ABSTRACT
DNA integration with silver and gold nanoparticles was carried out by the chemical reduction of silver and gold ions after the formation of their complexes with high molecular DNA in solution. It is shown that, for a good association of DNA with nanoparticles, the ions of silver and gold should be linked with DNA bases rather strongly. The proposed model of gold interaction with DNA is the coordination of gold to N7 guanine in a major groove followed by the transformation of the GC pair to Hoogsteen's type pairing, in which the gold atom is located between the bases and is bonded simultaneously to N7 guanine and N3 cytosine. For gold and silver nanoparticles associated with DNA, the peak of plasmon resonance shifts relative to that of free nanoparticles in solution. AFM (atomic force microscopy) images of both free and associated with DNA nanoparticles were obtained. Binding of high molecular DNA to gold and silver nanoparticles leads to a decrease in the size of its molecular coil in solution, but the bending rigidity of DNA helix (persistent length) does not change. The almost 3-fold increase in the optical anisotropy of DNA was observed when DNA was associated with gold nanoparticles. This result was obtained with the flow birefringence method using a light source with a wavelength of 550 nm, which is close to the peak of the plasmon resonance of gold nanoparticles. For DNA associated with silver nanoparticles, a similar result was obtained when using a light source with a wavelength of about 410 nm.
Subject(s)
DNA/metabolism , Metal Nanoparticles/chemistry , Anisotropy , Borohydrides/chemistry , DNA/chemistry , Gold/chemistry , Gold/metabolism , Nucleic Acid Conformation , Oxidation-Reduction , Silver/chemistry , Silver/metabolism , ViscosityABSTRACT
We examined emotional responses in Attention Deficit Hyperactivity and Oppositional Defiant/Conduct Disorder to affective pictures. Eighty seven children (42 female, Mage = 11.2), with clinical or subclinical symptoms and controls viewed joy, fear, sadness or neutral pictures while heart rate, skin conductance, corrugator and zygomaticus responses were recorded. The moderating role of Callous-Unemotional and anxiety traits was evaluated. Lower resting heart rate and decreased skin conductance across picture types was associated with ADHD symptoms. Decreased heart rate reactivity to fear and sad stimuli was associated with ADHD and ODD/CD. Corrugator and zygomaticus responses were not associated with ADHD or ODD/CD. Findings are mostly consistent with a fearlessness account of disruptive behavior, and seem to also pertain to ADHD, with intact valence systems. Findings are discussed in light of the significance of identifying common pathogenic mechanisms across traditional diagnostic categories, consistent with trans-diagnostic approaches to the study of psychopathology.
Subject(s)
Arousal , Attention Deficit Disorder with Hyperactivity/psychology , Attention Deficit and Disruptive Behavior Disorders/psychology , Emotions , Fear/physiology , Adolescent , Attention Deficit Disorder with Hyperactivity/physiopathology , Attention Deficit and Disruptive Behavior Disorders/physiopathology , Child , Fear/psychology , Female , Galvanic Skin Response/physiology , Heart Rate/physiology , Humans , Male , Problem Behavior , Psychopathology , Rest/psychologyABSTRACT
Both the human retinoic acid receptor alpha (hRARalpha) and a constitutively active mutant (F318A) of the mouse retinoid X receptor alpha (mRXR alpha F318A) ligand-binding domains were separately overexpressed in Escherichia coli, copurified as a heterodimer in a two-step procedure, and cocrystallized with an RAR alpha-specific antagonist by using polyethylene glycol 10,000 as precipitant. The crystals grew in the hexagonal space group P6(1)22 displaying the unit cell parameters a = b = 116.6 A and c = 207.8 A. They diffracted X-ray to a limit of 2.2-A resolution. The asymmetric unit comprises one heterodimer and the crystal contains 60% solvent. The structure was determined by molecular replacement and is currently being refined.
Subject(s)
Receptors, Retinoic Acid/chemistry , Transcription Factors/chemistry , Animals , Chromatography, Gel , Crystallization , Crystallography, X-Ray , Escherichia coli/metabolism , Humans , Ligands , Mass Spectrometry , Mice , Mutation , Protein Structure, Tertiary , Receptors, Retinoic Acid/genetics , Receptors, Retinoic Acid/isolation & purification , Receptors, Retinoic Acid/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/isolation & purification , Recombinant Proteins/metabolism , Retinoic Acid Receptor alpha , Retinoid X Receptors , Transcription Factors/genetics , Transcription Factors/isolation & purification , Transcription Factors/metabolismABSTRACT
RAR-RXR heterodimeric complexes (RARalphaDeltaAB-RXRalphaDeltaAB) bound to cognate DR5 DNA response elements were purified to apparent structural and functional homogeneity using a novel versatile immobilized metal affinity chromatography (IMAC) copurification procedure. Dynamic light scattering studies indicated that the complexes were more than 85% monodisperse. By electron microscopy the negatively stained RAR-RXR-DNA complexes appeared homogeneous and corresponded to a dimeric arrangement of the molecules. Using heterodimers purified according to this procedure we demonstrate ligand binding of RXR in the context of the RAR-RXR heterodimer-DNA complex. The present copurification procedure is rapid and has yielded high quality heterodimer-DNA complexes suitable for both structural and biochemical studies.
