George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Monolayer & 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.

Determination of binding constants of ligands to proteins by affinity capillary electrophoresis: compensation for electroosmotic flow.

Abstract: This paper describes the estimation of binding constants (Kb) between carbonic anhydrase B (CAB, EC 4.2.1.1, from bovine erythrocytes) and charged benzenesulfonamides by affinity capillary electrophoresis (ACE) under conditions in which the migration time is affected by changes in electroosmotic flow and by nonspecific interactions accompanying changes in the concentration of ligand. Comparisons of values of migration times of the protein of interest, and of "noninteracting" marker proteins, with those of a neutral internal standard provide the basis for corrections for variable electroosmotic flow; these corrections make possible the estimation of Kb and its uncertainty even in the presence of substantial variations in electroosmotic flow.

Unconventional Methods for Fabricating and Patterning Nanostructures

Abstract: 4.1. Nanomachining with Scanning Probes 1831 4.2. Soft Lithography 1832 4.3. Embossing with Rigid Masters 1835 4.4. Near-Field Phase-Shifting Photolithography 1835 4.5. Topographically Directed Photolithography 1837 4.6. Topographically Directed Etching 1837 4.7. Lithography with Neutral Metastable Atoms 1838 4.8. Approaches to Size Reduction 1839 5. Techniques for Making Regular or Simple Patterns 1839

Use of controlled reactive spreading of liquid alkanethiol on the surface of gold to modify the size of features produced by microcontact Printing

Abstract: This paper describes a procedure that uses the controlled reactive spreadingl 2 of a liquid on a solid surf'ace to reduce the size of features produced by microcontact printing (rCP).r It suggests a strategy for generating small f-eatures ( 100-500 nrnt in patterns on surfaces that relies on a physical process occuming on a surf-ace-lateral reactive spreading of a liquid-rather than on exposure to short-wavelength radiation or electrons. 4CP prints the patterned self-assembled monolayer' (SAM)r on the surface of gold, using an elastomeric stamp whose surface has itself been patterned in an appropriate relief structure. The stamp is wetted with an alkanethiol (typically hexadecanethiol, CH3(CH2)rsSH) and brought into contact with the gold in air for 10-20 s. I t is a very convenient technique for fornring patterned SAMs with features having dintensions of -2 lm or larger. The photolithography required to make the ntasters used to mold the e lastomer ic s tamps is s t ra ight lbrward ar th is sca le .5 and the edge resolution that can be obtained presentl)' using this method (about 50 nm)2 does not limit the resolutton of the overall pattern. It is more difficult to make t'eatures smaller than 2 ltmby pCP, primarily because fabricating the required stamps requires more complex photolithography. Features as small as 200 nm have, however, been made using masters prepared (with difficulty) by X-ray lithography.5-7 We are developing procedures that extend the capabilities of 4CP into the submicrometer range and that do not require highresolut ion photol i thography.8'e In part icular. we wish to f ind methods that start with an elastomeric stamp having features with dimensions of -2 pm or larger (that is, in the range that is easily prepared by routine photolithographic methods) and

Wetting and Protein Adsorption on Self-Assembled Monolayers of Alkanethiolates Supported on Transparent Films of Gold

Abstract: We have formed self-assembled monolayers (SAMs) of alkanethiolates on5-nmand l0-nm-thick films of gold supported on titanium-primed glass. These electrically-conductive films transmit visible light,s upport SAMs that have wetting properties superior to those of SAMs supported on opaque 200-nm-thick films commonly used in this area of surface chemistr),6 and have surfaces that are smoother than those of thicker films. We present two examples demonstrating the combination of flexibility in control of surface chemistry offered by SAMs of alkanethiols and optical transparency provided by these thin films: measurements of the adsorption of RNase A [EC 3.L27.51labeled with eosin-5-isothiocyanate (EITC) on methyland hexaethylene glycol-terminated SAMs using transmission spectroscopy, and observations of the differential attachment and growth of living MG63 osteosarcoma cells on patterned SAMs of hydroxyland methyl-terminated alkanethiolates using conventional phasecontrast microscopy. To prepare 5-nmand 10-nm-thick films of gold on titaniumprimed glass, we sequentially deposited I nm of titanium at 0.I nm/s and gold at 0.1 nm/s; thick fi lms of gold (200 nm) were deposited at 0.5 nm/s on glass primed with 5 nm of titanium at 0.2 nm/s.7'E For studies of protein adsorption,0.5 nm of t itanium and 5 nm of gold were deposited on each side of glass substrates. The continuity of these films of gold was verified using X-ray photoelectron spectroscopy (XPS).e They also were electrically conductive, with the resistivit ies (7.1 + 0.3) x lO{ O-cm (5nm-thick Au), (4.8 + 0.4) x l0-6 O-cm (10-nm-thick Au), and (3.7 + 1.5) x l0{O-cm (200-nm-thickAu).r0 SAMswere formed by chemisorption from I mM ethanolic solutions of co-functionalized alkanethiols for 2 h at room temperature. The transparency of SAMs on thin films of gold increased withdecreasing thicknessof gold (Figure l). Films became more blue and gray as the thickness of gold decreased (200-nm-thick gold had the same color as bulk gold). Formation of SAMs on these films did not affect their transparency or color.rr Transparency could be increased using a (3-mercaptopropyl)trimethoxysiloxy layer rather than titanium as an adhesion promoter between gold and glass, but evaporation of titanium was a more

Soft Machines That are Resistant to Puncture and That Self Seal

Abstract: A soft machine composed of a composite of elastomer and fibers resists puncture from sharp objects, and continues to operate even if punctured.

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.