Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sequence and structure of a second human kappa 1 immunoglobulin light-chain variable domain, Wat, has been determined. The R-factor is 15.7% for 1.9-A data. One hundred and ninety-five water molecules were identified; 30 water molecules were located in identical positions in each of the monomers. Some of the water molecules are integral parts of the domains. This light chain is encoded by the same variable domain gene that encoded the previously characterized kappa I variable domain, Rei. Due to limited somatic mutation, the two highly homologous proteins differ in only 20 of the 108 residues. Wat crystallized in space group P6(4) while Rei crystallized in space group P6(1); in both crystals, the asymmetric unit was the noncovalent dimer. Although the basic domain structure is the same for both proteins, the relative positions of the domains within the two dimers differ. This difference is most likely accounted for by the replacement of Tyr36 in Rei by Phe in the Wat protein. Residue Tyr36 is part of the hydrogen-bonding network in the interface between the domains in Rei. Losing the hydrogen-bonding capability of residue 36 by replacement of Tyr by Phe alters the network of hydrogen bonds between the domains, resulting in a different domain-domain contact. The details of lattice contacts in the two crystals were compared. One type of contact that extends the beta-sheet of the individual domains was conserved, but because it involved different symmetry elements within the crystal, different crystal packing resulted. In the Wat crystal, one of the contacts shows an example of how a symmetrical binding site can "bind" an asymmetrical object. Further, the examination of the Wat crystal also illustrates how the different crystalline environments of the domains of the dimer results in different distributions of temperature factors for the residues within the domains.
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PMID:Comparison of crystal structures of two homologous proteins: structural origin of altered domain interactions in immunoglobulin light-chain dimers. 799 11

The kinetics of water vapor absorption-desorption was studied in the porcine stratum corneum (sc) at 25 degrees C. Dry sc samples were exposed to several relative humidities followed by exposure to dry air, and the change in weight was monitored over time by use of a thermal gravimetric analysis technique. Diffusion coefficients were estimated by simulation and data fit optimization to modifications of the non-steady-state solution of Fick's law. Very good fits of experimental data to theoretical equations were obtained. The stratum corneum-water absorption isotherm was characterized by a linear increase from the origin, extending to about 55% relative humidity (10% water gain), followed by an upward curve where water gain increased further by increasing relative humidity. Water absorption and water desorption in the porcine sc were asymmetrical processes, desorption being the slower one. Water diffusivity for the absorption process was related to sc water content in two phases. In the first (water gain < 9%) diffusion coefficients increased as water concentration increased. In the second (water gain > 9%) diffusion coefficients were independent of water concentration, equal to 1.17 x 10(-10) cm2/s. Water diffusivity in the desorption phase was shown to decrease linearly as sc water content decreased. Analysis of the absorption isotherm and of the derived diffusion coefficients suggested at least two forms of water associated with the sc. The first, termed "firmly bound water" and characterized by low diffusion coefficients, was most apparent with dry sc and with a sc water gain of up to 10%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Kinetics of water vapor sorption in porcine stratum corneum. 807 23

In the present study, we investigated taste-taste, taste-vehicle, and simultaneous taste-vehicle-taste mixtures. Subjects made estimates of the sweetness and bitterness of 27 stimuli. Sucrose (292, 585, and 1170 mM), caffeine (13, 26, and 52 mM), and binary mixtures of low (292-13 mM), middle (585-26 mM), and high (1170-52 mM) levels of both components were dispersed in water, carboxymethylcellulose (CMC) 1% w/v, and gelatin 6% w/v. The sweetness and bitterness of the sucrose-vehicle-caffeine combinations were significantly weaker than the respective sucrose-vehicle and caffeine-vehicle combinations. The emerged mutual suppressive effects were asymmetrical and persisted when both tastants were presented in CMC and gelatin. Moreover, the increase in vehicle consistency and the simultaneous addition of another taste reduced the perceived intensity of a taste either presented alone or dissolved in water. For both sweetness and bitterness, the total taste suppression observed was always significant.
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PMID:Perception of sweetness and bitterness in different vehicles. 813 44

Stratum corneum lipid morphology was evaluated using attenuated total reflectance infrared spectroscopy (ATR-IR) in normal skin and surfactant-induced scaly skin to evaluate skin barrier function. To evaluate the degree of order of the intercellular lipid alkyl chain conformation, we measured the wavenumbers (frequency shifts) of the symmetrical and asymmetrical C-H stretching vibrations observed at approximately 2850 cm-1 and 2920 cm-1, respectively. There was a correlation between the wave-number and transepidermal water loss in normal skin. However, no difference was observed in surfactant-induced scaly skin from the baseline value in the wavenumbers of the C-H vibrations. These results suggest that in normal skin, lipid morphology plays an important role in the barrier function of the stratum corneum. However, the decline in barrier function in scaly skin is not due to conformational disorder of the lipid alkyl chain.
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PMID:Stratum corneum lipid morphology and transepidermal water loss in normal skin and surfactant-induced scaly skin. 814 11

