Chemistry of Epoxysulfones: Straightforward Synthesis of Versatile Chiral Building Blocks

[reaction: see text] Several chiral building blocks have been obtained easily in large quantities from an epoxysulfone (9) that could be obtained in both enantiomeric forms from accessible starting materials.

On the generation of catalytic antibodies by transition state analogues

The effective design of catalytic antibodies represents a major conceptual and practical challenge. It is implicitly assumed that a proper transition state analogue (TSA) can elicit a catalytic antibody (CA) that will catalyze the given reaction in a similar way to an enzyme that would evolve (or was evolved) to catalyze this reaction. However, in most cases it was found that the TSA used produced CAs with relatively low rate enhancement as compared to the corresponding enzymes, when these exist. The present work explores the origin of this problem, by developing two approaches that examine the similarity of the TSA and the corresponding transition state (TS). These analyses are used to assess the proficiency of the CA generated by the given TSA. Both approaches focus on electrostatic effects that have been found to play a major role in enzymatic reactions. The first method uses molecular interaction potentials to look for the similarity between the TSA and the TS and, in principle, to help in designing new haptens by using 3D quantitative structure-activity relationships. The second and more quantitative approach generates a grid of Langevin dipoles, which are polarized by the TSA, and then uses the grid to bind the TS. Comparison of the resulting binding energy with the binding energy of the TS to the grid that was polarized by the TS provides an estimate of the proficiency of the given CA. Our methods are used in examining the origin of the difference between the catalytic power of the 1F7 CA and chorismate mutase. It is demonstrated that the relatively small changes in charge and structure between the TS and TSA are sufficient to account for the difference in proficiency between the CA and the enzyme. Apparently the environment that was preorganized to stabilize the TSA charge distribution does not provide a sufficient stabilization to the TS. The general implications of our findings and the difficulties in designing a perfect TSA are discussed. Finally, the possible use of our approach in screening for an optimal TSA is pointed out.

Conformationally constrained butyrophenones as new pharmacological tools to study 5-HT 2A and 5-HT 2C receptor behaviours

This study presents new pharmacological and molecular modelling studies on a recently described series of conformationally constrained butyrophenones. Alignment-free three-dimensional quantitative structure-activity relationship models developed on the basis of GRid Independent descriptors and partial least squares regression analysis, allow feasible predictions of activity of new compounds and reveal structural requirements for optimal affinity, particularly in the case of the 5-HT(2A) receptor. The requirements for the 5-HT(2A) affinity consist in a precise distance between hydrogen bond donor (protonated amino group) and hydrogen bond acceptor groups, as well as an optimal distance between the protonated amino group and the farthest extreme of the compounds. Another significant result has been the characterisation of two structurally similar compounds as interesting pharmacological tools (1-[(4-Oxo-4,5,6,7-tetrahydrobenzo[b]furan-5-yl)ethyl]-4-(6-fluorobenzisoxazol-3-yl)piperidine and 1-[(4-Oxo-4,5,6,7-tetrahydrobenzo[b]furan-6-yl)methyl]-4-(6-fluorobenzisoxazol-3-yl)piperidine). In spite of their structural similarity, the first compound shows clearly higher affinity for the 5-HT(2C) receptor (about 100 fold) and higher Meltzer ratio (1.17 vs. 0.99) than the second. Moreover, the first compound inhibits arachidonic acid release in a biphasic concentration-dependent way in functional experiments at the 5-HT(2A) receptor and it acts as inverse agonist at the 5-HT(2C) receptor, behaviours that are not shown by the second compound.

Distant collaboration in drug discovery: the LINK3D project

The work describes the development of novel software supporting synchronous distant collaboration between scientists involved in drug discovery and development projects. The program allows to visualize and share data as well as to interact in real time using standard intranets and Internet resources. Direct visualization of 2D and 3D molecular structures is supported and original tools for facilitating remote discussion have been integrated. The software is multiplatform (MS-Windows, SGI-IRIX, Linux), allowing for a seamless integration of heterogeneous working environments. The project aims to support collaboration both within and between academic and industrial institutions. Since confidentiality is very important in some scenarios, special attention has been paid to security aspects. The article presents the research carried out to gather the requirements of collaborative software in the field of drug discovery and development and describes the features of the first fully functional prototype obtained. Real-world testing activities carried out on this prototype in order to guarantee its adequacy in diverse environments are also described and discussed.

[Anterior cervical diskectomy and interbody arthrodesis using Cloward technique: retrospective study of complications and radiological results of 167 cases]

PATIENTS AND METHODS

We performed a retrospective analysis of complications and radiological results in 167 patients surgically treated, for discal or spondylotic disease of the cervical spine, with Cloward procedure. Using uni and multivariate analysis, we tried to identify risk factors that might be correlated with surgical complications or radiological results.

