Accurate measurement of ^{13}C - ^{15}N distances with solid-state NMR

Solid-state NMR technique for measureing distances between hetero-nuclei in static powder samples is described. It is based on a two-dimensional single-echo scheme enhanced with adiabatic cross-polarization. As an example, the results for intra-molecular distances in $\alpha$-crystalline form of glycine are presented. The measured NMR distances ^13 C(2) - ^15 N and ^13 C(1) - ^15 N are 1.496 $\pm$ 0.002 \AA and 2.50 $\pm$ 0.02 \AA, respectively.Comment: 12 page

Cannabis use predicts shorter duration of untreated psychosis and lower levels of negative symptoms in first-episode psychosis: a South African study

Objective: Cannabis use/abuse is a common co-morbid problem in patients experiencing a first episode of psychotic illness (FEP). The relationship between the clinical presentation of FEP and cannabis abuse is complex and warrants further investigation, especially within the South African context. Method: We tested associations between recent/current cannabis use and duration of untreated psychosis (DUP), age of onset (AO), PANSS-rated (Positive and Negative Syndrome Scale) positive, negative and general psychopathology symptoms and depressive symptoms (Calgary Depression Scale for Schizophrenia) in a sample of 54 patients with FEP. Results: Mean DUP was 34.4 weeks, while mean AO was 24.7 years. Co-morbid cannabis use occurred in 35% of the sample and was significantly associated with shorter DUP (Mann-Whitney U, p=0.026). While not significant, there was also a trend association between cannabis use and lower negative symptoms (Mann-Whitney U, p=0.051). Conclusion: Current/recent cannabis use was associated with clinical features of psychosis onset that previously have been associated with better outcome. Medium and long-term outcome for cannabis users however, is likely to depend on whether or not cannabis use is ongoing.Keywords: First-episode psychosis, Cannabis; Duration of untreated psychosis; Age of onset; Symptom

Features and development of Coot

Coot is a molecular-graphics program designed to assist in the building of protein and other macromolecular models. The current state of development and available features are presented

Fidelity enhancement by logical qubit encoding

We demonstrate coherent control of two logical qubits encoded in a decoherence free subspace (DFS) of four dipolar-coupled protons in an NMR quantum information processor. A pseudo-pure fiducial state is created in the DFS, and a unitary logical qubit entangling operator evolves the system to a logical Bell state. The four-spin molecule is partially aligned by a liquid crystal solvent, which introduces strong dipolar couplings among the spins. Although the system Hamiltonian is never fully specified, we demonstrate high fidelity control over the logical degrees of freedom. In fact, the DFS encoding leads to higher fidelity control than is available in the full four-spin Hilbert space.Comment: 10 pages, 2 figure

Assessment of the protein interaction between coagulation factor XII and corn trypsin inhibitor by molecular docking and biochemical validation

Background: Corn trypsin inhibitor (CTI) has selectivity for serine proteases coagulation factor XII (FXII) and trypsin. CTI is in widespread use as a reagent that specifically inhibits the intrinsic pathway of blood coagulation but not the extrinsic pathway. Objectives: To investigate the molecular basis of FXII inhibition by CTI. Methods: We performed molecular docking of CTI, using its known crystal structure, with a model of the activated FXII (FXIIa) protease domain. The interaction model was verified using a panel of recombinant CTI variants tested for their ability to inhibit FXIIa enzymatic activity using a substrate cleavage assay. Results: The docking predicted that (i) the CTI central inhibitory loop P1 Arg34 side chain forms a salt bridge to the FXIIa S1 pocket Asp189 side chain (ii) residue Trp22 from the CTI helix α1 interacts with the FXIIa S3 pocket (iii) Arg43 from CTI helix α2 forms a salt bridge to FXIIa H1 pocket Asp60A. CTI amino acid substitution R34A negated all inhibitory activity whereas variants G32W, L35A, W22A or R42A-R43A reduced activity by a large degree of 108, 41, 158 and 100-fold respectively, with R27A, W37A, W39A, R42A having no effect. Synthetic peptides spanning CTI residues 20-44 had inhibitory activity 3-4000-fold less than full-length CTI. Conclusions: The data confirm the validity of a canonical model of the FXIIa-CTI interaction with helix α1 (Trp22), central inhibitory loop (Arg34) and helix α2 (Arg43) of CTI required for effective binding by contacting the S1, S3 and H1 pockets of FXIIa, respectively

First principles investigations of the electronic, magnetic and chemical bonding properties of CeTSn (T=Rh,Ru)

The electronic structures of CeRhSn and CeRuSn are self-consistently calculated within density functional theory using the local spin density approximation for exchange and correlation. In agreement with experimental findings, the analyses of the electronic structures and of the chemical bonding properties point to the absence of magnetization within the mixed valent Rh based system while a finite magnetic moment is observed for trivalent cerium within the Ru-based stannide, which contains both trivalent and intermediate valent Ce.Comment: 6 pages, 7 figures, for more information see http://www.physik.uni-augsburg.de/~eyert

A dissipative particle dynamics study of the realignment of a nanodroplet of a nematic in a weak external magnetic field

We present a dissipative particle dynamics (DPD) approach for simulating the realignment of a nematic nanodroplet suspended in an isotropic fluid following a switch in the direction of an applied external magnetic field. The interaction of the mesogens with the external field is weak relative to the inter-molecular interactions. The simulations were used to investigate the way orientational equilibrium is re-established. The results reveal that the realignment process of the nanodroplet is consistent with its fluid structure. The reorientation of the nanodroplet as a whole is found to be caused by an internal structural rearrangement rather than a coherent rotation of the centres of mass of the mesogens about the centre of the nanodroplet. The switch in the field direction furthermore is found to induce a transient spatial variation in the orientational order of the long axes of the mesogens: the orientational order parameters decreases on moving from the core of the nanodroplet to the surface in contact with the isotropic environment. The results highlight differences between the time evolution of the orientation of the long molecular axes in the field and the rotations of the centres of mass of the mesogens about the centre of the nanodroplet

Mental health literacy: focus on developing countries

Mental health literacy refers to knowledge and beliefs about mental disorders which aid their recognition, management and prevention. This is a non-systematic review of published articles on mental health literacy in the general population and among primary healthcare workers, in particular, in developing countries, sourced from Medline, PsychInfo and African Healthline databases (1990-2006). Our review of the literature suggests that public knowledge about mental disorders as medical conditions, and their evidence based treatment strategies, in developing countries may be generally poorly or inaccurately understood. The review also reveals that improving the mental health literacy among primary health care professionals is imperative. Poor mental health literacy can be an obstacle to providing treatment for those in need, and is of particular concern in low and middle-income countries where mental health services are already scarce. It is likely that strategies for improvement will need to be comprehensive and innovative, taking advantage of opportunities and meeting challenges faced in the developing world.African Journal of Psychiatry Vol. 11 (1) 2008: pp. 23-2