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A Orłowska

Publications and source records attributed to A Orłowska.

5 recordsLinked to original sources
PubMed2001

Tryptic hydrolysis of hGH-RH(1-29)-NH2 analogues containing Lys or Orn in positions 12 and 21.

Two analogues of the 29 amino acid sequence of human growth hormone-releasing hormone, namely [Nle27]hGH-RH(1-29)-NH2 and [Orn(12,21),Nle27]hGH-RH(1-29)-NH2, have been synthesized and subjected to digestion by trypsin. The course of degradation was followed using RP-HPLC and ESI-MS. Several intermediates and final products of degradation were identified and conclusions regarding the rate of cleavages at different positions occupied by Lys and Arg residues were drawn. The analogue containing ornithine was found to be less susceptible to hydrolysis by trypsin: the 12-13 and 21-22 peptide bonds were completely resistant to the cleavage. The results show that by replacing Lys with Orn, a possibility exists to design new peptides, which could be more stable in biological fluids.

Amino Acid Sequence↗
PubMed1998

Lymphocyte interactions with extracellular matrix proteins and endothelium in renal allograft recipients.

Recent data indicate that extracellular matrix (ECM) proteins can provide costimulatory signals during the process of T cell activation. Those proteins accumulate in situ during allograft rejection; therefore, it may be expected that local ECM: T cell interactions may be relevant in the immunopathology of rejection. T cell adhesion from allograft of recipients with stable renal function (RAR-S) and patients with biopsy-proven chronic rejection (RAR-CH) to ECM proteins (collagen type IV, fibronectin, elastin) was measured. Furthermore, T cell: endothelial interactions in vitro were studied. Adhesion of PHA-activated T cells from both groups of allograft recipients to fibronectin, collagen type IV and elastin was significantly lower than in healthy blood donors. Moreover, similar pattern of activity was observed when T cell attachment to resting and activated endothelium was studied. There were no significant differences in the number of circulating CD45RO and CD4 positive T cells. We observed a higher (although not significantly) adhesion of the T cells to resting human dermal microvascular endothelial cells (HMEC) in the chronic stages of rejection, which can suggest that the immunosuppressive protocol used in the treatment of chronic rejection is insufficient to control immunopathologic phenomena occurring in that process. Therefore, it may be argued that too low immunosuppression can be one of the factors responsible for the development of this complication.

Cell Adhesion↗
PubMed1994

N-cyclohexyl-N'-isopropylcarbodiimide: a hybrid that combines the structural features of DCC and DIC.

N-Cyclohexyl-N'-isopropylcarbodiimide was prepared and used for peptide couplings by various procedures. Reaction between Z-Val and Gly-OEt was used for yield studies and determination of the extent of the side reaction in solution. The value of this reagent for solid peptide synthesis was demonstrated by the synthesis of sequences comprising the 65-74 residues of acyl carrier protein. The efficiency of activation was determined by competition experiments. From all these studies the conclusion can be drawn that N-cyclohexyl-N'-isopropylcarbodiimide is comparable to or even better than the commonly used DCC for mediation of peptide bond formation in solid phase synthesis. By virtue of the solubility of N-cyclohexyl-N'-isopropylurea in dichloromethane, the carbodiimide seems to be a good candidate for practical execution of peptide bond formation by the standard carbodiimide procedure.

Carbodiimides↗
PubMed1994

Reinvestigation of the reactions of carbodiimides with alkoxycarbonylamino acid symmetrical anhydrides. Isolation of two N-acylureas.

Alkoxycarbonylamino acid symmetrical anhydrides were allowed to react with N,N'-diisopropylcarbodiimide. The determination of the decrease in carbodiimide concentration indicated that the reaction was slow and proceeded indirectly. It is presumed that symmetrical anhydride in the presence of basic carbodiimide is converted into oxazolone and alkoxycarbonylamino acid. The latter reacts with carbodiimide to give O-acylisourea which, in turn, rearranges to N-acylurea. A second minor product was found to be N-(N1,N2-bisalkoxycarbonyldipeptidyl)urea. The main pathway leading to the formation of this product starts with rearrangement of the symmetrical anhydride to N1,N2-bisalkoxycarbonyldipeptide acid. These experiments suggest that the reaction between anhydride and carbodiimide is not the source of N-acylurea in peptide synthesis.

Acylation↗