RESULTS

Surgical treatment was indicated for cervical radiculopathy in 68% of the patients and for myelopathy or radiculomyelopathy in the remaining 32%. The pathologic disease responsible of the symptomatology was soft disk herniation in 59% of the cases and spondylotic changes in 41%. The patients that underwent surgery because of myelopathy were one decade older, had a longer symptomatic period and presented multi-segmentary spondylotic disease with higher frequency than patients affected of radiculopathy. The most common segments operated were CS-C6 (44.3%) and C6-C7 (30.5%). Surgical mortality was 0.6% and morbidity 29.3%. Most of the complications were transient, although 4.8% of the patients developed permanent neurological deterioration.

CONCLUSIONS

Complications were most commonly seen in the group of the patients undergoing surgery because of long-lasting myelopathy with multi-segmentary spondylotic disease, in those with vascular risk factors and in those operated of more than one segment. Surgeon anatomic knowledge and experience are critical for diminishing such complications. Non-union rate was 9.6%, and another 9.6% of the patients developed post-surgical kyphosis. Both factors correlated with the need of re-operation.

Nuclease activity of [Cu(sulfathiazolato)(2)(benzimidazole)(2)]2MeOH. Synthesis, properties and crystal structure

The [Cu(sulfathiazolato)(2)(benzimidazole)(2)]2MeOH complex has been synthesised and characterised. It crystallises in the monoclinic system, space group C1c1, with unit cell dimensions a=18.829(7) A, b=12.206(3) A, c=17.233(5) A, alpha=90.06(2) degrees, beta=97.28(3) degrees, gamma=90.21(3) degrees and Z=4. The geometry around the copper(II) ion is intermediate between tetrahedral and square planar. The complex produces cleavage of plasmid pUC18 in presence of reducing agents. The efficiency of cleavage reaction of the title compound with pUC18 and with different reducing agents follows the order ascorbate-H(2)O(2)>ascorbate>MPA>dithiothreitol>H(2)O(2).

Nanoindentation: Toward the sensing of atomic interactions

The mechanical properties of surfaces of layered materials (highly oriented pyrolytic graphite, InSe, and GaSe) and single-crystal ionic materials (NaCl, KBr, and KCl) have been investigated at the nanometer scale by using nanoindentations produced with an atomic force microscope with ultrasharp tips. Special attention has been devoted to the elastic response of the materials before the onset of plastic yield. A new model based on an equivalent spring constant that takes into account the changes in in-plane interactions on nanoindentation is proposed. The results of this model are well correlated with those obtained by using the Debye model of solid vibrations.

Influence of pH on the binding of diphenylmethylenepiperidines by 5-HT2B receptors in rat stomach fundus

Cyproheptadine is one of the compounds exhibiting the highest activity at 5-HT2B receptors. In a previous work we analysed the relevance of the amino group in diphenylmethylenepiperidines (DPMP), which are open cyproheptadine analogues. Only compounds containing N-H or N-methyl motifs, showed significant 5-HT2B activity. Surprisingly, the corresponding quaternary ammonium salt demonstrated a total lack of activity. Therefore, the question arises whether protonation favours the interaction of these compounds with 5-HT2B receptors. Consequently, we studied the protonation influence (by varying the pH of the medium) on the antagonism of serotonin by some cyproheptadine analogues in rat stomach fundus. The main results were: 1) N-protonation increases the activity of DPMPs. 2) Alkaline pH facilitates the occurrence of a non-surmountable antagonism. 3) The contrast between the activity of protonated DPMPs and the lack of activity of the corresponding quaternary ammonium cation, suggests either that the latter is prevented from acting by steric hindrance, or that the mechanism by which protonation may increase the activity depends not only on the charge of the proton, but also on its ability to form hydrogen bonds.

Molecular diversity sample generation on the basis of quantum-mechanical computations and principal component analysis

The present study introduces a new strategy of selection of a maximum diversity sample of n compounds from N available in a molecular database. This strategy can be useful in pharmacological screening, combinatorial chemistry or parallel synthesis planning. It consists of first describing the compounds by means of parameters derived from quantum mechanical computations (water solvation deltaG, benzene solvation deltaG, octanol solvation deltaG, dipolar moment), as well as standard molecular parameters such as solvent-accessible surface area and molecular weight. Solvation parameters are used because of the importance of this phenomenon in the pharmacological behaviour. Redundant information in the description of the compounds is eliminated by using principal components (PC) instead of the original descriptors. Based on the similarity between the N compounds in the PC space, they are classified into n groups by k-means cluster analysis. The compounds that are nearest to the centroid of each cluster constituted the maximum diversity sample. When practical difficulties exist for the use of one of the proposed compounds, another also close to the cluster centroid can substitute for it. This strategy has been tested in the selection of a sample of 50 amines from the 923 available in the Aldrich catalogue. The results have been contrasted with those obtained from an optimal, distance-based experimental design, resulting in an 86% of agreement between both approaches. An R(2)-like diversity coefficient has been used to assess the quality of the proposed solutions.

