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A theoretical elucidation of bilirubin interaction with HSA's lysines: first electrostatic binding site in IIA subdomain.

The electrostatic interaction of amino acid lysines 190, 195 and 199 of human serum albumin (HSA) with bilirubin have been investigated using molecular dynamic simulations, QM and QM/MM minimization methods. In this study two methodological approaches have been employed. In the first approach X-ray structure and the structure obtained from the molecular dynamic simulation of subdomain IIA of HSA in vacuum have been utilized. Interactions have been evaluated with the segment 186-200 of the cited subdomain. Calculations on the X-ray structure of above segment indicate an effective interaction of the lysine 195 with bilirubin, although that of the lysine 190 is also found considerable in this structure. Performing simulation in vacuum, it has been revealed that except for the lysine 195, the other two lysine residues (190 and 199) could not be considered as centers of interaction. Such finding, which is in accord with experimental data, lends support to the procedure employed in this study. NBO analyses suggest that tasks to achieve a structure indicating bilirubin interaction with the lysine 195 from the 186-200 segment extracted from X-ray structure, results in a structure that lacks any electrostatic interaction. In fact, it has been found that the stability of the latter species can be attributed to the H-bonding interaction of the glutamate 188 with both bilirubin and the lysine 195. Further NBO analysis on the structure of the same species, while achieved after molecular dynamic simulation on subdomain IIA in vacuum has revealed that a favorable electrostatic interaction between the lysine 195 and bilirubin has occurred. Besides, H-bonding interaction of the glutamate 188 with bilirubin has been evident in the same species. For the second approach, presence of water molecules and ions has been considered to simulate condensed medium. Applying docking, conformational sampling, and QM/MM minimization steps in sequence, a structure has been achieved which presents a specific interaction between epsilon-NH3(+) group of the lysine 195 residue and the lactam oxygen atom of bilirubin. NBO analyses suggest that above electrostatic interaction is combined with hydrogen bonding interaction between same two groups. Moreover, a hydrogen bond between oxygen atom of bilirubin's acetate group and alpha-NH group of lysine 195 has been observed. Molecular orbital calculations have been presented which support the NBO analyses.

Bilirubin↗

Characterization of bovine serum albumin-tryptophan interaction by capillary isoelectric focusing with whole column imaging detection.

Capillary isoelectric focusing (cIEF) with whole column imaging detection (WCID) was explored for the characterization of bovine serum albumin (BSA)-tryptophan interaction, to further understand protein-drug interactions. The BSA-tryptophan interaction was dynamically monitored by cIEF-WCID, to provide the cIEF profiles of the BSA-tryptophan interaction system at different focusing times. Our study demonstrated that the cIEF behavior of BSA can serve as a probe into the study of BSA-tryptophan interaction, through monitoring the change in its cIEF profile when the interaction occurred. The study illustrated that the BSA peak split due to the BSA-tryptophan interaction, and the peak of BSA-tryptophan complex was clearly identified in the cIEF electropherograms. By comparing the cIEF profiles of BSA/L-tryptophan and BSA/D-tryptophan, respectively, our study demonstrated that BSA interacted with the enantiomers of tryptophan with a chiral recognition. L-Tryptophan demonstrated a very strong interaction with BSA, while D-tryptophan exhibited a much weaker interaction with BSA. The effects of the BSA concentration, the tryptophan concentration, the focusing time and the incubation time on the BSA-tryptophan interaction were investigated. This study offers a novel approach for the study of protein-drug interactions.

Animals↗

Specific ion effects via ion hydration: II. Double layer interaction.

