Picosecond kinetics of chlorophyll and chlorophyll/quinone solutions in ethanol

The mechanism of quenching by quinones of the lowest excited singlet state of chlorophyll has been investigated using picosecond laser spectroscopy. With chlorophyll alone, laser excitation resulted in immediate (< 10 ps) bleaching of the 665 nm band and production of new absorption bands in the regions 460–550 and 800–830 nm. The lifetimes of these changes were greater than 500 ps. Addition of 2,6-dimethyl-benzoquinone caused quenching of these absorbance changes. No indication of chlorophyll cation radical formation was obtained. Thus, the interaction between quinone and the chlorophyll excited singlet state results in energy dissipation without measurable formation of radical species having lifetimes longer than 10 ps. This is in marked contrast to the quenching of the chlorophyll lowest triplet state by quinones, during which easily detectable stable radical formation has been observed.     

Transition in the temperature-dependence of GFP fluorescence: from proton wires to proton exit

In green fluorescent protein, photo-excitation leads to excited-state proton transfer from its chromophore, leaving behind a strongly fluorescing anion, while the proton is commonly thought to migrate internally to Glu-222. X-ray data show that the protein contains more extended hydrogen-bonded networks that can support proton migration (i.e., proton wires). Here we study the temperature-dependence of the transient fluorescence from both the acid and anionic forms up to 15 ns. At low temperatures, we find that the (lifetime-corrected) fluorescence of the acidic form decays asymptotically as t^−1/2, following quantitatively the solution of a one-dimensional diffusion equation for reversible geminate recombination with quenching. This indicates proton migration along the internal proton wires. A small degree of geminate proton quenching is attributed to the formation of the zwitterion by proton migration on a side-branch of the proton wire. Above 230 K, the fluorescence kinetics undergo a transition, exhibiting an asymptotic t^−3/2 decay, and the quenching effect disappears. We interpret these findings as evidence for a conformational change enabling the rotation of Thr-203, which eventually allows the proton to escape to the exterior solution.     

Desflurane consumption during automated closed-circuit delivery is higher than when a conventional anesthesia machine is used with a simple vaporizer-O2-N2O fresh gas flow sequence

Background

Current analgesics have drawbacks such as delays in acquisition, lag-times for effect, and side effects. We recently presented a preliminary report of a new analgesic method involving a two-minute sciatic nerve press, which resulted in immediate short-term relief of pain associated with dental and renal diseases. The present study investigated whether this technique was effective for pain associated with other disease types, and whether the relief was effective for up to one hour.

Methods

This randomized, placebo-controlled, parallel-group trial was conducted in four hospitals in Anhui Province, China. Patients with pain were sequentially recruited by participating physicians during clinic visits, and 135 patients aged 15 – 80 years were enrolled. Dental disease patients included those with acute pulpitis and periapical abscesses. Renal disease patients included those with kidney infections and/or stones. Tumor patients included those with nose, breast, stomach and liver cancers, while Emergency Room patients had various pathologies. Patients were randomly assigned to receive a "sciatic nerve press" in which pressure was applied simultaneously to the sciatic nerves at the back of both thighs, or a "placebo press" in which pressure was applied to a parallel region on the front of the thighs. Each fist applied a pressure of 11 – 20 kg for 2 minutes. Patients rated their level of pain before and after the procedure.

Results

The "sciatic nerve press" produced immediate relief of pain in all patient groups. Emergency patients reported a 43.5% reduction in pain (p < 0.001). Significant pain relief for dental, renal and tumor patients lasted for 60 minutes (p < 0.001). The peak pain relief occurred at the 10 – 20^th minutes, and the relief decreased 47% by the 60^th minutes.

Conclusion

Two minutes of pressure on both sciatic nerves produced immediate significant short-term conduction analgesia. This technique is a convenient, safe and powerful method for the short-term treatment of clinical pain associated with a diverse range of pathologies.

Trial registration

Current Controlled Trials ACTRN012606000439549     

Perceptions of an ideal point-of-care test for sexually transmitted infections--a qualitative study of focus group discussions with medical providers

Background

A point-of-care test (POCT) for sexually transmitted infections (STIs), which offers immediate diagnosis resulting in patients receiving diagnosis and treatment in a single visit, has the ability to address some of the STI control needs. However, needs assessment from STI experts and end users about currently available STI POCTs and their future new development has not been evaluated since World Health Organization Sexually Transmitted Diseases Diagnostics Initiative was formed over 15 years ago. Therefore, our objective was to explore the perceptions of the ideal types of STI POCT for use in health care settings.

Methodology/Principal Findings

A qualitative study, encompassing eight focus groups, was conducted from March 2008 through April 2009. Participants included 6 STD clinic directors, 63 clinicians, and 7 public health/laboratory/epidemiology professionals in the STI field. Discussion topics included currently available POCT, perceived barriers to using POCT in clinics, priority STI for the development of new POCT, and characteristics of the ideal POCT. All discussions were recorded and transcribed verbatim. Themes raised as barriers for current POCT included complexity, long time frames of the so-called “rapid” test, multiple time-driven steps, requiring laboratory technician, difficulty in reading result, interruption of workflow, unreliability, and invasiveness. Chlamydia trachomatis was identified as the priority organism for development of a new STI POCT. Themes indicated for the ideal POCT included rapid turnaround (up to 20 minutes), ease of use, non-invasive, accurate (preferred sensitivity and specificity in the range of high 90s), Clinical Laboratory Improvement Amendments (CLIA)-waived, user-friendly (for both patients and staff), compact, durable, and sturdy.

Conclusions/Significance

Focus group discussions with STI experts and professionals highlighted chlamydia as the top priority pathogen for POCT development, and identified the qualities of new POCT for STIs. Participants endorsed ease of use, rapid turnaround and high accuracy as essential characteristics of an ideal POCT.     

Analysis of transmembrane domain mutants is consistent with sequential cleavage of Notch by gamma-secretase

gamma-Secretase is a lipid-embedded, intramembrane-cleaving aspartyl protease that cleaves its substrates twice within their transmembrane domains (TMD): once near the cytosolic leaflet (at S3/epsilon) and again in the middle of the TMD (at S4/gamma). To address whether this unusual process occurs in two independent or interdependent steps, we investigated how mutations at the S3/epsilon site in Notch1-based substrates impact proteolysis. We demonstrate that such mutations greatly inhibit not only gamma-secretase-mediated cleavage at S3 but also at S4, independent of their impact on NICD stability. These results, together with our previous observations, suggest that hydrolysis at the center of the Notch transmembrane domain (S4/gamma) is dependent on the S3/epsilon cleavage. Notch (and perhaps all gamma-secretase substrates) may be cleaved by sequential proteolysis starting at S3.