Screening of protease inhibitors as antiplasmodial agents. Part I: Aziridines and epoxides

A broad protease-based and cell-based screening of protease inhibitors yielded the aziridine-2-carboxylic acid derivative 2 a and the N-acylated aziridine-2,3-dicarboxylic acid derivatives 32 a and 34 b as the most potent inhibitors of falcipain-2 and falcipain-3 (IC(50) falcipain-2: 0.079-5.4 microM, falcipain-3: 0.25-39.8 microM). As the compounds also display in vitro activity against the P. falciparum parasite in the submicromolar and low micromolar range, these compound classes are leads for new antiplasmodial falcipain inhibitors.     

Antibody-mediated neutralization of human rhinovirus 14 explored by means of cryoelectron microscopy and X-ray crystallography of virus-Fab complexes

The structures of three different human rhinovirus 14 (HRV14)-Fab complexes have been explored with X-ray crystallography and cryoelectron microscopy procedures. All three antibodies bind to the NIm-IA site of HRV14, which is the beta-B-beta-C loop of the viral capsid protein VP1. Two antibodies, Fab17-IA (Fab17) and Fab12-IA (Fab12), bind bivalently to the virion surface and strongly neutralize viral infectivity whereas Fab1-IA (Fab1) strongly aggregates and weakly neutralizes virions. The structures of the two classes of virion-Fab complexes clearly differ and correlate with observed binding neutralization differences. Fab17 and Fab12 bind in essentially identical, tangential orientations to the viral surface, which favors bidentate binding over icosahedral twofold axes. Fab1 binds in a more radial orientation that makes bidentate binding unlikely. Although the binding orientations of these two antibody groups differ, nearly identical charge interactions occur at all paratope-epitope interfaces. Nucleotide sequence comparisons suggest that Fab17 and Fab12 are from the same progenitor cell and that some of the differing residues contact the south wall of the receptor binding canyon that encircles each of the icosahedral fivefold vertices. All of the antibodies contact a significant proportion of the canyon region and directly overlap much of the receptor (intercellular adhesion molecule 1 [ICAM-1]) binding site. Fab1, however, does not contact the same residues on the upper south wall (the side facing away from fivefold axes) at the receptor binding region as do Fab12 and Fab17. All three antibodies cause some stabilization of HRV14 against pH-induced inactivation; thus, stabilization may be mediated by invariant contacts with the canyon.     

The self-comparison process and self-discrepant feedback: Consequences of learning you are what you thought you were not.

In 4 experiments, college students received bogus personality-test feedback that they possessed an actual-self, ideal-self (desired but unpossessed), or rejected-self (unwanted and unpossessed) trait. When the test had low credibility, rejected-self feedback produced positive mood (PM), whereas ideal-self feedback produced negative mood (NM). Self-comparison of the feedback with self-representations apparently revealed the falsity of the feedback, making salient Ss' virtues or shortcomings. The pattern reversed when test credibility was high: Rejected-self feedback led to NM and ideal-self feedback to PM. These effects were not evident, however, when the feedback trait had high personal importance or when Ss generated counterexamples before feedback about an unimportant trait. This suggests that reactions to self-discrepant feedback depend on whether convincing counterexamples are readily accessed during self-comparison. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Crime seriousness as a determinant of accuracy in eyewitness identification .

65 university students witnessed a staged theft in which either an expensive object (high seriousness) or an inexpensive object (low seriousness) was stolen, and Ss either had prior knowledge of the object's value or learned of its value only after the theft. When witnesses had prior knowledge of the object's value, accurate identification of the thief was more likely when the theft was of high rather than of low seriousness. When knowledge of the crime's seriousness was gained after the theft, seriousness did not affect identification accuracy. Results suggest that the effect of perceived seriousness on accuracy is mediated by processes that operate during rather than after the viewing interval, processes such as selective attention and encoding. The study also found that certainty of choice in the identification task was unrelated to accuracy of choice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How do triers of fact infer the accuracy of eyewitness identifications? Using memory for peripheral detail can be misleading.

