Crystal structures of Scone: pseudosymmetric folding of a symmetric designer protein.

Recent years have seen an increase in the development of computational proteins, including symmetric ones. A ninefold-symmetric ß-propeller protein named Cake has recently been developed. Here, attempts were made to further engineer this protein into a threefold-symmetric nine-bladed propeller using computational design. Two nine-bladed propeller proteins were designed, named Scone-E and Scone-R. Crystallography, however, revealed the structure of both designs to adopt an eightfold conformation with distorted termini, leading to a pseudo-symmetric protein. One of the proteins could only be crystallized upon the addition of a polyoxometalate, highlighting the usefulness of these molecules as crystallization additives.

Fragment based drug design: from experimental to computational approaches.

Fragment based drug design has emerged as an effective alternative to high throughput screening for the identification of lead compounds in drug discovery in the past fifteen years. Fragment based screening and optimization methods have achieved credible success in many drug discovery projects with one approved drug and many more compounds in clinical trials. The fragment based drug design starts with the identification of fragments or low molecular weight compounds that generally bind with weak affinity to the target of interest. The fragments that form high quality interactions are then optimized to lead compounds with high affinity and selectivity. The weak affinity of fragments for their target requires the use of biophysical techniques such as nuclear magnetic resonance, X-ray crystallography or surface plasmon resonance to identify hits. These techniques are very sensitive and some of them provide detailed protein fragment interaction information that is important for fragment to lead optimization. Despite the huge advances in technology in the past years, experimental methods of fragment screening suffer several challenges such as low throughput, high cost of instruments and experiments, high protein and fragment concentration requirements. To address challenges posed by experimental screening approaches, computational methods were developed that play an important role in fragment library design, fragment screening and optimization of initial fragment hits. The computational approaches of fragment screening and optimization are most useful when they are used in combination with experimental approaches. The use of virtual fragment based screening in combination with experimental methods has fostered the application of fragment based drug design to important biological targets including protein-protein interactions and membrane proteins such as GPCRs. This review provides an overview of experimental and computational screening approaches used in fragment based drug discovery with an emphasis on recent successes achieved in discovering potent lead molecules using these approaches.

Long-term outcome after treatment of isolated pulmonary valve stenosis.

BACKGROUND: Few data are available on very long-term follow-up after treatment for isolated pulmonary valve stenosis (PVS), either surgically or by percutaneous balloon angioplasty (PBA). METHODS AND RESULTS: All patients with isolated PVS were selected from our database of congenital heart defects. Their records were reviewed systematically. We identified 79 surgically treated patients with a median follow-up of 22.5 years (range 0-45 years) and 139 PBA patients with median follow-up of 6.0 years (range 0-21 years). Echocardiographic and catheterization parameters indicate excellent results of both techniques in relieving the transpulmonary gradient. However, after initial surgery 20.3% of patients needed a cardiac re-intervention: 81% for severe pulmonary valve regurgitation, but none for residual pulmonary stenosis. After initial PBA a cardiac re-intervention was needed in 9.4% of patients. In 85% the indication was residual pulmonary stenosis, in none of them pulmonary regurgitation, although almost all patients developed a mild pulmonary regurgitation. Freedom of re-intervention after surgery was 98.4%, 93.5%, 87.7%, 70.9% and 55.7% at 5, 10, 20, 30 and 40 years postoperatively. Freedom of re-intervention in the PBA group was 95.1%, 87.5% and 84.4% at 5, 10 and 20 years post-procedure. CONCLUSIONS: Both surgery and PBA are safe and successful in relieving the acute transpulmonary gradient. Long-term results of surgery are worse than previously thought due to severe PR. After PBA re-interventions for residual stenosis are frequently needed and the incidence of mild PR is high. Very long-term results of PBA are still unknown.

Mediterranean spotted fever, a diagnostic challenge in travellers.

