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B Ivanov

Publications and source records attributed to B Ivanov.

47 records · Page 3Linked to original sources
PubMedDate not supplied

Synthesis and use of a new bromoacetyl-derivatized heterotrifunctional amino acid for conjugation of cyclic RGD-containing peptides derived from human bone sialoprotein.

A new amino acid derivative, N alpha-(tert-butyloxycarbonyl)-N beta-(bromoacetyl)diaminopropionic acid (BBDap), has been synthesized as a reagent for introducing side-chain bromaocetyl groups into any position of a peptide sequence during solid-phase peptide synthesis. By using minor modifications to the protocol of the automated peptide synthesizer and a two-step in situ neutralization procedure, the syntheses of (bromoacetyl)diaminopropionic acid (BDap) in Arg-Gly-Asp-containing peptides from human bone sialoprotein were optimized and completed. Following HPLC purification, the BDap-derivatized peptides were cyclized or/and conjugated to carrier protein or to glass cover slips. In addition, a new procedure for site-specific conjugation of cyclic peptides to protein carriers or to glass was developed. The cell attachment activity of the peptide derivatives and conjugates was tested in cell adhesion assays with human osteoblasts, and the specificity of the binding was confirmed by competition with linear and/or cyclic forms of GRGDS. The results show that conjugates containing the linear and cyclic derivatives of the peptide EPRGDNYR supported cell attachment and spreading in a dose-dependent manner when the peptides were immobilized as described. Cell attachment to the intact bone sialoprotein and to conjugates containing the linear peptides was abolished by competition with linear and cyclic RGD-containing peptides, whereas the attachment to conjugates containing the cyclic peptide was inhibited only partially, and the cell spreading was preserved even in the presence of RGD-peptides.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition and labeling of enzymes and abzymes by phosphonate diesters.

Reactive phosphonate diesters were designed and prepared as inhibitors of serine proteases and esterases. Inactivation of trypsin, chymotrypsin, and butyrylcholinesterase was determined by residual enzymatic activity as well as by the release of a chromogenic or fluorogenic product of the inhibition reaction. Second-order rate constants were determined from rates of nitrophenol formation. Application of the reaction for active-site titration of enzyme preparations is demonstrated. A basic functional group present in the nitrophenyl tropane phosphonate diester was shown to confer selectivity for inactivation of trypsin and chymotrypsin. Biotinylated derivatives of the phosphonate diesters were prepared to permit analysis of proteins modified in the inhibition reaction. Labeled polypeptides were resolved by SDS-PAGE, electroblotted, and detected by streptavidin-peroxidase staining. A detection limit of less than 4 ng, corresponding to 20 nM of trypsin, was demonstrated. Pretreatment of enzymes with DFP or nonbiotinylated phosphonates specifically blocks the labeling. This technique permits identification of serine proteases in complex mixtures with good sensitivity and specificity.

Animals↗
PubMedDate not supplied

[D2 lymph node dissection in gastric cancer surgery: long term results--analysis of an experience with 227 patients].

AIM: The main objective of the study was to evaluate the postoperative mortality and 5 year survival in gastric cancer patients undergoing a minimum of D2 lymphadenectomy. MATERIALS AND METHODS: A retrospective study was conducted on 1170 patients operated for gastric adenocarcinoma in the Department of General Surgery and Liver Transplantation of Fundeni Clinical Institute, between 1997 and April 2005. Only 443 patients underwent a curative resection, from which 216 patients had D1 resection and in 227 cases a D2 or D3/D4 lymphadenectomy was performed. Information about survival was available for 189 patients of those who had a D1 resection and for 210 of those who underwent a D2 or D3/D4 lymphadenectomy. RESULTS: Postoperative mortality was 6.5% in the group of curative resection, with 9.2% for D1 and 3.9% for D2/D3 D4. Five year survival according to Kaplan Meier curves was 32 % in the D1 group vs. 51,8% in D2/D3-D4 (p <0.0001). Significant differences were noted in the median survival-- D2/D3-D4 group 63 months vs. 28 months in D1 group. CONCLUSIONS: Our data support the gastric resection with a minimum of D2 lymphadenectomy in the radical surgery of gastric cancer. However, an accurate interpretation of the statistical interpretation between the different groups of patients is difficult, mainly because of the retrospective character of the study.

Adenocarcinoma↗
PubMedDate not supplied

[Effect of charged particles of relativistic energy on the number of chromosome aberrations in human blood lymphocytes. Dose-response relationship and the RBE of protons, deuterons and helium ions].

In experiments with human blood lymphocyte culture exposed to fast protons, deuterons and helium ions the frequency and types of chromosome aberrations have been studied. Fast charged particles of a relativistic energy are shown to have a pronounced harmful effect resulting in a sharply increased formation of exchange chromosome aberrations as compared to that produced by gamma-radiation. The RBE coefficients of the particles under study have been determined: their values vary depending on the type of radiation and the tests used.

Chromosome Aberrations↗