To explore the quantitative significance of passive water flow through tight junctions of leaky epithelia, transepithelial water flow rates were measured in Necturus gallbladder mounted in chambers. Osmotic flows generated by raffinose gradients were asymmetrical with the greater flow in the mucosal-to-serosal direction. In tissue fixed in situ, intercellular spaces were dilated during mucosal-to-serosal flow and closed during serosal-to-mucosal flow. Tight junctions were focally separated (blistered), which correlated with the magnitude of mucosal-to-serosal flow. Blisters were not observed during serosal-to-mucosal flow or in nontransporting gallbladders. In freeze-fracture replicas, blisters appeared as pockets between intramembranous strands. Protamine, which decreases electrical conductance and increases depth and complexity of the tight junction, reduced osmotic water flow by approximately 30% in the mucosal-to-serosal direction (100 mosmol/kg gradient) without altering serosal-to-mucosal flow. We suggest that in the steady state, at least 30% of osmotically driven water passes transjunctionally in the mucosal-to-serosal direction, but flow is transcellular in the serosal-to-mucosal direction. Directionally divergent pathways may account for flow asymmetry.
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PMID:Osmotic water flow pathways across Necturus gallbladder: role of the tight junction. 817 7

The different patterns of enzymatic cleavage of diadenosine polyphosphates, ApnAs, where n = 3-5, have been established by fast atom bombardment mass spectrometry, FAB MS, of the nucleotide products formed in the presence of H2(18)O. The three specific pyrophosphohydrolases, Ap3A hydrolase (EC 3.6.1.29) and (asymmetrical) Ap4A hydrolase (EC 3.6.1.17) from lupin and the (symmetrical) Ap4A hydrolase (EC 3.6.1.41) from Escherichia coli, manifest three different regiospecificities. The Ap3A hydrolase cleaves all four substrates tested, Ap3A, Ap4A, ApCH2ppA, and ApCHFppA, to give [18O]AMP and the corresponding unlabeled adenosine nucleotide. In each case, the enzyme cleaves at the phosphate proximate to the bound adenosine moiety. The (asymmetrical) Ap4A hydrolase cleaves both Ap4A and Ap5A to give unlabeled ATP plus [18O]AMP and [18O]ADP, respectively, and is thus seen to add water at the fourth phosphate from the bound adenosine moiety. Lastly, the (symmetrical) Ap4A hydrolase from E. coli gives beta-[18O]ADP from Ap3A, Ap4A, and Ap5A along with the unlabeled nucleotide coproducts. In addition, with Ap4A alpha S (ApspppA) as substrate for the bacterial enzyme, the products are beta-[18O]ADP and unlabeled ADP alpha S. This symmetrical enzyme is thus characterized as cleaving the polyphosphate chain at the second phosphate from the bound adenosine moiety.
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PMID:Regiospecificity of the hydrolysis of diadenosine polyphosphates catalyzed by three specific pyrophosphohydrolases. 828 47

The effect of energy resolution in detector systems on scatter fractions in scintigraphic imaging through Monte Carlo simulation is investigated. A 10-cm Tc-99m line source within a cylindrical water phantom 20 cm in diameter and 20 cm in length was modeled and energy spectra were calculated at three different line source positions. The energy resolution was changed from 8% to 16% FWHM at 140 keV and a symmetrical energy window width was varied from 8% to 23% on the photopeak of 140 keV in energy spectra corresponding to each energy resolution. The relationship between the scatter fraction and the symmetrical energy window width, and the relationship between the scatter fraction and the primary counts were presented for all energy resolutions investigated. Furthermore, the effect of the asymmetrical energy window on reducing the scatter fraction was also studied and compared with the narrow symmetrical energy window. The results quantitatively showed that improved energy resolution can considerably decrease the scatter fraction with a narrow symmetrical energy window or an asymmetrical energy window without significant primary count-loss compared to that obtained with lower quality energy resolution. The asymmetrical energy window could reduce scatter fraction as compared with the narrow symmetrical energy window when the same number of primary counts was required for both energy windows. Knowing the relationship between the scatter fraction and the primary counts is important in scintigraphic imaging to select the optimum energy window corresponding to the energy resolution.
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PMID:Effect of energy resolution on scatter fraction in scintigraphic imaging: Monte Carlo study. 841 19

