Research Article: Measuring science behind soap bubbles

Multiscale Modeling of Membrane Rearrangement, Drainage, and Rupture in Evolving Foams

Science 10 May 2013:
Vol. 340 no. 6133 pp. 720-724
DOI: 10.1126/science.1230623

Modeling the physics of foams and foamlike materials, such as soapy froths, fire retardants, and lightweight crash-absorbent structures, presents challenges, because of the vastly different time and space scales involved. By separating and coupling these disparate scales, we have designed a multiscale framework to model dry foam dynamics. This leads to a predictive and flexible computational methodology linking, with a few simplifying assumptions, foam drainage, rupture, and topological rearrangement, to coupled interface-fluid motion under surface tension, gravity, and incompressible fluid dynamics. Our computed results match theoretical analyses and experimentally observed physical effects, including thin-film drainage and interference, and are used to study bubble rupture cascades and macroscopic rearrangement. The developed multiscale model allows quantitative computation of complex foam evolution phenomena.

Synthesis and Self-assembly of Amphiphilic Homoglycopolypeptide

Vinita Dhaware †, Ashif. Y. Shaikh †, Mrityunjoy Kar†, Srinivas Hotha *‡, and Sayam Sen Gupta *†

^† Chemical Engineering Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008

^‡ Department of Chemistry, Indian Institute of Science Education & Research, Pune 411008, India

Langmuir, Article ASAP

DOI: 10.1021/la400144t

Publication Date (Web): April 11, 2013

The synthesis of the amphiphilic homoglycopolypeptide was carried out by a combination of NCA polymerization and click chemistry to yield a well-defined polypeptide having an amphiphilic carbohydrate on its side chain. The amphiphilicity of the carbohydrate was achieved by incorporation of an alkyl chain at the C-6 position of the carbohydrate thus also rendering the homoglycopolypeptide amphiphilic. The homoglycopolypeptide formed multimicellar aggregates in water above a critical concentration of 0.9 μM due to phase separation. The multimicellar aggregates were characterized by DLS, TEM, and AFM. It is proposed that hydrophobic interactions of the aliphatic chains at the 6-position of the sugar moieties drives the assembly of these rod-like homoglycopolypeptide into large spherical aggregates. These multimicellar aggregates encapsulate both hydrophilic as well as hydrophobic dye as was confirmed by confocal microscopy. Finally, amphiphilic random polypeptides containing 10% and 20% α-d-mannose in addition to glucose containing a hydrophobic alkyl chain at its 6 position were synthesized by our methodology, and these polymers were also found to assemble into spherical nanostructures. The spherical assemblies of amphiphilic random glycopolypeptides containing 10% and 20% mannose were found to be surface bioactive and were found to interact with the lectin Con-A.

Nanoscale Patterning of Membrane-Bound Proteins Formed through Curvature-Induced Partitioning of Phase-Specific Receptor Lipids

Maria O. Ogunyankin ‡, Dale L. Huber ¶, Darryl Y. Sasaki *§, and Marjorie L. Longo *‡

^‡ Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616, United States

^¶ Sandia National Laboratories, P.O. Box 5800 Albuquerque, New Mexico 87111, United States

^§ Sandia National Laboratories, P.O. Box 969, Livermore, California 94551, United States

Langmuir, Article ASAP

DOI: 10.1021/la401011d

Publication Date (Web): May 3, 2013

This work describes a technique for forming high-density arrays and patterns of membrane-bound proteins through binding to a curvature-organized compositional pattern of metal-chelating lipids (Cu²⁺-DOIDA or Cu²⁺-DSIDA). In this bottom-up approach, the underlying support is an e-beam formed, square lattice pattern of hemispheres. This curvature pattern sorts Cu²⁺-DOIDA to the 200 nm hemispherical lattice sites of a 600 nm × 600 nm unit cell in L_d - L_o phase separated lipid multibilayers. Binding of histidine-tagged green fluorescent protein (His-GFP) creates a high density array of His-GFP-bound pixels localized to the square lattice sites. In comparison, the negative pixel pattern is created by sorting Cu²⁺-DSIDA in L_d- L_β′ phase separated lipid multibilayers to the flat grid between the lattice sites followed by binding to His-GFP. Lattice defects in the His-GFP pattern lead to interesting features such as pattern circularity. We also observe defect-free arrays of His-GFP that demonstrate perfect arrays can be formed by this method suggesting the possibility of using this approach for the localization of various active molecules to form protein, DNA, or optically active molecular arrays.

Polymorph-Specific Kinetics and Thermodynamics of β-Amyloid Fibril Growth

Wei Qiang , Kevin Kelley , and Robert Tycko *

Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States

J. Am. Chem. Soc., 2013, 135 (18), pp 6860–6871

DOI: 10.1021/ja311963f

Publication Date (Web): April 22, 2013

Nanoscale Growth and Patterning of Inorganic Oxides Using DNA Nanostructure Templates

Sumedh P. Surwade †, Feng Zhou †, Bryan Wei ‡§,Wei Sun ‡§, Anna Powell †, Christina O’Donnell †,Peng Yin *‡§, and Haitao Liu *†

^† Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States

^‡ Wyss Institute for Biologically Inspired Engineering,Harvard University, Boston, Massachusetts 02115, United States

^§ Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, United States

J. Am. Chem. Soc., 2013, 135 (18), pp 6778–6781

DOI: 10.1021/ja401785h

Publication Date (Web): April 10, 2013

We describe a method to form custom-shaped inorganic oxide nanostructures by using DNA nanostructure templates. We show that a DNA nanostructure can modulate the rate of chemical vapor deposition of SiO₂ and TiO₂ with nanometer-scale spatial resolution. The resulting oxide nanostructure inherits its shape from the DNA template. This method generates both positive-tone and negative-tone patterns on a wide range of substrates and is compatible with conventional silicon nanofabrication processes. Our result opens the door to the use of DNA nanostructures as general-purpose templates for high-resolution nanofabrication.