Shift Of Tm Research Articles

Relaxor ferroelectricity in ceramics with composition Ba1−xKx(Ti1−xNbx)O3

Ceramics sintered at temperatures in the range 1200–1400°C and with composition Ba1−xKx(Ti1−xNbx)O3 (0.04≤x≤0.20) show a relaxor ferroelectric behaviour. All the corresponding dielectric characteristics, i.e., diffusivity of the ferroelectric–paraelectric transition, frequency dispersion of εr′, shift of Tm with frequency deviation from the Curie–Weiss law, are determined. The behaviour is all the more relaxor because the composition deviates from BaTiO3. This study shows the preparation of lead-free relaxor ceramics, which promotes environmental protection.

Studies on cytochrome c-heparin interactions by differential scanning calorimetry.

The effects of heparin on the thermotropic properties of ferricytochrome c have been studied using high-sensitivity differential scanning calorimetry. Saturating concentrations of heparin at low ionic strength induced an important shift of the transition temperature Tm from 84.1 degrees C to 59.8 degrees C. This was accompanied by unusually large cooperativity of thermal denaturation of this complex, indicating strong intermolecular interactions between protein molecules. The destabilization of cytochrome c when mixed with heparin was not observed at high ionic strength, under which conditions complex was not formed.

Quantum effects at TSCC1−xBxmonocrystals: The influence of an external electric field on the permittivity peak

Abstract The results of model calculations and of experimental investigations of the shift of the temperature TM of the maximum of the permittivity ∊b due to an external electric d.c. field on tris-sarcosine calcium chloride1−x bromidex (TSCC1−xBx) monocrystals with different concentrations x are described. It is shown that in the low temperature region a marked enhancement of the response of the permittivity maximum to an external electric d.c. field is caused by quantum effects.

Basic Polypeptides as Histone Models: Interaction of Block Copolymers of [LysnAlam] with Calf Thymus DNA

AbstractBlock copolymers were synthesized by blockwise copolymerization of Z‐L‐Lys‐NCA and D,L‐Ala‐NCA initiated by tert.‐butylamines. The lysine block consisted always of 20 residues, the length of the alanine block (Pn) was either 10 or 20 residues. Complexes of the copolymers with calf thymus DNA were prepared by mixing the dilute solutions of the polyelectrolytes at different ratios (cation/anion) rapidly. Melting curves of the complexes were recorded at 260 nm. The shift of the melting temperature Tm is discussed as a function of the input ratio of cations and the results are compared to the results obtained with CT‐DNA and polylysine.

Decrease of melting temperature and single strand scission of DNA by bleomycin in the presence of 2-mercaptoethanol.

Decrease of melting temperature (Tm) of Escherichia coli 15T- DNA, with little breakage of the DNA strand, was observed in the presence of bleomycin A2 and 2-mercaptoethanol. DNA digested more drastically with pancreatic deoxyribonuclease (E. C. 3.1.4.5) revealed no shift of Tm. When the DNA, treated with bleomycin and 2-mercaptoethanol, was dialyzed after heat denaturation, marked strand scission occurred. Tm of poly (dG)•poly (dC) decreased by 9°C with a change of transition width at 40μg/ml of bleomycin, although that of poly d(AT)•poly d(TA) showed no change. Single strand scission of synthetic deoxyribopolymers was observed to occur slightly in the presence of bleomycin and markedly when dialyzed after the incubation. Strand scission without dialysis was produced more significantly on poly (dG).poly (dC) than poly d(AT)•poly d(TA) in the presence of bleomycin.