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PubMed2005

Student perspectives on learning-oriented interactions in the tutorial group.

INTRODUCTION: In group learning settings like problem-based learning (PBL), the quality of interaction is closely related to group success. However, research and practice have shown that the interaction in tutorial groups is not optimal. In the present study, a questionnaire was used to measure students' perceptions of occurrence and desirability of three interaction types, i.e. exploratory questioning, cumulative reasoning, and handling knowledge conflicts. The discrepancies between the perceptions of occurrence and desirability enabled us to illustrate how the questionnaire can be used to improve the group interaction process in the tutorial group. METHOD: The subjects consisted of all second-year medical students of Maastricht University (N=240, response rate 73%). The questionnaire consisted of a list of eleven statements representing the three interaction types (factors). Students were asked to rate each statement on a 5-point Likert scale for two types of perceptions, i.e. occurrence and desirability. RESULTS: The average scores on occurrence and desirability of the interaction types varied between 3.4 and 3.7 (scale 1-5) and between 3.6 and 4.3, respectively. For two interaction types, significant differences between occurrence and desirability were found. CONCLUSION: The scores for occurrence were reasonable, and the desirability scores were significantly higher than the occurrence scores for two of the three interaction types, i.e., exploratory questioning and cumulative reasoning. The results of the present study imply that in the students' opinion, the interaction process in the tutorial group can be improved. The questionnaire provides useful information to detect shortcomings in the tutorial group interaction.

Cooperative Behavior↗

PubMed2006

Modelling of carbohydrate-aromatic interactions: ab initio energetics and force field performance.

Aromatic amino acid residues are often present in carbohydrate-binding sites of proteins. These binding sites are characterized by a placement of a carbohydrate moiety in a stacking orientation to an aromatic ring. This arrangement is an example of CH/pi interactions. Ab initio interaction energies for 20 carbohydrate-aromatic complexes taken from 6 selected ultra-high resolution X-ray structures of glycosidases and carbohydrate-binding proteins were calculated. All interaction energies of a pyranose moiety with a side chain of an aromatic residue were calculated as attractive with interaction energy ranging from -2.8 to -12.3 kcal/mol as calculated at the MP2/6-311+G(d) level. Strong attractive interactions were observed for a wide range of orientations of carbohydrate and aromatic ring as present in selected X-ray structures. The most attractive interaction was associated with apparent combination of CH/pi interactions and classical H-bonds. The failure of Hartree-Fock method (interaction energies from +1.0 to -6.9 kcal/mol) can be explained by a dispersion nature of a majority of the studied complexes. We also present a comparison of interaction energies calculated at the MP2 level with those calculated using molecular mechanics force fields (OPLS, GROMOS, CSFF/CHARMM, CHEAT/CHARMM, Glycam/AMBER, MM2 and MM3). For a majority of force fields there was a strong correlation with MP2 values. RMSD between MP2 and force field values were 1.0 for CSFF/CHARMM, 1.2 for Glycam/AMBER, 1.2 for GROMOS, 1.3 for MM3, 1.4 for MM2, 1.5 for OPLS and to 2.3 for CHEAT/CHARMM (in kcal/mol). These results show that molecular mechanics approximates interaction energies very well and support an application of molecular mechanics methods in the area of glycochemistry and glycobiology.

Carbohydrate Metabolism↗

PubMed1984

Binaural interaction effects on the auditory brainstem response of the cat and kitten.

The auditory brainstem response (ABR) is a series of volume conducted potentials that can be recorded from the scalp within 10 ms following auditory stimulation. Differences between ABRs evoked with binaural stimulation and those constructed by summing equivalent numbers of monaural stimulation to each ear indicate the presence of binaural interaction for some ABR potentials but not for others. In the present study, ABR binaural interactions were studied in both cats and kittens. Binaural interactions were not seen for waves 1-3 but were present at the latencies of waves 4, 5 and, in most cases, 6. The sound intensities used were selected to insure that acoustic cross-over, i.e. sound presented monaurally to one ear stimulating the other, did not influence binaural interaction effects. Experiments with cats that had been monaurally deafened confirmed that the effects observed were not due to acoustic cross-over. Systematic manipulation of stimulus rate and intensity produced marked changes in the level of binaural interaction. Increases in stimulation rate from 10 to 100 clicks/s reduced binaural interaction for wave 4 and reversed the direction of binaural interaction for wave 5. Wave 6 was not generally present at rates above 10 clicks/s. Reduction of stimulus intensity reduced binaural interaction for wave 4. Binaural interaction effects were at adult levels in kittens of 20 days for waves 4 and 5. Wave 6 was not present until 30 days of age. These data suggest a possible model of the physiological processes producing binaural interaction which is based on occlusion as seen in other areas of the nervous system. In such a model, convergent input becomes more important in driving the generators of some ABR potentials when the system is stressed (as, for example, by increased stimulus rate), than it is when the system is not stressed.

