Influence of heteroatom donors on the orders of relative gas-phase binding affinities of macrocyclic polyethers

1994 ◽  
Vol 18 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Hui-Fen Wu ◽  
Jennifer S. Brodbelt
Keyword(s):  
Gas Phase ◽  
Binding Affinities ◽  
Macrocyclic Polyethers

Rapid Evaluation of Suitable Substrates with High Affinity to Artificial Caffeine Receptors by MS Based Techniques

2005 ◽  
Vol 60 (10) ◽  
pp. 1077-1082 ◽  
Author(s):  
Daniela Mirk ◽  
Heinrich Luftmann ◽  
Siegfried R. Waldvogel
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Collision Induced Dissociation ◽  
Rapid Evaluation ◽  
Tandem Mass ◽  
Binding Affinities ◽  
Electrospray Tandem Mass Spectrometry ◽  
Relative Stabilities ◽  
Receptor Complexes ◽  
High Affinity

A modification of our triphenylene ketal based receptor facilitates electrospray tandem mass spectrometry investigations. Binding affinities of eleven potential substrates, e.g. caffeine and other xanthine alkaloids, are probed in the gas phase with collision induced dissociation. The relative stabilities of the substrate-receptor complexes are rapidly determined and the findings are correlated with the corresponding results in solution.

Exploring halide anion affinities to native cyclodextrins by mass spectrometry and molecular modelling

2017 ◽  
Vol 24 (3) ◽  
pp. 269-278 ◽  
Author(s):  
Chongsheng Xu ◽  
Nan He ◽  
Zhenhua Li ◽  
Yanqiu Chu ◽  
Chuan-Fan Ding
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Binding Constants ◽  
Density Functional Theory Calculations ◽  
Collision Induced Dissociation ◽  
Binding Affinities ◽  
Cyclodextrin Complex ◽  
Halide Anion ◽  
Mass Frame ◽  
The Stability

The binding affinities of cyclodextrins complexation with chlorine (Cl−), bromine (Br−) and iodine (I−), were measured by mass spectrometric titrimetry, and the fitting of the binding constants was based on the concentration measurement of the cyclodextrin equilibrium. The binding constants (lg Ka) for α-, β- or γ-cyclodextrin with Cl− were 3.99, 4.03 and 4.11, respectively. The gas-phase binding affinity of halide anions for native cyclodextrins was probed by collision-induced dissociation. In collision-induced dissociation, the centre-of-mass frame energy results revealed that in the gas phase, for the same type of cyclodextrin, the stability of the complexes decreased in order: Cl > Br > I, and for the same halide anion, the binding stability of the complex with α-, β- or γ-cyclodextrin decreased in the order: γ-cyclodextrin >β-cyclodextrin > α-cyclodextrin. The density functional theory calculations showed that halide anion binding on the primary face had a lower energy than the secondary face and hydrogen bonding was the main driving force for complex formation. The higher stability of the γ-cyclodextrin complex with the Cl anion can be attributed to the higher charge density of the Cl anion and better flexibility of γ-cyclodextrin.

Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

1968 ◽  
Vol 26 ◽  
pp. 292-293
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman ◽  
Peter L. Ramos
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Gas Phase ◽  
Absolute Temperature ◽  
Residual Gas ◽  
Gas Reactions ◽  
Image Position ◽  
The Right ◽  
Water Gas ◽  
Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

1996 ◽  
Vol 54 ◽  
pp. 154-155
Author(s):  
E. G. Rightor
Keyword(s):  
Excited State ◽  
Polymer Blends ◽  
Gas Phase ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Electronic States ◽  
Core Electron ◽  
Bulk Solids ◽  
Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

Specificity determinants of phosphoprotein phosphatases controlling kinetochore functions

2020 ◽  
Vol 64 (2) ◽  
pp. 325-336 ◽  
Author(s):  
Dimitriya H. Garvanska ◽  
Jakob Nilsson
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Activity Level ◽  
Phosphorylation Sites ◽  
Binding Affinities ◽  
Mitotic Kinases ◽  
Anaphase Onset ◽  
Phosphoprotein Phosphatases ◽  
Linear Motifs ◽  
Temporal And Spatial ◽  
Kinetochore Function

Abstract Kinetochores are instrumental for accurate chromosome segregation by binding to microtubules in order to move chromosomes and by delaying anaphase onset through the spindle assembly checkpoint (SAC). Dynamic phosphorylation of kinetochore components is key to control these activities and is tightly regulated by temporal and spatial recruitment of kinases and phosphoprotein phosphatases (PPPs). Here we focus on PP1, PP2A-B56 and PP2A-B55, three PPPs that are important regulators of mitosis. Despite the fact that these PPPs share a very similar active site, they target unique ser/thr phosphorylation sites to control kinetochore function. Specificity is in part achieved by PPPs binding to short linear motifs (SLiMs) that guide their substrate specificity. SLiMs bind to conserved pockets on PPPs and are degenerate in nature, giving rise to a range of binding affinities. These SLiMs control the assembly of numerous substrate specifying complexes and their position and binding strength allow PPPs to target specific phosphorylation sites. In addition, the activity of PPPs is regulated by mitotic kinases and inhibitors, either directly at the activity level or through affecting PPP–SLiM interactions. Here, we discuss recent progress in understanding the regulation of PPP specificity and activity and how this controls kinetochore biology.

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