"Invisible" Detergents Enable a Reliable Determination of Solution Structures of Native Photosystems by Small-Angle Neutron Scattering.

Photosystems I (PSI) and II (PSII) are pigment-protein complexes capable of performing the light-induced charge separation necessary to convert solar energy into a biochemically storable form, an essential step in photosynthesis. Small-angle neutron scattering (SANS) is unique in providing structural information on PSI and PSII in solution under nearly physiological conditions without the need for crystallization or temperature decrease. We show that the reliability of the solution structure critically depends on proper contrast matching of the detergent belt surrounding the protein. Especially, specifically deuterated ("invisible") detergents are shown to be properly matched out in SANS experiments by a direct, quantitative comparison with conventional matching strategies. In contrast, protonated detergents necessarily exhibit incomplete matching so that related SANS results systematically overestimate the size of the membrane protein under study. While the solution structures obtained are close to corresponding high-resolution structures, we show that temperature and solution state lead to individual structural differences compared with high-resolution structures. We attribute these differences to the presence of a manifold of conformational substates accessible by protein dynamics under physiological conditions.

Floquet spin states in OLEDs.

Electron and hole spins in organic light-emitting diodes constitute prototypical two-level systems for the exploration of the ultrastrong-drive regime of light-matter interactions. Floquet solutions to the time-dependent Hamiltonian of pairs of electron and hole spins reveal that, under non-perturbative resonant drive, when spin-Rabi frequencies become comparable to the Larmor frequencies, hybrid light-matter states emerge that enable dipole-forbidden multi-quantum transitions at integer and fractional g-factors. To probe these phenomena experimentally, we develop an electrically detected magnetic-resonance experiment supporting oscillating driving fields comparable in amplitude to the static field defining the Zeeman splitting; and an organic semiconductor characterized by minimal local hyperfine fields allowing the non-perturbative light-matter interactions to be resolved. The experimental confirmation of the predicted Floquet states under strong-drive conditions demonstrates the presence of hybrid light-matter spin excitations at room temperature. These dressed states are insensitive to power broadening, display Bloch-Siegert-like shifts, and are suggestive of long spin coherence times, implying potential applicability for quantum sensing.

Measuring the excitations in a new S = 1/2 quantum spin chain material with competing interactions.

Recently a new one-dimensional (1D) quantum spin chain system has been reported: catena-dichloro(2-Cl-3Mpy)copper(II), (where 2-Cl-3Mpy=2-chloro-3-methylpyridine). Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8 K and is a prime candidate for investigating frustration in a J 1/J 2 system (where the nearest neighbour interactions, J 1, are ferromagnetic and the next nearest neighbour interactions, J 2, are antiferromagnetic). Calculations predicted three possible magnetic interaction strengths for J 1 below 6 meV depending on the orientation of the ligand. For one of the predicted J 1 values, the existence of a quantum critical point is implied. A deuterated sample of catena-dichloro(2-Cl-3Mpy)copper(II) was synthesised and the excitations measured using inelastic neutron scattering. Scattering indicated the most likely scenario involves spin-chains where each chain consists of only one of the three possible magnetic excitations in this material, rather than the completely random array of exchange interactions within each chain as predicted by Herringer et al (2014 Chem. Eur. J. 20 8355-62). This indicates the possibility of tuning the chemical structure to favour a system which may exhibit a quantum critical point.

Mutations in codons 12 and 13 of K-ras exon 2 in colorectal tumors of Saudi Arabian patients: frequency, clincopathological associations, and clinical outcomes.