New serotonin 5-HT(2A), 5-HT(2B), and 5-HT(2C) receptor antagonists: synthesis, pharmacology, 3D-QSAR, and molecular modeling of (aminoalkyl)benzo and heterocycloalkanones

A series of 52 conformationally constrained butyrophenones have been synthesized and pharmacologically tested as antagonists at 5-HT(2A), 5-HT(2B), and 5-HT(2C) serotonin receptors, useful for dissecting the role of each 5-HT(2) subtype in pathophysiology. These compounds were also a consistent set for the identification of structural features relevant to receptor recognition and subtype discrimination. Six compounds were found highly active (pK(i) > 8.76) and selective at the 5-HT(2A) receptor vs 5-HT(2B) and/or 5-HT(2C) receptors. Piperidine fragments confer high affinity at the 5-HT(2A) receptor subtype, with benzofuranone- and thiotetralonepiperidine as the most selective derivatives over 5-HT(2C) and 5-HT(2B) receptors, respectively; K(i) (2A/2C) and/or K(B) (2A/2B) ratios greater than 100 were obtained. Compounds showing a more pronounced selectivity at 5-HT(2A)/5-HT(2C) than at 5-HT(2A)/5-HT(2B) bear 6-fluorobenzisoxazolyl- and p-fluorobenzoylpiperidine moieties containing one methylene bridging the basic piperidine to the alkanone moiety. An ethylene bridge between the alkanone and the amino moieties led to ligands with higher affinities for the 5-HT(2B) receptor. Significant selectivity at the 5-HT(2B) receptor vs 5-HT(2C) was observed with 1-1[(1-oxo-1,2,3,4-tetrahydro-3-naphthyl)methyl]-4-[3-(p-fluorobenzoyl)propyl]piperazine (more than 100-fold higher). Although piperidine fragments also confer higher affinity at 5-HT(2C) receptors, only piperazine-containing ligands were selective over 5-HT(2A). Moderate selectivity was observed at 5-HT(2C) vs 5-HT(2B) (10-fold) with some compounds bearing a 4-[3-(6-fluorobenzisoxazolyl)]piperidine moiety in its structure. Molecular determinants for antagonists acting at 5-HT(2A) receptors were identified by 3D-QSAR (GRID-GOLPE) studies. Docking simulations at 5-HT(2A) and 5-HT(2C) receptors suggest a binding site for the studied type of antagonists (between transmembrane helices 2, 3, and 7) different to that of the natural agonist serotonin (between 3, 5, and 6).

Ligands of neuronal nicotinic acetylcholine receptor (nAChR): inferences from the Hansch and 3-D quantitative structure-activity relationship (QSAR) Models

Neuronal acetylcholine ion channel receptors (nAChRs), that exist in several subtypes resulting from a different organisation of various subunits around the central ion channel, are involved in a variety of functions and disorders of the central nervous system. There is evidence to implicate a deficit of nAChRs in the symptomatology of severe neurologic pathologies, such as Alzheimer s and Parkinson s diseases. Reliable three-dimensional structures of nAChRs are not available yet, and this hampers adopting structure-based approaches in designing new ligands. Also pharmacophore models are not reliable enough to be used in ligand-based approaches to drug design and little structure-activity work has been reported so far. This paper deals with structure-activity relationships of a wide series of nicotinic ligands. It provides results from a study of the quantitative structure activity relationships (QSARs) based on literature data of about 270 nicotinic agonists, belonging to various chemical classes. The QSAR study was carried out by using either a classical Hansch approach or a Comparative Molecular Field Analysis (CoMFA). Within each congeneric series, Hansch-type equations revealed detrimental steric effects as the factors mainly modulating the receptor affinity, whereas CoMFA allowed us to merge progressively models obtained for each class of congeners into a more general one that showed good cross-validation statistics. The CoMFA coefficient isocontour maps illustrated, at the 3-D level, the most relevant interactions responsible for a high receptor affinity, whereas the robustness of the global three-dimensional QSAR/CoMFA (n = 206, q(2) = 0.749, r(2) = 0.847, s= 0.600) model was supported by the high value of the prediction statistics (r(2)pred = 0.961) and confirmed by the satisfactory predictions of the affinity data of an external set of 18 recently published ligands with chemical structures even quite diverse from those included in the training set.

