Effects of molecular crowding by saccharides on alpha-chymotrypsin dimerization

Given the importance of protein complexes as therapeutic targets, it is necessary to understand the physical chemistry of these interactions under the crowded conditions that exist in cells. We have used sedimentation equilibrium to quantify the enhancement of the reversible homodimerization of alpha-chymotrypsin by high concentrations of the osmolytes glucose, sucrose, and raffinose. In an attempt to rationalize the ostuolyte-mediated stabilization of the a-chymotrypsin homodimer, we have used models based on binding interactions (transfer-free energy analysis) and steric interactions (excluded volume theory) to predict the stabilization. Although transfer-free energy analysis predicts reasonably well the relatively small stabilization observed for complex formation between cytochrome c and cytochrome c peroxidase, as well as that between bobtail quail lysozyme and a monoclonal Fab fragment, it underestimates the sugar-mediated stabilization of the alpha-chymotrypsin dimer. Although predictions based on excluded volume theory overestimate the stabilization, it would seem that a major determinant in the observed stabilization of the a-chymotrypsin homodimer is the thermodynamic nonideality arising from molecular crowding by the three small sugars.

Characterization of redox centers in dimethyl sulfide dehydrogenase from Rhodovulum sulfidophilum

Dimethyl sulfide dehydrogenase from the purple phototrophic bacterium Rhodovulum sulfidophilum catalyzes the oxidation of dimethyl sulfide to dimethyl sulfoxide. Recent DNA sequence analysis of the ddh operon, encoding dimethyl sulfide dehydrogenase (ddhABC), and biochemical analysis (1) have revealed that it is a member of the DMSO reductase family of molybdenum enzymes and is closely related to respiratory nitrate reductase (NarGHI). Variable temperature X-band EPR spectra (120122 K) of purified heterotrimeric dimethyl sulfide dehydrogenase showed resonances arising from multiple redox centers, Mo(V), [3Fe-4S](+), [4Fe-4S](+), and a b-type heme. A pH-dependent EPR study of the Mo(V) center in (H2O)-H-1 and (H2O)-H-2 revealed the presence of three Mo(V) species in equilibrium, Mo(V)-OH2, Mo(v)-anion, and Mo(V)-OH. Above pH 8.2 the dominant species was Mo(V)-OH. The maximum specific activity occurred at pH 9.27. Comparison of the rhombicity and anisotropy parameters for the Mo(V) species in DMS dehydrogenase with other molybdenum enzymes of the DMSO reductase family showed that it was most similar to the low-pH nitrite spectrum of Escherichia coli nitrate reductase (NarGHI), consistent with previous sequence analysis of DdhA and NarG. A sequence comparison of DdhB and NarH has predicted the presence of four [Fe-S] clusters in DdhB. A [3Fe-4S](+) cluster was identified in dimethyl sulfide dehydrogenase whose properties resembled those of center 2 of NarH. A [4Fe-4S](+) cluster was also identified with unusual spin Hamiltonian parameters, suggesting that one of the iron atoms may have a fifth non-sulfur ligand. The g matrix for this cluster is very similar to that found for the minor conformation of center 1 in NarH [Guigliarelli, B., Asso, M., More, C., Augher, V., Blasco, F., Pommier, J., Giodano, G., and Bertrand, P. (1992) Eur. J. Biochem. 307,63-68]. Analysis of a ddhC mutant showed that this gene encodes the b-type cytochrome in dimethyl sulfide dehydrogenase. Magnetic circular dichroism studies revealed that the axial ligands to the iron in this cytochrome are a histidine and methionine, consistent with predictions from protein sequence analysis. Redox potentiometry showed that the b-type cytochrome has a high midpoint redox potential (E-o = +315 mV, pH 8).