A simple modified Poisson-Boltzmann formalism, which accounts also for those interactions between electrolyte ions and colloidal particles not included in the mean potential, is used to calculate the force between two parallel plates. It is shown that the short-range interactions between ions and plates, such as those due to the change in the hydration free energy of a structure-making/breaking ion that approaches the interface, affect the double layer interaction at large separations through the modification of the surface potential and surface charge density. While at short separations (below the range of the short-range ion-hydration forces) the interaction can be attractive, at larger separations the interaction is always repulsive, as in the traditional theory. When the long-range van der Waals interactions between the ions and the system (ion-dispersion interactions) are accounted for in the modified Poisson-Boltzmann approach, an attractive force between plates can be generated. At sufficiently large separations, this attraction can become even stronger than the traditional van der Waals attraction between plates of finite thickness, thus generating a dominant long-range 'double layer attraction'. At small plate separations, the attraction generated by the ion-dispersion forces combined with the electrostatic repulsion due to the double layers overlap can lead to a variety of interactions, from a weak attraction (which is typically by at least one order of magnitude smaller than the traditional van der Waals attraction between plates) to a strong double layer repulsion (for sufficiently large surface charges). Both types of ion interactions (long-range van der Waals or short-range ionic hydration) strongly affect the magnitude of the double layer interaction, and can account for the specific ion effects observed experimentally. However, they do not affect qualitatively the traditional theory of the colloid stability, which predicts that the colloid is stable when there is a sufficiently large charge on the surface, and coagulates when the van der Waals interactions between two colloidal particles dominate. The only qualitative difference found when the ion-dispersion interactions were incorporated into the traditional double layer theory was the emergence of a 'double layer attraction' at very large separations, which, however, does not affect much the stability of colloids.

Colloids↗

Analysis of the membrane-interacting domains of myelin basic protein by hydrophobic photolabeling.

Myelin basic protein is a water soluble membrane protein which interacts with acidic lipids through some type of hydrophobic interaction in addition to electrostatic interactions. Here we show that it can be labeled from within the lipid bilayer when bound to acidic lipids with the hydrophobic photolabel 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine (TID) and by two lipid photolabels. The latter included one with the reactive group near the apolar/polar interface and one with the reactive group linked to an acyl chain to position it deeper in the bilayer. The regions of the protein which interact hydrophobically with lipid to the greatest extent were determined by cleaving the TID-labeled myelin basic protein (MBP) with cathepsin D into peptides 1-43, 44-89, and 90-170. All three peptides from lipid-bound protein were labeled much more than peptides from the protein labeled in solution. However, the peptide labeling pattern was similar for both environments. The two peptides in the N-terminal half were labeled similarly and about twice as much as the C-terminal peptide indicating that the N-terminal half interacts hydrophobically with lipid more than the C-terminal half. MBP can be modified post-translationally in vivo, including by deamidation, which may alter its interactions with lipid. However, deamidation had no effect on the TID labeling of MBP or on the labeling pattern of the cathepsin D peptides. The site of deamidation has been reported to be in the C-terminal half, and its lack of effect on hydrophobic interactions of MBP with lipid are consistent with the conclusion that the N-terminal half interacts hydrophobically more than the C-terminal half. Since other studies of the interaction of isolated N-terminal and C-terminal peptides with lipid also indicate that the N-terminal half interacts hydrophobically with lipid more than the C-terminal half, these results from photolabeling of the intact protein suggest that the N-terminal half of the intact protein interacts with lipid in a similar way as the isolated peptide. The similar behavior of the intact protein to that of its isolated peptides suggests that when the purified protein binds to acidic lipids, it is in a conformation which allows both halves of the protein to interact independently with the lipid bilayer. That is, it does not form a hydrophobic domain made up from different parts of the protein.

1,2-Dipalmitoylphosphatidylcholine↗

Use of a biomimetic chromatographic stationary phase for study of the interactions occurring between inorganic anions and phosphatidylcholine membranes.