An organizational model for a primary care program of home health care in Spain: a description of the program

The National Institute of Health (INSALUD) in Spain has successfully used a model of home care that has two major components, each using the physician as part of the team that provides care at home. The first component is home health care that is provided to chronically ill, terminally ill and homebound patients, whereby professionals of primary care provide care for the patient at home, along with other professionals who provide specialized care as support elements. The second component is hospitalization at home, whereby care is provided to acutely ill patients or patients with a precocious medical or surgical discharge from the hospital. The professionals from the hospital provide the basis of care. and the primary health care professionals are the support elements. Both components incorporate a team of support.

Spatial and annual temporal distribution of ozone concentrations in the madrid basin using passive samplers

Passive samplers are useful tools for helping to describe the ozone distribution in complex terrain situations. They are also a good complement to continuous monitoring stations. This paper discusses the results of a pilot study that used ozone passive samplers to describe the spatial and annual temporal distribution of ozone in several forested areas around the city of Madrid. The ozone concentrations around Madrid were found to be higher on the elevated sites located at a certain distance from the city"s urban zone. A seasonal ozone cycle was observed, with maximum concentrations found in the basin in late spring or summer depending on the location. The information obtained allowed us to group the locations into four classes. Altitude and distance to the city during the summer and winter explained the observed ozone concentrations. However, during the transition periods, especially in early spring and to a lesser extent in autumn, there was not a good correlation between ozone levels and elevation or distance from precursor sources. These data strongly suggest that altitudinal gradients for ozone are not always the case in the Madrid Basin.

Self-assembly of the amphipathic helix (VHLPPP)8. A mechanism for zein protein body formation

gamma-Zein, a maize storage protein with an N-terminal proline-rich repetitive domain (gamma-ZNPRD), is located at the periphery of protein bodies. This domain appears to be indispensable for the aggregation of the protein on the surface of the organelle. The peptide (VHLPPP)8, spanning the gamma-ZNPRD, adopts a polyproline II (PPII) conformation that gives an amphipathic helix different from the alpha-helix. We used atomic force microscopy to study the surface organisation of the octamer, and transmission electron microscopy to visualise aggregates of the peptide in aqueous solution. We consider two self-assembly patterns that take account of the observed features. The micellar one fits best with the experimental results presented. Moreover, we found that this peptide has properties associated with surfactants, and form micelles in solution. This spontaneous amphipathic arrangement of the gamma-ZNPRD suggests a mechanism of gamma-zein deposition inside maize protein bodies.

Neuronal nicotinic receptor agonists: a multi-approach development of the pharmacophore

Based on the results obtained with different automated computational approaches as applied to the study of eleven high-affinity agonists of the neuronal nicotine acetylcholine receptor (nAChR), belonging to different chemical classes, new relevant features were detected which complement the existing pharmacophores. Convergent results from DISCO (Distance Comparison), QXP (Quick Explore), Catalyst/HipHop, and MIPSIM (Molecular Interaction Potential Similarity) allowed us to identify and locate, in a well defined spatial arrangement, three geometrically independent key structural features: (i) a positively charged nitrogen atom for ionic or hydrogen bond interactions, (ii) a lone pair of the pyridine nitrogen or a specific lone pair of a carbonyl oxygen, as a hydrogen bond acceptor, and (iii) a centre of a hydrophobic area generally occupied by aliphatic cycles. The pharmacophore presented herein, along with predictive 2D and 3D QSAR models recently developed in our group, could represent valuable computational tools for the design of new nAChR agonists having therapeutical potential.

Clinical significance of donor-unrecognized bacteremia in the outcome of solid-organ transplant recipients

We evaluated the clinical significance of unrecognized bacteremia in the organ donor (i.e., blood culture results that were reported to be positive after transplantation) on the outcome of transplant recipients. Twenty-nine of 569 liver and heart donors (5%) had bacteremia at the time of organ procurement, but there were no documented instances of transmission of the isolated bacteria from the donor to the recipient. Unrecognized bacteremia in the donor does not have a negative clinical impact on the outcome of organ transplant recipients.

Theoretical evidence of a salt bridge disruption as the initiating process for the alpha1d-adrenergic receptor activation: a molecular dynamics and docking study

This study reports the building of the three-dimensional structure of the rat alpha1d-adrenergic receptor through a topology approach based on the structure of the rhodopsin receptor from cryoelectron microscopy. The validity and reliability of the receptor model were assessed through exhaustive molecular dynamics and docking studies. Some interesting ligand-receptor interactions were identified along with significant differences between the binding mode of agonists and antagonists. The importance of the disruption of a salt bridge as a possible initial event leading to receptor activation is discussed on the basis of data from mutagenesis and molecular dynamics studies.