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Biomedical subjects

E Krause

Publications and source records attributed to E Krause.

174 records · Page 10Linked to original sources
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[Use of hydrogen peroxide for closing disulfide bridges in peptides].

The use of hydrogen peroxide for the formation of disulfide bridges was studied in 15 peptides of various lengths and structures. The oxidation of peptide thiols by hydrogen peroxide was shown to proceed under mild conditions without noticeable side reactions of Trp, Tyr, and Met residues. Yields of the corresponding cyclic disulfides were high and mostly exceeded those obtained with other oxidative agents, in particular, iodine. It was established that the use of hydrogen peroxide in organic medium also provided sufficiently high yields when large-scale syntheses of oxytocin and octreotide (up to 10 g) were carried out. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 2; see also http://www.maik.ru.

Amino Acid Sequence↗
PubMedDate not supplied

Agonist-stimulated pathways of calcium signaling in pancreatic acinar cells.

In pancreatic acinar cells stimulation of different intracellular pathways leads to different patterns of Ca2+ signaling. Bombesin induces activation of both phosphatidylinositol 4,5-bisphosphate (PIP2)-specific phospholipase C (PLC) and phospholipase D (PLD). The latter leads to generation of diacylglycerol (DAG) in addition to that produced by activation of PIP2-PLC. Strong activation of protein kinase C (PKC) results in inhibition of Ca(2+)-induced Ca2+ release from Ca2+ pools arranged in sequence to the luminally located IP3-sensitive Ca2+ pools. Consequently the Ca2+ wave which starts in the luminal cell pole is slower in the presence of bombesin (5 microm/s) as compared to that in the presence of acetylcholine (17 microm/s) which activates PIP2-PLC but not PLD. Activation of high-affinity CCK-receptors triggers a Ca2+ wave with slow propagation (5 microm/s) due to stimulation of phospholipase A2 (PLA2) and generation of arachidonic acid, which in turn leads to inhibition of Ca(2+)-induced Ca2+ release. Low-affinity CCK-receptors are coupled to both PIP2-PLC and PLD.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

Is venous patch grafting after carotid endarterectomy able to reduce the rate of restenosis? Prospective randomized pilot study with stratification.

Many studies have already demonstrated that the restenosis rate after carotid endarterectomy is greater as expected since ultrasound examination has become a routine procedure after endarterectomy. The purpose of our randomized study is to compare the rates of restenosis with two methods of carotid endarterectomy--direct suturing and autologous vein grafting. Sofar restenosis are found after endarterectomy and direct suturing. Different possible causes for restenosis are discussed. We hope to inform soon if patching with the autologous vein is the best method in order to prevent early restenosis after CEA.

Aged↗
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[Glycogen phosphorylase activity in infarct-affected and nonaffected parts of the human myocardium after death].

Distinct differences in activity of glycogen phosphorylase were not observed in various parts of an intact human myocardium. This enzymatic activity vas considerably decreased in the left ventricle of the myocardium impaired by infarction; with prolongation of the infarction period the enzymatic activity decreased further. Isozymes of glycogen phosphorylase I, II and III were liberated from ischemic myocardium according to their quantitative ratio in the heart. The glycogen phosphorylase activity, which was observed in blood serum of patients with acute myocardial infarction, was apparently liberated into blood due to the myocardium impairment. Evaluation of the enzymatic activity in blood serum of the patients might serve as an index of the necrosis degree.

Aged↗
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Instability of side-chain protecting groups during MALDI-TOF mass spectrometry of peptide fragments.

Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS), a well-suited method for the characterization of peptides and proteins, was used for analysis of protected peptide fragments. It is shown that acidic matrices, e.g. 2,5-dihydroxybenzoic acid, frequently used in MALDI-TOF MS of peptides, causes partial cleavage of acid-labile side-chain protecting groups. Because this effect is strongly related to the matrix used, the observed deprotection can be avoided by choosing an appropriate matrix such as 2,4,6-trihydroxyacetophenone or 2-amino-5-nitropyridine. The advantage of neutral matrix compounds for MALDI-TOF analysis of protected peptides is clearly demonstrated, confirming the potential of MALDI-TOF mass spectrometry.

Amino Acid Sequence↗
PubMedDate not supplied

Peptide destabilization by two adjacent D-amino acids in single-stranded amphipathic alpha-helices.

We recently described the local destabilizing effect of systematic double D-amino acid replacements for characterization of amphipathic helices in peptides. The objective of this study was to determine the destabilizing effect of two adjacent D-amino acids incorporated into the center of a single-stranded amphipathic alpha-helix by hydrogen exchange and guanidine hydrochloride denaturation studies in trifluoroethanol (TFE)/water. Data from guanidine hydrochloride titration experiments in the presence of 30% TFE suggest that double D-amino acid replacements at the center of the helix destabilize the secondary structure by 4.5 kJ/mol. While the exchange rate for one backbone proton was found to vary by a factor of 10 at the replacement position, the remaining backbone protons are not markedly influenced by double D-amino acid replacement. These results confirm the hypothesis that the energy of -4.5 kJ/mol per residue is a major contribution to the stability of helical peptides in water and in solvent mixtures of TFE/water.

Amino Acid Sequence↗