An atom counting strategy towards analyzing the biological activity of sex hormones

A simple and effective molecular descriptor, viz., the number of atoms in a molecule (N(A)) is made use of in the development of the quantitative structure-activity relationship (QSAR). A series of testosterone derivatives with various biological activities and estrogen derivatives with the activities in terms of relative binding affinity (RBA) are considered to find out the potential of N(A) in predicting the activities of those molecules. It is heartening to note that N(A) along with the electrophilicity index (omega) is capable of explaining the biological activities of the male and female hormones.

Management of dentoalveolar injuries in children: a case report

Children aged 6-15 years old experience more injuries to their teeth and the injuries sustained are more serious as evidenced by a higher percentage of luxations, avulsions, fractures and dislocations. The mandible is the most frequently fractured facial bone and mandibular alveolar injuries have been reported to range between 8.1-50.6%. Those with mandibular or midface fractures have a higher incidence of associated chest, extremity, abdomen and cervical spine injuries. The growing patient with facial injuries presents the clinician with a series of thought-provoking circumstances. Dentoalveolar and mandibular injuries are especially important to understand because of the potential complications related to tooth eruption, alveolar development, occlusion and facial growth. However, the principles involved in the treatment for children need to be modified by certain anatomical, physiological and psychological factors specifically related to childhood. This case report documents the trauma, management and follow-up care of an 11-year-old boy who sustained undisplaced infraorbital, nasal fractures and mandibular dentoalveolar fracture along with other associated injuries of the extremities.

Multiphilic Descriptor for Chemical Reactivity and Selectivity

In line with the local philicity concept proposed by Chattaraj et al. (Chattaraj, P. K.; Maiti, B.; Sarkar, U. J. Phys. Chem. A. 2003, 107, 4973) and a dual descriptor derived by Morell, Grand and Toro-Labbé, (J. Phys. Chem. A 2005, 109, 205), we propose a multiphilic descriptor. It is defined as the difference between nucleophilic (omega(k)+) and electrophilic (omega(k)-) condensed philicity functions. This descriptor is capable of simultaneously explaining the nucleophilicity and electrophilicity of the given atomic sites in the molecule. Variation of these quantities along the path of a soft reaction is also analyzed. Predictive ability of this descriptor has been successfully tested on the selected systems and reactions. Corresponding force profiles are also analyzed in some representative cases. Also, to study the intra- and intermolecular reactivities another related descriptor, namely, the nucleophilicity excess (Deltaomega(g)-/+) for a nucleophile over the electrophilicity in it, has been defined and tested on all-metal aromatic compounds.

Bowls, balls and sheets of boric acid clusters: the role of pentagon and hexagon motifs

Ab initio calculations suggest the possibility of forming boric acid clusters in the laboratory. The most stable form of the boric acid dimer contains two hydrogen bonds, similar to the carboxylic acid dimers. Though the trimer and the tetramer form extensions of this geometry, the pentamer prefers a bowl shape. Any addition of boric acid molecules to this geometry leads to bowl-shaped structures with the 15-mer forming a (3/4)buckyball and the 20-mer a full-fledged buckyball. The hexamer, on the other hand, prefers to stay planar as a hexagon-centered rosette. Any further extension of this geometry leads to planar structures as long as a pentagon is not included.

Bader's Electron Density Analysis of Hydrogen Bonding in Secondary Structural Elements of Protein

The hydrogen-bonding (H-bonding) interactions in alpha-helical and beta-sheet model peptides have been studied by using the atoms-in-molecule (AIM) approach. The relative importance of NH...O and CH...O H-bonding interactions in the different secondary elements such as alpha-helix, parallel, and antiparallel beta-sheets have been assessed. The electron density values at the NH...O bond are higher than those of the CH...O bonds in the alpha-helical conformation. The electron density values at the H-bonded critical points (HBCPs) corresponding to NH...O and CH...O interactions are nearly equal in the parallel beta-sheet of the order of 10(-3) au, whereas in the case of antiparallel beta-sheets, rho(rc) values for NH...O and CH...O interactions are of the order of 10(-2) and 10(-3) au, respectively. It is interesting to point out here that the weakening of NH...O interactions in the parallel beta-sheet arrangement is evident from the AIM analysis. This is concomitant with the increase in the NH...O distance in the parallel beta-sheet conformation. In addition to the clear description of H-bonding by electron density at the HBCP, possible good linear relationships between the electron density at ring critical points (RCP) and stabilization energy (SE) have been observed corresponding to the various beta-sheet conformations.

Hydrogen bonding without borders: an atoms-in-molecules perspective

It is shown that the electron density at the hydrogen bond critical point increases approximately linearly with increasing stabilization energy in going from weak hydrogen bonds to moderate and strong hydrogen bonds, thus serving as an indicator of the nature and gradual change of strength of the hydrogen bond for a large number of test intermolecular complexes.