A liquid chromatographic method for the study of ion-membrane interactions is reported. A phosphatidylcholine biomimetic stationary phase was established by loading dimyristoylphosphatidylcholine (DMPC) onto a reversed-phase octadecylsilica packed column. This column was then used to study the interaction of some inorganic anions with the stationary phase by UV and conductivity detection. Ten inorganic anions were selected as model ions and were analyzed with the proposed chromatographic system. Anion-DMPC interactions of differing magnitudes were observed for all of the model anions. Perchlorate-DMPC interactions were strongest, followed by thiocyanate-DMPC, iodide-DMPC, chlorate-DMPC, nitrate-DMPC, bromide-DMPC, chloride-DMPC, fluoride-DMPC, and then sulfate-DMPC. Cations in the eluent, especially H(+) ions and divalent cations such as Ca(2+), showed strong effects on anion-DMPC interactions. The chromatographic data suggest that DMPC interacts with both the anions and the cations. Anion-DMPC interactions were dependent on the surface potential of the stationary phase: at low surface potentials anion-DMPC interactions were predominantly solvation dependent in nature whereas at more positive surface potentials anion-DMPC interactions were predominantly electrostatic in nature. Cation-DMPC interactions served to raise the surface potential, causing the anion-DMPC interactions to vary from solvation dependent to electrostatic. The chromatographic data were used to provide quantitative estimates of the enthalpies of the anion-DMPC interactions.

Anions↗

MINT: a Molecular INTeraction database.

Protein interaction databases represent unique tools to store, in a computer readable form, the protein interaction information disseminated in the scientific literature. Well organized and easily accessible databases permit the easy retrieval and analysis of large interaction data sets. Here we present MINT, a database (http://cbm.bio.uniroma2.it/mint/index.html) designed to store data on functional interactions between proteins. Beyond cataloguing binary complexes, MINT was conceived to store other types of functional interactions, including enzymatic modifications of one of the partners. Release 1.0 of MINT focuses on experimentally verified protein-protein interactions. Both direct and indirect relationships are considered. Furthermore, MINT aims at being exhaustive in the description of the interaction and, whenever available, information about kinetic and binding constants and about the domains participating in the interaction is included in the entry. MINT consists of entries extracted from the scientific literature by expert curators assisted by 'MINT Assistant', a software that targets abstracts containing interaction information and presents them to the curator in a user-friendly format. The interaction data can be easily extracted and viewed graphically through 'MINT Viewer'. Presently MINT contains 4568 interactions, 782 of which are indirect or genetic interactions.

Amino Acid Sequence↗

Cellular interactions in vascular growth and differentiation.

In nature, mammalian cells do not exist in isolation, but rather are involved in interactions with other cells and matrix. In this review, several aspects of cellular interactions that are important in vascular growth and development will be highlighted. The cardiovascular system is the earliest to develop in the embryo. A number of growth factors and their receptors mediate the complex stages of migration, assembly, organization, and stabilization of developing vessels. In the adult organism, normal angiogenesis is restricted primarily to tissue growth (such as muscle and fat), the wound healing process and the female reproductive system. However, pathological angiogenesis, such as with tumor growth, diabetic retinopathy, and arthritis, is of great concern. The identification and/or development of exogenous and endogenous angiogenesis inhibitors has added to the understanding of these pathological processes. In addition to cellular interactions via ligands and receptors, cells also interact directly through physical contacts. These interactions facilitate anchorage, communication, and permeability. Since vessels serve as non-leaky conduits for blood flow as well as interfaces for molecular diffusion, the physical interactions between the cells that make up vessels must be specific for the function at hand. Permeability is a specialized function of vessels and is mediated by intracellular mechanisms and intercellular interactions. Cells also interact with the surrounding extracellular matrix. Integrin-matrix interaction is a two-way exchange critical for angiogenesis. Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases play major roles in embryonic remodeling, adult injury, and pathological conditions. Several experimental model systems have been useful in our understanding of cellular interactions. These in vitro models incorporate heterotypic cell-cell interactions and/or allow cell-matrix interactions to occur.

Animals↗

Social interactions among captive brushtail possums (Trichosurus vulpecula).

