Direct evidence for the role of haem doming as the primary event in the cooperative transition of haemoglobin

The study of cooperative ligand binding among the four subunits of haemoglobin has played a central role in the understanding of allosteric transitions in a large number of enzymes. Haem iron out-of-plane motion has been suggested to be the trigger for the cooperative transition of haemoglobin. To function as a trigger in a dynamic sense, haem-iron doming must be the first conformational change to occur following ligand dissociation. Here we present the first direct demonstration that haem-iron doming occurs on the same time scale as the breaking of the iron-ligand bond, thus establishing haem-iron doming as the primary event which lead to the R-->T transition in haemoglobin.     

Use of a multileaf collimator for the production of intensity-modulated beams

The continuous release of nitric oxide (NO) from the constitutive, endothelial isoform of nitric oxide synthase (e-NOS) serves mainly to keep the vasculature in a continuous state of active vasodilation. Although it has been suggested that NO production from e-NOS might also be affected by hemorrhagic shock (HS), this relationship is still controversial. Therefore, the roles of NO in the pathophysiology in hemorrhagic shock were reviewed. According to the previous reports, NO might play an important role in the pathophysioliogy of HS. In the early phase of HS, it may be possible that NO delivered from e-NOS serves a cytoprotective function in preventing shock-induced organ injury. This opinion suggests that endothelial NO production has a significant modulatory effect on vascular tone during hemorrhage, and that inhibition of NO production permits greater vasconstrictor influences leading to organ injury. NO production in the late phases of HS has an adverse effect on survival rate in the HS model. Moreover, the findings from an animal study of prolonged periods of HS suggest that excessive NO formation, including those produced from i-NOS, induces vascular hypoactivity and they have suggested that NOS inhibitors may improve the therapeutic outcome for patients suffering from HS. Therefore, it may be suggested that NO might play a biphasic role, cytoprotective during the early phase and cytotoxic late in HS.     

Mechanism of Rab geranylgeranylation: formation of the catalytic ternary complex

Rab proteins are geranylgeranylated on one or two C-terminal cysteines by Rab geranylgeranyl transferase (RabGGTase). The reaction is dependent on a Rab-binding protein, termed Rab escort protein (REP). Here, we studied the role of REP in the geranylgeranylation reaction. We first characterized the interaction between REP and ungeranylgeranylated Rab using analytical ultracentrifugation and a fluorescence-based assay. We measured an equilibrium dissociation constant of 0.2 microM for the formation of a 1:1 REP-Rab complex and showed that this interaction relies mostly on ionic bonds and does not involve the two C-terminal cysteine residues. Second, we show that REP is required for recognition of Rab by RabGGTase and therefore that the REP-Rab complex is the true substrate for RabGGTase. Third, we show that free REP inhibits the geranylgeranylation reaction, suggesting that the complex is recognized by RabGGTase primarily via a REP-binding site. Our data suggest a model whereby REP behaves kinetically as an essential activator of the reaction.     

Effects of growth hormone, insulin-like growth factor-I, and cortisol on periparturient antibody response profiles of dairy cattle

The objectives of this study were to determine hormone and antibody response profiles from the prepartum period to peak lactation, and evaluate potential immunomodulatory effects of the classic endocrine hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and cortisol. Specifically, 33 Holstein cows were immunized with ovalbumin (OVA) and Escherichia coli J5 at weeks -8 and -3 prior to parturition. At parturition (week 0), cows received an additional immunization of OVA. Blood was collected at weeks -8, -3, 0, 3 and 6 relative to parturition and various samples were used to determine plasma hormone concentration, serum immunoglobulin (Ig), and specific antibody response to OVA and E. coli. Colostrum and milk samples were also collected post-parturition to monitor local immunoglobulin and antibody responses. Results indicated that not all periparturient cows exhibited depressed immune response, and that antibody response to OVA could be used to partition cows into 3 groups recognizing animals with sustained measurable antibody response before and after parturition (Group 1), animals which responded poorly to immunization at parturition (Group 2), and animals which did not respond to immunizations at week -3 or parturition (Group 3). Cows with the highest antibody response to OVA (Group 1) also tended (P < or = 0.10) to have the highest response to E. coli J5 at parturition and had the lowest incidence of disease, particularly mastitis. Antibody response to OVA measured in milk tended to be higher in Group 1 cows, particularly at week 0 (P < or = 0.06) compared to cows of Group 3. IGF-I was higher (P < or = 0.05) in cows of Group 1 than Group 3 at peak lactation (week 6).     

