Theodor Funck

Volume and compressibility effects in the formation of metal-EDTA complexes

We used precise measurements of ultrasonic velocity and density to study the complexation of ethylendiaminetetraacetic acid (EDTA) with Mg2+, Ca2+, Sr2+, and Ba2+ at 25‡C and pH 12. From these measurements we obtained the changes in the molar concentration increment of the ultrasonic velocity δA, the apparent molar adiabatic compressibility δKsΦ, and the apparent molar volume δVΦ of complex formation. The hydration contributions δ(AVh) to the volume effect of binding range from 39.6 to 46.6 cm3-mol-1 while the hydration contribution to the adiabatic compressibility change in the binding, δ(δKh), ranges from 103.9X 10-4 to 131.1 X 10-4 cm3-mol-1-bar-1. These data are interpreted in terms of dehydration of interacting molecules,i.e., transfer of water molecules from the hydration shells of cations and EDTA into the bulk water. The ratio δ(δVh)/ δ(δVh) is in the range 0.35 to 0.38 bar, indicating a dominant contribution from the dehydration of charged atomic groups in the volume and the compressibility effects of complex formation.

Hydrolysis of cis- and trans-diammineplatinum(II) complexes: Hydration, equilibrium, and kinetics properties

We have used a combination of ultrasound and density techniques to measure the hydration parameters, apparent molar volume, and apparent molar adiabatic compressibility, of the antitumor drug cis-dichlorodiammineplatinum(II), cis-[Pt(NH3)2Cl2], and its inactive isomer trans-dichlorodiammineplatinum(II), trans-[Pt(NH3)2Cl2], in 10 mM NaNO3, pH 5.6 at 37°C. The data have been interpreted in terms of the overall hydration of each isomer, the actual hydration contribution to the adiabatic compressibility, ΔKh, ranges from −56.4 × 10−4 to −20.3 × 10−4 cm3-mol−1-bar−1, and the volume contribution, ΔVh, ranges from −16.3 to −6.4 cm3-mol−1. The negative signs of these hydration contributions indicate that the volume and compressibility of the water immobilized by the platinum complexes is smaller than the volume and compressibility of bulk water. The ΔVh and ΔKh parameters for all platinum complexes investigated are linearly dependent on the relative amount of hydrolyzed chlorides. The values of each parameter become more negative with increasing hydrolysis, and show that the degree of hydration increases. The similar dependence of the amount of hydrolyzed chloride ligands reveals similar hydration properties for these two complexes. Thus, the symmetry of the complexes, which is of crucial importance for anticancer activity, has no influence on their hydration properties. Under our experimental conditions, the equilibrium constants for the hydrolysis of cis-[Pt(NH3)2Cl2] are K1 = 2.52 mM and K2 = 0.04 mM. The equilibrium constant for the first step of hydrolysis of trans-[Pt(NH3)2Cl2] is 0.03 mM, while the second chloride ligand cannot be substituted by water, even in the irreversible reaction with AgNO3. Furthermore, continuous measurements of the ultrasonic velocity during hydrolysis permits the accurate evaluation of the pseudo-first-order rate constant k1 for the hydrolysis of the first chloride ligand of cis-[Pt(NH3)2Cl2], which is 16±1×10−5 s−1.

Isolation and dynamic hapten binding properties of 2,4,6-triphenyl-N-(4-hydroxyphenyl)-pyridinium (THP-) specific antibodies from bovine colostrum--I. 7S and 19S anti-THP antibodies. Preparation, Characterization and analytical application of immunoadsorption.

Abstract Antibodies against the solvatochromic dye 4-(3-aminophenyl)-2,6-diphenyl- N -(4-hydroxy-phenyl)-pyridinium betain (ATHP ∗ ) we produced by immunization of pregnants cows with an THP-edestin conjugate. Large amounts of 7S and 19S anti-THP antibodies were isolated from the colostrum of one of the immunized animals. The specific isolation was performed with the aid of an immunoadsorbent prepared by coupling ATHP to bovine γ-globulin, previously cross-linked with glutaraldehyde. Various conditions for antibody binding to, and elution from, the adsorbent were studied and compared. Using the adsorbent a test was developed which enabled quantitative determination of anti-THP antibodies, including the non-precipitating ones, which were found to be present in the colostrum in large quantities. The isolated anti-THP antibodies were fractionated by chromatography on Sephadex G-200 into 7S and 19S antibodies. The 7S anti-THP antibodies proved to belong the type IgG s whereas the 19S anti-THP antibodies were composed of 19S IgG s and IgM.

Isolation and dynamic hapten binding properties of 2,4,6-triphenyl-N-(4-hydroxyphenyl)-pyridinium (THP-) specific antibodies from bovine colostrum--II. Characteristic differences in hapten binding kinetics of 7S and 19S anti-THP antibodies.

Abstract The hapten binding properties of purified 7S and 19S 2,4,6-triphenyl-N-(4-hydroxyphenyl)-pyridinium (THP∗-) specific antibodies were studied by temperature-jumped spectrometry. In both cases a nearly diffusion-controlled hapten-antibody recombination process in the μsec range was observed. In the case of the 19S immunoglobulins an additional relaxation process in the msec range was found to be independent of reactant concentrations. This slow first-order process, suggesting structural rearrangements of the antibodies, is discussed with respect to hapten-dependent conformational changes of the immunoglobulins.

A novel acoustical approach to biomedical thermodynamics

The principal thermodynamic quantities that describe biomolecular structures and interactions (ΔG°, ΔH°, ΔS°, ΔCp) traditionally have been obtained indirectly by measuring the temperature dependence of some equilibrium property. A more direct approach for obtaining the relevant thermodynamic data is based on calorimetric techniques. Significantly, these thermodynamic parameters also can be derived by measuring the speed of sound U over a range of pressures and temperatures, since U is a function of the second derivative of the free energy over pressure. This talk will describe a novel approach that employs acoustical measurements for determining energetics of biologically relevant molecules and their interactions with small ligands (e.g., drug–biopolymer interactions). Preliminary results will be presented that illustrate how acoustic measurements allow for a thermodynamic characterization of model biomolecular systems. Advantages and complementary features of the acoustical versus calorimetric approaches...