Mutations in codons 12/13 of K-ras exon 2 are associated with reduced benefit from anti-epidermal growth factor receptor antibody treatment for metastatic colorectal cancer (CRC). Here, we evaluated the frequency of K-ras mutations and their relationship with clinicopathological features and treatment outcomes in Saudi Arabian patients with CRC. The genetic status of K-ras was determined in 300 patients diagnosed with CRC. Clinical information was collected retrospectively. K-ras was wild-type in 58% and mutated in 42% of the tumors. Most mutations were at codon 12 (89%) and were associated with metastasis [odds ratio (OR) = 1.38 (95%CI = 1.14-1.67] and occurrence of >40 µg/L carcinoembryonic antigen (CEA) [OR = 1.33 (1.1-1.74)] during diagnosis. Patients in stages I-III of the disease with wild-type K-ras tumors had a median relapse free survival (RFS) of 29 months in contrast to 22 months for those with the mutated K-ras tumor (P = 0.0357). In multivariate analysis, only the stage of the disease significantly predicted RFS (P = 0.001). Patients in stage IV of CRC with the wild-type K-ras tumor did not reach the median overall survival (OS), whereas patients with the mutated K-ras tumor survived for 23.5 months (P = 0.044). CEA level >40 µg/L (P = 0.004) and status of K-ras (P = 0.044) were independent predictors of OS. This is the largest study investigating K-ras mutations in patients with CRC in the Middle East. Mutations were associated with advanced stage of CRC, higher serum CEA, shorter RFS and OS.

Lapatinib-based therapy for women with advanced/metastatic HER2 positive breast cancer.

BACKGROUND: Lapatinib alone or in combination with other agents, mostly capecitabine is used for patients with advanced/metastatic HER2 positive breast cancer (HER2(+)BC) after progression on trastuzumab based therapy. Here we report our experience with lapatinib based therapy in this setting. MATERIAL AND METHODS: 67 consecutive patients received lapatinib based therapy. 58 (86.6%) received lapatinib + capecitabine (LC), 7 (10.4%) with other agents and 2 (3.0%) as single agent lapatinib. Data was collected from patients' records retrospectively. RESULTS: Objective response to lapatinib based therapy in 64 evaluable patients was 64.0% in all patients and 64.0% in patients who received LC. Median progression free survival and overall survival were 10 and 27 months in all patients and 10 and 17 months in patients who received LC, respectively. 16 (24.0%) patients had dose delay > 1 week and/or dose reduction. CONCLUSION: Lapatinib based therapy is an effective treatment for women with advanced/metastatic HER2(+)BC after prior exposure to trastuzumab. It yields meaningful response rates, progression free and overall survival. Some patients require dose adjustments.

The free-energy barrier to hydride transfer across a dipalladium complex.

We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.

Determination of natural and artificial radioactivity in soil at North Lebanon province.

The concentrations of natural and artificial radionuclides at 57 sampling locations along the North Province of Lebanon are reported. The samples were collected from uncultivated areas in a region not previously reported. The samples were analyzed by gamma spectrometers with High Purity Germanium detectors of 30% and 40% relative efficiency. The activity concentrations of primordial naturally occurring radionuclides of (238)U, (232)Th, and (40)K varied between 4-73 Bq kg(-1), 5-50 Bq kg(-1), and 57-554 Bq kg(-1) respectively. The surface activity concentrations due to the presence of these radionuclides were calculated and Kriging-geostatistical method was used to plot the obtained data on the Lebanese radioactive map. The results for (238)U, (232)Th, and (40)K ranged from 0.2 kBq m(-2) to 9 kBq m(-2), from 0.2 kBq m(-2) to 3 kBq m(-2), and from 3 kBq m(-2) to 29 kBq m(-2) respectively. For the anthropogenic radionuclides, the activity concentrations of (137)Cs founded in soil ranged from 2 Bq kg(-1) to 113 Bq kg(-1), and the surface activity concentration from 0.1 kBq m(-2) to 5 kBq m(-2). The total absorbed gamma dose rates in air from natural and artificial radionuclides in these locations were calculated. The minimum value was 6 nGy h(-1) and the highest one was 135 nGy h(-1) with an average of 55 nGy h(-1) in which the natural terrestrial radiation contributes in 99% and the artificial radionuclides mainly (137)Cs contributes only in 1%. The total effective dose calculated varied in the range of 7 µSv y(-1) and 166 µSv y(-1) while the average value was 69 µSv y(-1) which is below the permissible limit 1000 µSv y(-1).

Assessment of the plasma desorption time-of-flight mass spectrometry technique for pesticide adsorption and degradation on 'as-received' treated soil samples.

