The role of free ions in reactions of olefins with soluble complex catalysts

2007 ◽  
Vol 16 (4) ◽  
pp. 2333-2339 ◽  
Author(s):  
F. S. Dyachkovskii ◽  
A. K. Shilova ◽  
A. E. Shilov
Keyword(s):  
Soluble Complex ◽  
Free Ions

scholarly journals The release of N-acetyl- and N-glycolloyl-neuraminic acid from soluble complex carbohydrates and erythrocytes by bacterial, viral and mammalian sialidases

1981 ◽  
Vol 197 (2) ◽  
pp. 293-299 ◽  
Author(s):  
A P Corfield ◽  
R W Veh ◽  
M Wember ◽  
J C Michalski ◽  
R Schauer
Keyword(s):  
Submandibular Gland ◽  
Human Liver ◽  
Soluble Complex ◽  
Ganglioside Gm3 ◽  
Acetylneuraminic Acid ◽  
Liver Lysosomes ◽  
Acid Release ◽  
Physiological Systems ◽  
Virus Influenza

A series of substrates, sialyl(2 leads to 6)GalNAc and ganglioside GM3, containing either N-acetylneuraminic acid (AcNeu) or N-glycolloylneuraminic acid (GcNeu), has been prepared. The trisaccharide GcNeu(2 leads to 3)lactose was preapred by ozonolysis of GcNeu-GM3, and the disaccharides AcNeu(2 leads to 6)GalNAc and GcNeu(2 leads to 6)GalNAc were isolated from bovine submandibular-gland mucin by alkali elimination. Sialidases from Newcastle-disease virus, fowl-plague virus, influenza virus A2, Clostridium perfringens, Vibrio cholerae, Arthrobacter ureafaciens and human liver lysosomes were studied with the above substrates and all showed poorer cleavage of GcNeu-containing substrates when compared with the corresponding AcNeu-containing compounds. This was reflected in the Km and Vmax. values of these sialidases. Differences between viral and bacterial sialidases could be detected on the basis of their kinetic constants and time curves of sialic acid release. Preferred release of AcNeu relative to GcNeu was also observed with bovine submandibular gland mucin and a mixture of human and porcine erythrocytes, macromolecular substrates containing both AcNeu and GcNeu. The significance of differential cleavage of AcNeu and GcNeu by sialidases is considered together with examples of the role of GcNeu in physiologicaL systems.

Structural and Functional Evidence on the Role of Sulfated Tyrosine Residues In Glycoprotein Ib Binding to α-Thrombin Exosites

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 326-326
Author(s):  
Alessandro Zarpellon ◽  
Reha Celikel ◽  
Richard McClintock ◽  
James R. Roberts ◽  
G. Loredana Mendolicchio ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Conflicts Of Interest ◽  
Crystal Packing ◽  
Binding Activity ◽  
Wild Type ◽  
Soluble Complex ◽  
Structural Explanation ◽  
Amino Terminal

Abstract Abstract 326 In spite of two known crystal structures, the mechanisms supporting the interaction between the amino terminal domain of glycoprotein (GP) Ibα (GPIb-N) and α-thrombin (FIIa) are still debated, and a controversial issue concerns the involvement of FIIa exosites I and II in binding. Competition for exosite I could influence processes important for hemostasis and thrombosis. Both known crystal structures show two independent contact interfaces between GPIb-N and bound FIIa in a conformation that involves each exosite interacting with a different GPIb-N molecule. This notwithstanding, a majority of investigators in the field has concluded that exosite II is solely required for FIIa binding to GPIb-N, suggesting that the interface with exosite I is the consequence of crystal packing. The goal of this work was to probe experimentally the role of FIIa exosites in GPIb-N binding. Human GPIb-N contains three Tyr residues (at positions 276, 278 and 279) that can undergo post-translational sulfation (sulfated Tyr = Tys), although this was not the case for Tyr278 in the known crystal structures. To address this discrepancy, we expressed GPIb-N in Drosophila cells - which endogenously contain a single tyrosylprotein sulfotransferase (TPST) gene - co-transfected with human TPST-2, and showed that we could obtain different GPIb-N species with 0 to 3 sulfate moles/protein moles. Using these different GPIb-N forms immobilized onto a surface plasmon resonance (SPR) chip, we determined that the kD of human FIIa binding decreased from 1290 to 89 nM going from 0 to 3 sulfate moles/protein moles. We crystallized the fully sulfated GPIb-N complexed with FIIa and found that Tys278 established contacts not previously seen with exosite II (residues Arg35 and Lys236), thus explaining the contribution of full sulfation to maximal binding efficiency. To establish the effect of TPST-2 on the process of sulfation, we compared the affinity of FIIa binding to distinct wild type GPIb-N species of known sulfate content with that to GPIb-N mutants containing distinct single, double or triple Tyr “Phe substitutions (Phe differs from Tyr for the lack of an OH group and cannot be sulfated) in which the identity of Tys residues could be established. We found that TPST-2 favors Tyr sulfation in the order 276–278-279, which is more efficient for a complete process than the order 276–279 predominant in the absence of TPST-2. We then used different Tyr "Phe (Y to F) mutants to evaluate the effects of the substitution preventing sulfation on FIIa binding to GPIb-N in solution or immobilized onto a SPR chip. We fount that the Y276F mutant had no capacity to form a soluble complex with FIIa, while Y279F could complex about as much FIIa as fully sulfated wild type GPIb-N (82 vs 99% FIIa incorporation). Of note, both Y276F and Y279F mutants had a complete to nearly complete loss of FIIa binding activity in the SPR system. In the crystal structure, the sulfate group on Tys279 establishes three close contacts (3.1, 3.3, 2.8 □) with Trp148 in a FIIa loop neighboring exosite I. On the other hand, Tys276 has closer contacts than Tys279 with residues in exosite II, suggesting that the latter may be sufficient for FIIa binding when GPIb-N is in solution but not immobilized onto a surface. To confirm this hypothesis, we used specific aptamer inhibitors of FIIa exosite II (HD22) or I (HD1) and found that the latter, similar to the Y279F substitution, indeed had no effect on FIIa-GPIb-N soluble complex formation (thus ruling out possible allosteric effects on exosite II influencing GPIb-N binding) but completely prevented FIIa binding to immobilized GPIb-N. Of note, as shown by crystallographic evidence, bound HD1 alters the orientation of Trp148 in manner that would oppose the interaction with Tys279 in GPIb-N, providing a structural explanation for the similar functional effects of the mutation and the inhibitor. Finally, we expressed transgenically wild type or Y279F mutant human GPIbα to replace the homologous chain in the GPIb-IX-V complex of murine platelets and showed that the mutation almost completely impairs FIIa binding to platelets, which is also prevented by inhibition of exosite I with HD1. These results provide functional evidence and a structural explanation for a key role of exosite I, concurrently with exosite II, for FIIa binding to GPIbα. Additional studies are now demonstrating that interfering with this interaction modifies responses to vascular injury in vivo. Disclosures: No relevant conflicts of interest to declare.

