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W Pfeil

Publications and source records attributed to W Pfeil.

46 records · Page 3Linked to original sources
PubMed1980

Thermodynamic investigations of cytochrome b5 unfolding. I. The tryptic fragment of cytochrome b5.

Thermal unfolding of the tryptic fragment of the membrane-bound protein, cytochrome b5, which contains the residues 1-90, was investigated by scanning calorimetry, circular dichroism and absorption spectroscopy. The fragment undergoes a reversible two-state transition at about 70 degrees C (neutral pH). The fragment exhibits all the thermodynamic properties of small globular proteins with respect to heat capacity and transitional changes of enthalpy, Gibbs energy and heat capacity. The heat capacity change at unfolding fits into the correlation with the specific amount of nonpolar contacts, which has been found to be valid for small globular proteins (Privalov, P.L. and Khechinashvili, N.N. (1974) J. Mol. Biol. 86, 665-684). The relatively low stabilization energy of the cytochrome b5 fragment (delta trsG25 degrees C = 25 kJ/mol) is discussed in terms of the functional requirements of electron-transfer proteins.

Animals↗
PubMed1980

Optical and thermodynamical properties of proteolytic fragments of cytochrome b5.

Haem containing fragments of cytochrome b5 prepared from rabbit liver microsomes by trypsin and chymotrypsin treatment, and checked by isoelectrofocussing, were identified as sequences 1--90 (tryptic fragment) and 12--97 (chymotryptic fragment) of the protein. The two fragments exhibit the same helix content as judged from circular dichroism spectra. Thermal unfolding measured by scanning microcalorimetry proceeds as a two-state process at transition temperatures Ttrs equals 70 degrees C (fragment 1--90) and Ttrs equals 73 degrees C (fragment 12--97) at neutral pH. The Gibbs energy change at unfolding of the fragments calculated from the calorimetric results amounts to delta G25 degrees equals 26 + or minus 2 kJ mol-1. The results indicate that the region ranging at least from residues 90--97 does not essntially contribute to the secondary structure and stability of the haem containing domain of cytochrome b5. The findings confirm the existence of a junction region between the membrane binding moiety and the haem containing domain of cytochrome b5 which enables lateral movement of the functionally important part of the molecule to certain extent.

Animals↗
PubMed1978

Thermodynamic investigations of proteins. IV. Calcium binding protein parvalbumin.

The conformational transitions of calcium binding protein parvalbumin III from carp muscle were studied by scanning calorimetry, potentiometric titration and isothermal calorimetric titration. Changes of Gibbs energy, enthalpy and partial heat capacity were determined. The removal of calcium ions by EDTA is accompanied by 1) a heat absorption of 75 +/- 10 kJ per mole of the protein, 2) a decrease in the Gibbs energy of protein structure stabilisation of about 42 kJ mol-1 and 3) a decrease in thermostability by more than 50 K. The protonation of the acidic groups leads to a loss of calcium followed by denaturation, while the pH of the transition strongly depends on calcium activity. The enthalpy and heat capacity changes at denaturation are comparable with the values observed for other compact globular proteins.

Animals↗
PubMed1977

[Studies on tooth migration in animal experiments].

The migration of the germ of the 2nd lower molars after the extraction of all adjacent teeth in comparison to the health side was investigated in Vietnamese hanging belly pigs. The animals were killed in seven age groups so that the results could be evaluated in dependence upon the time. The biometric results reveal migratory phenomena similar to those described for humans after tooth extraction.

Age Factors↗
PubMed1976

Thermodynamic investigations of proteins. I. Standard functions for proteins with lysozyme as an example.

A direct method is proposed for obtaining thermodynamic standard functions for native and denatured proteins using experimental data from scanning calorimetry, isothermal calorimetry and potentiometric titrations. The possibility of this approach is demonstrated on the example of lysozyme in the range of pH 1.5-7.0 and temperature 0-100 degrees C. Tests for the validity of the obtained functions of enthalpy and entropy are presented in the form of cyclic processes using experimental data obtained from thermodynamically different pathways. The Gibbs function is checked by comparison with results of an independent method. The methodic problems in determining and checking standard functions for proteins are discussed in detail.

Calorimetry↗
PubMed1976

Thermodynamic investigations of proteins. II. Calorimetric study of lysozyme denaturation by guanidine hydrochloride.

The thermodynamic parameters of the denaturation of lysozyme are determined at various temperatures (25-60 degrees C) by isothermal calorimetric titrations with guanidine hydrochloride (GuHCl) and by scanning calorimetry in the presence of GuHCl. An approach for the determination of the enthalpy of preferential binding of GuHCl is proposed. It has been shown from GuHCl denaturation experiments that the net enthalpies of denaturation and the denaturational change in the heat capacity of protein can be obtained if preferential binding is taken into consideration. These results are nearly the same as in the case of thermal denaturation in the absence of denaturants. It is concluded that the states of both heat- and GuHCl-denatured lysozyme are thermodynamically indistinguishable.

Binding Sites↗
PubMed1976

Thermodynamic investigations of proteins. III. Thermodynamic description of lysozyme.

Standard functions of enthalpy, entropy and the Gibbs energy of native and denatured lysozyme in the range of 0-100 degrees C and pH 1.5-7.0 are represented in three-dimensional projections. The denaturational Gibbs energy change reaches 16 kcal mol-1 at conditions of maximal protein stability (0 degrees C, pH 4.5-7.0) and equals 14.5 kcal mol-1 at 25 degrees C and neutral pH. This result was found to be in agreement with the data reported from guanidine hydrochloride denaturation studies. Partial thermodynamic functions of the conformational and ionizational changes of the protein are obtained from entropy and Gibbs-energy changes in denaturation. The conformational partial entropy and Gibbs-energy change are found to be independent of pH. The pH-dependent partial ionizational entropy and Gibbs-energy changes are induced by normalization of the ionization behaviour of buried groups and cause a decrease of protein stability.

Binding Sites↗
PubMed1975

[Molecular and complex-chemical studies on methemoglobin from Chironomus thummi thummi and various isolated fractions].

1. Six different hemoglobin (Hb) fractions were isolated and characterized from the larvae of Chironomus thummi thummi using column chromatographic procedures. 2. Chromatographic and sedimentation-analytic studies (sedimentation coefficients of 2.0 +/- 0.2 (S)) have shown three Hb fractions to exist basically in a monomeric form. The molecular weight of component M-2 was determined by sedimentation equilibrium technique to be 15,470 +/- 400. The dimeric Hb was found to have sedimentation coefficients of 3.0 +/- 0.1 (S) in the weakly acidic pH region. In alkaline milieu, the reversible dissociation proceeds into the monomeric molecules (S20, W = 1.9 +/- 0.1 (S)). Molecular weights vary between pH 5.7 and 9.8 not only with hydrogen ion concentration, but also with protein concentration in correspondence with a dissociation-association equilibrium consisting of monomers and dimers. 3. For the Hb fraction M-2, a friction ratio of f/fo = 1.03 was calculated, suggesting an almost spherical shape of this protein. In contrast, the dimeric component appears to have a much more asymmetric structure (f/fo = 1.19). 4. The indivdual MetHb fractions bind the ligands: fluoride, imidazole and azide with different affinities.

Diptera↗