Investigating radical pair reaction dynamics of B12 coenzymes 1: Transient absorption spectroscopy and magnetic field effects.

B12 coenzymes are vital to healthy biological function across nature. They undergo radical chemistry in a variety of contexts, where spin-correlated radical pairs can be generated both thermally and photochemically. Owing to the unusual magnetic properties of B12 radical pairs, however, most of the reaction and spin dynamics occur on a timescale (picoseconds-nanoseconds) that cannot be resolved by most measurement techniques. Here, we describe a method that combines femtosecond transient absorption spectroscopy with magnetic field exposure, which enables the direct scrutiny of such rapid processes. This approach should provide a means by which to investigate the apparently profound effect protein environments have on the generation and reactivity of B12 radical pairs.

Investigating radical pair reaction dynamics of B12 coenzymes 2: Time-resolved electron paramagnetic resonance spectroscopy.

The chemistry of B12 coenzymes is highly sensitive to the nature of their upper axial ligand and can be further tuned by their environment. Methylcobalamin, for example, generates RPs photochemically but undergoes non-radical biochemistry when bound to its dependent enzymes. Owing to the transient nature of the reaction intermediates, it remains a challenge to investigate how their environment controls reactivity. Here, we describe how to use time-resolved electron paramagnetic spectroscopy to directly monitor the generation and evolution of transient radicals that result from the photolysis of a B12 coenzyme. This method produces evolving, spin-polarized spectra that are rich in mechanistic detail.

Infrared Spectroscopy Reveals the Preferred Motif Size and Local Disorder in Parallel Stranded DNA G-Quadruplexes.

Infrared spectroscopy detects the formation of G-quadruplexes in guanine-rich nucleic acid sequences through shifts in the guanine C=O stretch mode. Here, we use ultrafast 2D infrared (IR) spectroscopy and isotope substitution to show that these shifts arise from vibrational delocalization among stacked G-quartets. This provides a direct measure of the sizes of locally ordered motifs in heterogeneous samples with substantial disordered regions. We find that parallel-stranded, potassium-bound DNA G-quadruplexes are limited to five consecutive G-quartets and 3-4 consecutive layers are preferred for longer polyguanine tracts. The resulting potassium-dependent G-quadruplex assembly landscape reflects the polyguanine tract lengths found in genomes, the ionic conditions prevalent in healthy mammalian cells, and the onset of structural disorder in disease states. Our study describes spectral markers that can be used to probe other G-quadruplex structures and provides insight into the fundamental limits of their formation in biological and artificial systems.

Observation of the Δg mechanism resulting from the ultrafast spin dynamics that follow the photolysis of coenzyme B12.

Throughout nature, both free radicals and transient radical reaction intermediates are vital to many biological functions. Coenzyme B12 is a case in point. This organometallic cofactor generates a radical pair upon activation in its dependent enzymes by substrate binding and following photolysis. The resulting cob(ii)alamin/5'-deoxyadenosyl radical pair has unusual magnetic properties that present a challenge to detailed investigation at ambient temperatures. Here, we use femtosecond transient absorption spectroscopy adapted for magnetic field exposure to reveal that the spin dynamics of the B12 radical pair are sufficiently fast for magnetic field effects to be observed on the ultrafast reaction kinetics. Moreover, the large difference in g-values between the radicals of the pair means that effects of the Δg mechanism are observed for the first time for a radical pair system exposed to magnetic fields below 1 T. Spin dynamic simulations allow a value of the cob(ii)alamin radical g-value (2.105) at ambient temperature to be extracted and, because the spin dynamic time scale is faster than the diffusional rotation of the cob(ii)alamin radical, the observed value corresponds to the anisotropic g|| value for this radical.

Enhancing Primary School Children's Knowledge of Online Safety and Risks with the CATZ Cooperative Cross-Age Teaching Intervention: Results from a Pilot Study.

Children are heavy users of the Internet and prior studies have shown that many of them lack a good understanding of the risks of doing so and how to avoid them. This study examined if the cross-age teaching zone (CATZ) intervention could help children acquire important knowledge of online risks and safety. It allowed older students to act as CATZ tutors to design and deliver a lesson to younger schoolmates (tutees), using content material about online risks and safety provided by adults. Students in Year 6 (mean age = 11.5 years) were randomly assigned to act as either CATZ tutors (n = 100) or age-matched controls (n = 46) and students in Year 4 (mean age = 9.5 years) acted as either CATZ tutees (n = 117) or age-matched controls (n = 28) (total N = 291). CATZ tutors, but not matched controls scored significantly higher on objective measures of knowledge of both online risks and safety, and CATZ tutees, but not matched controls did so for online safety. Effect sizes were moderate or large. CATZ was highly acceptable to participants. The results suggest that CATZ is a viable way to help school students learn about online dangers and how to avoid them.