107 undergraduate eyewitnesses to a staged theft made identifications from a photo spread and then responded to 11 questions that measured their memory for peripheral details. Results indicate that witnesses who accurately identified the thief (n?=?57) averaged fewer correct answers on the peripheral details test than did eyewitnesses who identified an innocent person (n?=?32). The remaining witnesses (n?=?18) made no identification. 94 undergraduates acting as jurors viewed cross-examinations of 47 accurate and 24 inaccurate eyewitnesses and indicated their belief that the witness had or had not properly identified the thief. The cross-examination that scrutinized and documented the witnesses' memory for trivial details lowered Ss' belief of the eyewitnesses' identification accuracy. This discrediting effect was stronger for accurate than for inaccurate eyewitnesses. It is argued that jurors inappropriately assumed a positive correlation between accuracy in identifying the thief and memory for peripheral details. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When motives clash: Issue involvement and response involvement as determinants of persuasion.

College students heard a strong or weak message after learning whether the message issue would have relevance to their personal lives outside the laboratory (high or low issue involvement) and whether they would later discuss the message issue (high or low response involvement). Judging from subjects' recall of message information, either high issue involvement or high response involvement was sufficient to instigate high levels of attention to the message. Issue-involved-only subjects, however, were most strongly influenced by message quality. They agreed more with and had more favorable thoughts about strong relative to weak messages, and they were most likely to engage in attitude-consistent behavior. Response-involved-only subjects were not affected by message quality, either on public attitude and thought measures or on a private behavioral measure. Response-and-issue-involved subjects were in between these extremes. Message quality had modest effects on their thoughts and attitudes, but not on their behavior. These results suggest that issue involvement encourages systematic processing that is sensitive to how well message arguments concur with personal standards. In contrast, response involvement encourages expression of attitudes that satisfy self-presentational needs. This expression may be mediated by message processing that is either biased toward moderation or nonintegrative, or by outward impression management, or both. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self‐Immolative Bioluminogenic Quinone Luciferins for NAD(P)H Assays and Reducing Capacity‐Based Cell Viability Assays

Highly sensitive self‐cleavable trimethyl lock quinone‐luciferin substrates for diaphorase were designed and synthesized to measure NAD(P)H in biological samples and monitor viable cells via NAD(P)H‐dependent cellular oxidoreductase enzymes and their NAD(P)H cofactors.     

Necrosis versus apoptosis as the mechanism of target cell death induced by Entamoeba histolytica

The human pathogen Entamoeba histolytica is known to kill a variety of host cells, including leukocytes. Using human myeloid cells as targets, we studied whether cytotoxicity of amoebic trophozoites in vitro is equivalent to the induction of apoptosis or whether these target cells die via necrosis. Based upon morphological criteria, incubation of target cells with amoebae resulted in necrosis, with cell swelling, rupture of plasma membrane, and release of cell contents including nucleic acids being detected by light and transmission electron microscopy. On the other hand, the characteristic features of apoptosis such as cell shrinking, surface blebbing, and chromatin condensation were not observed. Moreover, internucleosomal fragmentation of genomic DNA within target cells as a characteristic feature of apoptotic cell death did not occur as judged by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling technique in combination with flow cytometry. Consistently, cleavage of DNA was detectable upon agarose gel electrophoresis only after a substantial part of the target cell population had already been lysed. We also analyzed the mechanism of cell death induced by amoebapores, pore-forming peptides and primary candidate molecules for mediating the cytolytic activity of E. histolytica. At a time point at which the majority of target cells showed membrane injury upon incubation with purified amoebapores, no DNA degradation was detectable in the victim cells. The data suggest that the target cells used in our study undergo necrosis rather than apoptosis when they are killed by viable trophozoites as well as by isolated amoebapores.     

Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes

Three peptides with pore-forming activity were isolated from the cytoplasmic granules of pathogenic Entamoeba histolytica by acidic extraction, gel filtration and reversed-phase high-performance liquid chromatography. Partial amino acid sequence analysis of the three active peptides revealed that the most abundant of them was amoebapore and the other two were isoforms thereof. Cloning and sequencing of genomic DNA resolved the amino acid sequence of the two newly recognized peptides. The three peptides designated amoebapores A, B and C were found to have the same molecular size but to differ markedly in their primary structure, although all six cysteine residues are conserved. Despite sequence divergence, structural implications predict for the three peptides a similar amphipathic alpha-helical conformation stabilized by disulphide bonds. All three isoforms exhibit pore-forming activity toward lipid vesicles, but they differ in their kinetics. They also are capable of perturbing the integrity of bacterial cytoplasmic membranes and thereby kill Gram-positive bacteria. The amoebapores represent a distinct family of membrane-active peptides that may function intracellularly as antimicrobial agents but may also confer cytolytic activity on the parasite.