Search results for "Denaturation"
showing 10 items of 107 documents
Modulation of DNA binding by reversible metal-controlled molecular reorganizations of scorpiand-like ligands.
2012
DNA interaction with scorpiand azamacrocycles has been achieved through modulation of their binding affinities. Studies performed with different experimental techniques provided evidence that pH or metal-driven molecular reorganizations of these ligands regulate their ability to interact with calf thymus DNA (ctDNA) through an intercalative mode. Interestingly enough, metal-driven molecular reorganizations serve to increase or decrease the biological activities of these compounds significantly.
Thermal induced conformational changes involved in the aggregation pathways of beta-lactoglobulin.
2004
Aggregation of proteins appears to be associated most often with conformational and structural changes that lead to exposure of some apolar residues. Depending on the native structure of the protein in exam, aggregation is a process that involves different mechanisms, whose time of occurrence and interplay can depend upon temperature. To single out information about the multistages of the aggregation pathway, here we investigate the thermally induced conformational and structural changes of the beta-lactoglobulin (BLG). The experimental approach consists in studying steady-state fluorescence spectra of intrinsic chromophores, two tryptophans, and Anylino-Naphthalene-Sulfonate dye (ANS) mole…
Synthesis and cytotoxic activity of a new potential DNA bisintercalator: 1,4-Bis{3-[N-(4-chlorobenzo[g]phthalazin-1-yl)aminopropyl]}piperazine
2010
The synthesis of new 1,4-bisalkylamino (2-4) and 1-alkylamino-4-chloro (5-6) substituted benzo[g]phthalazines is reported. Compounds 2-4 and 6 were prepared both in the free and heteroaromatic ring protonated forms. Bifunctional 6 contains the 1,4-bisaminopropylpiperazine chain as a linker between the two heteroaromatic units, whereas 5 is its monofunctional analogue. The in vitro antitumour activity of the synthesized compounds has been tested against human colon, breast and lung carcinoma cells, and also against human glioblastoma cells. Results obtained show that all of them are active in all cases, but bifunctional 6·2HCl is remarkably effective against the four cell lines tested, exhib…
Mechanism of Oligomerisation of Cyclase-associated Protein from Dictyostelium discoideum in Solution
2006
Abstract Cyclase-associated protein (CAP) is a highly conserved modular protein implicated in the regulation of actin filament dynamics and a variety of developmental and morphological processes. The protein exists as a high molecular weight complex in cell extracts and purified protein possesses a high tendency to aggregate, a major obstacle for crystallisation. Using a mutagenesis approach, we show that two structural features underlie the mechanism of oligomerisation in Dictyostelium discoideum CAP. Positively charged clusters on the surface of the N-terminal helix-barrel domain are involved in inter-molecular interactions with the N or C-terminal domains. Abolishing these interactions m…
Genomic determinants of protein folding thermodynamics in prokaryotic organisms.
2004
Here we investigate how thermodynamic properties of orthologous proteins are influenced by the genomic environment in which they evolve. We performed a comparative computational study of 21 protein families in 73 prokaryotic species and obtained the following main results. (i) Protein stability with respect to the unfolded state and with respect to misfolding are anticorrelated. There appears to be a trade-off between these two properties, which cannot be optimized simultaneously. (ii) Folding thermodynamic parameters are strongly correlated with two genomic features, genome size and G+C composition. In particular, the normalized energy gap, an indicator of folding efficiency in statistical…
Chicken Avidin-related Protein 4/5 Shows Superior Thermal Stability when Compared with Avidin while Retaining High Affinity to Biotin
2003
The protein chicken avidin is a commonly used tool in various applications. The avidin gene belongs to a gene family that also includes seven other members known as the avidin-related genes (AVR). We report here on the extremely high thermal stability and functional characteristics of avidin-related protein AVR4/5, a member of the avidin protein family. The thermal stability characteristics of AVR4/5 were examined using a differential scanning calorimeter, microparticle analysis, and a microplate assay. Its biotin-binding properties were studied using an isothermal calorimeter and IAsys optical biosensor. According to these analyses, in the absence of biotin AVR4/5 is clearly more stable (T…
DNA Binding Studies and Cytotoxicity of a Dinuclear PtII Diazapyrenium- Based Metallo-supramolecular Rectangular Box
2012
The interaction with native DNA of a 2,7-diazapyrenium-based ligand 1 and its Pt II rectangular metal- lacycle 2 is explored through circular and linear dichroism and fluorescence spectroscopies. The metal-free ligand 1 binds through intercalation, with a binding constant of approximately 5 � 10 5 m � 1 , whereas the metallacycle 2 binds and bends the DNA with a bind- ing constant of 7 � 10 6 m � 1 . PCR assays show that metallo-supramolecular box 2 interferes with DNA transactions in vitro whereas the intercalator 1 does not. The metallacycle is active against four human cancer cell lines, with IC50 values ranging between 3.1 and 19.2 mm and shows similar levels of efficacy, but a differen…
Direct measurement of the melting temperature of supported DNA by electrochemical method
2003
The development of biosensors based on DNA hybridization requires a more precise knowledge of the thermodynamics of the hybridization at a solid interface. In particular, the selectivity of hybridization can be affected by a lot of parameters such as the single-strand (ss)DNA density, the pH, the ionic strength or the temperature. The melting temperature, T(m), is in part a function of the ionic strength and of the temperature and therefore provides a useful variable in the control of the selectivity and sensitivity of a DNA chip. The electrochemical technique has been used to determine the T(m) values when the probe is tethered by a DNA self-assembled monolayer (SAM). We have built a speci…
Thermische Denaturierung von Kaltblüter-Enzymproteinen
1960
The temperature, which leads to 50% reduction of catalytic activity by heat denaturation, has been determined for 8 different enzymes from cod muscle, as being in the range between 30 and 52°C. Therefore, there are no indications of a generally different heat resistance of enzymes from cold-blooded animals as compared with those from warm-blooded animals. The same conclusion is derived from calculations ofQ10-values, measured between +37 and − 37°C for cathepsin and glycylglycine dipeptidase.
Myoglobin embedded in saccharide amorphous matrices: water-dependent domains evidenced by small angle X-ray scattering
2010
We report Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin (MbCO) embedded in low-water trehalose glasses. Results showed that, in such samples, "low-protein" trehalose-water domains are present, surrounded by a protein-trehalose-water background; such finding is supported by Infrared Spectroscopy (FTIR) measurements. These domains, which do not appear in the absence of the protein and in analogous sucrose systems, preferentially incorporate the incoming water at the onset of rehydration, and disappear following large hydration. This observation suggests that, in organisms under anhydrobiosis, analogous domains could play a buffering role against th…