NMR characterization of the ligand dependent dynamic changes in Cytochrome P450s

Cytochrome P450s are a large superfamily of enzymes in humans with little sequence homology, but a conserved fold. A characteristic feature of P450s is their ability to recognize and detoxify by mono-oxygenating a large number of drug ligands with diverse physico-chemical properties in humans. This is attributed to the flexibility of their substrate binding region. CYP101A1, the first solved structure of any cytochrome P450, is a bacterial enzyme that has been used as a model for P450s to study the binding and catalytic events. Recently, our laboratory in collaboration with other groups used neutron scattering spectroscopy to detect the presence of collective functional motions throughout the structure of this protein, that dynamically create access to the catalytic site for the substrate (1). However, the exact nature of these motions in terms of the range of timescales and identity of specific residues involved could not be determined. I sought to characterize a subset of these motions by studying the slow timescale dynamic changes of CYP101A1 when binding to a diverse set of ligands. Using amide exchange experiments monitored by 1H-15N two-dimensional solution NMR spectroscopy, dynamics were characterized at the residue level with 4 different ligands, including both substrates and inhibitors of assorted sizes and chemical properties. Comparing the dynamic changes between different ligands and the ligand free form showed surprising results. CYP101A1 exhibits differential dynamics for binding various ligands even though they all have the same affinity to the enzyme. Large ligands such as the anti-fungal drug ketoconazole shows increased dynamics while the much smaller substrate camphor shows highly reduced dynamics, pointing to a distinct enthalpy-entropy compensation mechanism. Moreover, these dynamic changes are observed throughout the protein and not just limited to regions in and around the active site, arguing that dynamics of the protein as a whole should be considered to properly understand ligand binding by this class of enzymes

Nasal decontamination for the prevention of surgical site infection in Staphylococcus aureus carriers (Protocol)

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:To assess the effects of nasal decontamination on preventing surgical site infections (SSIs) in people who are S aureus carriers undergoing surgery, treated in any setting

Auditory-visual integration modulates location-specific repetition suppression of auditory responses.

Space is a dimension shared by different modalities, but at what stage spatial encoding is affected by multisensory processes is unclear. Early studies observed attenuation of N1/P2 auditory evoked responses following repetition of sounds from the same location. Here, we asked whether this effect is modulated by audiovisual interactions. In two experiments, using a repetition-suppression paradigm, we presented pairs of tones in free field, where the test stimulus was a tone presented at a fixed lateral location. Experiment 1 established a neural index of auditory spatial sensitivity, by comparing the degree of attenuation of the response to test stimuli when they were preceded by an adapter sound at the same location versus 30° or 60° away. We found that the degree of attenuation at the P2 latency was inversely related to the spatial distance between the test stimulus and the adapter stimulus. In Experiment 2, the adapter stimulus was a tone presented from the same location or a more medial location than the test stimulus. The adapter stimulus was accompanied by a simultaneous flash displayed orthogonally from one of the two locations. Sound-flash incongruence reduced accuracy in a same-different location discrimination task (i.e., the ventriloquism effect) and reduced the location-specific repetition-suppression at the P2 latency. Importantly, this multisensory effect included topographic modulations, indicative of changes in the relative contribution of underlying sources across conditions. Our findings suggest that the auditory response at the P2 latency is affected by spatially selective brain activity, which is affected crossmodally by visual information

Challenges in defining the rates of ADHD diagnosis and treatment: trends over the last decade

Abstract Background There is a global trend of large increases in the prevalence and incidence of Attention Deficit Hyperactivity Disorder (ADHD). This study aimed to address potential causes of these major changes. Methods The authors used a large cohort to analyze data employing patients’ electronic medical records, with physicians’ diagnosis of ADHD, including records of medication purchases. Results The prevalence of ADHD diagnoses rose twofold from 6.8% to 14.4% between 2005 and 2014 (p < 0.001), while the ratio of males to females with ADHD decreased from 2.94 in 2005 to 1.86 in 2014 (p < 0.001). The incidence increased, peaking in 2011 before declining in 2014. ADHD medication usage by children and adolescents was 3.57% in 2005 and 8.51% by 2014 (p < 0.001). Conclusions We report a dramatic increase in the rate of ADHD diagnoses. One of the leading factors to which we attribute this increase is the physicians’ and parents’ changed attitude towards diagnosing attention/hyperactivity problems, with more parents appear to consider ADHD diagnosis and treatment as a means to improve their child’s academic achievements, commonly with the aid of medications. This change in attitude may also be associated with the dramatic increase in female ADHD diagnosis prevalence