The crystal structure of human procathepsin K

Cathepsin K is a cysteine protease present in human osteoclasts that plays an important role in bone resorption. Cathepsin K is synthesized as an inactive proenzyme and activated under conditions of low pH. Autoproteolytic processing of the N-terminal 99 amino acid propeptide produces the active, mature form of cathepsin K. It is presumed that the activation of procathepsin K in vivo occurs in the bone resorption pit, which has a low-pH environment. We have determined the structure of human procathepsin K at 2.8 A resolution. The structure of the mature enzyme domain within procathepsin K is virtually identical to that of mature cathepsin K. The fold of the propeptide of procathepsin K is similar to that observed in procathepsins B and L despite differences in length and sequence. A portion of the propeptide occupies the active site cleft of cathepsin K. Hydrophobic interactions, salt bridges, and hydrogen-bonding interactions are observed in the structure of the propeptide and between the propeptide and the mature enzyme of procathepsin K. These interactions suggest an explanation for the stability of the proenzyme. The structure of procathepsin K contributes to an understanding of the molecular basis of inhibition by the propeptide portion of the molecule and activation of this important member of the cysteine protease family.     

Imaging of surface strain and polishing artefacts in fused silica by environmental scanning electron microscopy

The recently developed application of charge contrast imaging (CCI), available in variable pressure or environmental scanning electron microscopes (ESEM), has been found to provide images of near surface strain around micro-indentations in fused silica glass. Results suggest this strain contrast information is derived from within a few nanometres of the material surface, making CCI an invaluable tool for the study of nanometre scale surface deformation. Images of indentation strain have also been imaged using backscattered electron (BSE) imaging. The CCI technique has also been applied to the study of fused silica surfaces polished by chemically active polishing abrasives. In the samples studied, CCI provides unique images of linear defects residing below layers of chemically adhered polishing compound. Visualisation of surface strain on sub-nm rms glasses provides supporting evidence for plastic (permanent) deformation of the glass surface at the nanometre level during polishing with certain abrasives and for chemical interactions between the polishing abrasive and glass surface.     

Mechanical and tribological properties of TiN/Ti multilayer coating

A large area filtered arc deposition (LAFAD) technique was used to deposit TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thickness. Nanoindention and pin-on-disk tribometer were used to characterize the hardness, elastic modulus, plasticity, friction coefficient, and wear rate of the multilayer coatings. The dependence of the mechanical and tribological properties of the coating on the Ti interlayer thickness was systematically studied. It was found that the increase in the Ti layer thickness resulted in a decrease in the effective hardness and elastic modulus, and an increase in the wear rate, plasticity, and toughness. The coatings with a Ti layer thicknesses of 0, 25 nm and 50 nm possess an excellent combination of high effective hardness (> 20 GPa), high plasticity (> 69%), low friction coefficient, and high wear resistance.     

Allelotype influence at glutathione S-transferase M1 locus on breast cancer susceptibility

PURPOSE: To compare development of visual acuity and binocular vision in preterm and full-term infants in a prospective study that used testers masked to subject's gestational age. METHODS: Seventy-nine healthy full-term infants, mean gestational age 40 weeks, and 18 low-risk preterm infants, mean gestational age 33 weeks, were examined biweekly between the 44th and 54th weeks of postmenstrual age. Ocular alignment, convergence, fusion, grating acuity, and onset of optokinetic nystagmus (OKN) were assessed at each examination. RESULTS: The mean postnatal ages of onset of ocular alignment, convergence, fusion, grating acuity to 1.6 cycles per degree, and OKN from temporal to nasal and nasal to temporal were, respectively, 5, 7, 7, 11, 6, and 9 weeks for the full-term and 12, 13, 14, 18, 13, and 16 weeks for the preterm infants. The mean postmenstrual ages of onset for the corresponding parameters were 46, 48, 48, 51, 46, and 50 weeks for full-term and 46, 47, 48, 52, 47, and 49 weeks for preterm infants. The onset of all parameters was earlier in full-term infants than in preterm infants of the same postnatal age (P < or = 0.0001). However, no differences were found when the parameters were compared at postmenstrual ages. CONCLUSIONS: Additional visual experience of preterm infants does not influence development of visual acuity or binocular vision during the first months of life as measured from the time of conception.     

Effects of humorous heroes and villains in violent action films

This experimental investigation explores the use of humor in violent action films, focusing on the effects of wisecracking heroes and villains on audience distress. An action film was edited to create control film versions without wisecracking dialogue. The research revealed contrast effects. Among female viewers, hero wisecracks in an action film increased distress reactions to the film, but lessened distressful reactions to subsequent televised depictions of real, nonhumorous violence. Conversely, males exposed to hero humor found the film marginally less distressing, but rated depictions of real violence more distressing. For all viewers, effects of villain wisecracks tended to parallel females' reactions to hero wisecracks. Disposition theory is offered as a plausible explanations of study findings.     

Purification and crystallization of complexes modeling the active state of the fragile histidine triad protein

Fragile histidine triad protein (Fhit) is a diadenosine triphosphate (ApppA) hydrolase encoded at the human chromosome 3 fragile site which is frequently disrupted in tumors. Reintroduction of FHIT coding sequences to cancer cell lines with FHIT deletions suppressed the ability of these cell lines to form tumors in nude mice even when the reintroduced FHIT gene had been mutated to allow ApppA binding but not hydrolysis. Because this suggested that the tumor suppressor activity of Fhit protein depends on substrate-dependent signaling rather than ApppA catabolism, we prepared two crystalline forms of Fhit protein that are expected to model its biologically active, substrate-bound state. Wild-type and the His96Asn forms of Fhit were overexpressed in Escherichia coli, purified to homogeneity and crystallized in the presence and absence of ApppA and an ApppA analog. Single crystals obtained by vapor diffusion against ammonium sulfate diffracted X-rays to beyond 2.75 A resolution. High quality native synchrotron X-ray data were collected for an orthorhombic and a hexagonal crystal form.