Małgorzata Wszelaka-Rylik

Spectroscopic and thermodynamic determination of three distinct binding sites for Co(II) ions in human serum albumin.

Human serum albumin (HSA) is the most abundant protein of blood serum, involved in the transport of metal ions, including Co(II). Using circular dichroism spectroscopic titrations we characterized three distinct Co(II) binding sites in HSA. Applying Cu(II), Ni(II) and Cd(II) ions as competitors we determined that these sites are identical with three binding sites known for other metal ions. We ordered these sites according to their binding affinities as cadmium site B (CdB)>multi-metal binding site (MBS)>N-terminal binding site (NTS). Using isothermal titration calorimetry (ITC) we confirmed the presence of these three binding sites and determined their conditional binding constants at pH 7.4 as 9+/-5, 1.1+/-0.5, and 0.9+/-0.3x10(4)M(-1), respectively. The impact of these results on the albumin cobalt binding (ACB) clinical assay for myocardial ischemia is discussed.

Thermochemistry of Aqueous Solutions of Alkylated Nucleic Acid Bases. X. Enthalpies of Hydration of Cytosine and some Methylated, Hydroxy and Methoxy Derivatives of Cytosine

Enthalpies of solution in water, vapor pressures, and enthalpies of sublimation were determined for cytosine and a number of crystalline derivatives of cytosine: 1-methylcytosine, 1-methyl-N4-hydroxycytosine, 1,5-methyl-N4-methoxycytosine, 1,N4,N4-trimethylcytosine, 1,5,N4-trimethylcytosine, 1,5-dimethyl-N4-methoxycytosine, and l,N4-dimethyl-5-ethylcytosine. Enthalpies of hydration were calculated. The latter were analyzed on the basis of the group additivity method. The relation between enthalpy of hydration and polarity of compounds is discussed.

Molecular interactions of macrocycles with dipeptides in aqueous solutions. Partial molar volumes and heat capacities of transfer of a chiral 18-crown-6 and of a calix[4]resorcinarene derivative from water to aqueous dipeptide solutions at 25°C

Densities and specific heat capacities of ternary aqueous systems containing a dipeptide (alanyl-alanine, alanyl-glutamic acid, alanyl-serine or L-seryl-L-leucine) and a macrocycle (D-α-manno-naphtho-18-crown-6-ether or 2,8,14,20-tetrakis[-methyl (aminoformyl)]-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene) were determined at 25°C by flow densimetry and flow calorimetry. The partial molar volume and heat capacity of transfer of a macrocycle from water to the dipeptide solution was determined as a function of the dipeptide concentration. Positive values for transfer volumes and transfer heat capacities are observed with all the solutions studied. With the crown ether, except for alanyl-glutamic acid where a 1:1 complex is clearly evidenced due to specific interactions of the side-chain functional group of the peptide with the crown ether, no stoichiometric complexes are confirmed and the partial molar quantities of transfer increase with the hydrophobic character of the dipeptide. Partial quantities of transfer are smaller with the calixarene than with the crown ether and stoichiometric complexes [calixarene]/[dipeptide] from 2:1 to 1:4 are evidenced, depending on the nature and the concentration of the dipeptide.

A dodecameric self-assembled calix[4]arene aggregate with two types of cavities

Twelve molecules of β-carbonyl-para-octyl-calix[4]arene assemble in an aggregate containing two types of cavities filled by water molecules and they pack in a cubic structure. Both the aggregates and the packing resemble that observed for inverse micelles.

Thermodynamic investigations of cytosine and its methyl, methoxy and hydroxy derivatives. Enthalpies of solvation in methanol and N, N -dimethylformamide

Abstract The enthalpies of solution Δ sol H m ∞ of cytosine, 1-methylcytosine, 1,5-dimethylcytosine, 1-methyl-N 4 -hydroxycytosine, 1,5-dimethyl-N 4 -hydroxycytosine, 1-methyl-N 4 -methoxycytosine, 1,5-dimethyl-N 4 -methoxycytosine in methanol and in N, N - dimethylformamide were determined and discussed with previously obtained data of the enthalpy of sublimation Δ s g H m , partial molar volumes V 0 2 and structural parameters {e.g. molecular accessible surface areas S M and their atomic partition S N , S O , S H(N,O) , molecular volumes V M 2 } for compounds investigated. The enthalpies of solvation Δ solv H m , the transfer enthalpies of solution Δ tr H m , water-methanol, water- N, N -dimethylformamide and enthalpies of interaction Δ int H m were calculated. Correlation between the enthalpy of solvation, volumetric and structural parameters was elaborated. It was demonstrated that the enthalpy of solvation and transfer enthalpy of solution correlate with surface accessible areas as well as with volumetric properties characterized by parameter β, corresponding to the difference between the partial molar and molecular volumes of compounds studied.

Influence of complex formation with tetraantraquinoporphyrazines and tetrasulphophthalocyanine on thermal stability of bovine serum albumin

Interaction between bovine serum albumin (BSA) and tetraantraquinoporphyrazines (TAP) and tetrasulphophthalocyanine (Pc) aluminum hydroxide was studied by means of electron absorption spectroscopy, IR spectroscopy, fluorescence spectroscopy and differential scanning calorimetry. It was found that the complex formation of BSA with the TAPs results in increase of thermal stability of the protein while Pc does not have remarkable influence on the protein thermal denaturation.

Interaction Between Yeast Eukaryotic Initiation Factor eIF4E and mRNA 5′ Cap Analogues Differs from That for Murine eIF4E

Abstract Measurements of interaction of 7-methyl-GTP eIF4E from S. cerevisiae were performed by means of two methods: Isothermal Titration Calorimetry (ITC) and fluorescence titration. The equilibrium association constants (Kas) derived from the two methods show significantly different affinity of yeast eIF4E for the mRNA 5′ cap than those of the murine and human proteins. The observed differences in the Kas values and the enthalpy changes of the association (ΔH°) suggest some dissimilarity in the mode of binding and stabilization of cap in the complexes with eIF4E from various sources.

Volumetric investigations of solute-solvent interactions of some alkylated derivatives of uracil in methanol, and N,N-dimethylformamide at 25°C

Abstract Densities of uracil, thymine, 1,3-dimethyluracil, 1,3,6-trimethyluracil, 1,3-dimethyl-6-ethyluracil, 1,3-dimethyl-6-propyluracil, 1,3-diethylthymine in methanol and N,N-dimethylformamide solutions at 25°C by means of Anton Paar DMA 60/602 digital densimeter were determined, then the partial molar volumes V 2 0 were evaluated. The contribution of CH 2 groups present at the molecules studied in the V 2 0 value, using the simple additivity scheme, were calculated. The linear correlations V 2 0 = f ( n CH 2 ) were found. The model based on the assumption that the density of the solvation shell depends on the structure and polarity P of the solute molecule was applied. The structural parameters of the compounds investigated: molecular volumes V 2 M , volumes of solvation shell V 1, solv and molecular surface areas S M , and their atomic partitions S N , S 0 , S H(N) were calculated. The determinations of P values were made assuming that both acceptors and donors of protons in aqueous solutions are involved into the specific solute-solvent interactions. Methanol more active as a donor than acceptor of protons interacts with the oxygen and nitrogen atoms, whereas DMF interacts solely with the hydrogen atom of the solute molecule. The transfer functions of ΔV 2,tr 0 water-methanol, water-N,N-dimethylformamide were also calculated.