Evaluating the ability to detect change of health-related quality of life in children with Hodgkin disease.

BACKGROUND: We evaluated 4 different health-related quality of life (HRQL) measures prospectively to determine their ability to detect change over time: the Health Utilities Index Mark 2 and Mark 3, the Pediatric Quality of Life Inventory (PedsQL) 4.0 Generic Core and Cancer Module, the EuroQol EQ-5D visual analogue scale (EuroQol), and the Lansky Play-Performance Scale. METHODS: Children with all stages of Hodgkin disease from 12 centers across Canada were asked to complete the 4 measures at 4 time points: 2 weeks after the first course of chemotherapy, on the third day of the second course of chemotherapy, during the third week of radiation, and 1 year after diagnosis. RESULTS: Fifty-one patients were enrolled in the study between May 1, 2002 and March 31, 2005. Two patients were excluded: 1 patient died shortly after the first time point and the other patient failed to complete any of the questionnaires. All measures showed a significant change between Time 1 and Time 4 (<0.05). When the change in child scores was analyzed between the time points using the child's self-reported change in HRQL, the PedsQL and the EuroQol showed significant change at all time points. CONCLUSIONS: All of the measures were able to detect change in a diverse group of children with Hodgkin disease. The PedsQL and the EuroQol appeared to be the most sensitive to change.

Nurses provide valuable proxy assessment of the health-related quality of life of children with Hodgkin disease.

BACKGROUND: We prospectively compared the proxy reporting of health-related quality of life (HRQL) by parents and nurses of children with Hodgkin disease to see how well they correlated with the children's report. METHODS: Children with all stages of Hodgkin disease, their parents, and the clinic nurse were all asked to complete 4 different HRQL measures at 4 time points: 2 weeks after the first course of chemotherapy, on the third day of the second course of chemotherapy, during the third week of radiation, and 1 year after diagnosis. RESULTS: Fifty-one patients from 12 centers across Canada were enrolled in the study between May 1, 2002 and March 31, 2005. Two patients were excluded. The children's Pediatric Quality of Life Inventory (PedsQL) generic scores increased from 64 at base line to 81 at the end of the study. There was substantial agreement (intraclass correlation coefficient >0.6) among the participants' scores at most time points except when the child was actively receiving inpatient chemotherapy. At that time, there was only fair to moderate agreement between the child and parent, with the parents on average rating the PedsQL generic score 5 points lower than the child. The nurses still had substantial agreement at that time point with the PedsQL generic and cancer module as well as the EuroQol EQ-5D visual analogue scale visual analogue scale. CONCLUSIONS: Over the course of treatment for Hodgkin disease, there was substantial agreement among the parent's, nurse's, and children's reported HRQL scores. Nurses contribute valuable additional information as proxy respondents.

The pharmacokinetics and pharmacodynamics of micafungin in experimental hematogenous Candida meningoencephalitis: implications for echinocandin therapy in neonates.

BACKGROUND: Hematogenous Candida meningoencephalitis (HCME) is a relatively frequent manifestation of disseminated candidiasis in neonates and is associated with significant mortality and neurodevelopmental abnormalities. The outcome after antifungal therapy is often suboptimal, with few therapeutic options. Limited clinical data suggest that echinocandins may have role to play in the treatment of HCME. METHODS: We studied the pharmacokinetics and pharmacodynamics of micafungin in a rabbit model of neonatal HCME and bridged the results to neonates by use of population pharmacokinetics and Monte Carlo simulation. RESULTS: Micafungin exhibited linear plasma pharmacokinetics in the range of 0.25-16 mg/kg. Micafungin penetrated most compartments of the central nervous system (CNS), but only with doses >2 mg/kg. Micafungin was not reliably found in cerebrospinal fluid. With few exceptions, drug penetration into the various CNS subcompartments was not statistically different between infected and noninfected rabbits. A dose-microbiological response relationship was apparent in the brain, and near-maximal effect was apparent with doses of 8 mg/kg. Monte Carlo simulations revealed that near-maximal antifungal effect was attained at human neonatal doses of 12-15 mg/kg. CONCLUSIONS: These results provide a foundation for clinical trials of micafungin in neonates with HCME and a model for antimicrobial bridging studies from bench to bedside in pediatric patients.