The options for investigating solubilised G protein-coupled receptors (GPCRs) by biophysical techniques have long been hampered by their instability. A thermostabilised adenosine A2A receptor ...expressed in insect cells, purified in detergent and reconstituted into high-density lipoprotein (HDL) particles was immobilised onto a Surface Plasmon Resonance sensor chip. This allowed measurement of affinities and kinetics for A2A antagonists with affinities ranging from 50 pM to almost 2 μM. Compared with other formats, reproduction of affinities, and dissociation and association rate constants are good, reasonable and poor respectively, indicating stabilised receptors in HDL particles are useful for investigating specific aspects of GPCR-ligand interactions.
•We performed SPR experiments on a stabilised A2A receptor in lipid discs.•This allowed measurement of affinities and kinetics for nine A2A antagonists.•New approach to characterise interactions ...between small molecules and GPCRs.•GPCRs in rHDLs can be useful for ligands with low solubility and high logP.
The options for investigating solubilised G protein-coupled receptors (GPCRs) by biophysical techniques have long been hampered by their instability. A thermostabilised adenosine A2A receptor expressed in insect cells, purified in detergent and reconstituted into high-density lipoprotein (HDL) particles was immobilised onto a Surface Plasmon Resonance sensor chip. This allowed measurement of affinities and kinetics for A2A antagonists with affinities ranging from 50pM to almost 2μM. Compared with other formats, reproduction of affinities, and dissociation and association rate constants are good, reasonable and poor respectively, indicating stabilised receptors in HDL particles are useful for investigating specific aspects of GPCR-ligand interactions.
Growth and maturation impact the selection, development and progression of youth athletes. Individual differences in the growth and maturity may afford a performance advantage, clouding coaches and ...practitioners' perceptions regarding current ability and future potential. This may result in the exclusion of talented, yet less physically gifted athletes. Participants were 91 male (n = 47) and female (n = 44) elite British Junior tennis players, 8-17 years of age (12.5 ± 1.9 years). Height and body mass were measured and compared to growth charts; hand-wrist radiographs were taken. Skeletal age (SA) was estimated with the Fels method and contrasted to chronological age (CA). Mean height and body mass of individual players ranged between the 50th and 90th centiles for age and sex. Females were advanced in SA relative to CA (0.3-0.89 years.) from 8 years. Males were average to delayed in maturation from 8 to 12 years, but advanced in SA from 14 to 16 years (0.75-1.23 years). Individual differences in growth and maturation appear to contribute towards the selection of elite junior tennis players, with a bias towards males and females who are advanced in maturation and comparatively tall and heavy for their age. This has important implications for talent identification and development.
Cerium dioxide CeO2 (ceria) is an important material in catalysis and energy applications. The intrinsic Frenkel and Schottky defects can impact a wide range of material properties including the ...oxygen storage capacity, the redox cycle, and the ionic and thermal transport. Here, we study the impact of Frenkel and Schottky defects on the structural dynamics and thermal properties of ceria using density functional theory. The phonon contributions to the free energy are found to reduce the defect formation free energies at elevated temperature. The phonon dispersions of defective CeO2 show significant broadening of the main branches compared to stoichiometric ceria. Phonon modes associated with the defects are identifiable in the infrared spectra through characteristic shoulders on the main features of the stoichiometric fluorite structure. Finally, the presence of Frenkel and Schottky defects are also found to reduce the thermal conductivity by up to 88% compared to stoichiometric CeO2.
The cell-penetrating trans-activator of transcription (TAT) is a cationic peptide derived from human immunodeficiency virus-1. It has been used to facilitate macromolecule delivery to various cell ...types. This cationic peptide is capable of crossing the blood–brain barrier and therefore might be useful for enhancing the delivery of drugs that target brain tumors. Here we test the efficiency with which relatively small (20 nm) micelles can be delivered by an intra-arterial route specifically to gliomas. Utilizing the well-established method of flow-arrest intra-arterial injection we compared the degree of brain tumor deposition of cationic TAT-decorated micelles versus neutral micelles. Our in vivo and post-mortem analyses confirm glioma-specific deposition of both TAT-decorated and neutral micelles. Increased tumor deposition conferred by the positive charge on the TAT-decorated micelles was modest. Computational modeling suggested a decreased relevance of particle charge at the small sizes tested but not for larger particles. We conclude that continued optimization of micelles may represent a viable strategy for targeting brain tumors after intra-arterial injection. Particle size and charge are important to consider during the directed development of nanoparticles for intra-arterial delivery to brain tumors.
