PDZ7 of Glutamate Receptor Interacting Protein Binds to Its Target via a Novel Hydrophobic Surface Area

Abstract. Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ~236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min−1 or held at constant sub-zero temperatures. The time and temperature at which individual 10–50 μm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min−1, the median nucleation temperature of 10–40 μm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future.

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Disruption of Glutamate Receptor-Interacting Protein in Nucleus Accumbens Enhances Vulnerability to Cocaine Relapse

Neuropsychopharmacology ◽

10.1038/npp.2013.265 ◽

2013 ◽

Vol 39 (3) ◽

pp. 759-769 ◽

Cited By ~ 16

Author(s):

Lisa A Briand ◽

Blake A Kimmey ◽

Pavel I Ortinski ◽

Richard L Huganir ◽

R Christopher Pierce

Keyword(s):

Nucleus Accumbens ◽

Glutamate Receptor ◽

Interacting Protein

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Adsorption of unfolded Cu/Zn superoxide dismutase onto hydrophobic surfaces catalyzes its formation of amyloid fibrils

Protein Engineering Design and Selection ◽

10.1093/protein/gzz033 ◽

2019 ◽

Vol 32 (2) ◽

pp. 77-85

Author(s):

Mohammad Ashhar I Khan ◽

Ulrich Weininger ◽

Sven Kjellström ◽

Shashank Deep ◽

Mikael Akke

Keyword(s):

Superoxide Dismutase ◽

Surface Area ◽

Amyloid Fibrils ◽

Hydrophobic Surface ◽

Fibril Formation ◽

Hydrophobic Surfaces ◽

Molecular Features ◽

Denaturant Concentration

Abstract Intracellular aggregates of superoxide dismutase 1 (SOD1) are associated with amyotrophic lateral sclerosis. In vivo, aggregation occurs in a complex and dense molecular environment with chemically heterogeneous surfaces. To investigate how SOD1 fibril formation is affected by surfaces, we used an in vitro model system enabling us to vary the molecular features of both SOD1 and the surfaces, as well as the surface area. We compared fibril formation in hydrophilic and hydrophobic sample wells, as a function of denaturant concentration and extraneous hydrophobic surface area. In the presence of hydrophobic surfaces, SOD1 unfolding promotes fibril nucleation. By contrast, in the presence of hydrophilic surfaces, increasing denaturant concentration retards the onset of fibril formation. We conclude that the mechanism of fibril formation depends on the surrounding surfaces and that the nucleating species might correspond to different conformational states of SOD1 depending on the nature of these surfaces.

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