A biological control strategy relying on a self-disseminating agent may provide the only affordable long-term technique for reducing brushtail possum (Trichosurus vulpecula) numbers throughout New Zealand. The objective of this study was to determine the frequency and patterns of social interactions in single and mixed-sex groups of possums, in order to identify interactions that may assist in the dissemination of biocontrol agents. Thirty-two sexually mature wild-caught possums (16 female, 16 male) were housed in captive groups (of four) in enclosures during the breeding and non-breeding seasons. Groups consisted of either all females, females and males or all males. Four types of social interactions were defined: threats, fights, affiliative and sexual interactions. Interactions only occurred between two animals at one time and were most frequent in the non-breeding season. Within all female groups, possums readily engaged in interactions that had either an agonistic or affiliative nature. Mixed-sex groups interacted less frequently than females, but also engaged in both agonistic and affiliative interactions. In contrast, possums in all male groups rarely interacted, with only a few fights and no affiliative interactions observed. Some mixed-sex dyads appeared to 'associate' during the breeding period. Young were produced by three females that regularly associated with a male and one female that showed little associative behaviour. Given the different interaction patterns observed in each group type, biological control agents that rely on specific interaction patterns for dissemination, are likely to spread at different rates among different possum groups and in different seasons.

Journal Article↗

Application of hierarchical thermodynamic interactions to the protonation equilibria of organic polyprotic acids.

A general method for formulating complex thermodynamic systems in terms of hierarchical interactions has been developed, and has been applied in a previous analyses to the theoretical analysis of cooperativity in a dimeric protein, to the statistical analysis of hemoglobin oxygen binding data, and to the protonation equilibria of inorganic polyprotic acids. Organic polyprotic acids have served as a demonstration system for the development of concepts and methods for treating complex biochemical equilibria. Glutamic acid is the classic test case for understanding proton-proton interactions in organic polyprotic acids, and this system is analyzed using the concept of hierarchical interactions. Second order interactions were apparent between all three possible proton interactions, as has been established previously. The third order interaction between the three protons was found to be insignificant, indicating that protonation of one site on glutamate has no effect on the interaction between the other two protonation sites. This further reinforces the premise that higher order terms, representing more complex interactions, are less likely to be significant than lower order terms. To allow correlation of the interaction values from glutamate with other organic acids, pairwise interaction values between protonation events were then calculated from known pKd values for a number of diprotic acids and bases. For simple straight chain acids and bases a linear log-log relationship was apparent between the number of intervening atoms between the protons and the pK(d,hh) (pKd of interaction). This relationship extended from three atoms (carbonate) up to 11 atoms (azelaic acid) and applied to both dicarboxylic acids and diamine bases. The pairwise interactions in glutamate also followed this simple relationship.

Acids↗

Interactions and associations between age and sex classes in mouflon sheep (Ovis gmelini) during winter.

The fact that sexual segregation can occur in wild ruminants independently of sex-related differences in habitat use suggests that it results at least partly from social mechanisms. One of the simplest mechanisms which can be hypothesised is that individuals avoid the congener classes which frequently try to interact with them (be these interactions 'agonistic' or 'sexual', since courtship behaviour components typically induce withdrawal when performed outside the rut). The aim of the present study was to test, in mouflon sheep (Ovis gmelini), whether the age-sex classes which exchange frequent interactions on meeting occur rarely inside the same groups. Observations were made during winter, on a small population in Germany. Interactions were recorded at an attractive site where all age-sex classes met daily. Foot transects were conducted in parallel over the whole study area in order to determine group composition. As expected, adults of different sexes exchanged frequent interactions at the attractive site and were rarely found in the same groups under free-ranging conditions, while adult females, who interacted little with one another, were quite frequently associated. However, adult males simultaneously exhibited the highest rate of interaction at the attractive site and the highest frequency of association under free-ranging conditions. Unlike female-female and male-female pairs, in which interactions with a clear initiator and a clear recipient predominated, male-male pairs exchanged often spectacular but 'symmetrical' interactions (during which the two individuals behaved in the same way). The hypothesis that sexual segregation results from the avoidance of the congener classes which frequently engage interactions only holds for females. Adult rams interact frequently and seek companions with whom symmetrical interactions can be performed.

Journal Article↗

Functional connectivity: studying nonlinear, delayed interactions between BOLD signals.

