J. Równicka

Interaction of anticancer drugs with human and bovine serum albumin

Abstract The properties of 5-fluorouracil (5FU), 6-azauracil (6AU), 6-mercaptopurine (6MP), thiouracil (2TU) and thioimidazole (TI), as a quencher of fluorescence of tryptophanyl Trp 214 residue in serum albumin were studied. For the molar ratio [ligand]: [BSA]=30: 1 the decrease of protein fluorescence due to the presence of thiouracil as a quencher attains 90%, while imidazole derivative-thiamazole quenches the BSA fluorescence only by 25%. To estimate the character of the binding between studied quencher and human and bovine serum albumin the Scatchard and Stern–Volmer methods were used. The binding stoichiometry of allopurinol–mercaptopurine–serum albumin complex was studied.

Effect of urea on serum albumin complex with antithyroid drugs: fluorescence study

Abstract Comparative study of the ligand effect on the conformational stability of human (HSA) and bovine (BSA) serum albumin was performed using fluorescence spectroscopy. Tryptophan fluorescence emission spectra of serum albumin in the presence of mercaptopyrimidine (MPI) were recorded at the excitation wavelengths of 280 and 295 nm. The quenching of the fluorescence of protein in the presence of MPI resulted from the interactions with the drug in the subdomain IIA of α-helix where Trp 214 is located. The unfolding process of serum albumin on increasing the concentration of urea (1÷8 M) was studied. It was suggested that the destabilization of serum albumin structure in the presence of increasing urea concentration runs probably through intermediate state at 4÷6 M urea. The binding and quenching constants MPI–HSA and MPI–BSA has been calculated and compared with those obtained under urea-denatured conditions. An unfolding of serum albumin, induced by urea (within the concentration range 1÷5 M), involved diminishing of binding constant by ∼27% for HSA and by ∼49% for BSA. When concentration of urea exceeded 6 M, the binding constant raised by 21 and 27% for HSA and BSA, respectively. Anti-denaturant action of MPI was shown.

Changes of serum albumin affinity for aspirin induced by fatty acid

Saturated fatty acids such as myristic acid play an important role in the pathogenesis of cardiovascular disorders. Using the quenching fluorescence method we examined the influence of myristate on the changes of transporting protein affinity towards aspirin-the most popular anticoagulant. Our results showed that the presence of the myristic acid alters the stability of the anticoagulant-albumin complex. The ranges of [myristate]/[albumin] molar ratio at which the stability of drug-protein complex increases or decreases were determined. The differences in interaction between ligands and human or bovine serum albumins were identified. The competition in binding of ligands with these albumins was also described.

The influence of dietary habits and pathological conditions on the binding of theophylline to serum albumin

The influence of fatty acids (FA) on theophylline (Th) binding to human serum albumin (HSA) in its high and low affinity binding sites was investigated. The content of studied FA solutions corresponds to the ones associating with different dietary habits and pathological states in vivo. Using fluorescence and (1)H NMR spectroscopy two high and two low affinity binding sites of Th in HSA structure were found. For each site several binding parameters in the absence and presence of FA were estimated. The results showed that the impact of FA on the affinity of HSA towards Th in high affinity binding sites is negligible whereas binding of the drug in low affinity sites decreases significantly in the presence of FA. It was observed that this effect is dependent on the number of fatty acid molecules bound to the protein while the chemical structure of fatty acids contained in the solution plays a minor role.

Alterations of furosemide binding to serum albumin induced by increased level of fatty acid

Localization of high and low affinity binding sites of furosemide in human serum albumin (HSA) as well as the influence of myristic acid on the drug binding to the albumin using fluorescence quenching method was investigated. Two independent classes of binding site in subdomain IIA of HSA structure were found. Alteration of protein affinity towards the drug and the participation of tryptophanyl and tyrosil residues in drug-albumin interaction for the determined binding sites were studied. It was concluded that association of myristic acid in its low affinity binding sites which corresponds to elevated fatty acid level in vivo, significantly decreases albumin affinity towards furosemide.

Influence of myristic acid on furosemide binding to bovine serum albumin. Comparison with furosemide–human serum albumin complex

Fluorescence studies on furosemide (FUR) binding to bovine serum albumin (BSA) showed the existence of three or four binding sites in the tertiary structure of the protein. Two of them are located in subdomain IIA, while the others in subdomains IB and/or IIIA. Furosemide binding in subdomain IB is postulated on the basis of run of Stern-Volmer plot indicating the existence of two populations of tryptophans involved in the interaction with FUR. In turn, the significant participation of tyrosil residues in complex formation leads to the consideration of the subdomain IIIA as furosemide low-affinity binding site. The effect of increasing concentration of fatty acid on FUR binding in all studied binding sites was also investigated and compared with the previous results obtained for human serum albumin (HSA). For BSA the lesser impact of fatty acid on affinity between drug and albumin was observed. This is probably a result of more significant role of tyrosines in the complex formation and different polarity of microenvironment of the fluorophores when compared HSA and BSA. The most distinct differences between FUR-BSA and FUR-HSA binding parameters are observed when third fatty acid molecule is bound with the protein and rotation of domains I and II occurs. However these structural changes mostly affect FUR low affinity binding sites.

The Effect of Serum Albumin on Binding of Protoporphyrin IX to Phospholipid Membrane

ABSTRACT The protoporphyrin (PPIX) incorporated liposomes were prepared and the change of PPIX UV-Vis spectra in this system were analyzed. The effect of serum albumin (BSA) on the lipo-PPIX system has been presented. Different changes in absorbance of peaks I (at λmax 279 nm) and II-V, observed in the lipo-PPIX spectrum in the presence of BSA, suggest that PPIX associated with liposome exists in two different microenvironments, i.e., hydrophobic and polar. The latter is located near the membrane surface close to the polar phospholipid head. The release of the PPIX from these sites is not observed in the presence of BSA. Time dependence of the spectral properties of solution PPIX in water has been presented. It was found that BSA forms a complex with PPIX at PPIX/BSA molar ratio 0.2/1.

Study of Polyolefines Waste Thermo-Destruction in Large Laboratory and in Industrial Installations

Polymer materials packagings are quickly deposited in dumps due to the short life time as a useable product. Recycling of polymer waste, mainly polyolefines, which constitute 60% of them, on the technological lines operating according to the Polish technology seems to be a long-term solution. According to this technology, the used polymers after melting flow down to the reactor, where they undergo thermal degradation in the presence of catalyst. A product which can be processed in refineries for fuel is obtained. The studies leading to the improvement of the properties of the obtained product are still conducted.