Biomedical subjects

S Lapanje

Publications and source records attributed to S Lapanje.

8 recordsLinked to original sources

PubMed1992

Apparent specific volumes of some dipeptides (containing L-valine and L-leucine in aqueous alkylurea solutions).

The apparent molal volumes of nine dipeptides containing glycine, L-valine, and L-leucine have been determined in methyl, N,N'-dimethyl and ethylurea solutions from precise density measurements. Limiting partial molal volumes. V2(0), at various solute concentrations have also been calculated. The experimental values of V2(0) in water agree reasonably well with those calculated as the sum of V2(0) of both acids after accounting for the electrostrictive effect and loss of water. There is no correlation between the values of V2(0) of individual dipeptides in alkylureas which means that the intrinsic volume and the electrostrictive effect make the largest contribution to V2(0). The contribution from other effects is within the limit of experimental error. The volumes of transfer from water to alkylurea solutions are all positive and reflect by and large the electrostrictive effect.

Amino Acid Sequence↗

PubMed1989

Calorimetric and circular dichroic studies of the thermal denaturation of beta-lactoglobulin.

The thermal denaturation of beta-lactoglobulin in aqueous solutions at pH 5.5 and 2.0 was investigated by differential scanning calorimetry (DSC) and circular dichroic (CD) measurements. By calorimetry, the denaturation temperatures (Td), denaturation enthalpies, and specific heat capacity changes for thermal denaturation in the temperature range scanned, i.e., 20-100 degrees C. The unfolding process was found to be only partially reversible. Analysis of the far-ultraviolet CD spectra reveals that with increasing temperature the mean residue ellipticity [( theta]) becomes less negative, which reflects unfolding of the native protein. At the highest temperature of CD measurements, i.e., 80 degrees C, conformational changes are to a large extent reversible.

Calorimetry, Differential Scanning↗

PubMed1978

Thermodynamics of the isothermal interaction of human immunoglobulin G with guanidinium chloride.

A thermodynamic study of the isothermal interaction of human immunoglobulin G with guanidinium chloride, a strong denaturant, has been performed. Free energies of interaction were calculated using preferential binding data obtained by measuring densities at constant chemical potential and constant composition, respectively. Enthalpies of interaction were determined calorimetrically. The values of both thermodynamic parameters as well as those of entropies of interaction have been found to depend crucially on the extent of denaturant binding.

Guanidines↗

PubMed1978

Osmometric studies of human immunoglobulin G.

Osmometric studies of solutions of IgG and its H and L chains were performed in various solvents. It has been found that in aqueous solutions and in guanidinium chloride solutions of low and moderate concentrations IgG molecules are associated which prevents molecular weight determination. On the other hand, in 6 M guanidinium chloride the molecular weight of IgG was determined to be 145,000. Addition of sodium dodecyl sulfate to aqueous solutions of IgG does not prevent association.

Guanidines↗

PubMed1977

Thermodynamics of the isothermal interaction of beta-lactoglobulin with guanidinium chloride and urea.

A thermodynamic study of the isothermal interaction of beta-lactoglobulin with guanidinium chloride and urea has been performed. Enthalpies of interaction of the two denaturants have been obtained by calorimetric measurements, and the free energy of interaction calculated from previously determined preferential binding of denaturants. In separate dilatometric experiments the volume changes accompanying the interaction of guanidinium chloride with beta-lactoglobulin have also been determined.

Binding Sites↗

PubMed1977

Studies on bovine spleen cathepsin D.

The purification procedure of cathepsin D which includes autolysis results in the destruction of the molecule to smaller polypeptide chains. Pure catepsin D obtained by the method which includes affinity chromatography, contains single polypeptide chain of 42000 daltons. The N-terminal amino acid is glycine. The specificity was studied using synthetic substrates. CD measurement of cathepsin D shows mainly unordered structure, about 26% of beta-structure and only 5% of alpha-helix. Binding of pepstatin shows pronounced changes in the CD spectrum between 250 and 300 nm; above 7.5 no interaction was observed.

Animals↗

PubMed1976

Thermodynamics of the isothermal denaturation of lysozyme by guanidinium chloride.

A thermodynamic analysis of the isothermal denaturation of lysozyme by guanidinium chloride has been performed. The analysis is based on the equation which relates the equilibrium constant for denaturation to the preferential binding of denaturant. The equation has been derived previously by thermodynamic methods, whereas in this article a derivation based on statistical mechanics is given. By application of the equation the free energy of denaturation is first calculated and from it, by subtracting the calorimetrically-determined enthalpy of denaturation, the entropy of denaturation is determined.

Binding Sites↗

PubMed1975

Dilatometry, a neglected method in immunological studies.

Dilatometry has become a useful method for the study of proteins owing to its simplicity and accuracy. However, it has seldom been used in the study of immunoglobulins. Therefore possible applications of the method for that study are being discussed. A description is also given of the most common experimental set-up and procedure for dilatometric experiments. Finally, several papers describing the application of dilatometry to the study of immunoglobulins are reviewed.

Antigen-Antibody Reactions↗