We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X-ray crystallography to reveal the binding mode of an ...antagonist series to the A
adenosine receptor (AR). Eight A
AR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A
AR were experimentally determined and investigated through a cycle of ligand-FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X-ray crystallography of the A
AR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A
AR, an emerging target in immuno-oncology.
Multi-aperture photometry of Comet 29P/Schwassmann-Wachmann 1 was conducted on Johnson-Cousins R-band observations spanning 2011 May 1-9 and 2012 June 6-July 3. The comet was observed in outburst on ...2011 May 3 and 2012 July 1, during which its brightness increased by 2.2 and 2.1 mag, respectively, as measured through a 10 arcsec aperture. Dust production before and after each outburst is calculated using the parameter Af rho, which is converted to a lower limit on the dust production rate based on dust models and derived nuclear properties from other studies. Both outbursts are accompanied by large increases in dust production, Af rho by a factor of ~6.5-7 and dust production rate by a factor of ~18-23. In addition, variations in the dust brightness profile of the coma are examined during the events. The profile is observed to steepen significantly at the beginning of each outburst and then slowly return to pre-outburst values, mirroring the behavior of Af rho. The start of an outbound "ripple" of dust in the profile might be observed as the comet returns to its pre-outburst state, although this cannot be confirmed. Using a simple model of the 2011 May 3 outburst, an estimated lower limit of (2.6 + or - 0.7) x 10 super(8) kg of dust was released during the event. If this is representative of a typical outburst of 29P, then it is estimated that outbursts account for a lower limit of 80 super(+20) sub(-30)% of the total material ejected by the comet per year.
To evaluate relationships among skeletal maturity, body size, and functional capacities of elite junior tennis players.
Participants were 88 elite British Junior tennis players (44 male; 44 female), ...8-16 years of age (12.4 } 1.9 years). Skeletal age estimated maturty. Anthropometry, grip strength, countermovement jump, squat jump, forehand agility, backhand agility, Yo-Yo, 5-m, 10-m and 20-m sprints were measured. Comparative analysis for each sex was performed, relating advanced maturers (Male: 15; Female: 29) to a combination of on-time and late maturers (Male: 29; Female: 31). ANCOVAs were used to determine absolute differences between male and female players and between the 2 maturity subgroups, with chronological age as the covariate.
Advanced maturity afforded male players advantages in absolute measures of grip strength, speed, upper and lower body power but not in acceleration, agility or aerobic endurance. Male players were significantly taller than females in the U13-U16 age group. Advanced maturity in female players afforded advantages in absolute measures of grip strength, agility and overhead power, but not in backhand agility, aerobic endurance or squat jump power.
It is important that talent identification protocols consider the maturity of youth athletes to more satisfactorily address athletic potential rather than transient physical capabilities.
The adenosine A
and A
receptors belong to the purinergic family of G protein-coupled receptors, and regulate diverse functions of the cardiovascular, respiratory, renal, inflammation, and CNS. ...Xanthines such as caffeine and theophylline are weak, non-selective antagonists of adenosine receptors. Here we report the structure of a thermostabilized human A
receptor at 3.3 Å resolution with PSB36, an A
-selective xanthine-based antagonist. This is compared with structures of the A
receptor with PSB36 (2.8 Å resolution), caffeine (2.1 Å), and theophylline (2.0 Å) to highlight features of ligand recognition which are common across xanthines. The structures of A
R and A
R were analyzed to identify the differences that are important selectivity determinants for xanthine ligands, and the role of T270
in A
R (M270
in A
R) in conferring selectivity was confirmed by mutagenesis. The structural differences confirmed to lead to selectivity can be utilized in the design of new subtype-selective A
R or A
R antagonists.
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