We have semi-synthesized 52 molecular species of saturated diacyl mixed-chain phosphatidylcholines. All 52 phosphatidylcholine molecules are highly asymmetrical with delta C/CL values in the range of 0.43-0.63. The aqueous dispersions of these phosphatidylcholines have been studied by the high-resolution differential scanning calorimetric (DSC) technique. Upon heating, the lipid dispersions prepared individually from these 52 phosphatidylcholines all exhibit a sharp, single, endothermic peak at a characteristic temperature or Tm, implying that the self-assembled lipid molecules in excess water undergo the mixed interdigitated gel to the liquid-crystalline phase transition. The Tm values obtained from aqueous lipid dispersions prepared from these mixed-chain phospholipids have been analyzed based on the molecular packing model of the mixed interdigitated bilayer, and a linear relationship between the Tm and (delta C)-1 for various phospholipids at a constant value of delta is observed. Based on these linear relationships, empirical equations are derived to predict the Tm values for highly asymmetrical mixed-chain phosphatidylcholines with delta C/CL values in the range of 0.43-0.63. The predictive power of these empirical equations is shown to be very good, since a comparison between the predicted and the experimental data indicates that the largest relative error in Kelvin is only 0.4%. A table containing 81 predicted Tm values for highly asymmetrical mixed-chain phosphatidylcholines is presented. The definitions of the various structural parameters such as delta C, CL, delta C/CL and delta are given in the text.
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PMID:Calorimetric studies of fully hydrated phosphatidylcholines with highly asymmetric acyl chains. 843 63

The ethanol-like discriminative stimulus effects of N-methyl-D-aspartate (NMDA) antagonists that act at the NMDA recognition site [(D)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid (CPPene) and cis-4-phosphonomethyl-2-piperidine carboxylic acid] or within the NMDA associated cation channel [phencyclidine (PCP) and dizocilpine] were evaluated in rats trained to discriminate ethanol or PCP from vehicle in a two-lever discrimination procedure. Three groups of rats were trained to discriminate 1.0, 1.5 or 2.0 g/kg of ethanol from water and one group was trained to discriminate 1.5 mg/kg of PCP from saline. In the ethanol-trained groups, both PCP (1.0-5.6 mg/kg; i.p.) and dizocilpine (0.03-0.3 mg/kg; i.p.) completely substituted for ethanol in every rat tested, although the dizocilpine resulted in only partial substitution in rats trained to discriminate 1.0 g/kg of ethanol. As the training dose of ethanol increased, the potency of PCP and dizocilpine to substitute for ethanol increased. In contrast, CPPene (1-17 mg/kg; i.p.) and cis-4-phosphonomethyl-2-piperidine carboxylic acid (5.6-17 mg/kg; i.p.) resulted in partial substitution for ethanol, with lower amounts of ethanol-appropriate responding as the training dose of ethanol increased. These data indicate that uncompetitive antagonism of NMDA neurotransmission at sites within the cation channel produce discriminative stimulus effects that are similar to those of ethanol, particularly to higher ethanol doses. Neither ethanol (0.5-1.5 g/kg; i.p.) nor CPPene (5.6 and 10 mg/kg) completely substituted for the discriminative effects of PCP. The asymmetrical generalizations between ethanol and PCP are discussed in terms of the mixed discriminative effects of ethanol.
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PMID:Discriminative stimulus effects of ethanol: effect of training dose on the substitution of N-methyl-D-aspartate antagonists. 845 Apr 61

To obtain a molecular basis for the similarities and dissimilarities in the functional, chemical, and biochemical properties between beta-casein and the other caseins, a predicted three-dimensional model is presented. The predicted structure was assembled using molecular modeling techniques, as well as secondary structural prediction algorithms, in conjunction with global secondary structural information from Raman spectroscopy. To add validity to this model, the structure was refined using energy minimization techniques to diminish the likelihood of structural overlaps and energetically unfavorable van der Waals contacts arising from the large number of proline residues present in the beta-casein sequence. The refined model overall showed a loosely packed, asymmetrical structure with an axial ratio of 2:1. Hydrophobic side chains were uniformly dispersed over one end (C terminal) and the center surface of the structure; the other end (N terminal) was hydrophilic. The hydrophobic section also possessed a large loop through which water could easily travel. Such a suprasurfactant structure could account for the micellar type of hydrophobically driven self-association exhibited by beta-casein. Other chemical and biochemical data are in good agreement with the refined structure.
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PMID:Three-dimensional molecular modeling of bovine caseins: an energy-minimized beta-casein structure. 848 44


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