Age Factors↗

PubMed1996

Social isolation increases aggressive behaviour and alters the effects of diazepam in the rat social interaction test.

Isolation rearing in the early stages of life has been shown to modify a variety of behaviours in many animals and the responsitivity to psychotropic drugs. The aims of the present study were to investigate the effects of isolation rearing on anxiety using the social interaction paradigm and to compare the effects of diazepam on social interaction behaviours in isolation and socially reared rats. Male Lister hooded rats were reared from weaning either alone (isolation reared) or in groups of four (socially reared) for 6 weeks and then were tested for social interaction. Both isolation and socially reared rats were exposed to the social interaction test either without drug treatment or following saline or diazepam (1 and 2.5 mg/kg, i.p., 30 min before testing). The results demonstrate that under high light in an unfamiliar arena, the isolation compared to the socially reared rats showed a significantly (P < 0.01) higher level of social interaction, manifested as increases in aggressive and avoidance behaviours, and that this interaction occur for a greater length of time during the test period (10 min). However, when the light level was decreased or when the arena was familiar, active social interaction of isolation reared rats decreased but increased in the socially reared rats. In both conditions the isolation reared rats displayed more aggressive behaviours, in particular biting and boxing the partners which did not occur with the socially reared rats. Pretreatment of diazepam (1 and 2.5 mg/kg., i.p.) caused a dose-related reduction in aggressive behaviours in rats reared under both conditions but increased passive interactions in the socially reared rats. In contrast diazepam (2.5 mg/kg) reduced active interaction in the isolation reared rats but had no effect on passive interaction. These results indicate that isolation rearing increases aggressive behaviours and alters the effects of diazepam.

Aggression↗

PubMed1995

Auditory time-intensity cues in the binaural interaction component of the auditory evoked potentials.

Binaural interaction in the brainstem and middle latency auditory evoked potentials to intensity (dI) and timing differences (dT) between the two ears was studied in 10 normal hearing young adults. A component reflecting binaural interaction in the brainstem potentials occurred at approximately 7 ms and was of largest amplitude when dI and dT were 0. The latency of the binaural interaction component gradually shifted and its amplitude decreased as dI or dT increased and binaural interaction became undetectable when dI = 16 dB or when dT > or = 1.6 ms. In the middle latency potentials binaural interaction components peaking at 20, 32, and 45 ms were defined that were also largest when dI and dT = 0. The latency of the interaction did not shift with changes in dT and dI whereas the amplitude gradually decreased but binaural interaction components were still evident even at the largest values of dI (30 dB) and dT (3 ms). Psychophysical judgments of binaural perceptions showed binaural fusion of the stimuli to persist with dT values up to 1.6 ms and that lateralization of the intracranial image was complete when either dT = 1.6 ms or when dI = 16 dB. The results suggest that the presence of a binaural interaction component of auditory brainstem potentials correlates with the fusion of binaural click stimuli and the amplitude of the binaural interaction component correlates inversely with the degree of lateralization of the intracranial image. Binaural interaction components of middle latency potentials persist and continue to change even after the binaural stimuli cannot be fused.

Acoustic Stimulation↗

PubMed2004

Direct detection of cell surface interactive forces of sessile, fimbriated and non-fimbriated Actinomyces spp. using atomic force microscopy.

