are compared with the current world literature.

Cerebral Infarction↗
PubMed1981

Synthesis of histone model sequences for immobilization on a cross-linked polyacrylate matrix.

The synthesis of three peptide sequences which are useful as histone models, [Lys]5, [Lys]5-Pro and the sequence 17-27 of the lysine-rich histone from rabbit thymus Pro-Ala-Lys-Lys-Lys-Lys-Ala-Ala-Lys-Lys-Pro is described. Three different methods for the synthesis are applied. [Lys] 5 is synthesized from the amino end beginning with N alpha-acryloyl-N epsilon-Cbo-lysine by successive coupling of Cbo-lysine to yield the pentalysine monomer CH2=CH-CO-[Lys(Cbo)]5 which can be used directly for radical copolymerization. [Lys]5-Pro is synthesized according to the conventional peptide synthesis using the carbobenzoxy group for N alpha-protection and the tert,-butyl group for side chain protection. The carboxyl function is protected as tert.-butyl ester. The undecapeptide is synthesized in a similar manner. Instead of purifying the intermediate peptides by extraction, chromatography is used exclusively. The isolation of the unprotected peptides Lys-Pro, [Lys]3-Pro, [Lys]4-Pro, [Lys]5-Pro and Pro-Ala-[Lys]4-[Ala]2-[Lys]2-Pro and their characterization using amino acid analysis, electrophoreses and field desorption mass spectrometry is also reported.

Acrylic Resins↗
PubMed1980

Studies on interactions between immobilized lysine residues and oligomers of thymidylic and deoxyadenylic acids.

Two groups of crosslinked polyacrylic gels with immobilized lysine and lysine peptides (Lys)5 and (Lys)5-Pro have been used as models for the chromatographic investigation of lysine-peptide-oligonucleotide interactions. One group carries carboxylic groups in addition to the peptide residues in the gel matrix; the other gel type contains no such carboxylic groups in the gel matrix. Nucleotides of the series (dT)2-5, p(dT)1-4, p(dT)1-4p, (dA)2-5, p(dA)1-5 and p(dA)1-4p were chromatographed on these gels under various conditions in an aqueous buffer. On the gels of the first group the nucleotides were retarded only slightly, the positive charges of the epsilon-amino groups being compensated partially or totally by the negatively charged carboxyl groups of the polymer matrix. On the gels of the second group, however, the oligonucleotides underwent specific interactions. These interactions were based primarily upon electrostatic forces between the positively charged epsilon-amino groups of the immobilized peptides and the negatively charged phosphate groups of the oligonucleotides. Our results indicate that, in addition to the electrostatic interaction, the conformation plays a crucial role. We explain the selectivity of the interaction with a conformation-fit mechanism. The origin of this mechanism, which creates specific interactions from unspecific forces, is discussed.

Adenine↗
PubMed1979

[Determination of the interaction of oligopeptides and oligonucleotides by a chromatographic technique (author's transl)].

Homologues of deoxyriboadenylic and deoxyribothymidylic acid show different degrees of retardation in a pentalysine gel. This chromatographic retardation is directly related to the strength of the interaction between the oligonucleotides and the immobilized pentalysine peptide residues. The strength of this interaction is determined by the total negative charge of the oligonucleotide, and by the nature of the constituent base of the oligonucleotide. The specificity of the interaction depends upon differences in conformation of the oligonucleotides.

Chromatography, Gel↗
PubMed1977

Conformation affinity of cross-linked polyacrylic gels towards nucleobases, nucleosides and nucleotides.

By radical copolymerisation of monofunctional acrylic derivatives with 1,4-tetramethylene dimethacrylate, cross-linked polyacrylic gels which show a high affinity towards nucleic acid residues have been synthesised. Using these polyacrlic gels, mixtures of nucleobases, nucleosides and nucleotides can be chromatographically separated to differing extents, in some cases quantitatively. The elution of nucleobases and nucleosides from the gel in the order Cyt, Gua, Thy, Ade (or dC, dG, dT, dA and C, G, U, A, respectively) shows that Ade (dA, A) is retarded to the highest degree from the gel matrix, Cyt (dC, C) to the lowest degree. Further, the results of the separations prove that the affinity of the polyacrylic gels is much stronger towards deoxyribonucleosides than towards ribonucleosides and nucleobases. The affinity of the polyacrylic gels towards nucleobases and nucleosides depends mainly upon their tertiary structure whereas the functional side groups of the polyacrylate matrix do not contribute significantly to the interaction of the gels.

Acrylic Resins↗
PubMed1976

[A micro method for the determination of the configuration of histidine in peptides: evidence for partial racemization during peptide synthesis (author's transl)].

A gas chromatographic method for the determination of small portions of D-histidine together with an excess of L-histidine (or vice versa) is described. Histidine is degraded to aspartic acid by reaction with ozone. The enantiomers are esterified with (+)-3-methyl-2-butanol. After N-trifluoroacetylation the volatile diastereoisomers are separated in glass capillaries coated with a chiral stationary phase and determined quantitatively. For precise evaluations the partial racemization during peptide hydrolysis must be accounted for. The method was applied to some histidine peptides and about 5% racemization was measured.

Chromatography, Gas↗
PubMed1975

The investigation of peptide-oligodeoxythymidylic acid interactions using template chromatography.

Poly(vinyl alcohol) has been substituted with oligodeoxythymidylic acid and the resulting polyanion irreversibly attached to DEAE-cellulose via ionic bonding. Peptide-oligonucleotide interactions have been studied using a column chromatography technique with the PV(pT)n-DEAE-cellulose as stationary phase. Of all the naturally occurring amino acids, only tryptophan and to a lesser extent tyrosine intreact significantly with the immobilized oligodeoxythymidylic acid residues under the conditions for base pairing. The homopolymers of tryptophan and tyrosine undergo greater retardation than the monomers, such that the effect is not additive but multiplicative. Thus Tyr-Tyr-Tyr shows an eightfold and Trp-Trp-Trp an approximately 30-fold larger retardation than tyrosine and tryptophan, respectively. The peptide-oligonucleotide interaction decreases considerably when nonaromatic amino acids are present in the peptide. Consequently, naturally occurring peptides and proteins which contain relatively small amounts of tryptophan and tyrosine compared with the nonaromatic amino acids undergo at the most only slight retardation on the PV(pT)n-DEAE-cellulose. The retention of oligonucleotides and peptides containing these aromatic amino acids is due in both cases mainly to base stacking (roughly 67% of the total interaction) but involves different mechanisms. Thus, the peptides interact preferably with the cellulose matrix whereas the oligonucleotides with the immobilized oligonucleotides. Interaction via hydrogen-bond formation makes up the remaining 33% of the total interaction. The oligonucleotides and peptides of the mobile phase interact with each other also via this mechanism. The strength of the d(pA-A-A) interaction is roughly that of Trp-Trp whereas d(pA-A-A-A) is weaker than Trp-Trp-Trp.

Binding Sites↗