Correlation analysis has been widely used in the study of functional connectivity based on fMRI data. It assumes that the relevant information about the interactions of brain regions is reflected by a linear relationship between the values of two signals at the same time. However, this hypothesis has not been thoroughly investigated yet. In this work, we study in depth the information shared by BOLD signals of pairs of brain regions. In particular, we assess the amount of nonlinear and/or nonsynchronous interactions present in data. This is achieved by testing models reflecting linear, synchronous interactions against more general models, encompassing nonlinear, nonsynchronous interactions. Many factors influencing measured BOLD signals are critical for the study of connectivity, such as paradigm-induced BOLD responses, preprocessing, motion artifacts, and geometrical distortions. Interactions are also influenced by the proximity of brain regions. The influence of all these factors is taken into account and the nature of the interactions is studied using various experimental conditions such that the conclusions reached are robust with respect to variation of these factors. After defining nonlinear and/or nonsynchronous interaction models in the framework of general linear models, statistical tests are performed on different fMRI data sets to infer the nature of the interactions. Finally, a new connectivity metric is proposed which takes these inferences into account. We find that BOLD signal interactions are statistically more significant when taking into account the history of the distant signal, i.e., the signal from the interacting region, than when using a model of linear instantaneous interaction. Moreover, about 75% of the interactions are symmetric, as assessed with the proposed connectivity metric. The history-dependent part of the coupling between brain regions can explain a high percentage of the variance in the data sets studied. As these results are robust with respect to various confounding factors, this work suggests that models used to study the functional connectivity between brain areas should in general take the BOLD signal history into account.

Algorithms↗

Role of important hydrophobic amino acids in the interaction between the glucocorticoid receptor tau 1-core activation domain and target factors.

In this work, we determined how altered-function mutants affecting hydrophobic residues within the tau 1-core activation domain of the human glucocorticoid receptor (GR) influence its physical interaction with different target proteins of the transcriptional machinery. Screening of putative target proteins showed that the tau 1-core can interact with the C-terminal part of the CREB-binding protein (CBP). In addition, the previously identified interactions of the tau 1-core with the TATA-binding protein (TBP) and the Ada2 adaptor protein were localized to the C- and N-terminal regions of these proteins, respectively. A panel of mutations within the tau 1-core that either decrease or increase activation potential was used to probe the interaction of the tau 1-core domain with TBP, Ada2, and CBP. We found that the pattern of effects caused by the mutations was similar for each of the interactions and that the effects on binding generally reflected effects on gene activation potential. Thus, the predominant effect of the mutations appears to influence a property of the tau 1-core that is common to all three interactions, rather than properties that are differentially required by each of the target factor interactions, individually. Such a property could be the ability of the domain to adopt a folded conformation that is generally necessary for interaction with target factors. We have also shown that TBP, Ada2, and CBP can interact with both the tau 1-core and the GR ligand-binding domain, offering a possible mechanism for synergistic interaction between the tau 1-core and other receptor activation domains. However, other target proteins (e.g., RIP140, and SRC-1), which interact with the GR C terminus, did not show significant interactions with the tau 1-core under our conditions.

Amino Acid Sequence↗

Investigation of aromatic-backbone amide interactions in the model peptide acetyl-Phe-Gly-Gly-N-methyl amide using molecular dynamics simulations and protein database search.

Weakly polar interactions between the side-chain aromatic rings and hydrogens of backbone amides (Ar-HN) are found in unique conformational regions. To characterize these conformational regions and to elucidate factors that determine the conformation of the Ar-HN interactions, four 4-ns molecular dynamics simulations were performed using four different low-energy conformations obtained from simulated annealing and one extended conformation of the model tripeptide Ac-Phe-Gly-Gly-NH-CH(3) as starting structures. The Ar(i)-HN(i+1) interactions were 4 times more frequent than were Ar(i)-HN(i+2) interactions. Half of the conformations with Ar(i)-HN(i+2) interactions also contained an Ar(i)-HN(i+1) interaction. The solvent access surface area of the Phe side chain and of the amide groups of Phe1, Gly2, and Gly3 involved in Ar-HN interactions was significantly smaller than in residues not involved in such interactions. The number of hydrogen bonds between the solvent and Phe1, Gly2, and Gly3 amide groups was also lower in conformations with Ar-HN interactions. For each trajectory, structures that contained Ar(i)-HN(i), Ar(i)-HN(i+1), and Ar(i)-HN(i+2) interactions were clustered on the basis of similarity of selected torsion angles. Attraction energies between the aromatic ring and the backbone amide in representative conformations of the clusters ranged from -1.98 to -9.24 kJ mol(-1) when an Ar-HN interaction was present. The most representative conformations from the largest clusters matched well with the conformations from the Protein Data Bank of Phe-Gly-Gly protein fragments containing Ar-HN interactions.