Actinomyces species are predominant early colonizers of the oral cavity and prime mediators of inter-bacterial adhesion and coaggregation. Previous workers have evaluated the adhesion of Actinomyces spp. by quantitative assessment of sessile, as opposed to planktonic cells attached to substrates, but did not quantify the cell surface interactive forces. Therefore we used atomic force microscopy to directly detect the interactive force between an approaching silicon tip and sessile Actinomyces spp. adhering to a substrate, at nanonewton (nN) range force levels. A total of eight strains each belonging to fimbriated and non-fimbriated Actinomyces species were employed, namely A. bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii genospecies 1 and 2, A. odontolyticus and A. viscosus. The sterile mica discs, used as the adhesion substrate, were immersed in mono-species bacterial suspensions for five days to obtain a thin bacterial biofilm. Interactive forces were measured using a silicon nitride cantilever attached to a Nanoscope IIIA atomic force microscope. The interactive forces between the approaching silicon nitride tip and bacterial biofilm surfaces were randomly quantified at three different locations on each cell; namely, the cell surface proper, the periphery of the cell and the substrate and, the interface between two cells. When the interactive forces at these locations of the same species were compared, significantly higher force levels at the cell-cell interface than the other two locations were noted with A. gerencseriae (P < 0.001), A. viscosus (P < 0.01) and A. israelii (P < 0.05). When the interactive forces of different Actinomyces spp. at an identical location were compared, fimbriated A. naeslundii genospecies 2 showed the greatest interactive force at the cell surface proper (-32.6 +/- 8.7 nN, P < 0.01). A. naeslundii genospecies 1, 2 and A. viscosus demonstrated greater interactive force at the cell-mica periphery than the other five species (P < 0.05); A. viscosus (-34.6 +/- 10.5 nN) displayed greater interactive force at the cell-cell interface than the others (P < 0.01), except for A. gerencseriae (P > 0.05). These data indicate that fimbriated Actinomyces spp., including A. naeslundii genospecies 1, 2 and A. viscosus exert higher cell surface interactive forces than those devoid of fimbriae and, such variable force levels may modulate their adhesion and coaggregation during biofilm formation.

Actinomyces↗

PubMed2005

A systematic study of yeast sterol biosynthetic protein-protein interactions using the split-ubiquitin system.

Sterol biosynthesis occurs in the ER and most sterol biosynthetic enzymes have transmembrane domains. However, due to difficulties in characterizing membrane protein-protein interactions, the nature of the sterol biosynthetic complex as well as in vivo interactions between various enzymes have not been described. We employed a split-ubiquitin membrane protein yeast two-hybrid system to characterize interactions between sterol biosynthetic proteins. Fourteen bait constructs were co-transformed into a reporter yeast strain with 14 prey constructs representing all sterol enzymatic reactions beginning with the synthesis of squalene. Our results not only confirmed several previous interactions, but also allowed us to identify novel interactions. Based on these results, ergosterol biosynthetic enzymes display specific protein-protein interactions forming a functional complex we designate, the ergosome. In this complex, Erg11p, Erg25p, Erg27p, and Erg28p appear to form a core center that can interact with other enzymes in the pathway. Also Erg24p and Erg2p, two enzymes that are sensitive to morpholine antifungals, appear to interact with one another; however, the profile of protein interaction partners appears to be unique. Erg2p and Erg3p, two enzymes catalyzing sequential reactions also appear to have different interaction partners. Our results provide a working model as to how sterol biosynthetic enzymes are topologically organized not only in yeast but in plant and animal systems that share many of these biosynthetic reactions.

Base Sequence↗

PubMed2004

Quantum chemical analysis explains hemagglutinin peptide-MHC Class II molecule HLA-DRbeta1*0101 interactions.

We present a new method to explore interactions between peptides and major histocompatibility complex (MHC) molecules using the resultant vector of the three principal multipole terms of the electrostatic field expansion. Being that molecular interactions are driven by electrostatic interactions, we applied quantum chemistry methods to better understand variations in the electrostatic field of the MHC Class II HLA-DRbeta1*0101-HA complex. Multipole terms were studied, finding strong alterations of the field in Pocket 1 of this MHC molecule, and weak variations in other pockets, with Pocket 1>>Pocket 4>Pocket 9 approximately Pocket 7>Pocket 6. Variations produced by "ideal" amino acids and by other occupying amino acids were compared. Two types of interactions were found in all pockets: a strong unspecific one (global interaction) and a weak specific interaction (differential interaction). Interactions in Pocket 1, the dominant pocket for this allele, are driven mainly by the quadrupole term, confirming the idea that aromatic rings are important in these interactions. Multipolar analysis is in agreement with experimental results, suggesting quantum chemistry methods as an adequate methodology to understand these interactions.