Syntactic and pragmatic constraints on processing relative clauses

Thc oen itninteureasc ttioo nb eo fa pcreangtmraal tiiscs uaen di ns ymnotadcetlisc ocfo nsestnrtaeinnctse processing. It is well established that object relatives (1) are harder to process than subject relatives (2). Passivization, other things being equal, increases sentence complexity. However, one of the functions of the passive construction is to promote an NP into the role of subject so that it can be more easily bound to the head NP in a higher clause. Thus, (3) is predicted to be marginally preferred over (1). Passiviazation in this instance may be seen as a way of avoiding the object relative construction. 1. The pipe that the traveller smoked annoyed the passengers. 2. The traveller that smoked the pipe annoyed the passengers. 3.The pipe that was smoked by the traveller annoyed the 4.The traveller that the pipe was smoked by annoyed the 5.The traveller that the lady was assaulted by annoyed the In (4) we have relativization of an NP which has been demoted by passivization to the status of a by-phrase. Such relative clauses may only be obtained under quite restrictive pragmatic conditions. Many languages do not permit relativization of a constituent as low as a by-phrase on the NP accessibility hierarchy (Comrie, 1984). The factors which determine the acceptability of demoted NP relatives like (4-5) reflect the ease with which the NP promoted to subject position can be taken as a discourse topic. We explored the acceptability of sentences such as (1-5) using pair-wise judgements of samddifferent meaning, accompanied by ratings of easeof understanding. Results are discussed with reference to Gibsons DLT model of linguistic complexity and sentence processing (Gibson, 2000)

Well-formedness judgment: A comparison of offline and online performance in Broca's aphasics

0na eg rcarmitimcaal tfieca tcuorem opfr ethhee nospieornat iodneafli cdietf i(nAitiCoDn )o ft hthaet frequently co-occurs with Broca’s aphasia is above-chance performance on well-formedness judgment tasks for many syntactic constructions, but impaired performance where syntactic binding of traces to their antecedents occurs. However, the methodologies used to establish this aspect of the performance profile of the ACD have been predominantly offline. Offline well-formedness tasks entail extralinguistic processing (e.g. perception, attention, short-term memory, conscious reflection) in varying amounts and the influence of such processes on parsing mechanisms is yet to be fully established. In order to (a) further understand the role of extra-linguistic processing on parsing, and (b) gain a more direct insight into the online nature of parsing in Broca’s aphasia, 8 subjects underwent a series of wellformedness judgment investigations using both offline and online test batteries. The sentence types and error types used were motivated by three current theories about the nature of the ACD, namely, the Trace-Based Account (Grodzinsky, 2000), the Mapping Hypothesis (Linebarger et al., 1983) and Capacity proposals (e.g. Frazier & Friederici, 1991). The results from the present investigation speak directly to the three aforementioned theories and also demonstrate the important role that extralinguistic processing plays during offline assessment. The clinical implications of the different outcomes from the offline vs. online tasks are also discussed.

Harmful drinking in military veterans with post-traumatic stress disorder: Association with the D2 dopamine receptor A1 allele

Aims: The frequency of the Taq I A alleles (A1 and A2) of the D2 dopamine receptor (DRD2) gene was examined in Caucasian post-traumatic stress disorder (PTSD) patients and controls. Results: In 91 PTSD patients, the frequency of the A1 allele was higher (P = 6.12 x 10(-3)) than in the 51 controls. In the 38 PTSD harmful drinkers (greater than or equal to60 g alcohol/day), A1 allelic frequency was higher (P = 3.91 x 10(-2)) than in the 53 non-harmful drinkers (

D2 dopamine receptor gene polymorphism discriminates two kinds of novelty seeking

Cloninger's psychobiological model of personality as applied to substance misuse has received mixed support. Contrary to the model, recent data suggest that a combination of high novelty seeking (NS) and high harm avoidance (HA) represents a significant risk for the development of severe substance misuse. A genetic polymorphism previously implicated in severe substance dependence, the A1 allele of the D2 dopamine receptor (DRD2) gene, was examined in relation to NS and HA amongst 203 adolescent boys. Specifically, we hypothesized that subjects with the A1 + allele (A1/A1 and A1/A2 genotypes) would report stronger NS and would exhibit a more positive relationship between NS and HA than those with the A1-allele (A2/A2 genotypes). These predictions were supported. The correlation between NS and HA in 81 A1 + allelic boys (r = 0.27, P = 0.02), and that in the 122 A1- allelic boys (r = -0.15, P = 0.09), indicated that this relationship differed according to allelic status (F = 8.52, P < 0:004). Among those with the A1-allele, the present results are consistent with the traditional view that novelty seeking provides positive reinforcement, or the fulfillment of appetitive drives. In contrast, novelty seeking in those with the A1 + allele appears to include a negative reinforcement or self-medicating function. (C) 2002 Elsevier Science Ltd. All rights reserved.