Amides↗

Spectroscopic investigations of solvent effect on chiral interactions.

The spectrophotometric method was used to determine the mechanism of chiral interactions between a known chiral selector, tert-butyl carbamoylated quinine (t-BuCQN), and N-derivative amino acids (DNB-Leu). Results obtained on binding constants, free energy of binding (DeltaG), and difference in free energy of binding (DeltaDeltaG) values seem to suggest that there are three possible types of interactions between DNB-Leu and t-BuCQN: electrostatic interaction between the carboxylate group of the DNB-Leu and the ammonium group of the t-BuCQN, the donor-acceptor charge-transfer type of interaction between the (acceptor) aromatic group of the amino acid and the (donor) aromatic group of the t-BuCQN, and the hydrogen-bonding interaction between the amide group of the DNB-Leu and the carbonyl group of t-BuCQN. The strongest interaction will be observed if all of three interactions are in operation as in the case of DNB-Leu. The electrostatic interaction seems to play the dominant role in the interactions. While the charge-transfer interaction is relatively weaker, it seems, however, to be responsible for enantiomeric selectivity, namely, the closer the electron acceptor dinitrophenyl group is to the electron donor quinoline group, the higher is the enantiomeric selectivity. Specifically, in solvent with high polarity, both donor and acceptor are solvated by solvent molecules, thereby preventing them from being close. As a consequence, the interaction will be weaker and, hence, lower enantiomeric selectivity. Solvation will be less in less polar solvent which, in turn, leads to stronger interaction and higher enantiomeric selectivity.

Molecular Structure↗

Subject-by-formulation interaction in bioequivalence: conceptual and statistical issues. FDA Population/Individual Bioequivalence Working Group. Food and Drug Administration.

PURPOSE: The FDA has proposed replacing the current average bioequivalence criterion with population and individual bioequivalence criteria that consider variances in addition to the difference of averages. One of these variances in the individual bioequivalence criterion measures subject-by-formulation interaction, the extent to which the test-reference difference varies from person to person. This paper discusses conceptual and statistical issues raised in various publications and presentations with respect to the presence and estimation of such an interaction. METHODS: We focus on the importance of subject-by-formulation interaction, an understanding of what is a large interaction, and the assessment of the magnitude of this interaction in bioequivalence studies. Simulation studies, examples from the literature, and data from FDA files are used to demonstrate the magnitude of the interaction and its distribution under various conditions. RESULTS: The concept of a large interaction is tied to the concept of a large mean difference. We suggest that an interaction greater than 0.15 is a conservative criterion for a large interaction. Magnitudes of estimated interaction are affected by variability, sample size, and the selection of data sets that pass average bioequivalence. CONCLUSIONS: Examples of substantial interactions are beginning to appear. More data is needed before reaching definitive conclusions regarding the frequency and importance of observed interactions.

Chemistry, Pharmaceutical↗

A case study in designing speech interaction with a patient monitor.