Binding Sites↗

PubMed2005

Detection of temporal patterns in dog-human interaction.

A new time structure model and pattern detection procedures developed by (Magnusson, M.S., 1996. Hidden real-time patterns in intra- and inter-individual behaviour description and detection. Eur. J. Psychol. Assess. 12, 112-123; Magnusson, M.S., 2000. Discovering hidden time patterns in behaviour: T-patterns and their detection. Behav. Res. Methods, Instrum. Comput. 32, 93-110) enables us to detect complex temporal patterns in behaviour. This method has been used successfully in studying human and neuronal interactions (Anolli, L., Duncan, S. Magnusson, M.S., Riva G. (Eds.), 2005. The Hidden Structure of Interaction, IOS Press, Amsterdam). We assume that similarly to interactions between humans, cooperative and communicative interaction between dogs and humans also consist of patterns in time. We coded and analyzed a cooperative situation when the owner instructs the dog to help build a tower and complete the task. In this situation, a cooperative interaction developed spontaneously, and occurrences of hidden time patterns in behaviour can be expected. We have found such complex temporal patterns (T-patterns) in each pair during the task that cannot be detected by "standard" behaviour analysis. During cooperative interactions the dogs' and humans' behaviour becomes organized into interactive temporal patterns and that dog-human interaction is much more regular than yet has been thought. We have found that communicative behaviour units and action units can be detected in the same T-pattern during cooperative interactions. Comparing the T-patterns detected in the dog-human dyads, we have found a typical sequence emerging during the task, which was the outline of the successfully completed task. Such temporal patterns were conspicuously missing from the "randomized data" that gives additional support to the claim that interactive T-patterns do not occur by chance or arbitrarily but play a functional role during the task.

Animals↗

PubMed2006

Behavioural comparison of human-animal (dog) and human-robot (AIBO) interactions.

The behavioural analysis of human-robot interactions can help in developing socially interactive robots. The current study analyzes human-robot interaction with Theme software and the corresponding pattern detection algorithm. The method is based on the analysis of the temporal structure of the interactions by detecting T-patterns in the behaviour. We have compared humans' (children and adults) play behaviour interacting either with an AIBO or a living dog puppy. The analysis based on measuring latencies and frequencies of behavioural units suggested limited differences, e.g. the latency of humans touching the dog/AIBO was similar. In addition other differences could be accounted for by the limited abilities of the robot to interact with objects. Although the number of interactive T-patterns did not significantly differ among the groups but the partner's type (whether humans were playing with dog or AIBO) had a significant effect on the structure of the patterns. Both children and adults terminated T-patterns more frequently when playing with AIBO than when playing with the dog puppy, which suggest that the robot has a limited ability to engage in temporally structured behavioural interactions with humans. As other human studies suggest that the temporal complexity of the interaction is good measure of the partner's attitude, we suggest that more attention should be paid in the future to the robots' ability to engage in cooperative interaction with humans.

Adult↗

PubMed2004

Coexistence of phosphotyrosine-dependent and -independent interactions between Cbl and Bcr-Abl.

Cbl is one of the major tyrosine-phosphorylated proteins in Bcr-Abl-expressing cells. A direct association between the SH2 domain of Bcr-Abl and tyrosine-phosphorylated Cbl has been demonstrated. The purpose of this study was to determine if and how unphosphorylated Cbl and Bcr-Abl may associate. Interactions between Cbl and Bcr-Abl were investigated in yeast two- and three-hybrid systems, gel overlay assays, and immunoprecipitates from mammalian cells expressing wild-type and the Y177F mutant of Bcr-Abl. No direct interaction between Bcr-Abl and unphosphorylated Cbl was observed. Bcr-Abl did, however, associate with Grb2, an adaptor protein that binds tyrosine 177 of Bcr-Abl. Additionally, Grb2 interacted with Cbl. In a yeast three-hybrid assay, Grb2 mediated an interaction between Cbl and Bcr-Abl that was dependent on a functional Grb2 binding site. This interaction was confirmed in vitro using purified proteins. In cells expressing Bcr-Abl with a mutation in the Grb2 binding site, binding of Cbl to Bcr-Abl was significantly reduced, but Cbl tyrosine phosphorylation was maintained. Imatinib treatment of these cells further reduced but did not abrogate Cbl binding, reflecting residual kinase activity. Multiple phosphotyrosine-dependent and -independent interactions stabilize the interaction between Cbl and Abl. Grb2 or another, yet unidentified, protein may mediate an initial interaction between Cbl and Bcr-Abl that is independent of Cbl tyrosine phosphorylation. Following this initial interaction, Cbl can then become tyrosine phosphorylated and interact with the SH2 domain of Bcr-Abl, further stabilizing the complex.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Solid phase proteomics: dramatic reinforcement of very weak protein-protein interactions.

