George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Microcontact printing & Self-assembled monolayer. The author has an hindex of 240, co-authored 1739 publications receiving 269833 citations. Previous affiliations of George M. Whitesides include University of California, Davis & University of Texas at Austin.

Microscopic patterning of orientated mesoscopic silica through guided growth

Abstract: The supramolecular assembly of surfactant molecules at a solid–liquid interface can produce tubular structures with diameters of around 10 nm (refs 1,2,3,4), which can be used for the templated polymerization of mesoporous silica thin films3,4,5. The orientation of the tubules depends primarily on the nature of the substrate–surfactant interaction. These nanostructured films hold much promise for applications such as their use as orientated nanowires6, sensor/actuator arrays7,8,9 and optoelectronic devices10. But a method of patterning the tubules and orientating them into designed arrangements is required for many of these possibilities to be realized. Here we describe a method that allows the direction of growth of these tubules to be guided by infiltrating a reaction fluid into the microcapillaries of a mould in contact with a substrate11. An electric field applied tangentially to the surface within the capillaries induces electro-osmotic flow, and also enhances the rates of silica polymerization around the tubules by localized Joule heating. After removal of the mould, patterned bundles of orientated nanotubules remain on the surface. This method permits the formation of orientated mesoporous channels on a non-conducting substrate with an arbitrary microscopic pattern.

Compatibility of mammalian cells on surfaces of poly(dimethylsiloxane).

Abstract: This paper describes the influence of the composition of poly(dimethylsiloxane) (PDMS) on the attachment and growth of several different types of mammalian cells: primary human umbilical artery endothelial cells (HUAECs), transformed 3T3 fibroblasts (3T3s), transformed osteoblast-like MC3T3-E1 cells, and HeLa (transformed epithelial) cells. Cells grew on PDMS having different ratios of base to curing agent: 10:1 (normal PDMS, PDMSN), 10:3 (PDMSCA), and 10:0.5 (PDMSB). They were also grown on “extracted PDMS” (normal PDMS that has reduced quantities of low molecular-weight oligomers, PDMSN,EX) and normal PDMS that had been extracted and then oxidized (PDMSN,EX,OX); all surfaces were exposed to a solution of fibronectin prior to cell attachment. Generally, fibronectin-coated PDMS is a suitable substrate for culturing mammalian cells. Compatibility of cells on some surfaces, however, was dependent on the cell type: PDMSN,EX,OX caused cell detachment of 3T3 fibroblasts and MC3T3-E1 cells, and PDMSCA caused...

Microcontact printing on surfaces and derivative articles

Abstract: Improved methods of forming a patterned self-assembled monolayer on a surface and derivative articles are provided. According to one method, an elastomeric stamp is deformed during and/or prior to using the stamp to print a self-assembled molecular monolayer on a surface. According to another method, during monolayer printing the surface is contacted with a liquid that is immiscible with the molecular monolayer-forming species to effect controlled reactive spreading of the monolayer on the surface. Methods of printing self-assembled molecular monolayers on nonplanar surfaces and derivative articles are provided, as are methods of etching surfaces patterned with self-assembled monolayers, including methods of etching silicon. Optical elements including flexible diffraction gratings, mirrors, and lenses are provided, as are methods for forming optical devices and other articles using lithographic molding. A method for controlling the shape of a liquid on the surface of an article is provided, involving applying the liquid to a self-assembled monolayer on the surface, and controlling the electrical potential of the surface.

Rate constants and equilibrium constants for thiol-disulfide interchange reactions involving oxidized glutathione

Abstract: The rate of reduction of oxidized glutathione (GSSG) to glutathione (GSH) by thiolate anions (RS-) follows a Br/nsted relation in pK"s of the conjugate thiols (RSH):pnu" - 0.5. This value is similar to that for reduction of Ellman's re- agent: 0nu" = 0.4-0.5. Analysis of a number of rate and equilibrium data, taken both from this work and from the literature. indicates that rate constants, k, for a range of thiolate-disulfide interchange reactions are correlated well by equations of the formlogk=C*0nu.p Kunu"*0"pK""*0re pKule(nuc=nucleo phile.c=central, andlg=leavinggro upsulfur):eq36-3 8 give representative values of the Br/nsted coefficients. The values of these Br/nsted coefficients are not sharply defined by the available experimental data. although eq 36-38 provide useful kinetic models for rates of thiolate-disulfide interchange reac- tions. The uncertainty in these parameters is such that their detailed mechanistic interpretation is not worthwhile. but their qualitative interpretation-that all three sulfur atoms experience a significant effective negative charge in the transition state, but that the charge is concentrated on the terminal sulfurs-is justified. Equilibrium constants for reduction oiCSSG using a,cr-dithiols have been measured. The reducing potential of the dithiol is strongly influenced by the size of the cyclic disulfide formed on its oxidation: the most strongly reducing dithiols are those which can form six-membered cyclic disulfides. Separate equilibrium constants for thiolateanion-di sulfide interchange (Ks-) and for thiol-disulfide interchange (KsH) have been esti- mated from literature data: Ks- is roughly proportionalto 2ApK. is the difference between the pKus of the two thiols involved in the interchange. The contributions of thiol pKu values to the observed equilibrium constants for reduction of GSSG with a,co-dithiols appear to be much smaller than those ascribable to the influence of structure on intramolecular ring forma- tion. These equilibrium and rate constants are helpful in choosing dithiols for use as antioxidants in solutions containing pro- teins: dithiothreitol (DTT), 1.3-dimercapto-2-propanol (DMP), and 2-mercaptoethanol have especially useful properties. 201 I

An Axisymmetric Flow‐Focusing Microfluidic Device

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I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Large-scale pattern growth of graphene films for stretchable transparent electrodes

Abstract: Problems associated with large-scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications. Recently, macroscopic-scale graphene films were prepared by two-dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides. However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of approximately 280 Omega per square, with approximately 80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm(2) V(-1) s(-1) and exhibit the half-integer quantum Hall effect, implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene. Employing the outstanding mechanical properties of graphene, we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics.

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.