Search results for "denaturation"
showing 10 items of 107 documents
Effect of Ligands on HP-Induced Unfolding and Oligomerization of β-Lactoglobulin
2020
ABSTRACTTo probe intermediate states during unfolding and oligomerization of proteins remains a major challenge. High pressure (HP) is a powerful tool for studying these problems, revealing subtle structural changes in proteins not accessible by other means of denaturation. Bovine β-lactoglobulin (BLG), the main whey protein, has a strong propensity to bind various bioactive molecules, such as retinol and resveratrol, two ligands with different affinity and binding sites. By combining in situ HP-small-angle neutron scattering (SANS) and HP-UV/visible absorption spectroscopy, we report the specific effects of these ligands on 3D conformational and local changes in BLG induced by HP. Dependin…
PolyAT chemical denaturation in w/o microemulsion
2004
CD and UV spectroscopies have been used to investigate the effects caused by the addition of either strong acid-or base-containing microemulsions on the behaviour of the synthetic polynucleotide polyAT entrapped in the aqueous core of a cationic quaternary water-in-oil microemulsion (μE). The titrations were performed in the presence of variable concentrations of NaCl, in the range 0.00 to 0.60 M. In both cases, the primary effect was the reversible transition from B-double helix to random coil of the guest polynucleotide. However, in the microemulsive medium, the number of moles of protons (RH) and hydroxide ions (ROH) per mole of titrable sites are independent of the salt concentration bu…
Effects of isoflurane on the Dnase I activity in an isolated enzyme preparation and on the Dnase I-G actin complex
1991
Effects of isoflurane on the DNase I activity in an isolated enzyme preparation and in the DNase I-globular (G) actin complex were investigated. DNase I, DNase I-G actin complex, and G actin were exposed to various (0.2–4.0 vol%) isoflurane concentrations for 180 min. Thereafter, DNase I activity was determined. DNase I activity was inhibited in relation to time and concentration of isoflurane exposure. At concentrations ranging from 0.2 to 1.0 vol% of isoflurane inactive DNase I was activated in the DNase I-G actin complex. The DNase I inhibitor G actin showed a reduced capability to inhibit DNase I following isoflurane exposure. Albumin can inhibit the DNase I inactivation possibly by com…
Influence of Several Effectors on the Structure-Activity Relationship of Spleen Phosphodiesterase
1993
The influence of Mg(II) and organic solvents on the structure-activity relationship of spleen phosphodiesterase II was analyzed using UV and fluorescence spectroscopies. An increase in the RNase activity found in the presence of Mg(II) was related to the enzyme-Mg(II) interaction detected by UV spectroscopy. In the fluorescence spectra of phosphodiesterase strong hypochromic and bathochromic effects were observed when RNA was present at a concentration (52 μg ml−1) of the same magnitude as the concentration that inhibits the activity (Ki = 40 μg ml−1). The strong quenching observed in the presence of RNA shows the importance of large dynamic and static quenching of the Trp residues of the e…
Distinct amino acids of the Oenococcus oeni small heat shock protein Lo18 are essential for damaged protein protection and membrane stabilization
2010
The small heat shock protein (smHsp) Lo18 from lactic acid bacteria Oenococcus oeni reduces in vitro thermal aggregation of proteins and modulates the membrane fluidity of native liposomes. An absence of information relating to the way in which the smHsp demonstrates a stabilizing effect for both proteins and membranes prompted this study. We expressed three Lo18 proteins with amino acid substitutions in Escherichia coli to investigate their ability to prevent E. coli protein aggregation and their capacity to stabilize E. coli whole-cell membranes. Our results showed that the alanine 123 to serine substitution induces a decrease in chaperone activity in denaturated proteins, and that the ty…
MbCO embedded in trehalosyldextrin matrices: thermal effects and protein-matrix coupling
2010
Saccharide-based biopreservation is widely studied because of its scientific importance and possible technological outcomes for food and pharmaceutical industries. Ternary protein/saccharide/water systems have been extensively exploited to model the characteristics of the in vivo biopreservation process. A tight, water dependent, protein–matrix coupling has been shown to occur in various simple saccharide amorphous matrices, which is stronger in trehalose. The efficiency as bioprotectant of trehalose has been ascribed to this tight coupling, since the appearance of damages on biological structures will more involve structural variations of the surrounding matrix. Here we present, as an appl…
Simple models for nonlinear states of double-helix DNA
2006
Review type introduction is given to the simple modeling of DNA. Intrinsically simple modeling aims at understanding or explaining of some “core” phenomena, not giving any all-embracing model of the underlying system. As a consequence the amount of this type of models and their versions is large. Here we have restricted our contemplation to the most important lines in the path of theoretical understanding of DNA melting or denaturation which is one of the important phases occurring during DNAs replication and transcription processes. The model “line” initiated by Peyrard and Bishop shows the richness these simple models can have.
Spectroscopic study of polynucleotides in cationic W/O microemulsions
2007
Water has an active and key role in determining the structure of DNA. Entrapment of DNA and of synthetic model polynucleotides in reverse micelles, where the water activity can easily be modulated, may be a useful way of assessing the influence of water on DNA characteristics; it may also offer useful ideas on the problem of how the giant DNA molecule can be confined in the limited space of cell nuclei. The quaternary microemulsion CTAB n-hexane|n-pentanol| water was used to entrap calf thymus DNA, and the model polynucleotides single-strand polyA, single-strand polyT and duplex polyAT. Ultraviolet spectros-copy, specifically the band at 260 nm, was used to compare the pairing of complement…