Beata Kolesinska

Bacterial Urease and its Role in Long-Lasting Human Diseases

Urease is a virulence factor found in various pathogenic bacteria. It is essential in colonization of a host organism and in maintenance of bacterial cells in tissues. Due to its enzymatic activity, urease has a toxic effect on human cells. The presence of ureolytic activity is an important marker of a number of bacterial infections. Urease is also an immunogenic protein and is recognized by antibodies present in human sera. The presence of such antibodies is connected with progress of several long-lasting diseases, like rheumatoid arthritis, atherosclerosis or urinary tract infections. In bacterial ureases, motives with a sequence and/or structure similar to human proteins may occur. This phenomenon, known as molecular mimicry, leads to the appearance of autoantibodies, which take part in host molecules destruction. Detection of antibodies-binding motives (epitopes) in bacterial proteins is a complex process. However, organic chemistry tools, such as synthetic peptide libraries, are helpful in both, epitope mapping as well as in serologic investigations. In this review, we present a synthetic report on a molecular organization of bacterial ureases - genetic as well as structural. We characterize methods used in detecting urease and ureolytic activity, including techniques applied in disease diagnostic processes and in chemical synthesis of urease epitopes. The review also provides a summary of knowledge about a toxic effect of bacterial ureases on human body and about occurrence of anti-urease antibodies in long-lasting diseases.

P-Acylphosphonium salts and their vinyloges — application in synthesis

Review with 101 refs. of progress in synthetic applications and properties of P-acylphosphonium salts including acylation via P-acylphosphonium salts, enantioselective acylation using chiral phosphine ligands, nucleophilic (β)-oniovinylation, and reaction involving vinyloges of P-acylphosphonium salts formed by treatment conjugated alkenoates or alkynoates with phosphines.

Design, synthesis, and application of enantioselective coupling reagent with a traceless chiral auxiliary.

Stable chiral N-triazinylbrucinium tetrafluoroborate enantioselectively activates racemic carboxylic acids yielding enantiomerically enriched amides, esters, and dipeptides with er from 8:92 to 0.5:99.5. Due to the departure of a chiral auxiliary after the activation of the carboxylic function, all of the subsequent stages of the coupling reaction proceed without any perturbation caused by a chirality discriminator (traceless). Therefore, the advantageous coupling conditions, configuration, and enantiomeric purity of the final product are entirely predictable from the model experiment.

Mild and Efficient Synthesis of Carboxylic Acid Anhydrides from Carboxylic Acids and Triazine Coupling Reagents

Abstract Anhydrides of carboxylic acids were obtained in 53%–95% yield by treatment of appropriate carboxylic acids with 2‐chloro‐4,6‐dimethoxy‐1,3,5‐triazine (CDMT) or 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine (DCMT) in the presence of N‐methylmorpholine. It has been proved that synthesis proceeds via triazine active esters 3a,b, which are able to acylate carboxylate anion but not less nucleophilic carboxylic acid.

Benzyloxy Derivatives of Triazine-based Coupling Reagents Designed for an Efficient Solid Phase Peptide Synthesis on Polystyrene Resin

Coupling reagents resembling the structure of Merrifield resin were designed and prepared from 2-chloro-4,6-dibenzyloxy-1,3,5-triazine and the different tertiary bases N-methylmorpholine, N-methylpiperidine, and DABCO. As previously observed for DMTMM, the appropriate N-(4,6-dibenzyloxy-1,3,5-triazin-2-yl) ammonium chloride salts were not suitable as efficient coupling reagents because of their low stability. On the other hand, the stability of the N-(4,6-dibenzyloxy-1,3,5-triazin-2-yl) ammonium tetrafluoroborates was suitable enough for prolonged storage and convenient application in SPPS. Moreover, we observed that the superactive intermediates formed during activation of Fmoc–Aib–OH with 4,6-dibenzyloxy-1,3,5-triazine-based coupling reagents lead to an increase in its concentration inside the polystyrene resin. Therefore, we hypothesize that this increase can enhance efficiency of 4,6-dibenzyloxy-1,3,5-triazine-based coupling reagents in SPPS.

Synthesis and cytotoxicity studies of bifunctional hybrids of nitrogen mustards with potential enzymes inhibitors based on melamine framework

The new class of hybrid anticancer drugs were obtained by selective functionalization of the triazine scaffold. These were prepared by rearrangement of mono-, bis- and/or tris-(1,3,5-triazin-2-yl)-1,4-diazabicyclo[2.2.2]octanium chlorides leading to formation of 2-chloroethylamino fragments attached to 1,3,5-triazine via one, two or three piperazine rings respectively. Their inhibitory effect was found strongly dependent on the structure of substituents in triazine ring. The anti-proliferative activity of the hybrids evaluated in vitro by using mammalian tumour cells estimated as IC50 was in the range 0.62–139,78 µM. Both cytotoxicity and alkylating activity depended on the substituents of triazine ring, however, also the mono-functional analogues of nitrogen mustards, which are unable to form liaisons between two DNA strands, induced apoptosis and necrosis in the tested cells.