OBJECTIVE: New developments in speech interaction technology warrant the assumption that some of the interaction problems at anesthesia workplaces can be solved using speech interaction. One application might be the documentation of the anesthetic procedure. METHOD: To investigate this hypothesis, a speech input system was developed for a commercially available patient monitor (Datex-Ohmeda AS/3 Anesthesia Monitor with Record-Keeper), which in addition to standard functions also facilitates the generation of the anesthesia record. The speech input system was based on the IBM ViaVoice speech recognition technology (version Millennium Pro). The speech input device was preliminarily tested by 5 anesthetists wearing surgical masks under laboratory conditions and through retrospectively documenting 4 to 5 anesthetic procedures (each 12 to 17 documentation entries) in a calm situation. The speech interactive documentation procedure was compared with the conventional keyboard documentation procedure. RESULTS: The test persons achieved an overall word recognition rate between 72% and 92.4%. Between 76.5% and 97.7% of the single word commands could be completed without any corrections. The same qualifier held for 58.5% to 86.3% of the two- and three-word commands. Despite high speech recognition error rates, almost all documentation entries (236 of 238) could be finished using speech interaction. Comparing both documentation techniques, speech interaction was said to be more intuitive and caused less frustration than the keyboard documentation procedure. However, speech interactive documentation was rated less controllable because of the high speech recognition error rates and bccause the auditive feedback dialogues took too long. CONCLUSIONS: Modern speech recognition tools are still not advanced enough to facilitate the design of applications with an almost natural speech interface and widespread user acceptance. Nevertheless, many tasks in anesthesia have the necessary characteristics to be optimally supported by speech interaction. In contrast to earlier approaches to speech-interactive anesthesia workplaces, successful application today depends on the question of design rather than solely on that of technology. Many of the constraints and drawbacks of current technology can be overcome through appropriate design measures. The goals must focus first on identifying task areas in intensive care where speech-interaction can yield real benefit in terms of work efficiency, and second on developing and evaluating an ergonomic design of speech interaction. The intended users seem to look forward to the incorporation of speech interaction at the workplace.

Anesthesiology↗

Self-presentation in everyday interactions: effects of target familiarity and gender composition.

This study examined people's self-presentation motives in unstructured, everyday social interaction as a function of participants' gender similarity to, and general familiarity with, the targets of their self-presentations. Participants maintained a variant of the Rochester Interaction Record for 1 week. For every interaction that lasted 10 min or more, they rated the degree to which they wanted to make each of 4 impressions (likable, competent, ethical, and attractive), how much they thought about the impressions others in the interaction formed of them, and how nervous they felt in the interaction. In general, participants' self-presentational motives were lower in interactions with highly familiar people of their own sex than they were either in interactions with less familiar people of their sex or in interactions with people of the other sex regardless of familiarity. When participants' interactions with only their 3 most familiar interactants were examined, self-presentational concerns decreased with familiarity in same-sex interactions but increased with familiarity in cross-sex interactions.

Analysis of Variance↗

Interactions between plant RING-H2 and plant-specific NAC (NAM/ATAF1/2/CUC2) proteins: RING-H2 molecular specificity and cellular localization.

Numerous, highly conserved RING-H2 domains are found in the model plant Arabidopsis thaliana (thale cress). To characterize potential RING-H2 protein interactions, the small RING-H2 protein RHA2a was used as bait in a yeast two-hybrid screen. RHA2a interacted with one of the plant-specific NAC [NAM ('no apical meristem'), ATAF1/2, CUC2 ('cup-shaped cotyledons 2')] transcription factors, here named ANAC (abscisic acid-responsive NAC). The core RING-H2 domain was sufficient for the interaction. The ability of 11 structurally diverse RING-H2 domains to interact with ANAC was then examined. Robust interaction was detected for three of the domains, suggesting multi-specificity for the interaction. The domains that interacted with ANAC contain a glutamic acid residue in a position corresponding to a proline in many RING-H2 domains. Conversion of this glutamic acid residue into proline in RHA2a decreased its ability to interact with ANAC, most likely by changing the interaction surface. This suggested that a short, divergent region in RING-H2 domains modulate interaction specificity. ANAC contains a degenerate bipartite nuclear localization signal (NLS), while RHG1a, also identified as an ANAC interaction partner, contains a basic NLS. Both signals localized beta-glucuronidase reporter fusions to the nucleus. N-terminally truncated RHA2a also directed nuclear localization, apparently dependent on basic amino acids in the RING-H2 domain. Nuclear co-localization of the RING-H2 proteins and ANAC may enable their interaction in vivo to regulate the activity of the ANAC transcription factor.

Amino Acid Sequence↗