Preparation and characterization of polystyrene-multiwalled carbon nanotube composite fibers by electrospinning

Electrospinning is a simple technique to prepare polymer fibers in nanometer diameters using very high electrostatic fields. These nanofibers are useful in many applications since the surface area to volume ratio in these fibers is very high. Here we have prepared nanofibers of composites of Polystyrene (PS) with different concentrations (0.05% to 2% w/w) of multi-walled carbon nanotubes (MWCNT) by electrospinning. The fibers are characterized by SEM, TEM, Raman spectra, and TGA. The room temperature electrical conductivity of single fibers of these composites are measured and found to show dramatic improvement in the conductivity due to the addition of MWCNT to the polymer matrix compared to the pure PS.

Determining the proximal extent of ulcerative colitis: white cell scan correlates well with histological assessment

BACKGROUND

Assessing the extent of ulcerative colitis determines therapeutic strategies and provides prognostic information. Colonoscopy with mucosal biopsy is considered unsafe in patients with severe disease.

AIM

To assess the correlation between proximal extent of ulcerative colitis as determined by Technitium-99-m hexamethylpropylene amine oxime labelled leucocyte scan (white cell scan) with that determined by histological assessment.

METHODS

One hundred and thirty-five patients, with histologically-confirmed ulcerative colitis, who had a white cell scan and histological assessment of colonic inflammation within 6 months of each other, during the years 1991-2004, were included. Overall agreement, quadratic-weighted kappa (kappa) and polychoric correlations (rho) were calculated to estimate the inter-rater reliability.

RESULTS

The correlation between white cell scan and histological extent was excellent (kappa = 0.7 rho = 0.8). Macroscopic appearance on colonoscopy did not correlate as well with histological extent (kappa = 0.62 and rho = 0.67). White cell scans correlated significantly better in patients with extensive disease (P = 0.02). Colonoscopy predicted disease extent more accurately in patients with limited colitis (P = 0.002).

CONCLUSIONS

Proximal extent of ulcerative colitis determined by white cell scans correlates well with histological assessment especially in patients with more extensive disease. White cell scans offer a reasonable alternative to colonoscopy with mucosal biopsies in determining the proximal extent of colitis.

Electrophilicity-Based Charge Transfer Descriptor

In line with the charge transfer (DeltaNmax = -mu/eta) proposed by Parr et al. (Parr, R. G.; Szentpály, L. V.; Liu, S. J. Am. Chem. Soc. 1999, 121, 1922), we propose an electrophilicity-based charge transfer (ECT) descriptor in this paper and validate it through the interaction between a series of chlorophenols and DNA bases. Application of ECT can be extended to the interaction of any toxin with the biosystem.

Solvation of H3O+ by Phenol: Hydrogen Bonding vs π Complexation

Ab initio calculations at the second-order Møller-Plesset perturbation theoretic level have been carried out to study the solvation of protonated water by phenol molecules. The results show that in addition to classical O-H...O hydrogen bonds, C-H...O, pi...H-O, and pi...H-C bonds are also formed, thus stabilizing the H3O+(C(6)H(5)OH)3 complex.

P450ome of the white rot fungus Phanerochaete chrysosporium: structure, evolution and regulation of expression of genomic P450 clusters

The model white rot fungus Phanerochaete chrysosporium has the extraordinary ability to degrade (to CO2) lignin and detoxify a variety of chemical pollutants. Whole genome sequencing of this fungus has revealed the presence of the largest P450ome in fungi comprising approx. 150 P450 genes, most of which have unknown function. On the basis of our genome-wide structural and evolutionary analysis, these P450 genes could be classified into 12 families and 23 subfamilies and under 11 fungal P450 clans. The analysis further revealed an extensive gene clustering with a total of 16 P450 clusters constituted of up to 11 members per cluster. In particular, evidence and role of gene duplications and horizontal gene transfer in the evolution of these P450 clusters have been discussed using two of the P450 families [CYP63 and CYP505 (where CYP is cytochrome P450)] as examples. In addition, the observed differential transcriptional induction of the clustered members of the CYP63 gene family, in response to different xenobiotic chemicals and carbon sources, indicated functional divergence within the P450 clusters, of this basidiomycete fungus.

Role of Aspartic Acid in Collagen Structure and Stability: A Molecular Dynamics Investigation

A molecular dynamics (MD) simulation study has been carried out to understand the stability of the triple helical collagen models. The calculations show that the presence of the aspartic acid residue in different positions leads to the local variation in the structure. Analyses of root-mean-square deviation (RMSD), radial distribution function (RDF), puckering effect, dihedral angle variation, hydrogen bond (H-bond), and conformational changes during molecular dynamics simulation reveal that the local perturbation in the sequences, increase in chain flexibility due to removal of five membered rings in the collagen by aspartic acid, change of intermolecular H-bonding pattern, and differences in the association of water are mainly influencing the nature of stabilization of collagen by aspartic acid.