scholarly journals GAP45 Phosphorylation Controls Assembly of the Toxoplasma Myosin XIV Complex

2008 ◽  
Vol 8 (2) ◽  
pp. 190-196 ◽  
Author(s):  
Stacey D. Gilk ◽  
Elizabeth Gaskins ◽  
Gary E. Ward ◽  
Con J. M. Beckers
Keyword(s):  
Myosin Light Chain ◽  
Integral Membrane Protein ◽  
Soluble Complex ◽  
Inner Membrane ◽  
Motor Complex ◽  
Membrane Complex ◽  
Final Assembly ◽  
Parasite Survival ◽  
Inner Membrane Complex

ABSTRACT Toxoplasma gondii motility is powered by the myosin XIV motor complex, which consists of the myosin XIV heavy chain (MyoA), the myosin light chain (MLC1), GAP45, and GAP50, the membrane anchor of the complex. MyoA, MLC1, and GAP45 are initially assembled into a soluble complex, which then associates with GAP50, an integral membrane protein of the parasite inner membrane complex. While all proteins in the myosin XIV motor complex are essential for parasite survival, the specific role of GAP45 remains unclear. We demonstrate here that final assembly of the motor complex is controlled by phosphorylation of GAP45. This protein is phosphorylated on multiple residues, and by using mass spectroscopy, we have identified two of these, Ser163 and Ser167. The importance of these phosphorylation events was determined by mutation of Ser163 and Ser167 to Glu and Ala residues to mimic phosphorylated and nonphosphorylated residues, respectively. Mutation of Ser163 and Ser167 to either Ala or Glu residues does not affect targeting of GAP45 to the inner membrane complex or its association with MyoA and MLC1. Mutation of Ser163 and Ser167 to Ala residues also does not affect assembly of the mutant GAP45 protein into the myosin motor complex. Mutation of Ser163 and Ser167 to Glu residues, however, prevents association of the MyoA-MLC1-GAP45 complex with GAP50. These observations indicate that phosphorylation of Ser163 and Ser167 in GAP45 controls the final step in assembly of the myosin XIV motor complex.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor

Role of the allergist in diagnosis and management of patients with uveitis

JAMA ◽  
1966 ◽  
Vol 195 (3) ◽  
pp. 167-172 ◽  
Author(s):  
T. E. Van Metre
Keyword(s):  
Diagnosis And Management

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

Elaborating the role of reflection and individual differences in the study of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
Kevin Arceneaux
Keyword(s):  
Decision Making ◽  
Individual Differences ◽  
Cognitive Processes ◽  
Evolutionary History ◽  
Behavioral Responses ◽  
History Of ◽  
Economic Beliefs

AbstractIntuitions guide decision-making, and looking to the evolutionary history of humans illuminates why some behavioral responses are more intuitive than others. Yet a place remains for cognitive processes to second-guess intuitive responses – that is, to be reflective – and individual differences abound in automatic, intuitive processing as well.

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