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We report here molecular characterization of a new method derived from reactive microcontact printings microstamping on an activated polymer surface (MAPS)swhich enables biological ligands and proteins to be patterned on a polymer surface with a spatial resolution of at least 5 µm and good reproducibility. MAPS is a multistep procedure: first, the surface of a polymer is modified, in one or more steps, to introduce a reactive group of interest. In a subsequent step, an elastomeric stamp, inked with a biological ligand containing a complementary terminal reactive group, is brought into contact with the activated surface of the polymer. This results in spatially resolved transfer and coupling of the biological ligand to the reactive surface of the polymer. We used MAPS to pattern biotin on carboxylic acid derivatized poly-(ethylene terephthalate) (PET), and subsequently with streptavidin, mediated by the high affinity streptavidin-biotin interaction. X-ray photoelectron spectroscopy of biotin-derivatized PET showed that approximately one in five PET repeat units in the top 50-100 Å were functionalized with biotin. Timeof-flight secondary ion mass spectrometry (TOF-SIMS) suggested an increased concentration of PET oligomers in the top 10 Å due to chain scission during modification and clearly identified the derivatization of PET with biotin. TOF-SIMS imaging mapped biotin and streptavidin to the stamped regions. TOF-SIMS also imaged the spatial distribution of residual reagents from the multistep derivatization in MAPS, such as pentafluorophenol, Tween 20 surfactant, as well as poly(dimethylsiloxane) (PDMS), which was transferred from the elastomeric PDMS stamp to the surface during MAPS.

α-Functionalized terthiophenes containing disulfide (−S−T3−H)2 and alkanethiol (HS−(CH2)11−T3−H) anchoring groups have been synthesized for direct immobilization onto gold. Monolayer structures of these compounds are prepared by spontaneous assembly from ethanol solutions on evaporated gold substrates and thoroughly characterized by ellipsometry, contact angle goniometry, infrared and X-ray photoelectron spectroscopy, and cyclic voltammetry. The two molecules coordinate to the gold substrate exclusively via the anchoring groups upon formation of gold−thiolate bonds. The kinetics of monolayer formation vary dramatically for the two compounds. The alkanethiol analogue assembles rapidly, within a few minutes, and forms a densely packed and highly organized monolayer, with the alkyl chains in an almost perfect all-trans conformation and the Cα−Cα axis of the α-T3 units tilted about 14° away from the surface normal. The assembly process is much slower for the disulfide, but an organized monolayer with an average α-T3 chain tilt of about 33° will eventually form when the assembly is allowed to equilibrate with a solution containing the disulfide for at least 1 day. Moreover, the two monolayer assemblies also display a remarkably different electrochemical behavior. The heterogeneous electron-transfer rate at the disulfide-covered gold substrate is almost indistinguishable from that at bare gold, suggesting that the assembly contains a large number of easily accessible defects. An alternative mechanism for explaining the large electron-transfer rate involving electronic coupling via the conjugated π-system of the α-T3 units is also proposed. The electrochemical response is significantly reduced for the HS−(CH2)11−T3−H assembly, but another type of defects, the so-called “shallow defects” originating from sparsely populated areas on the electrode surface, can be identified.

We describe a method to pattern proteins onto a photolabile “caged” biotin-derivatized self-assembled monolayer (SAM) on gold, which we term light-activated affinity micropatterning of proteins (LAMP). LAMP is a multistep patterning process with considerable flexibility in its implementation. First, a reactive SAM on gold is formed from a mixture of 11-mercaptoundecanol and 16-mercaptohexadecanoic acid. Next, the carboxylic acid end groups in the SAM are coupled to methyl α-nitropiperonyloxycarbonyl biotin succinimidyl ester (caged biotin ester) through a diamine linker. The caged biotin is then deprotected in regions irradiated by masked UV light, and subsequent incubation with streptavidin results in selective binding of streptavidin to the irradiated regions. Micropatterning of various proteins has been demonstrated with a spatial resolution of ∼6 μm by confocal microscopic imaging of fluorophore-labeled proteins, and a contrast ratio of ∼4:1 was determined by direct ellipsometric imaging of streptavidin. Immobilization of biotinylated antibodies on the streptavidin pattern indicates that LAMP can enable spatially resolved micropatterning of different biomolecules by repeated cycles of spatially defined photodeprotection of biotin, streptavidin incubation, followed by immobilization of the biotinylated moiety of interest.

Abstract. The aim of the present study is to evaluate the potential ecological risk and trend of soil heavy-metal pollution around a coal gangue dump in Jilin Province (Northeast China). The concentrations of Cd, Pb, Cu, Cr and Zn were monitored by inductively coupled plasma mass spectrometry (ICP-MS). The potential ecological risk index method developed by Hakanson (1980) was employed to assess the potential risk of heavy-metal pollution. The potential ecological risk in the order of ER(Cd) > ER(Pb) > ER(Cu) > ER(Cr) > ER(Zn) have been obtained, which showed that Cd was the most important factor leading to risk. Based on the Cd pollution history, the cumulative acceleration and cumulative rate of Cd were estimated, then the fixed number of years exceeding the standard prediction model was established, which was used to predict the pollution trend of Cd under the accelerated accumulation mode and the uniform mode. Pearson correlation analysis and correspondence analysis are employed to identify the sources of heavy metals and the relationship between sampling points and variables. These findings provided some useful insights for making appropriate management strategies to prevent or decrease heavy-metal pollution around a coal gangue dump in the Yangcaogou coal mine and other similar areas elsewhere.

The formation of thiocholesterol (TC) monolayers on gold has been studied by ellipsometry, contact angle measurements, infrared spectroscopy, and cyclic voltammetry. Subsequent treatment of the TC assembly with 11-mercaptodeuterioundecanoic acid (MDUA) shows that the average surface coverage is about 65% of that of a self-assembled alkanethiolate monolayer and that it has a large number of molecular defects. These defects exist because of a mismatch between the size and shape of the TC molecule and the pinning distance at the Au(111) crystal lattice. Potential uses of these defect-rich structures are microelectrode arrays for electroanalytical and biosensor applications.

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