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Gorbitz C.H.,University of Oslo | Dalhus B.,Institute for Clinical Biochemistry | Day G.M.,University of Cambridge
Physical Chemistry Chemical Physics | Year: 2010

Ab initio prediction of the crystal packing in complexes between two flexible molecules is a particularly challenging computational chemistry problem. In this work we present results of single crystal structure determinations as well as theoretical predictions for three 1 1 complexes between hydrophobic l- and d-amino acids (pseudoracemates), known from previous crystallographic work to form structures with one of two alternative hydrogen bonding arrangements. These are accurately reproduced in the theoretical predictions together with a series of patterns that have never been observed experimentally. In this bewildering forest of potential polymorphs, hydrogen bonding arrangements and molecular conformations, the theoretical predictions succeeded, for all three complexes, in finding the correct hydrogen bonding pattern. For two of the complexes, the calculations also reproduce the exact space group and side chain orientations in the best ranked predicted structure. This includes one complex for which the observed crystal packing clearly contradicted previous experience based on experimental data for a substantial number of related amino acid complexes. The results highlight the significant recent advances that have been made in computational methods for crystal structure prediction. © 2010 The Owner Societies. Source

Geiser F.,University of Bonn | Conrad R.,University of Bonn | Imbierowicz K.,University of Bonn | Meier C.,University of Bonn | And 4 more authors.
Psychiatry and Clinical Neurosciences | Year: 2011

Aims: Anxiety disorders have been shown to be correlated with an activation of coagulation and impairment of fibrinolysis. The aim of the study was to assess whether medication with a serotonergic antidepressant, which has been associated with abnormal bleeding, may modify this effect. Methods: Thirty-one anxiety patients, mostly with comorbid depression, and 31 healthy controls were included in the study. Group differences between anxiety patients medicated with a serotonergic antidepressant, patients without serotonergic antidepressant and controls were assessed for activated partial thromboplastin time, fibrinogen, factor VII, factor VIII, von Willebrand factor, von Willebrand ristocetin cofactor activity, prothrombin fragment 1 + 2, thrombin-antithrombin complex, d-dimer, α2-antiplasmin, plasmin-α2-antiplasmin complex (PAP), tissue plasminogen activator and plasminogen activator inhibitor. Intervening variables, such as age, sex, body mass index and smoking, were accounted for. Results: We found lower coagulation measures for fibrinogen (P = 0.03) and plasminogen activator inhibitor (P = 0.01), and higher levels of PAP (P = 0.046) in patients with serotonergic antidepressant than in patients without serotonergic antidepressant. When controlling for smoking and body mass index, differences between the two groups were significant for PAP (P = 0.02), von Willebrand ristocetin cofactor activity (P = 0.02) and activated partial thromboplastin time (P = 0.046). Coagulation scores were similar in patients with serotonergic antidepressant to those of healthy controls. Conclusions: Serotonergic antidepressants may counteract a procoagulant effect of anxiety and/or depression in anxiety patients. © 2011 Japanese Society of Psychiatry and Neurology. Source

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