Very weak protein-protein interactions may play a critical role in cell physiology but they are not easily detectable in "in vitro" experiments. To detect these weak interactions, we have developed a strategy that included: (a) design of a rapid and very effective crosslinking of protein-protein complexes with poly-functional reagents; (b) selective adsorption of very large proteins on lowly activated ionic exchangers, based on the need of a multipoint physical adsorption to incorporate the proteins into the matrix; (c) purification by selective adsorption of protein-protein complexes formed by strong protein-protein interactions, via selective adsorption of the complexes on lowly activated ionic exchangers via multi-protein physical adsorption and leaving the non-associated proteins in the solution; (d) reinforcement of very weak protein-protein interactions by selective adsorption of the complex on lowly activated ionic exchange supports via a synergetic cooperation of the weak protein-protein interaction plus the interactions of both proteins with the support enabling the almost full shifting of the equilibrium towards the association position; (e) control of the aggregation state of proteins like BSA, formed by weak protein-protein interactions. In this last case, it seems that the interaction of the protein molecules placed on the borders of the aggregate with the groups on the support partially stabilizes the whole aggregate, although, some molecules of the aggregate cannot interact with the support. The size of the aggregates may be defined by controlling the concentration of ionised groups on the support: the less activated the supports are, the bigger the complexes. In this way, solid-phase proteomics could be a very interesting tool to detect weak protein-protein interactions.

Adsorption↗

PubMed2005

Microcalorimetric study on the interaction of dissymmetric gemini surfactants with DNA.

The interaction of a series of dissymmetric gemini surfactants, [C(m)H(2m+1)(CH(3))(2)N(CH(2))(6)N(CH(3))(2)C(n)H(2n+1)]Br(2) (designated as C(m)C(6)C(n)Br(2), with constant m+n=24, and m=12, 14, 16, and 18) with DNA in 10 mM NaCl solution has been investigated by isothermal titration microcalorimetry (ITC). The curves for titration of the surfactants into DNA solution show noticeable differences from those into 10 mM NaCl solution without DNA. It is attributed to the interaction between DNA and surfactants. The critical aggregation concentration (CAC), the saturation concentration (C(2)), and the thermodynamic parameters for the aggregation and interaction processes were obtained from the calorimetric titration curves. The results show that the dissymmetry degree (m/n) has a marked effect on the interaction of the C(m)C(6)C(n)Br(2) surfactants with DNA. The CAC and C(2) tend to become smaller with increased m/n. The enthalpy change (DeltaH(agg)) and the Gibbs free energy change (DeltaG(agg)) for aggregation become more negative down the series, indicating that the hydrophobic interaction between the hydrophobic chains of the surfactant molecules increases and the aggregation process is more spontaneous with increased m/n. The entropy changes of aggregation (DeltaS(agg)) are all positive and TDeltaS(agg) is much larger than |DeltaH(agg)|, revealing that the aggregation process is mainly entropy-driven. However, the calculated Gibbs free energy (DeltaG(DS)) for the interaction between the gemini surfactants and DNA becomes less negative with increased m/n, which reveals that the interaction between the gemini surfactants and DNA tends to be weaker with increased m/n. This is induced by the disruption of the chain-chain hydrophobic interaction between the surfactant molecules at higher m/n, where the entropy change DeltaS(DS) for the interaction process tends to be an unfavorable factor. In addition, the DNA concentration also has a remarkable influence on the interaction.

Binding, Competitive↗

PubMed2004

Multiple domains of Ruk/CIN85/SETA/CD2BP3 are involved in interaction with p85alpha regulatory subunit of PI 3-kinase.