The assessment of the plasma desorption time-of-flight mass spectrometry (PD-TOFMS) technique as a tool for direct characterization of pesticides adsorbed on agricultural soil is made for the first time in this study. Pellets of soils impregnated by solutions of three pesticides, namely norflurazon, malathion and oxyfluorfen, as well as deposits of these solutions onto aluminum surfaces, were investigated to this end. The yield values of the most characteristic peaks of the negative ion mass spectra were used to determine both the lowest concentrations detected on soils and limits of detection from thin films. The lowest values on soils are for malathion (1000 ppm range), and the largest for norflurazon (20,000 ppm), which is close to the limit of detection (LOD) found for the pesticide on the aluminum substrate (approximately 0.2 microg . cm(-2)). Different behaviors were observed as a function of time of storage in the ambient atmosphere or under vacuum; norflurazon adsorbed on soil exhibited high stability for a long period of time, and a rapid degradation of malathion with the elapsed time was clearly observed. The behavior of oxyfluorfen was also investigated but segregation processes seem to occur after several days. Although by far less sensitive than conventional methods based on extraction processes and used for real-world analytical applications, this technique is well suited to the study of the transformations occurring at the sample surface. A discussion is presented of the future prospects of such experiments in degradation studies.

A randomized EPOCH vs. CHOP front-line therapy for aggressive non-Hodgkin's lymphoma patients: long-term results.

BACKGROUND: The value of continuous-infusion chemotherapy (EPOCH) vs. the standard CHOP combination was evaluated in 78 patients with previously untreated aggressive non-Hodgkin's lymphoma in a randomized phase III clinical trial. PATIENTS AND METHODS: The EPOCH regimen given to 38 patients consisted of the drugs etoposide (50 mg/m2), vincristine (0.4 mg/m2), and doxorubicin (10 mg/m2), all given in a continuous infusion on days 1-4. Cyclophosphamide (750 mg/m2) was administered on day 6 as i.v. bolus, while prednisone was given orally 60 mg/m2 on days 1-6. Courses were repeated every three weeks. CHOP was given to 40 patients as routinely prescribed. RESULTS: Forty-eight patients were males and thirty were females. Their ages ranged from 19-75 years (median 45 years). Forty-three (55%) had grade 2 and thirty-five (45%) had grade 3 pathologic subtype. Nine patients (12%) presented with stage I, fourteen (18%) with stage II, forty (51%) with stage III, and fifteen (19%) with stage IV disease. The different clinico-pathologic characteristics, including international index categories, were comparable in the two groups. The number of courses given ranged between 3 and 9 (median 6) for both the EPOCH and CHOP regimens. Complete remission (CR) was achieved in 19 (50%), and 27 (67%) of the 38 and 40 patients for both the EPOCH and CHOP combinations, respectively. After a median observation time of 27 months, the four-year overall and failure-free survival rates were 42% and 30% for the EPOCH and 71% and 54% for the CHOP regimen (P = 0.006 and 0.1 for the overall and FFS rates, respectively). Toxicities were comparable and were mostly of grades 1 and 2, except for hair loss, hematologic toxicities, and infectious episodes which were more common in the EPOCH group. In the EPOCH group, overall survival rates were 55% vs. 22% (P < 0.04) at four years for the low-risk (2 prognostic factors) and high-risk (> 2 factors) groups, respectively. CONCLUSIONS: Thus, it may be concluded that continuous-infusion (EPOCH) chemotherapy did not improve treatment outcome over that of the CHOP regimen for aggressive non-Hodgkin's lymphoma patients.

Panic disorder. An overlapping or independent entity?

We compared three groups of patients with panic disorder, generalised anxiety disorder and major depressive episode with a control group. Methods of comparison included a clinical profile of the patients, assessed by the Arabic version of the Present State Examination (PSE), a psychological battery of tests measuring personality traits and depressive and anxiety states, and the dexamethasone suppression test (DST) as a biological marker. Our data showed that psychological assessment and DST did not significantly differentiate between the three disorders. Despite a symptom overlap between the disorders, however, some symptoms were associated significantly more often with one disorder than another. Patients with panic disorder differed from patients with major depressive episode in showing more situational, avoidance and free floating anxiety, and more anxious foreboding. They showed less self-negligence, ideas of guilt, early awakening and social withdrawal. Compared with patients with generalised anxiety disorder, patients with panic disorder showed more loss of interest and muscle tension and less anxious foreboding, restlessness, inefficient thinking, social withdrawal and delayed sleep. Our conclusion is that the clinical course and the symptom profile of panic disorder justifies its existence as an independent diagnostic category.