Synthesis of Chiral 2,4-Chiral 2,4-Dichloro-6-menthoxy-1,3,5-triazines and 2-Chloro-4, 6-Dimenthoxy-1,3,5-triazines as Enantiodifferentiating Coupling Reagents. An X-ray Study on 2,4,6-Trimenthoxy-1,3,5-triazine

Abstract Chiral mono-di-and trimenthoxy-1,3,5-triazines ware obtained from natural menthol and cyanuric chloride and applied as enantioselective coupling reagents in the synthesis of dipeptides.

Probing an artificial polypeptide receptor library using a series of novel histamine H3 receptor ligands.

An artificial polypeptide receptor (APR) library was created by using the self-organization of N-lipidated peptides attached to cellulose via m-aminophenylamino-1,3,5-triazine. The response of the library was probed using a series of novel H3 receptor ligands. Since no guidelines on how to design an APRs selective vs certain receptor types exist, a diverse set of amino acids (Ala, Trp, Pro, Glu, His, Lys and Ser) were used and coupled with one of three gating fatty acids (palmitic, ricinoleic or capric). A competitive adsorption-desorption of an appropriate reporter dye was used for the indirect visualization of the interactions of guests with particular receptors. The resulted library response to individual inhibitors was then arranged in a matrix, preprocessed and analyzed using the principal component analysis (PCA) and partial least squares (PLS) method. The most important conclusion obtained from the PCA analysis is that the library differentiates the probed compounds according to the lipophilicity of the gating unit. The PC3 with a dominant absolute contribution of the receptors containing Glu allowed for the best separation of the ligands with respect to their activity. This conclusion is in agreement with the fact that Glu 206 is a genuine ligand counterpart in the natural histamine receptor.

Are anti-Helicobacter pylori urease antibodies involved in atherosclerotic diseases?

OBJECTIVES The ureB subunit of urease is a major target recognized by the antibodies of Helicobacter pylori-infected patients. The minimal epitope was determined to be an 8-mer peptide (H-SIKEDVQF-OH). DESIGN AND METHODS The aim of this study was to discover whether this synthetic 8-mer peptide (BK-61A) directly recognizes the anti-ureB subunit antibodies of H. pylori-infected and atherosclerotic patients. To achieve a better presentation of the epitopes to antibodies, a new isocyanuric linker was designed and used for to immobilize the peptides on a cellulose support. RESULTS In this study a new peptide synthesis method is presented. Anti-ureB antibodies were evaluated by the dot blot technique in 26 H. pylori-infected donors and the sera of 20 H. pylori-infected patients with atherosclerosis using the 8-mer peptide. CONCLUSIONS The results reveal that the BK-61A peptide could be used for diagnosing the presence of anti-ureB antibodies that may be involved in the initiation of atherosclerosis.

Heavy atom induced phosphorescence study on the influence of internal structural factors on the photophysics of tryptophan in aqueous solutions.

In this study the effect of alanyl residue insertion into tryptophan and to some extent the effect of peptide bond on the photophysics of tryptophan chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous AW, WA and AWA peptides have been determined applying our previously proposed methodology based on the heavy atom effect and compared with the previously reported values for tryptophan (Kowalska-Baron et al., 2012). The obtained results clearly indicated that the presence of alanyl residue and the peptide bond results in the changes in the fluorescence and phosphorescence decay kinetics of tryptophan. The fluorescence decays of the oligopeptides studied at pH 7 were biexponential. The longer lifetime component of WA arises from anionic form of this dipeptide, while the shorter one may be assigned to the zwitterionic form of WA. The observed invariance of the lifetimes of anionic and zwitterionic forms of WA throughout the pH studied supports the idea that these two components of WA fluorescence decay correspond to nearly independent species, possibly interconverting but at a rate slower than the fluorescence decay rates. Comparing the determined phosphorescence spectra of the oligopeptides studied with that of tryptophan, a slight blue-shift and more evident red-shift was observed in the spectrum of AW and WA, respectively. On the basis of the results of the phosphorescence measurements performed at pH 10, the 170 μs lifetime of WA, observed even at pH 7, may be assigned to the anionic form of the compound. It may be suggested that at pH 7 during the excited triplet state lifetime of WA there is a shift in the equilibrium towards the anionic form of this dipeptide. In the case of AW and AWA at pH 7 the obtained monoexponential decay kinetics, most probably, arise from zwitterionic forms of these peptides. The determined triplet quantum yield of AWA is slightly lower than that of tryptophan, while the quantum yield of AW is twofold lower than that of tryptophan. The highest value of the determined triplet quantum yield of WA confirms the presence of anionic form of this dipeptide at pH 7.