Ruk/CIN85/SETA/CD2BP3 and CD2AP/CMS/METS-1 comprise a new family of proteins involved in such fundamental processes as clustering of receptors and rearrangement of the cytoskeleton in regions of specialised cell-cell contacts, ligand-activated internalisation and targeting to lysosome degradation pathway of receptor tyrosine kinases, and apoptotic cell death. As typical adapter proteins they execute these functions by interacting with other signalling molecules via multiple protein-protein interaction interfaces: SH3 domains, Pro-rich region and coiled-coil domain. It has been previously demonstrated that Ruk is able to interact with the p85alpha regulatory subunit of PI 3-kinase and that the SH3 domain of p85alpha is required for this interaction. However, later observations hinted at a more complex mechanism than simple one-way SH3-Pro-rich interaction. Because interaction with p85alpha was suggested to be important for pro-apoptotic activity of the long isoform of Ruk, Ruk(l)/CIN85, we carried out detailed studies of the mechanism of this interaction and demonstrated that multiple domains are involved; SH3 domains of Ruk are required and sufficient for efficient interaction with full-length p85alpha but the SH3 domain of p85alpha is vital for their "activation" by ousting them from intramolecular interaction with the Pro-rich region of Ruk. Our data also suggest that homodimerisation via C-terminal coiled-coil domain affects both intra- and intermolecular interactions of Ruk proteins.

Adaptor Proteins, Signal Transducing↗

PubMed2006

A novel mechanism of interaction between alpha-synuclein and biological membranes.

Conformational abnormalities and aggregation of alpha-synuclein (alpha-syn) have been linked to the pathogenesis of Parkinson's (PD) and related diseases. It has been shown that alpha-syn can stably bind artificial phospholipid vesicles through alpha-helix formation in its N-terminal repeat region. However, little is known about the membrane interaction in cells. In the current study, we determined the membrane-binding properties of alpha-syn to biological membranes by using bi-functional chemical crosslinkers, which allow the detection of transient, but specific, interactions. By utilizing various point mutations and deletions within alpha-syn, we demonstrated that the membrane interaction of alpha-syn in cells is also mediated by alpha-helix formation in the N-terminal repeat region. Moreover, the PD-linked A30P mutation causes reduced membrane binding, which is concordant with the artificial membrane studies. However, contrary to the interaction with artificial membranes, the interaction with biological membranes is rapidly reversible and is not driven by electrostatic attraction. Furthermore, the interaction of alpha-syn with cellular membranes occurs only in the presence of non-protein and non-lipid cytosolic components, which distinguishes it from the spontaneity of the interaction with artificial membranes. More interestingly, addition of the cytosolic preparation to artificial membranes resulted in the transient, charge-independent binding of alpha-syn similar to the interaction with biological membranes. These results suggest that in cells, alpha-syn is engaged in a fundamentally different mode of membrane interaction than the charge-dependent artificial membrane binding, and the mode of interaction is determined by the intrinsic properties of alpha-syn itself and by the cytoplasmic context.

Animals↗

PubMed2006

Exploring the black box of a decision aid: what information do patients select from an interactive Cd-Rom on treatment options in breast cancer?

OBJECTIVE: It is thought that patients fare better when they participate in treatment decision-making, and when they have more control over the amount and type of information they receive. To facilitate informed decision-making, interactive decision aids have been introduced in health care. This article describes how much, and which information patients select from an interactive decision aid on breast cancer. To explore whether the interactive system facilitates that different patients receive different information, associations between patients' characteristics and information selection are inspected. METHODS: The interactive decision aid was provided to 106 patients after an initial discussion with their surgeon about their diagnosis and treatment options. Information regarding patients' age, completed education, treatment preference, psychological functioning, decision uncertainty and decision style was collected with a written, structured questionnaire. The questionnaire was completed before patients used the interactive decision aid. To create categories, a median-split procedure was employed on the scores of the continuous background variables. The information patients selected from the interactive decision aid were registered into logfiles. Associations between patients' background variables and information selection were investigated by means of univariate statistics. RESULTS: Patients (n=97; 92%) used the interactive decision aid intensively. On average, patients spent almost 70min searching for information and selected 21 information topics. Overall, treatment related information was clearly more selected than other types of information. Age, education, and decision style factors were associated with information selection. CONCLUSION: The interactive breast cancer decision aid was utilized intensively. The interactive system was found to facilitate that different patients received different amounts and types of information. PRACTICE IMPLICATIONS: Interactive decision aids may improve information giving to patients, and as a result, the quality of care. To safeguard informed-choice, decision aids should be used in conjunction with other communication strategies. Decision aids should be available continuously and throughout the patients' disease journey. The Internet may help to achieve broad dissemination and enduring access.