Compromise Between Bromate Ion Formation and Pesticides Degradation and/or Manganese Removal

Ozonation is a widely used technology within the water industry. Bromate ion formed by oxidation of water containing bromide ion was studied with the Gas Ozone Test and Pilot Scale Ozonation. Bromate ion formation was investigated along with the removal of triazines and/or manganese. Under identical conditions of ozonation, BrO₃ ^? formation is specific for each water and depends on parameters such as Total Organic Carbon, UV absorbance at 254 nm, applied ozone and ozone residual. Pesticides degradation by ozonation alone cannot be achieved without the formation of BrO₃ ^? at a high concentration. Hydrogen peroxide, at a constant ozone dose, reduces the BrO₃ ^? formation. However, even with the use of hydrogen peroxide, the concentration of BrO₃ ^? can remain in excess of the provisional Maximum Contaminant Level (10 μg/L). For certain types of water, pesticide degradation is difficult to achieve if the MCL for BrO₃ ^? has to be met. Manganese oxidation by ozone appears to be achieved without high bromate formation; indeed the presence of manganese hinders BrO₃ ^? formation.     

Biaxial deformation of polyamide‐6: Assessment of orientation by means of infrared trichroism

Infrared spectroscopy was used to study the evolution of structure in films of polyamide‐6 drawn on a Cellier tenter frame laboratory tester under conditions of simultaneous equibiaxial stretching and planar uniaxial stretching. The “tilted film” method was used to obtain trichroic spectra corresponding to the machine, transverse, and normal directions, as well the “structural factor” spectrum. From these it was possible to obtain information on the molecular orientation and the evolution of the crystalline structure. The starting films, prepared by melt casting from an extruder on a chilled roll, contained predominantly the mesomorphic β form. The structural factor spectra confirmed that strain‐induced transformation into the α form occurred upon drawing, and that the amount of α form increased with the extent of drawing. The trichroic spectra showed that the molecular orientation was localized mainly, but not exclusively, in the α form. Orientation functions could be determined for both the molecular chain axis and the normal to the hydrogen‐bonded sheets. For both the equibiaxial and planar uniaxial films, these sheets were found to be strongly oriented parallel to the plane of the film, with the degree of orientation increasing with overall draw ratio. For the biaxial samples, the molecular chain orientation was found to be equibiaxial, as expected. Mechanical test results indicated that the chains are evenly distributed in the film plane rather than showing a preference for the two orthogonal draw directions. For the planar uniaxial samples, the chain orientation was predominantly in the draw direction, but some degree of orientation in the transverse direction was also observed. The variation of orientation functions with draw ratio suggested that the α structure evolves in two stages, the first involving chain orientation in the draw direction and the second involving rotation of the sheets into the plane of the film.     

A Stress Singularity Approach for the Prediction of Fatigue Crack Initiation in Adhesive Bonds. Part 1: Theory

Since crack initiation in adhesive bonds tends to occur near the interface corners where the stress fields are singular, we define a fatigue initiation criterion using stress singularity parameter, Q (a generalized stress intensity factor) and the singular eigenvalue, λ.

Hattori et al., successfully used a generalized stress intensity factor to characterize the static strength of bimaterial interfaces. We show that this criterion is only appropriate for situations in which the adhesive contact angle is no larger than 90° and the modulus ratio (adhesive to adherend) is smaller than 0.1. Fortunately, these conditions are often met in real joints, permitting the use of a single eigenvalue approach. We then extend this criterion to the case of fatigue arising from mechanical, thermal, or hygroscopic cycling.

In preparation for Part 2 (experimental), the special case of an epoxy wedge on a flat aluminum substrate is considered. The singularity is analyzed both analytically and numerically. The scale of the region dominated by the singularity is found to be of the order of 100 μm. The size of the plastically yielded zone near the apex is found to decrease extremely rapidly as the stress intensity factor goes down, thereby increasing the applicability of the method at the low stress levels often encountered in fatigue.