Intracellular sorting and transport of proteins

The secretory and endocytic pathways of eukaryotic organelles consist of multiple compartments, each with a unique set of proteins and lipids. Specific transport mechanisms are required to direct molecules to defined locations and to ensure that the identity, and hence function, of individual compartments are maintained. The localisation of proteins to specific membranes is complex and involves multiple interactions. The recent dramatic advances in understanding the molecular mechanisms of membrane transport has been due to the application of a multi-disciplinary approach, intergrating membrane biology, genetics, imaging, protein and lipid biochemistry and structural biology. The aim of this review is to summarise the general principles of protein sorting in the secretory and endocytic pathways and to highlight the dynamic nature of these processes. The molecular mechanisms involved in this transport along the secretory and endocytic pathways are discussed along with the signals responsible for targeting proteins to different intracellular locations. (C) 2003 Elsevier Science Ltd. All rights reserved.

Climate of fear in organisational settings: Construct definition, measurement and a test of theory

This paper reports a study that explored a new construct: climate of fear. We hypothesised that climate of fear would vary across work sites within organisations, but not across organisations. This is in contrast a to measures of organisational culture, which were expected to vary both within and across organisations. To test our hypotheses, we developed a new 13-item measure of perceived fear in organisations and tested it in 20 sites across two organisations (N = 209). Culture variables measured were innovative leadership culture, and communication culture. Results were that climate of fear did vary across sites in both organisations, while differences across organisations were not significant, as we anticipated. Organisational culture, however, varied between the organisations, and within one of the organisations. The climate of fear scale exhibited acceptable psychometric properties.

Believing is not enough: Predicting support for the NTEU on an Australian campus

Asurvey-based field study was conducted with 232 members and nonmembers of the National Tertiary Education Union to investigate the psychological processes underpinning union support. Drawing on value-expectancy models and social identity/self-categorisation theory, this study investigated the role that both individual and grouprelated factors play in predicting attitudinal and behavioural support for the union. Variables investigated included instrumental and ideological attitudes, perceptions of a normative climate of union-support, and perceptions of higher education being under threat. Further to support for previous findings for the role of instrumental and ideological attitudes it was found that the perceived workplace norm had the anticipated direct effect on behaviour and evaluation and also moderated the behavioural expression of ideological and instrumental attitudes. The perception of threat to employment and higher education also directly impacted on behaviour and moderated the behavioural expression of ideological beliefs. The implications of these findings for collective action research will he discussed.

Mantle source heterogeneity, magma generation and magmatic evolution at Terceira Island (Azoresarchipelago): Constraints from elemental and isotopic (Sr, Nd, Hf, and Pb) data

This work addresses the present-day (<100 ka) mantle heterogeneity in the Azores region through the study of two active volcanic systems from Terceira Island. Our study shows that mantle heterogeneities are detectable even when "coeval" volcanic systems (Santa Barbara and Fissural) erupted less than 10 km away. These volcanic systems, respectively, reflect the influence of the Terceira and D. Joao de Castro Bank end-members defined by Beier et at (2008) for the Terceira Rift Santa Barbara magmas are interpreted to be the result of mixing between a HIMU-type component, carried to the upper mantle by the Azores plume, and the regional depleted MORB magmas/source. Fissural lavas are characterized by higher Ba/Nb and Nb/U ratios and less radiogenic Pb-206/Pb-204, Nd-143/Nd-144 and Hf-176/Hf-177, requiring the small contribution of delaminated sub-continental lithospheric mantle residing in the upper mantle. Published noble gas data on lavas from both volcanic systems also indicate the presence of a relatively undegassed component, which is interpreted as inherited from a lower mantle reservoir sampled by the ascending Azores plume. As inferred from trace and major elements, melting began in the garnet stability field, while magma extraction occurred within the spinel zone. The intra-volcanic system's chemical heterogeneity is mainly explained by variable proportions of the above-mentioned local end-members and by crystal fractionation processes. (C) 2011 Elsevier By. All rights reserved.

Avaliação, tratamento e consolidação de madeira em edifícios antigos

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil