Search results for "denaturation"
showing 10 items of 107 documents
Local dynamics of DNA probed with optical absorption spectroscopy of bound ethidium bromide
1997
We have studied the local dynamics of calf thymus double-helical DNA by means of an "optical labeling" technique. The study has been performed by measuring the visible absorption band of the cationic dye ethidium bromide, both free in solution and bound to DNA, in the temperature interval 360-30 K and in two different solvent conditions. The temperature dependence of the absorption line shape has been analyzed within the framework of the vibronic coupling theory, to extract information on the dynamic properties of the system; comparison of the thermal behavior of the absorption band of free and DNA-bound ethidium bromide gave information on the local dynamics of the double helix in the prox…
A synchrotron radiation X-ray scattering study of aqueous solutions of native DNA
1999
Synchrotron radiation small-angle X-ray scattering (SAXS) was used to investigate solutions of native DNA at different ionic strengths and temperatures. The mass per unit length, radius of gyration of the cross-section of DNA and apparent second virial coefficient (A2) were obtained from Zimm plots in the rodlike particle approximation. The values of A2 obtained in this way are positive and almost constant indicating that the repulsive interactions still influence the scattering patterns at resolutions as high as 5-8 nm. SAXS measurements in continuous temperature scans indicate that the rod approximation is valid over a wide temperature range during DNA melting and confirm that the rodlike…
4-4-20 anti-fluorescyl IgG Fab' recognition of membrane bound hapten: direct evidence for the role of protein and interfacial structure.
1995
The surface forces apparatus was used to identify the molecular forces that control the interactions of monoclonal 4-4-20 antifluorescyl IgG Fab' fragments with fluorescein-presenting supported planar bilayers. At long range, the electrostatic force between oriented Fab' and fluorescein monolayers was controlled by the composition of the protein exterior surrounding the antigen-combining site rather than by the overall protein charge. The measured positive electrostatic potential of the Fab' monolayer at pH > pI(Fab') was consistent with the structure of the exposed Fab' surface in which a ring of positive charge at the mouth of the antigen-combining site dominates the local electrostatic s…
Protein-lipid interactions at the air-water interface.
2010
International audience; Protein−lipid interactions play an important role in a variety of fields, for example in pharmaceutical research, biosensing, or food science. However, the underlying fundamental processes that govern the interplay of lipids and proteins are often very complex and are therefore studied using model systems. Here, Langmuir monolayers were used to probe the interaction of a model protein with lipid films at the air−water interface. The protein β-lactoglobulin (βlg) is the major component in bovine milk serum, where it coexists with the milk fat globular membrane. During homogenization of milk, βlg adsorbs to the interface of lipid fat globules and stabilizes the oil-in-…
Calorimetric study of myoglobin embedded in trehalose-water matrixes
2009
It has been suggested that in ‘dry’ protein–trehalose–water systems, water–mediated hydrogen bond network, whose strength increases by drying, anchors the protein to its surroundings. To further characterize this effect, we performed a DSC study on low-water myoglobin–trehalose systems. The denaturation temperature resulted to increase by decreasing hydration, and linearly correlated to the glass transition temperature of both the ternary protein–water–trehalose and the binary water–trehalose systems. Further measurements are being performed to investigate eventual differences among different saccharides.
New propylamine oligopyrrole carboxamides linked to a heterocyclic or anthraquinone system: synthesis, DNA binding, topoisomerase I inhibition and cy…
2003
Continuing our studies on combilexines, compounds consisting of a DNA intercalator linked to a minor groove ligand, new results are presented. The synthesis of a series of new propylamine oligopyrrole carboxamides closely related to netropsin and distamycin A, linked to a heterocyclic or anthraquinone system is reported. The cytotoxic activity in vitro, the DNA binding characteristics and the inhibition of the topoisomerase I of the compounds were studied in order to explain the biological mechanism of action of these new potential combilexines. Some of the synthesised compounds showed cytotoxic activity against human tumour cell lines, as well as DNA binding and topoisomerase I inhibiting …
Thermal Denaturation of Pea Globulins (Pisum sativum L.)—Molecular Interactions Leading to Heat-Induced Protein Aggregation
2013
The heat-induced denaturation and aggregation of mixed pea globulins (8%, w/w) were investigated using differential scanning calorimetry (DSC), SDS-PAGE, and size-exclusion chromatography (SEC-HPLC). DSC data showed that the pea proteins denaturation temperature (T(d)) was heating-rate dependent. The T(d) value decreased by about 4 °C by lowering the heating rate from 10 to 5 °C/min. The SDS-PAGE analysis revealed that protein denaturation upon heating at 90 °C was mainly governed by noncovalent interaction. The SEC-HPLC measurements indicated that low-denatured legumin (≈350-410 kDa) and vicilin/convicilin (≈170 kDa) globulins were heat-denatured and most of their subunits reassociated int…
Production of the Sweet Protein Monellin in Transgetic Plants
1992
Monellin is a protein that elicits a flavor approximately 100,000 times sweeter than sugar on a molar basis. The protein exists naturally as a heterodimer, with its sweet flavor lost upon denaturation. A single–chain monellin gene, encoding both polypeptide chains linked by a hinge sequence, was placed under the control of constitutive and fruit–ripening specific promoters and transferred to lettuce and tomato. Expression of these genes in transgenic tomato and lettuce resulted in the accumulation of monellin protein in fruit and leaf, respectively, to significant levels. Production of monellin in transgenic fruits and vegetables represents an alternative strategy to enhance their flavor an…
Interaction of the Alternating Double Stranded Copolymer poly(dA-dT)·poly(dA-dT) with NiCl2and CdCl22: Solution Behavior
2007
The thermal denaturation of the synthetic high molecular weight double stranded polynucleotide poly(dA-dT) x poly(dA-dT) has been studied in aqueous buffered solution (Tris 1.0 mM; pH 7.8+/-0.2) in the presence of increasing concentrations of either Ni(2+) (borderline cation) or Cd(2+) (soft cation) at four different constant ionic strength values (NaCl), making use of UV and circular dichroism (CD) spectroscopies. The experimental results show that the B-type double helix of the polymer is stabilized against thermal denaturation in the presence of both cations at low concentrations, relative to the systems where only NaCl is present, in the same conditions of ionic strength and pH. The eff…
The impact of whey protein preheating on the properties of emulsion gel bead
2014
Thermal treatment effect (70 or 80 °C for 5 or 30 min) was evaluated on functional properties of whey protein isolate (WPI) dispersions used for the development of novel vitamin A delivery systems based on emulsion gel beads. This process combines an (O/W) emulsion diluted by a polysaccharide solution and a cold-set gelation induced by salt addition. Pre-heated WPI had a significant impact on the denaturation degree and on the surface hydrophobicity, respectively studied by differential scanning calorimetry and fluorescence. Stronger heating conditions (i.e. duration or temperature) induced complete denaturation, an increase of surface hydrophobicity and of viscosity. Under these conditions…