45 research outputs found
Natively Unfolded Protein Stability as a Coil-to-Globule Transition in Charge/Hydropathy Space
Temperature Extrapolation of Henry’s Law Constants and the Isosteric Heat of Adsorption
Computational screening of adsorbent materials often
uses the Henry’s
law constant (KH) (at a particular temperature)
as a first discriminator metric due to its relative ease of calculation.
The isosteric heat of adsorption in the limit of zero pressure (qst∞) is often calculated along with the Henry’s law constant,
and both properties are informative metrics of adsorbent material
performance at low-pressure conditions. In this article, we introduce
a method for extrapolating KH as a function
of temperature, using series-expansion coefficients that are easily
computed at the same time as KH itself;
the extrapolation function also yields qst∞. The extrapolation
is highly accurate over a wide range of temperatures when the basis
temperature is sufficiently high, for a wide range of adsorbent materials
and adsorbate gases. Various results suggest that the extrapolation
is accurate when the extrapolation range in inverse-temperature space
is limited to |β – β0 | < 0.5 mol/kJ. Application of the extrapolation
to a large set of materials is shown to be successful provided that KH is not extremely large and/or the extrapolation
coefficients converge satisfactorily. The extrapolation is also able
to predict qst∞ for a system that shows an unusually
large temperature dependence. The work provides a robust method for
predicting KH and qst∞ over a
wide range of industrially relevant temperatures with minimal effort
beyond that necessary to compute those properties at a single temperature,
which facilitates the addition of practical operating (or processing)
conditions to computational screening exercises
Temperature Extrapolation of Henry’s Law Constants and the Isosteric Heat of Adsorption
Computational screening of adsorbent materials often
uses the Henry’s
law constant (KH) (at a particular temperature)
as a first discriminator metric due to its relative ease of calculation.
The isosteric heat of adsorption in the limit of zero pressure (qst∞) is often calculated along with the Henry’s law constant,
and both properties are informative metrics of adsorbent material
performance at low-pressure conditions. In this article, we introduce
a method for extrapolating KH as a function
of temperature, using series-expansion coefficients that are easily
computed at the same time as KH itself;
the extrapolation function also yields qst∞. The extrapolation
is highly accurate over a wide range of temperatures when the basis
temperature is sufficiently high, for a wide range of adsorbent materials
and adsorbate gases. Various results suggest that the extrapolation
is accurate when the extrapolation range in inverse-temperature space
is limited to |β – β0 | < 0.5 mol/kJ. Application of the extrapolation
to a large set of materials is shown to be successful provided that KH is not extremely large and/or the extrapolation
coefficients converge satisfactorily. The extrapolation is also able
to predict qst∞ for a system that shows an unusually
large temperature dependence. The work provides a robust method for
predicting KH and qst∞ over a
wide range of industrially relevant temperatures with minimal effort
beyond that necessary to compute those properties at a single temperature,
which facilitates the addition of practical operating (or processing)
conditions to computational screening exercises
Computational Study of the Stability of the Miniprotein Trp-Cage, the GB1 β‑Hairpin, and the AK16 Peptide, under Negative Pressure
Although hot, cold, and high pressure
denaturation are well characterized,
the possibility of negative pressure unfolding has received much less
attention. Proteins under negative pressure, however, are important
in applications such as medical ultrasound, and the survival of biopoloymers
in the xylem and adjacent parenchyma cells of vascular plants. In
addition, negative pressure unfolding is fundamentally important in
obtaining a complete understanding of protein stability and naturally
complements previous studies of high pressure denaturation. We use
extensive replica-exchange molecular dynamics (REMD) simulations and
thermodynamic analysis to obtain folding/unfolding equilibrium phase
diagrams for the miniprotein trp-cage (α-structure, 20-residue),
the GB1 β-hairpin (β-structure, 16-residue), and the AK16
peptide (α-helix, 16-residue). Although the trp-cage is destabilized
by negative pressure, the GB1 β-hairpin and AK16 peptide are
stabilized by this condition
Monte Carlo simulation of cylinders with short-range attractions
Cylindrical or rod-like particles are promising materials for the applications of fillers in nanocomposite materials and additives to control rheological properties of colloidal suspensions. Recent advances in particle synthesis allows for cylinders to be manufactured with short-ranged attractions to study the gelation as a function of packing fraction, aspect ratio and attraction strength. In order to aid in the analysis of small-angle scattering experiments of rod-like particles, computer simulation methods were used to model these particles with specialized Monte Carlo algorithms and tabular superquadric potentials. The attractive interaction between neighboring rods increases with the amount of locally-accessible surface area, thus leading to patchy-like interactions. We characterize the clustering and percolation of cylinders as the attractive interaction increases from the homogenous fluid at relatively low attraction strength, for a variety of aspect ratios and packing fractions. Comparisons with the experimental scattering results are also presented, which are in agreement