Statistical-thermodynamic model for light scattering from eye lens protein mixtures

Bell, Michael M.; Ross, David S.; Bautista, Maurino P.; Shahmohamad, Hossein; Langner, Andreas; Hamilton, J. F.; Lahnovych, Carrie N.; Thurston, George M.

doi:10.1063/1.4974155

Cited by 5 publications

(3 citation statements)

References 68 publications

(182 reference statements)

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“…23 Interestingly, K D values in the range of tens of mM correspond to protein concentrations at half-saturation comparable to the total protein in the nucleus of the lens, and therefore may play a significant role in maintaining a spatial organization with high packing density with short-range order that ensures transparency while avoiding crystallization, aggregation, and liquid–liquid phase separation. 15,52,54,61 In fact, it has been calculated that interaction energies as low as −1.3 kJ/mol between α- and γ-crystallin can already impact lens transparency significantly. 15…”

Section: Resultsmentioning

confidence: 99%

Measuring Ultra-Weak Protein Self-Association by Non-ideal Sedimentation Velocity

et al. 2019

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Ultra-weak self-association can govern the macroscopic solution behavior of concentrated macromolecular solutions ranging from food products to pharmaceutical formulations and the cytosol. For example, it can promote dynamic assembly of multi-protein signaling complexes, lead to intracellular liquid–liquid phase transitions, and seed crystallization or pathological aggregates. Unfortunately, weak self-association is technically extremely difficult to study, as it requires very high protein concentrations where short intermolecular distances cause strongly correlated particle motion. Additionally, protein samples near their solubility limit in vitro frequently show some degree of polydispersity. Here we exploit the strong mass-dependent separation of assemblies in the centrifugal field to study ultra-weak binding, using a sedimentation velocity technique that allows us to determine particle size distributions while accounting for colloidal hydrodynamic interactions and thermodynamic non-ideality (Chaturvedi, S. K.; et al. Nat. Commun.2018, 9, 4415; DOI: 10.1038/s41467-018-06902-x). We show that this approach, applied to self-associating proteins, can reveal a time-average association state for rapidly reversible self-associations from which the free energy of binding can be derived. The method is label-free and allows studying mid-sized proteins at millimolar protein concentrations in a wide range of solution conditions. We examine the performance of this method with hen egg lysozyme as a model system, reproducing its well-known ionic-strength-dependent weak self-association. The application to chicken γS-crystallin reveals weak monomer–dimer self-association with KD = 24 mM, corresponding to a standard free energy change of approximately −9 kJ/mol, which is a large contribution to the delicate balance of forces ensuring eye lens transparency.

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Section: Resultsmentioning

confidence: 99%

Measuring Ultra-Weak Protein Self-Association by Non-ideal Sedimentation Velocity

et al. 2019

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“…The relative population of oligomers and monomers is determined from the equilibrium condition where ρ i and γ i are the density and activity coefficient for component i , respectively, where 1 denotes monomer and n denotes an oligomer with n monomer units. The activity coefficients, which include the nonidealities arising from the adhesive hard-sphere interactions, are calculated using a virial equation of state with analytical expressions for the second and third virial coefficients . The structure factor is calculated using the analytical solution for the binary mixture of sticky hard sphres obtained with the Percus–Yevick approximation .…”

Section: Methodsmentioning

confidence: 99%

Cluster Percolation Causes Shear Thinning Behavior in Concentrated Solutions of Monoclonal Antibodies

et al. 2021

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High-concentration (>100 g/L) solutions of monoclonal antibodies (mAbs) are typically characterized by anomalously large solution viscosity and shear thinning behavior for strain rates ≥10 3 s −1 . Here, the link between protein−protein interactions (PPIs) and the rheology of concentrated solutions of COE-03 and COE-19 mAbs is studied by means of static and dynamic light scattering and microfluidic rheometry. By comparing the experimental data with predictions based on the Baxter sticky hard-sphere model, we surprisingly find a connection between the observed shear thinning and the predicted percolation threshold. The longest shear relaxation time of mAbs was much larger than that of model sticky hard spheres within the same region of the phase diagram, which is attributed to the anisotropy of the mAb PPIs. Our results suggest that not only the strength but also the patchiness of short-range attractive PPIs should be explicitly accounted for by theoretical approaches aimed at predicting the shear rate-dependent viscosity of dense mAb solutions.

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“…Those studies used morphological and biochemical knowledge about the eye media. Important further studies are from the groups of Benedek and Thurston, 3,4 Bettelheim, 5,6 Tardieu and Delaye, 7 McCally and Farrell, 8 and Meek. 9,10 The relationship with functional in vivo straylight measurements was not made.…”

Section: Slit Lamp Image and Rayleigh Scattermentioning

confidence: 99%

Intraocular light scatter, reflections, fluorescence and absorption: what we see in the slit lamp

Berg

2017

Ophthalmic Physiologic Optic

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Purpose: Much knowledge has been collected over the past 20 years about light scattering in the eye-in particular in the eye lens-and its visual effect, called straylight. It is the purpose of this review to discuss how these insights can be applied to understanding the slit lamp image. Results: The slit lamp image mainly results from back scattering, whereas the effects on vision result mainly from forward scatter. Forward scatter originates from particles of about wavelength size distributed throughout the lens. Most of the slit lamp image originates from small particle scatter (Rayleigh scatter). For a population of middle aged lenses it will be shown that both these scatter components remove around 10% of the light from the direct beam. For slit lamp observation close to the reflection angles, zones of discontinuity (Wasserspalten) at anterior and posterior parts of the lens show up as rough surface reflections. All these light scatter effects increase with age, but the correlations with age, and also between the different components, are weak. For retro-illumination imaging it will be argued that the density or opacity seen in areas of cortical or posterior subcapsular cataract show up because of light scattering, not because of light loss. Notes: (1) Light scatter must not be confused with aberrations. Light penetrating the eye is divided into two parts: a relatively small part is scattered, and removed from the direct beam. Most of the light is not scattered, but continues as the direct beam. This non-scattered part is the basis for functional imaging, but its quality is under the control of aberrations. Aberrations deflect light mainly over small angles (<1°), whereas light scatter is important because of the straylight effects over large angles (>1°), causing problems like glare and hazy vision. (2) The slit lamp image in older lenses and nuclear cataract is strongly influenced by absorption. However, this effect is greatly exaggerated by the light path lengths concerned. This obviates proper judgement of the functional importance of absorption, and hinders the appreciation of the Rayleigh nature of what is seen in the slit lamp image.

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Statistical-thermodynamic model for light scattering from eye lens protein mixtures

Cited by 5 publications

References 68 publications

Measuring Ultra-Weak Protein Self-Association by Non-ideal Sedimentation Velocity

Measuring Ultra-Weak Protein Self-Association by Non-ideal Sedimentation Velocity

Cluster Percolation Causes Shear Thinning Behavior in Concentrated Solutions of Monoclonal Antibodies

Intraocular light scatter, reflections, fluorescence and absorption: what we see in the slit lamp

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