Adaptation, Psychological↗

PubMed2005

Range of HOX/TALE superclass associations and protein domain requirements for HOXA13:MEIS interaction.

AbdB-like HOX proteins form DNA-binding complexes with the TALE superclass proteins MEIS1A and MEIS1B, and trimeric complexes have been identified in nuclear extracts that include a second TALE protein, PBX. Thus, soluble DNA-independent protein-protein complexes exist in mammals. The extent of HOX/TALE superclass interactions, protein structural requirements, and sites of in vivo cooperative interaction have not been fully explored. We show that Hoxa13 and Hoxd13 expression does not overlap with that of Meis1-3 in the developing limb; however, coexpression occurs in the developing male and female reproductive tracts (FRTs). We demonstrate that both HOXA13 and HOXD13 associate with MEIS1B in mammalian and yeast cells, and that HOXA13 can interact with all MEIS proteins but not more diverged TALE superclass members. In addition, the C-terminal domains (CTDs) of MEIS1A (18 amino acids) and MEIS1B (93 amino acids) are necessary for HOXA13 interaction; for MEIS1B, this domain was also sufficient. We also show by yeast two-hybrid assay that MEIS proteins can interact with anterior HOX proteins, but for some, additional N-terminal MEIS sequences are required for interaction. Using deletion mutants of HOXA13 and HOXD13, we provide evidence for multiple HOX peptide domains interacting with MEIS proteins. These data suggest that HOX:MEIS interactions may extend to non-AbdB-like HOX proteins in solution and that differences may exist in the MEIS peptide domains utilized by different HOX groups. Finally, the capability of multiple HOX domains to interact with MEIS C-terminal sequences implies greater complexity of the HOX:MEIS protein-protein interactions and a larger role for variation of HOX amino-terminal sequences in specificity of function.

Amino Acid Sequence↗

PubMed2001

Specific neosaxitoxin interactions with the Na+ channel outer vestibule determined by mutant cycle analysis.

The voltage-gated Na+ channel alpha-subunit consists of four homologous domains arranged circumferentially to form the pore. Several neurotoxins, including saxitoxin (STX), block the pore by binding to the outer vestibule of this permeation pathway, which is composed of four pore-forming loops (P-loops), one from each domain. Neosaxitoxin (neoSTX) is a variant of STX that differs only by having an additional hydroxyl group at the N1 position of the 1,2,3 guanidinium (N1-OH). We used this structural variant in mutant cycle experiments to determine interactions of the N1-OH and its guanidinium with the outer vestibule. NeoSTX had a higher affinity for the adult rat skeletal muscle Na+ channel (muI or Scn4a) than for STX (DeltaG approximately = 1.3 kcal/mol). Mutant cycle analysis identified groups that potentially interacted with each other. The N1 toxin site interacted most strongly with muI Asp-400 and Tyr-401. The interaction between the N1-OH of neoSTX and Tyr-401 was attractive (DeltaDeltaG = -1.3 +/- 0.1 kcal/mol), probably with formation of a hydrogen bond. A second possible attractive interaction to Asp-1532 was identified. There was repulsion between Asp-400 and the N1-OH (DeltaDeltaG = 1.4 +/- 0.1 kcal/mol), and kinetic analysis further suggested that the N1-OH was interacting negatively with Asp-400 at the transition state. Changes in pH altered the affinity of neoSTX, as would be expected if the N1-OH site were partially deprotonated. These interactions offer an explanation for most of the difference in blocking efficacy between neoSTX and STX and for the sensitivity of neoSTX to pH. Kinetic analysis suggested significant differences in coupling energies between the transition and the equilibrium, bound states. This is the first report to identify points of interaction between a channel and a non-peptide toxin. This interaction pattern was consistent with previous proposals describing the interactions of STX with the outer vestibule (Lipkind, G. M., and H. A. Fozzard. 1994. Biophys. J. 66:1-13; Penzotti, J. L., G. Lipkind, H. A. Fozzard, and S. C. Dudley, Jr. 1998. Biophys. J. 75:2647-2657).

Animals↗