Mediterranean spotted fever or boutonneuse fever is caused by Rickettsia conorii and transmitted by the brown dog tick. The commonest symptoms are pyrexia, a maculopapular rash, lymphadenopathies and an inoculation eschar. Increasingly, it is recognised as a cause of serious illness in southern Europe. Rickettsial infections of the spotted fever group are rarely reported in Belgium. We report the case of a 20-year-old traveller returning from Morocco who presented with fever and a markedly swollen inguinal lymph node. Our case report illustrates the challenges rickettsioses can pose to physicians facing febrile travellers. Awareness of the epidemiology and the spectrum of clinical manifestations of this acute zoonosis can help physicians to promptly start appropriate empiric antibiotic therapy.

New-onset and persistent migraine early after percutaneous atrial septal defect closure disappear at follow-up.

AIMS: Recently we reported that percutaneous atrial septal defect (ASD) closure had no influence on the prevalence of migraine during a short followup period. 12 % of patients however developed a new-onset migraine after the ASD closure. As it has been suggested that the closing device might induce or maintain migraine temporarily, we were interested in the prevalence of migraine at longer follow-up. METHODS: All 75 patients included in the previous study, received the same structured headache questionnaire. A neurologist, blinded to previous data, diagnosed migraine with or without aura (MA+ or MA-) according to the International Headache Criteria. McNemar paired X2 test was used to evaluate changes in the occurrence of migraine. RESULTS: Seventy-one patients (94.7%) answer the questionnaire (55 women, mean age at closure 51 +/- 18 years). Mean follow-up time was 52 +/- 13 months. The overall migraine prevalence decreased from 30.7% before to 22.5% after closure (P=0.21). A significant reduction was noted in patients with new-onset migraine early after closure (n=7), where migraine disappeared in 6 patients (P=0.031). In the group with persistent migraine early after closure (n=13), another 6 patients became migraine-free (P=0.031). CONCLUSION: Percutaneous ASD closure was not related to a significant decrease in overall migraine prevalence. However, new-onset and persistent migraine early after closure disappeared.

Structural characteristics of methanogenic cofactors in the non-methanogenic archaebacterium Archaeoglobus fulgidus.

Archaeoglobus fulgidus is an extremely thermophilic, sulphate reducing archaebacterium thought to represent a biochemical missing-link between sulphur-metabolizing bacteria and methanogenic bacteria. Whereas the phylogenetic position of A.fulgidus is closer to the sulphur-metabolizing bacteria, there is a partial overlap in the biochemical machinery of A.fulgidus with both groups of bacteria. In particular, the presence of a number of aberrant cofactors up to now thought to be involved exclusively in the process of methanogenesis in methanogenic archaebacteria, i.e. coenzyme F420, methanofuran and methanopterin, has been indicated by previous studies. Here we present evidence for the structural identity of the methanopterin cofactor of A.fulgidus with the methanopterin isolated from Methanobacterium thermoautotrophicum and show that this non-methanogenic bacterium contains two as yet unknown analogues of coenzyme F420. The levels of the various cofactors were determined in cultures grown either on formate or lactate as the carbon source and sulphate or thiosulphate as the sulphur source.

Recent progress in the prebiotic chemistry of HCN.

This article reports some recent results on the mechanisms of synthesis of biologically important molecules in oligomerizing solutions of HCN. It will also attempt to summarize, as completely as possible, our present state of knowledge concerning the range of products obtained under a variety of conditions in this reaction system.

Uracil synthesis via HCN oligomerization.

Uracil is released from HCN oligomers upon acid hydrolysis in concentrations of 0.001% for 1 M HCN solutions to 0.005% for 0.1 M solutions. This yield is comparable with earlier reported, minor or nonbiological pyrimidines such as 5-hydroxyuracil and orotic acid. This is the first report of uracil itself via HCN oligomerization. Data are presented which establish that the observed uracil is not formed by decarboxylation of previously formed orotic acid, but via acid hydrolysis of at least two other precursors.

Prebiotic adenine synthesis via HCN oligomerization in ice.

Adenine is produced (after hydrolysis) when 0.01 M solutions of HCN are adjusted to pH 9.2 with NH4OH and are frozen at -2 degrees C for 60-100 days. The addition of glycolonitrile (the cyanohydrin of formaldehyde) increases the yield of adenine under these conditions by about five-fold. These results confirm and extend an earlier suggestion that purine synthesis on the prebiotic Earth might have occurred in frozen, dilute solutions of HCN.