A vesicle microrheometer for high-throughput viscosity measurements of lipid and polymer membranes

Viscosity is a key property of cell membranes that controls mobility of embedded proteins and membrane remodeling. Measuring it is challenging because existing approaches involve complex experimental designs and/or models, and the applicability of some is limited to specific systems and membrane compositions. As a result there is scarcity of systematic data and the reported values for membrane viscosity vary by orders of magnitude for the same system. Here, we show how viscosity of bilayer membranes can be easily obtained from the transient deformation of giant unilamellar vesicles. The approach enables a non-invasive, probe-independent and high-throughput measurement of the viscosity of bilayers made of lipids or polymers with a wide range of compositions and phase state. Using this novel method, we have collected a significant amount of data that provide insights into the relation between membrane viscosity, composition, and structure

Assessing membrane material properties from the response of giant unilamellar vesicles to electric fields

Knowledge of the material properties of membranes is crucial to understanding cell viability and physiology. A number of methods have been developed to probe membranes in vitro, utilizing the response of minimal biomimetic membrane models to an external perturbation. In this review, we focus on techniques employing giant unilamellar vesicles (GUVs), model membrane systems, often referred to as minimal artificial cells because of the potential they offer to mimick certain cellular features. When exposed to electric fields, GUV deformation, dynamic response and poration can be used to deduce properties such as bending rigidity, pore edge tension, membrane capacitance, surface shear viscosity, excess area and membrane stability. We present a succinct overview of these techniques, which require only simple instrumentation, available in many labs, as well as reasonably facile experimental implementation and analysis

Symposium: Can intellectual history be done otherwise?

Using Shahzad Bashir’s open-access publication A New Vision for Islamic Pasts and Futures as a baseline, this symposium debates whether and how intellectual history can be done otherwise. Mohamed ‘Arafa follows Bashir’s invitation to explore the potential of open-ended historiographies when he thinks about the viability of a flexible method to interpret Sharī͑a. Nader El-Bizri interrogates whether the assemblage of personal experiential accounts offered by Bashir can be framed within the discourse of intellectual history at all. Nauman Faizi reads Bashir’s approach as a radical attempt to open up hermeneutical possibilities. Lena Salaymeh suggests that modern aesthetics can contribute to neo-colonial distortions of the Islamic tradition, rather than offering alternatives to positivist historiography. Bashir proposes in his response that academics adopt generosity as an analytical gesture in their academic writing, a generosity that would enable different ways of being human in the world

2 and 3-dimensional Hamiltonians with Shape Invariance Symmetry

Via a special dimensional reduction, that is, Fourier transforming over one of the coordinates of Casimir operator of su(2) Lie algebra and 4-oscillator Hamiltonian, we have obtained 2 and 3 dimensional Hamiltonian with shape invariance symmetry. Using this symmetry we have obtained their eigenspectrum. In the mean time we show equivalence of shape invariance symmetry and Lie algebraic symmetry of these Hamiltonians.Comment: 24 Page