Pyrrolidine based chiral organocatalyst for efficient asymmetric Michael addition of cyclic ketones to β-nitrostyrenes

An efficient asymmetric Michael addition of cyclic ketones to β-nitrostyrenes using secondary diamine as an organocatalyst derived from l-proline and (R)-α-methylbenzyl amine has been described. This pyrrolidine based catalyst 1 was found to be very effective to synthesize various γ-nitrocarbonyl compounds in good yield (up to 81%) with excellent stereoselectivity (up to >99:1 dr and >99% ee).     

Isocytosine-based inhibitors of xanthine oxidase: Design,synthesis, SAR,PK and in vivo efficacy in rat model of hyperuricemia

Structure–activity relationship studies were carried out for lead generation following structure-guided design approach from an isocytosine scaffold identified earlier for xanthine oxidase inhibition. A 470-fold improvement in in vitro IC₅₀ was obtained in the process. Five most potent compounds with nanomolar IC₅₀ values were selected for pharmacokinetics and in vivo experiments. The best compound showed good in vivo activity when administered intraperitoneally but was not active by oral route. The results suggest that improvement in oral exposure could improve the in vivo efficacy of this series.     

2-Substituted 4,5-dihydrothiazole-4-carboxylic acids are novel inhibitors of metallo-β-lactamases

Bacterial resistance to β-lactam antibiotics caused by class B metallo-β-lactamases (MBL), especially for certain hospital-acquired, Gram-negative pathogens, poses a significant threat to public health. We report several 2-substituted 4,5-dihydrothiazole-4-carboxylic acids to be novel MBL inhibitors. Structure activity relationship (SAR) and molecular modeling studies were performed and implications for further inhibitor design are discussed.     

How do thermophilic proteins resist aggregation?

Aggregation is an ancient threat that must be overcome by proteins from all organisms to maintain their native functional states. This is essential for the maintenance of metabolic flux and viability of their cellular machineries. Here, we compare the aggregation-resistance strategies adapted by the thermophilic proteins and their mesophilic homologs using a dataset of 373 protein families. Like their mesophilic homologs, the thermophilic protein sequences also contain potential aggregation prone regions (APRs), capable of forming cross-β motif and amyloid-like fibrils. Tetrapeptide and hexapeptide amyloid-like fibril forming sequence patterns and experimentally proven amyloid-like fibril forming peptide sequences were also detected in the thermophilic proteins. Both the thermophilic and the mesophilic proteins use similar strategies to resist aggregation. However, the thermophilic proteins show superior utilization of these strategies. The thermophilic protein monomers show greater ability to "stow away" the APRs in the hydrophobic cores to protect them from solvent exposure. The thermophilic proteins are also better at gatekeeping the APRs by surrounding them with charged residues (Asp, Glu, Lys, and Arg) and Pro to a greater extent. While thermophilic and mesophilic proteins in our dataset are highly homologous and show strong overall sequence conservation, the APRs are not conserved between the homologs. These findings indicate that evolution is working to avoid amyloidogenic regions in proteins. Our results are also consistent with the observation that thermophilic cells often accumulate small molecule osmolytes capable of stabilizing their proteins and other macromolecules. This study has important implications for rational design and formulation of therapeutic proteins and antibodies.     

Determination of the dipole moments of RNAse SA wild type and a basic mutant

In this study, we report the effects of acidic to basic residue point mutations (5K) on the dipole moment of RNAse SA at different pHs. Dipole moments were determined by measuring solution capacitance of the wild type (WT) and the 5K mutant with an impedance analyzer. The dipole moments were then (1) compared with theoretically calculated dipole moments, (2) analyzed to determine the effect of the point mutations, and (3) analyzed for their contribution to overall protein-protein interactions (PPI) in solution as quantitated by experimentally derived second virial coefficients. We determined that experimental and calculated dipoles were in reasonable agreement. Differences are likely due to local motions of residue side chains, which are not accounted for by the calculated dipole. We observed that the proteins' dipole moments increase as the pH is shifted further from their isoelectric points and that the wild-type dipole moments were greater than those of the 5K. This is likely due to an increase in the proportion of one charge (either negative or positive) relative to the other. A greater charge disparity corresponded to a larger dipole moment. Finally, the larger dipole moments of the WT resulted in greater attractive overall PPI for that protein as compared to the 5K.     

Characterization of the interaction between endostatin short Peptide and VEGF receptor 3

Corneal angiogenesis and lymphangiogenesis are induced by vascular endothelial growth factors (VEGFs) signaling through its receptors VEGFR-1, -2, and -3. Endostatin is a peptide antagonist of these receptors that causes inhibition of bFGF-induced corneal angiogenesis and lymphangiogenesis. Here we show that binding of VEGF-C and endostatin to recombinant VEGFR-3 is competitive. Alignments of the primary amino acid sequences of VEGF-C and the C-terminal endostatin peptide (mEP: LEQKAASCHNSYIVLCIENSFMTSFSK) identified two conserved cysteine residues separated by seven amino acids. Peptides of VEGF-C and mEP containing these conserved residues bound toVEGFR-3. However, substitution of alanine for either of the cysteines in the mEP peptide perturbed the secondary structure, and this mutated peptide was unable to bind to VEGFR-3. Analysis by surface plasmon resonance demonstrated that the binding of the mEP peptide for recombinant VEGFR-3 had a Ka of 1.41x107M-1s-1, Kd of 0.6718 s-1, and a KD of 4.78x10-8M. Characterization of the mechanism of endostatin binding to VEGFR-3 may lead to the development of novel therapies for lymphangiogenesis-related disorders, such as transplant rejection, lymphedema, and cancer metastasis.     

The evolved psychology of voice: evaluating interrelationships in listeners' assessments of the size,masculinity, and attractiveness of unseen speakers

A growing body of research has examined how voice characteristics advertise personal dimensions relevant in mate competition and mate choice. This work has centered on two key voice features, namely, fundamental frequency (F₀) and formants (Fn), and has consistently found that speakers with low F₀, low Fn, or both are rated as being larger, more masculine, and more attractive if men but less attractive if women. However, this consistency in listeners' perceptions is not matched by an equivalent consensus in how these mate-relevant dimensions are causally related or signaled by voice characteristics. Consequently, it is critical to test whether the strong correlations in listeners' perceptions reflect reliable causal relationships between these dimensions or, alternatively, whether they reflect some perceptual or cognitive nonindependence, for example, “what is large is masculine” and “what is small is feminine.” To test this latter possibility, we report detailed analyses of interdependence in listeners' ratings of perceived size, masculinity or femininity, and attractiveness of natural and manipulated voices of the opposite sex. We found strong correlations in listeners' ratings of all three dimensions, confirming past research. Principal component analysis corroborated these interrelationships but also revealed some independence in women's ratings of men's attractiveness and additional (but weaker) independence in men's ratings of women's size. We discuss possible implications for future research on the evolved psychology of voice and whether and how it reflects adaptive functional heuristics for discriminating mates.     

Methicillin-Resistant Staphylococcus aureus Phage Plaque Size Enhancement Using Sublethal Concentrations of Antibiotics

Phage therapy presents an alternative approach against the emerging methicillin-resistant Staphylococcus aureus (MRSA) threat. Some of the problems encountered during isolation of MRSA phages include the high prevalence of enteric phages in natural sources, nonspecific absorption of viable phage, and the formation of pinpoint or tiny plaques. The phage isolated in this study, MR-5, also formed tiny plaques against its host S. aureus ATCC 43300 (MRSA), making its detection and enumeration difficult. An improved method of increasing the plaque size of MRSA phage by incorporating sublethal concentrations of three different classes of antibiotics (inhibitors of protein synthesis) in the classical double-layer agar (DLA) method was investigated. The β-lactam and quinolone antibiotics commonly employed in earlier studies for increasing the plaque size did not show any significant effect on the plaque size of isolated MR-5 phage. Linezolid (oxazolidinone class), tetracycline, and ketolide antibiotics brought significant enhancements (3 times the original size) in the plaque size of MR-5 phage. Prior treatment with these antibiotics resulted in significant reductions in the time of adsorption and the latent period of MR-5 phage. To rule out whether the action of linezolid (which brought the maximum increase in plaque size) was specific for a single phage only, its effect on the plaque size of seven other S. aureus-specific phages was also assessed. Significant enhancements in the plaque size of these phages were observed. These results indicate that this modification can therefore safely be incorporated in the traditional DLA overlay method to search for new MRSA-virulent phages.